J Neurosurg 73:360-367, 1990
Leptomyelolipoma: analysis of 20 cases MICHAEL J. HARRISON, M.D., ROBIN J. MITNICK, M.D., BRUCE R. ROSENBLUM, M.D., AND ALLEN S. ROTHMAN, M.D. Department of Neurosurgery and Division of Neuroradiology, Mount Sinai Hospital, New York, New York v" Leptomyelolipoma (lumbosacral lipoma) is a common form of spinal dysraphism. The deficits produced include sensory, motor, bowel, and bladder dysfunction, and vary in incidence between the pediatric and adult populations. Twenty patients treated surgically at the Mount Sinai Hospital between 1972 and 1988 are reviewed. Fifty percent were 12 years of age or less and 50% were older than 18 years of age. The surgical approach was designed to accomplish untethering of the conus medullaris, debulking of the lipomatous mass compressing the cord, reconstruction of the dural canal, and reapproximation of the paraspinal muscles and lumbosacral fascia to prevent future trauma. Postoperatively, no patient experienced deterioration of neurological function. Of the symptomatic patients, 67 % displayed dramatic improvement or became asymptomatic and 33% experienced stabilization of their deficits. The symptoms most resistant to surgical correction were orthopedic foot deformities and bowel dysfunction, whereas bladder dysfunction, motor weakness, and radiculopathies were most amenable to surgical therapy. Early surgical repair is recommended in these cases to forestall irreversible neurological damage. KEY WORDS
"
leptomyelolipoma
L
EPTOMYELOLIPOMA is the most c o m m o n form of spinal dysraphism reported in many series. 3,~8,43 Although this entity was first reported more than a century ago, 26'33'34 in the majority of cases data regarding leptomyelolipomas have been grouped with the category of spinal lipomas, which often do not demonstrate a dural defect. 12'17'25'31'32'38'53'58'66Some of this surgical literature was tabulated prior to the microsurgical era.I~ Composing between 1% and 5 % of all intramedullary spinal cord tumors, 13'21'24"28'49'58'59"70'74 leptomyelolipomas usually involve an abnormally lowlying conus which is tethered by a lipomatous mass traversing a dural defect. 12'18'19'32'56'62Compression and tethering of the conus leads to progressive neurological deficits. Based on the excellent outcome reported in the recent surgical literature, early decompression and untethering of the spinal cord with reconstruction of the dural canal is advocated. This study is a retrospective review of 20 surgically treated patients with leptomyelolipoma. Summary of Cases
Case Material Between July, 1972, and December, 1988, 25 patients underwent microsurgical correction of spinal cord li360
9 lumbosacral lipoma
9 pathophysiology
pomas at the Mount Sinai Hospital. Two lipomas were thoracic and thus excluded, and an additional three cases could not be analyzed due to insufficient data. Of the remaining 20 patients, there were 13 males (65%) and seven females (35%), ranging in age from 7 months to 57 years (Table 1). Clinical Presentation All but one of the patients had cutaneous stigmata of spinal dysraphism (Table 2), accompanied by a lowlying conus medullaris with tethering of the cord by an intramedullary lipoma in all cases. Spina bifida was seen in 17 (85%) of the patients. At the time of presentation, 13 patients (65%) had gradually progressive deficits, five (25%) were neurologically intact, and two (10%) had stable fixed deficits (Table 3). Both of the latter patients were 1 year of age or less. The majority of patients were neurologically intact as infants. In the age range under 6 years old, three children (50%) were neurologically intact preoperatively, while only one child (25%) in the 6- to 12year-old age range and one (10%) in the category older than 18 years were without deficit. Four patients aged 12 years or less presented with cutaneous malformations. Motor weakness and sphincter abnormalities were equally c o m m o n among the six J. Neurosurg. / Volume 73 /September, 1990
Leptomyelolipoma TABLE 1
TABLE 3
Age and sex distribution in 20 patients
Surgical results in 20 patients
Age (yrs)
Sex male
< 6 5
Total
6-12 2
> 18 6
female
1
2
totals
6 (30%)
4 (20%)
No.
Percent
13
65
7
35
4 10 (50%)
20
patients in this age group who had neurological deficits. Only one of the six symptomatic children complained of paresthesias. Two of the six patients had orthopedic foot deformities (talipes cavovalgus). Of the nine symptomatic patients in the adult group (> 18 years old), six presented with sphincter abnormalities and four with radiculopathy or paresthesias. Although weakness and diminished sensation were universally present, these complaints were minor. Only one of nine symptomatic adults had an orthopedic deformity: namely, a talipes cavovalgus deformity which had been present since childhood. A subcutaneous lipoma with an accompanying dimple, hypopigmentation, and hypertrichosis had been present in one neurologically intact adult patient since birth. At the age of 25 years, she sought medical advice when a blow to the back elicited transient paraplegia. Two other adult patients experienced several similar episodes dating back to childhood; however, they presented only after persistent neurological deficits appeared. Abnormal reflexes were frequently found. Absent or hypoactive reflexes were five times as common as hyperactive reflexes (Table 4).
Surgical Results Postoperatively, our patients were classified as improved, stabilized, or deteriorated. None of these cases deteriorated after surgery, consistent with the results of most other series. 4,12A8,32,4s A mean postoperative fol-
Preop Status
lipoma hyperpigmentation* hypopigmentation dimple or sinus hypertrichosis hemangioma no cutaneous lesion spina bifida intrameduUary tumor
Cases No.
Percent
18 7 2 6 5 1 1 17 20
90 35 10 30 25 5 5 85 100
* Hyperpigmentation included port-wine stain, caf6-au-lait areas, and pigmented nevi.
J. Neurosurg. / Volume 73/September, 1990
> 18
no change
3
1
1
gradually progressive deficits
improved no change
1 0
2 1
6~ 3J
stable fixed deficits
no change
2
0
0
No.
%
5
25
13
65
2
10
TABLE 4
Abnormal reflexes among 20 patients Cases
Reflex Abnormality absent or hypoactive hyperactive both hypoactive & hyperactive* extensor plantar responses absent anal wink
No.
%
10 2 2 1 4
50 10 10 5 20
* Both present in the same limb.
low-up period of 22 months was obtained in these patients (range 6 months to 12 years). All patients who were neurologically intact on presentation have remained so (Table 3). Patients with gradually progressive deficits fared better with early surgical intervention. Three (75 %) of four such patients 12 years of age or less improved postoperatively, while six (67%) of nine such patients older than 18 years of age improved. Diminished sensation was the symptom most frequently encountered at presentation, with motor weakness and sphincter abnormalities occurring less commonly (Table 5). Urinary TABLE 5
Surgical results correlated with symptoms in 20 patients
TABLE 2
Cutaneous Stigma
< 6 6-12
Total
neurologically intact
Symptom
Dermal stigmata among 20 patients
Age (yrs)
Postop Status
sensory deficit motor weakness decreased sphincter tone urinary incontinence other urinary symptoms* orthopedic deformities paresthesias/radicular pain fecal incontinence posttraurnatic deficitst abnormalgait neurologically intact
Postop Stabilized No. of % of ImproveCases Total ment~ Postop~ 13 12 9 6 7 5 6 5 3 2 5
65 60 45 30 35 25 30 25 15 10 25
6 (46%) 7 (54%) 8 (67%) 4 (33%) 4 (44%) 5 (56%) 5 (83%) 1 (17%) 5 (71%) 2 (29%) 0 (0%) 5 (100%) 3 (50%) 3 (50%) 3 (60%) 2 (40%) transient 1 (50%) 1 (50%) no change postop
* Other urinary symptoms: hesitancy, retention, urgency, frequency. t Transient paraplegia with dysesthesias. :~ Percentages are of the number of cases presenting with that symptom. 361
M. J. Harrison, et al. incontinence was most amenable to improvement. The findings most resistant to treatment were orthopedic foot deformities and abnormalities of rectal sphincter tone. Discussion
Embryology and Pathophysiology Closure of the medullary tube and ectodermal differentiation into neural and epithelial tissue occur between the 3rd and 5th week of intrauterine development. Errors in this differentiation can lead to central nervous system and cutaneous abnormalities categorized as spinal dysraphism, j-a,7,15"a~ Leptomyelolipomas are one group of dysraphic states.16'27'41'55'73 The posterior neuropore is the last region of the tube to fuse, and therefore the caudal end of the spine is the most common area in which to encounter dysraphism. In addition, it is known that the more severe the caudal dysraphism, the greater the affiliation with cranial dysraphic states and other congenital anomalies. Although Chiari malformations have been reported with leptomyelolipoma in as many as 7% of some series, 53 they are generally considered to be rare in these patients.12,14,56 At the 15-mm stage of fetal development, the cord is a structure extending to the lower end of the sacrum. 64 The process of tube closure and formation of the vertebral column by mesodermal investment of the spinal cord must be altered early in order to account for the partial dorsal myeloschisis53 and the presence of spina bifida (identified in 85% of our patients). It is the developmental process to this point which must give rise to leptomyelolipoma. Alvord, et al.,2 proposed that these abnormalities arise from a clone of lipomatous cells that has escaped normal controls. The presence of ependyma, neuroglia, smooth and striated muscle, and other elements in leptomyelolipomas supports this contention.48'52'61,71 In the case of leptomyelolipomas, the conus is tethered and compressed by the lipoma and is unable to undergo its normal ascent. 9,7j With progressive lengthening of the vertebral axis, greater traction is placed upon the cord, producing the low-lying conus medullaris. Leptomyelolipomas produce neurological impairment by traction, compression, and direct transmission of force. Patients frequently become symptomatic during growth spurts. Childbirth, sexual intercourse, and bending during exercise have all been implicated in the precipitation of symptoms. 54 Although adipose tissue in leptomyelolipomas does not undergo mitotic activity, the tumor does change in size, depending on the nutritional status of the individual. Patients may experience neurological deterioration with weight gain. Coexisting conditions which narrow the spinal canal will also increase the compressive effect of the lipomatous mass and exacerbate symptoms. 54 Transient paralysis due to a blow on the back is caused by the direct transmission of force to the lipoma 362
FlG. 1. Supine abdominal radiograph showing spina bifida at multiple sacral levels (large arrow) and a scoliosis convex to the right. The interpedicular distances in the lumbar spine and sacrum are increased (small arrow).
by a water-hammer effect?2 Hilal and Keim 29 and others 61'75 demonstrated that tension on the conus caused impaired blood flow with resultant ischemia and spinal cord damage.
Evaluation of Cases Clinical Studies. Leptomyelolipoma can produce both upper and lower motor neuron deficits, mimicking a myriad of urological and orthopedic problems. Urinary tract infections may be the first symptom of the disease, along with the onset of an orthopedic foot deformity. Apparently neurologically intact patients may have abnormal electromyographic (EMG) studies, 56and EMG examination of the perineum and lower extremities is advisable in all patients. The presence of neurogenic bladder and other urological abnormalities is reported in between 21% and 64% of patients. 12'18,32,56Intravenous pyelograms with cystometry and EMG evaluation of urethral and rectal sphincters are particularly important in younger patients. 45 Somatosensory evoked potentials (SSEP) monitoring may help to measure baseline neurological function. Neuroradiographic Studies. Plain radiographs may offer details of bone in cases of spina bifida (seen in 100% of patients in many series 4,37,43,62)and other spinal abnormalities (Fig. 1). Although in the past the neuroradiographic mainstay has been metrizamide myelography followed by computerized tomography (CT) J. Neurosurg. / Volume 73/September, 1990
Leptomyelolipoma
FIG. 3. Sagittal T~-weighted magnetic resonance image showing a lipoma with high signal intensity (arrow) within the spinal canal, extending pc~.'eriorly into the subcutaneous soft tissues through a neural arch defect. FIG. 2. Axial computerized tomography scans in two patients. Upper: Scan obtained through the midlumbar spine showing a lipoma, which is located posteriorly within the spinal canal (arrow). Lower." Scan obtained through the lower lumbar spine showing fatty tissue (arrow) which surrounds a cord-like structure (arrowhead) extending through a neural arch defect.
scanning, 8'12'18'25'32'39'42'43'45'53'56'59'62'63this has been replaced by magnetic resonance (MR) imaging. M a l i s 48'49 and Carem, et al., 17 do not suggest myelography for fear of traumatizing the low-lying conus or an undiagnosed Chiari malformation. The use of CT scanning with contrast enhancement allows delineation of nerve root emergence and the lipoma-cord relationship (Fig. 2 upper) in a complementary fashion to the studies obtained by MR imaging. Other abnormalities, such as diplomyelia, thickened ilium, diastematomyelia, dermoid cyst, and terminal hydromyelia may also be diagnosed by CT 1'23'32'35'39'56'59(Fig. 2 lower). The usefulness of MR studies in visualizing cord lesions is well d o c u m e n t e d . 6,39,44,6~ On T~-weighted spin-echo images, the lipoma shows a high signal intensity, the cord an intermediate intensity, and the cerebrospinal fluid (CSF) a low intensity (Fig. 3). On T2-weighted images, the lipoma and cord show inter-
J. Neurosurg. / Volume 73/September, 1990
mediate intensity, the lipoma being of equal or slightly lower intensity than the cord. In general, CSF shows high intensity on Tz-weighted images. Axial images demonstrate a low-intensity band between the lipoma and the spinal cord. On sagittal images, the band is cephalad and anterior to the lipoma, separating it from the cord (Fig. 4 left). The lowintensity band has been likened to a halo, 3~but is more accurately described as a chemical shift artifact. 72 It has a characteristic appearance and occurs Perpendicular to the direction of the frequency-encoding gradient and the interface of tissues with different chemical-shift properties. The greater the magnetic field, the greater is the intensity of this artifact? 9,72 With leptomyelolipomas, this phenomenon is particularly fortuitous in providing exact demarcation at the lipoma-cord interface. This line assists in demonstrating the relationship of the nerve roots to this interface (Fig. 4 right). Magnetic resonance imaging is particularly adept at revealing the presence of terminal hydromyelia, and allows for evaluation of the paraspinal structures; MR imaging is now the diagnostic method of choice for leptomyelolipoma.
Surgical Indications All patients with leptomyelolipoma should undergo surgical correction. If the neoplasm is asymptomatic, 363
M. J. Harrison, et al.
FIG. 4. Sagittal T~-weighted magnetic resonance images. Left: A lipoma with high signal intensity (large arrow) is seen in the posterior spinal canal and a syringohydromyelia with low signal intensity (small arrow) is shown in the distal spinal cord. Right: In another patient, a lipoma (arrow) is seen lying anterior to a meningocele (arrowhead), which extends through a neural arch defect.
the goal is to prevent the onset of neurological symptoms. If it is symptomatic, the goal is to halt progression and alleviate deficits where possible. Bassett,~~ recognizing the progressive nature of the disease, advocated early prophylactic surgery. Others have recommended surgical repair only after the onset of neurological deficit 65 or for the repair of cosmetic deformity alone, s~ Malis 48 and others ~8,43 have observed that superficial removal of the mass leads to intense arachnoidal scarfing with escalated neurological deterioration and the need for a more dangerous second exploration often resulting in a poor outcome. It has been advocated that surgery be delayed until 1 year of age in asymptomatic infants to allow technically easier removal. A sudden neurological deterioration has been described; four of these patients were under 6 months of age. 56 It is our belief that all patients with leptomyelolipoma should undergo surgical correction as early as possible. Only rarely do neonates demonstrate severe abnormalities. This situation has been encountered by other investigators, 18'56 and is probably due to congenitally absent or malformed nerve roots. Many reports describe a neurological deficit increasing with age. Although neurologically intact patients aged in their 50's have been reported, this is rare?'~l'46 Our oldest patient without a deficit was 25 years old.
If the mass is not situated in the midline, it will deviate and rotate the cord toward the lipoma (Fig. 5). There is a small dural defect through which the lipoma passes. The dura and pia arachnoid fuse to the interface of the
Anatomical Considerations Leptomyelolipomas have been classified into four types, as follows. 18'45,62
Type 1 (Dorsal Type). In Type 1, the lipomatous mass inserts itself directly into the dorsum of the cord. 364
FIG. 5. Coronal T~-weighted magnetic resonance image showing a lipoma on the left side of the lumbar spine (large arrow). The distal spinal cord is pulled to that side (small
arrow).
J. Neurosurg. / Volume 73/September, 1990
Leptomyelolipoma lipoma and cord, but the sensory nerve roots emerge anterior to the interface and none of the nerve roots run through the lipoma. The nerves that emerge at this level are shorter than normal and demonstrate abnormal angulation.
Type 2 (Caudal Type). Type 2 lipoma traverses a defect in the most distal part of the dural sac. There is no fusion of the leptomeninges to the lipoma-cord interface. The lipoma extends cephalad through the subarachnoid space to engulf the tip of the conus. The rootlets run within the fibrous fatty mass, usually in the anterolateral regions. The filum terminale may not be identifiable. 62 Type 3 (Transitional Type). In Type 3, the lipomacord interface resembles the dorsal lipoma superiorly, then extends around the conus inferiorly to resemble the caudal type. The leptomeninges fuse with the cord at the lipoma-cord interface and attach to the exiting nerve roots. Type 4 (Filar Type). Type 4 is relatively rare 22"5~'62 and is not discussed by many authors. 18,32.45,56It consists of a short thick filum terminale widened by infiltrating fat and fibrous tissue. The fat may extend into the conus medullaris. Although the conus is tethered, the nerve roots have a normal configuration. Surgical Approach In the management of our patients we followed the protocol established by Malis. 48'49Monitoring of SSEP's was employed throughout positioning and the surgical procedure. The procedure was performed with the patient in the lateral oblique position and the side of greatest lipomatous involvement upward, allowing free movement of the thorax and abdomen without compression. The SSEP and sphincteric E M G findings were used to avoid damage to functional neural elements. 12,18,32,45,48,49.59 An omega-shaped flap was created so that the base lay inferiorly over the natal cleft, as previously depicted by Rosenblum, et al. 59The vascularity from the lumbar and gluteal arteries was incorporated into the flap. The flap design prevented urinary and fecal contamination of the wound, particularly in younger patients. A margin of adipose tissue was left adherent to the skin to prevent vascular compromise. Amputation of the lip o m a at the point where it penetrated the lumbosacral fascia defect allowed reflection of the flap inferiorly. A laminectomy above the lipomatous insertion was needed to visualize the cephalic extent of the dural dehiscence and the transitional area between the lipoma and normal cord. When the laminae were exposed, a vascular fibrous band might be seen bridging the gap between the laminae of the most superior bifid arches. 2~ If present, this band produced kinking of the herniating meningocele and cord in a configuration Malis has likened to a hairpin turn. 48 This band should be tested for neural function prior to its division.
J. Neurosurg. / Volume 73/September, 1990
The remainder of the procedure entailed untethering the conus from lipomatous, leptomeningeal, and dural attachments, 18'45 and debulking the lipomatous mass with decompression of the conus. The filum terminale was severed as it was shortened and acted as a further tethering agent, with occasional lipomatous infiltration. 59 Reconstruction of the dural canal with a watertight closure provided ample space for CSF to flow around the cord, preventing adhesions with retethering. Reapproximation of muscle mass and lumbosacral fascia was performed over the canal to avoid future trauma to the repaired region. If the dura was deficient, we preferred to use tensor fascia lata for reconstruction of the dural tube. If the canal was too tight, increases in the size of the residual adipose tissue might produce compression and neurological symptoms during periods of weight gain. A watertight closure will prevent accumulation of CSF in the subcutaneous s p a c e . 32'36'59 Conclusions
Leptomyelolipomas are c o m m o n dysraphic lesions produced by aberrant neural tube closure during early embryological development. They may be associated with anomalies in other organ systems. The abnormal spinal development produces four discrete anatomical configurations of the lipoma-spinal cord interface. In our experience the natural history of the disease is that of progressive neurological deterioration with deficits arising during periods of rapid growth and weight gain. Deficits are produced by traction, compression, and direct transmission of force to the cord. Although improvement is c o m m o n with surgical correction, only a minority of patients are cured and few will regain full function after deficits appear. In view of the recent advances in neuroimaging, intraoperative monitoring, and microsurgical techniques, early surgery is recommended for all patients. Acknowledgment
The authors thank Ms. Gloria Minet-Johnson for her assistance in the preparation of this manuscript. References
1. Altman N, Harwood-Nash DC, Fitz CR, et al: Evaluation of the infant spine by direct sagittal computed tomography. AJNR 6:65-69, 1985 2. Alvord EC Jr, Shaw CM, Sumi SM: Central nervous system developmental abnormalities, in Thompson RA, Green JR (eds): Pediatric Neurology and Neurosurgery. New York: Spectrum, 1978, pp 97-166 3. Anderson FM: Occult spinal dysraphism. Diagnosis and management. J Pediatr 73:163-177, 1968 4. Anderson FM: Occult spinal dysraphism. A series of 73 cases. Pediatrics 55:826-835, 1975 5. Balagura S: Late neurological dysfunction in adult lumbosacral lipoma with tethered cord. Neurosurgery 15: 724-726, 1984 6. Barnes PD, Lester PD, Yamanashi WS, et al: MRI in infants and children with spinal dysraphism. AJR 147: 339-346, 1986 365
M. J. Harrison, et al. 7. Barry A, Patten BM, Stewart BH: Possible factors in the development of the Arnold-Chairi malformation. J Neurosurg 14:285-301, 1957 8. Barry FB, Harwood-Nash DC, Fitz CR, et al: Metrizamide in pediatric myelography. Radiology 124:409-418, 1977 9. Barson AJ: The vertebral level of termination of the spinal cord during normal and abnormal development. J Anat 106:489-497, 1970 10. Bassett RC: The neurologic deficit associated with lipomas of the cauda equina. Ann Surg 131:109-116, 1950 11. Bourque PR, D'Alton JG, Russell NA, et al: Congenital lumbosacral lipoma causing primary enuresis in an adult (case report). Can Med Assoe J 135:1007-1008, 1986 12. Bruce DA, Schut L: Spinal lipomas in infancy and childhood. Childs Brain 5:192-203, 1979 13. Burrows FGO: Some aspects of occult spinal dysraphism: a study of 90 cases. Br J Radiol 41:496-507, 1968 14. Cameron AH: The Arnold-Chiari and other neuro-anatomicat malformations associated with spina bifida. J Pathol Bacteriol 73:195-211, 1957 15. Cameron AH: Malformations of the neuro-spinal axis, urogenital tract, and foregut in spina bifida attributable to disturbances of the blastopore. J Pathol Bacteriol 73: 213-221, t957 16. Cameron AH: The spinal cord lesion in spina bifida cystica. Lancet 2:171, 1956 17. Caram PC, Scarcella G, Carton CA: Intradural lipomas of the spinal cord with particular emphasis on the "intramedullary" lipomas. J Neurosurg 14:28-41, 1957 18. Chapman PH: Congenital intraspinal lipomas. Anatomic considerations and surgical treatment. ChUds Brain 9: 37-47, 1982 19. de Jonge MC, Kornelis JA, van Berg JW, et al: The evaluation of functional disorders of the urinary tract in children with spina bifida. Dev Med Child Neurol 20 (Suppl):51-56, 1969 20. Dubowitz V, Lorber J, Zachary" RB: Lipoma of the cauda equina. Arch Dis Child 40:207-213, 1965 21. Ehni G, Lore JG: Intraspinai lipomas. Report of cases, review of the literature, and clinical and pathologic study. Arch Neurol Psychiatry 53:1-28, 1945 22. Emery JL, Lendon RG: Lipomas of the cauda equina and other fatty tumours related to neurospinal dysraphism. Dev Meal Child Neurol 20 (Suppl):62-70, 1969 23. Fitz CR, Harwood-Nash DC: The tethered conus. AJ R 125:515-523, 1975 24. Giuffre R: Intradural spinal lipomas. Review of literature (99 cases) and report of an additional case. Aeta Neurochit 14:69-95, 1966 25. Gold LHA, Kieffer SA, Peterson HO: Lipomatous invasion of the spinal cord associated with spinal dysraphism: myelographic evaluation. AJR 107:479-485, 1969 26. Gowers WR: Myo-lipoma of spinal cord. Trans Pathol Soc Lond 27:19-22, 1876 27. Hall DE, Udvarhelyi GB, Altman J: Lumbosacral skin lesions as markers of occult spinal dysraphism. JAMA 246:2606-2608, 1981 28. Hamby WB: Tumors in the spinal canal in childhood II. Analysis of the literature of a subsequent decade (1933-1942); report of a case of meningitis due to an intramedullary epidermoid communicating with a dermal sinus. J Neuropathol Exp Neurol 3:397-412, 1944 29. Hilal SK, Keim HA: Selective spinal angiography in adolescent scoliosis. Radiology 102:349-359, 1972 30. Hircak H, Williams RD, Moon KL Jr, ct al: Nuclear magnetic resonance imaging of the kidney: renal masses. Radiology 147:765-772, 1983 31. Hoffman H J, Hendrick EB, Humphreys RP: The tethered 366
32.
33. 34. 35. 36.
37. 38. 39. 40. 41. 42.
43. 44. 45. 46. 47. 48. 49. 50. 51.
52. 53.
54.
spinal cord: its protean manifestations, diagnosis and surgical correction. Childs Brain 2:145-155, 1976 Hoffman HJ, Taecholarn C, Hendrick EB, et al: Management of lipomyelomeningoceles. Experience at the Hospital for Sick Children, Toronto. J Neurosnrg 62:1-8, 1985 Johnson A: Fatty tumour connected with the interior of the spinal canal of the sacrum. Trans Pathol Soc Lond 8: 28-29, 1857 Johnson A: Fatty turnout from the sacrum of a child, connected with the spinal membranes. Trans Pathoi Soc Lond 8:16-18, 1857 Kaiser MC, Pettersson H, Harwood-Nash DC, et al: Direct coronal CT of the spine in infants and children. AJNR 2:465-466, 1981 Kallen B: Early embryogenesis of the central nervous system with special reference to closure defects (Casey Holter Memorial Lecture). Dev Med Child Neurol 16 (Suppl):44-53, 1968 Kaplan JO, Quencer RM: The occult tethered conus syndrome in the adult. Radiology 137:387-391, 1980 Kieck DF, De Villiers JC: Subcutaneous lumbosacral lipomas. S Afr Med J 49:1563-1566, 1975 Komiyama M, Hakuba A, Inoue Y, et al: Magnetic resonance imaging: lumbosacral lipoma. Surg Neurol 28: 259-264, 1987 Kunimoto K: The development and reduction of the tail and of the caudal end of the spinal cord in the human embryo. Contrib Embryol 8:161-198, 1918 Langman J: Medical Embryology, ed 4. Baltimore: Williams & Wilkins, 1981, pp 50-56 Lapras CL, Pater JD, Huppert J, et al: Syndrome de traction du cone terminal ou syndrome de la m6elle attachee. Lipomes lombo-sacres. Rev Neurol 141: 207-215, 1985 Lassman LP, James CCM: Lumbosacral lipomas: critical survey of 26 cases submitted to laminectomy. J Neural Neurosurg Psychiatry 30:174-181, 1967 Lee BCP, Zimmerman RD, Manning J J, et al" MR imaging of syringomyelia and hydromyelia. AJNR 6:1-8, 1985 Lhowe D, Ehrlich MG, Chapman PH, et al: Congenital intraspinal lipomas. Clinical presentation and response to treatment. J Pediatr Orthop 7:53t-537, 1987 Loeser JD, Lewin RJ: Lumbosacral lipoma in the adult. Case report. J Neurosnrg 29:405-409, 1968 Luce EA, Walsh J: Wound closure of the myelomeningocele defect. Piast Reconstr Surg 75:389-393, 1985 Malis LI: Intramedullary spinal cord tumors. Clin Neurosurg 25:512-539, 1978 Malis LI: Spinal cord tumors, in Davidoff RA (ed): Handbook of the Spinal Cord. Basel: Marcel Dekker, 1986, Vol 5, pp 319-370 Matson DD: Neurosurgery of Infancy and Childhood, ed 2. Springfield, II1:Charles C Thomas, 1969, p 46 McLendon RE, Oakes W J, Heinz ER, et ai: Adipose tissue in the filum terminale: a computed tomographic fnding that may indicate tethering of the spinal cord. Neurosurgery 22:873-876, 1988 Mickle JP, McLennan JE: Malignant teratoma arising within a lipomeningocele. Case report. J Neurosurg 43: 761-763, 1975 Naidich TP, McLone DG, Mutluer S: A new understanding of dorsal dysraphism with lipoma (lipomyeloschisis): radiologic evaluation and surgical correction. AJNR 4: 103-116, 1983 Pang D, Wilberger JE Jr: Tethered cord syndrome in adults. J Neurosurg 57:32-47, 1982
J. Neurosurg. / Volume 73/September, 1990
Leptomyelolipoma 55. Patten BM: Embryological stages in establishing myeloschisis with spina bifida. Am J Anat 25:1-11, 1953 56. Pierre-Kahn A, Lacombe J, Pichon J, et al: Intra-spinal lipomas with spina bifida. Prognosis and treatment in 73 cases. J Neurosurg 65:756-761, 1986 57. Ramirez OM, Ramasastry SS, Granick MS, et al: A new surgical approach to closure of large lumbo-sacral meningomyelocele defects. Plast Reeonstr Surg 80:799-809, 1987 58. Rogers HM, Long DM, Chou SN, et al: Lipomas of the spinal cord and cauda equina. J Neurosurg 34:349-354, 1971 59. Rosenblum BR, Harrison M J, Rothman AS: Lumbosacral lipomas. Contemp Neurosurg 10 (17): 1-8, 1988 60. Rosenthal DI, Scott JA, Mankin H J, et al: Sacrococcygeal chordoma: magnetic resonance imaging and computed tomography. AJR 145:143-147, 1985 61. Rosenthal M, LaManna J, Yamada S, et al: Oxidative metabolism, extracellular potassium and sustained potential shifts in cat spinal cord in situ. Brain Res 162: 113-127, 1979 62. Sato K, Shimoji T, Sumie H, et al: Surgically confirmed myelographic classification of congenital intraspinal lipoma in the lumbosacral region. Childs Nerv Syst 1: 3-11, 1985 63. Skalpe IO: Lumbar myelography with Comray Meglumin 282. Report of 100 investigations with special reference to the adverse effects. Acta Neurol Scand 47:569-578, 1971 64. Streeter GL: Factors involved in the formation of the filum terminale. Am J Anat 25:1-11, 1919 65. Swanson HS, Barnett JC Jr: Intradural lipomas in children. Pediatrics 29:911-926, 1962 66. Thomas JE, Miller RH: Lipomatous tumors of the spinal canal. A study of their clinical range. Mayo Clin Proc 48: 393-400, 1973 67. Till K: Spinal dysraphism. A study of congenital malfor-
J. Neurosurg. / Volume 73/September, 1990
68. 69. 70. 71. 72. 73. 74. 75. 76.
mations of the lower back. J Bone Joint Surg (Br) 51: 415-422, 1969 Traill MR, Runge VM, Wolpert SM: Dysraphism: MRI strategies. MRI Decisions 2:2-9, 1988 van Hoytema G J, van den Berg R: Embryological studies of the posterior fossa in connection with Arnold-Chiari malformation. J Anat 106:489-497, 1970 Villarejo FJ, Blazquez MG, Gutierrez-Diaz JA: Intraspinal lipomas in children. Childs Brain 2:361-370, 1976 Walsh JW, Markesbery WR: Histological features of congenital lipomas of the lower spinal canal. J Neurosurg 52:564-569, 1980 Weinreb JC, Brateman L, Babcock EE, et al: Chemical shift artifact in clinical magnetic resonance images at 0.35 T. AJR 145:183-185, 1985 Willis RA: The Borderland of Embryology and Pathology, London: Butterworths, 1962, pp 147-163 and 364 Wood BP, Harwood-Nash DC, Berger P, et al: Intradural spinal lipoma of the cervical cord. AJR 145:174-176, 1985 Yamada S, Zinke DE, Sanders D: Pathophysiology of "tethered cord syndrome." J Neurosurg 54:494-503, 1981 Yashon D, Beatty RA: Tethering of the conus medullaris within the sacrum. J Neurol Neurosurg Psychiatry" 29: 244-250, 1966
Manuscript received September 14, 1989. Accepted in final form January 23, 1990. Address reprint requests to: Michael J. Harrison, M.D., c/o Bruce R. Rosenblum, M.D., 1160 Fifth Avenue, Suite 106, New York, New York 10029.
367
Leptomyelolipoma: analysis of 20 cases MICHAEL J. HARRISON, M.D., ROBIN J. MITNICK, M.D., BRUCE R. ROSENBLUM, M.D., AND ALLEN S. ROTHMAN, M.D. Department of Neurosurgery and Division of Neuroradiology, Mount Sinai Hospital, New York, New York v" Leptomyelolipoma (lumbosacral lipoma) is a common form of spinal dysraphism. The deficits produced include sensory, motor, bowel, and bladder dysfunction, and vary in incidence between the pediatric and adult populations. Twenty patients treated surgically at the Mount Sinai Hospital between 1972 and 1988 are reviewed. Fifty percent were 12 years of age or less and 50% were older than 18 years of age. The surgical approach was designed to accomplish untethering of the conus medullaris, debulking of the lipomatous mass compressing the cord, reconstruction of the dural canal, and reapproximation of the paraspinal muscles and lumbosacral fascia to prevent future trauma. Postoperatively, no patient experienced deterioration of neurological function. Of the symptomatic patients, 67 % displayed dramatic improvement or became asymptomatic and 33% experienced stabilization of their deficits. The symptoms most resistant to surgical correction were orthopedic foot deformities and bowel dysfunction, whereas bladder dysfunction, motor weakness, and radiculopathies were most amenable to surgical therapy. Early surgical repair is recommended in these cases to forestall irreversible neurological damage. KEY WORDS
"
leptomyelolipoma
L
EPTOMYELOLIPOMA is the most c o m m o n form of spinal dysraphism reported in many series. 3,~8,43 Although this entity was first reported more than a century ago, 26'33'34 in the majority of cases data regarding leptomyelolipomas have been grouped with the category of spinal lipomas, which often do not demonstrate a dural defect. 12'17'25'31'32'38'53'58'66Some of this surgical literature was tabulated prior to the microsurgical era.I~ Composing between 1% and 5 % of all intramedullary spinal cord tumors, 13'21'24"28'49'58'59"70'74 leptomyelolipomas usually involve an abnormally lowlying conus which is tethered by a lipomatous mass traversing a dural defect. 12'18'19'32'56'62Compression and tethering of the conus leads to progressive neurological deficits. Based on the excellent outcome reported in the recent surgical literature, early decompression and untethering of the spinal cord with reconstruction of the dural canal is advocated. This study is a retrospective review of 20 surgically treated patients with leptomyelolipoma. Summary of Cases
Case Material Between July, 1972, and December, 1988, 25 patients underwent microsurgical correction of spinal cord li360
9 lumbosacral lipoma
9 pathophysiology
pomas at the Mount Sinai Hospital. Two lipomas were thoracic and thus excluded, and an additional three cases could not be analyzed due to insufficient data. Of the remaining 20 patients, there were 13 males (65%) and seven females (35%), ranging in age from 7 months to 57 years (Table 1). Clinical Presentation All but one of the patients had cutaneous stigmata of spinal dysraphism (Table 2), accompanied by a lowlying conus medullaris with tethering of the cord by an intramedullary lipoma in all cases. Spina bifida was seen in 17 (85%) of the patients. At the time of presentation, 13 patients (65%) had gradually progressive deficits, five (25%) were neurologically intact, and two (10%) had stable fixed deficits (Table 3). Both of the latter patients were 1 year of age or less. The majority of patients were neurologically intact as infants. In the age range under 6 years old, three children (50%) were neurologically intact preoperatively, while only one child (25%) in the 6- to 12year-old age range and one (10%) in the category older than 18 years were without deficit. Four patients aged 12 years or less presented with cutaneous malformations. Motor weakness and sphincter abnormalities were equally c o m m o n among the six J. Neurosurg. / Volume 73 /September, 1990
Leptomyelolipoma TABLE 1
TABLE 3
Age and sex distribution in 20 patients
Surgical results in 20 patients
Age (yrs)
Sex male
< 6 5
Total
6-12 2
> 18 6
female
1
2
totals
6 (30%)
4 (20%)
No.
Percent
13
65
7
35
4 10 (50%)
20
patients in this age group who had neurological deficits. Only one of the six symptomatic children complained of paresthesias. Two of the six patients had orthopedic foot deformities (talipes cavovalgus). Of the nine symptomatic patients in the adult group (> 18 years old), six presented with sphincter abnormalities and four with radiculopathy or paresthesias. Although weakness and diminished sensation were universally present, these complaints were minor. Only one of nine symptomatic adults had an orthopedic deformity: namely, a talipes cavovalgus deformity which had been present since childhood. A subcutaneous lipoma with an accompanying dimple, hypopigmentation, and hypertrichosis had been present in one neurologically intact adult patient since birth. At the age of 25 years, she sought medical advice when a blow to the back elicited transient paraplegia. Two other adult patients experienced several similar episodes dating back to childhood; however, they presented only after persistent neurological deficits appeared. Abnormal reflexes were frequently found. Absent or hypoactive reflexes were five times as common as hyperactive reflexes (Table 4).
Surgical Results Postoperatively, our patients were classified as improved, stabilized, or deteriorated. None of these cases deteriorated after surgery, consistent with the results of most other series. 4,12A8,32,4s A mean postoperative fol-
Preop Status
lipoma hyperpigmentation* hypopigmentation dimple or sinus hypertrichosis hemangioma no cutaneous lesion spina bifida intrameduUary tumor
Cases No.
Percent
18 7 2 6 5 1 1 17 20
90 35 10 30 25 5 5 85 100
* Hyperpigmentation included port-wine stain, caf6-au-lait areas, and pigmented nevi.
J. Neurosurg. / Volume 73/September, 1990
> 18
no change
3
1
1
gradually progressive deficits
improved no change
1 0
2 1
6~ 3J
stable fixed deficits
no change
2
0
0
No.
%
5
25
13
65
2
10
TABLE 4
Abnormal reflexes among 20 patients Cases
Reflex Abnormality absent or hypoactive hyperactive both hypoactive & hyperactive* extensor plantar responses absent anal wink
No.
%
10 2 2 1 4
50 10 10 5 20
* Both present in the same limb.
low-up period of 22 months was obtained in these patients (range 6 months to 12 years). All patients who were neurologically intact on presentation have remained so (Table 3). Patients with gradually progressive deficits fared better with early surgical intervention. Three (75 %) of four such patients 12 years of age or less improved postoperatively, while six (67%) of nine such patients older than 18 years of age improved. Diminished sensation was the symptom most frequently encountered at presentation, with motor weakness and sphincter abnormalities occurring less commonly (Table 5). Urinary TABLE 5
Surgical results correlated with symptoms in 20 patients
TABLE 2
Cutaneous Stigma
< 6 6-12
Total
neurologically intact
Symptom
Dermal stigmata among 20 patients
Age (yrs)
Postop Status
sensory deficit motor weakness decreased sphincter tone urinary incontinence other urinary symptoms* orthopedic deformities paresthesias/radicular pain fecal incontinence posttraurnatic deficitst abnormalgait neurologically intact
Postop Stabilized No. of % of ImproveCases Total ment~ Postop~ 13 12 9 6 7 5 6 5 3 2 5
65 60 45 30 35 25 30 25 15 10 25
6 (46%) 7 (54%) 8 (67%) 4 (33%) 4 (44%) 5 (56%) 5 (83%) 1 (17%) 5 (71%) 2 (29%) 0 (0%) 5 (100%) 3 (50%) 3 (50%) 3 (60%) 2 (40%) transient 1 (50%) 1 (50%) no change postop
* Other urinary symptoms: hesitancy, retention, urgency, frequency. t Transient paraplegia with dysesthesias. :~ Percentages are of the number of cases presenting with that symptom. 361
M. J. Harrison, et al. incontinence was most amenable to improvement. The findings most resistant to treatment were orthopedic foot deformities and abnormalities of rectal sphincter tone. Discussion
Embryology and Pathophysiology Closure of the medullary tube and ectodermal differentiation into neural and epithelial tissue occur between the 3rd and 5th week of intrauterine development. Errors in this differentiation can lead to central nervous system and cutaneous abnormalities categorized as spinal dysraphism, j-a,7,15"a~ Leptomyelolipomas are one group of dysraphic states.16'27'41'55'73 The posterior neuropore is the last region of the tube to fuse, and therefore the caudal end of the spine is the most common area in which to encounter dysraphism. In addition, it is known that the more severe the caudal dysraphism, the greater the affiliation with cranial dysraphic states and other congenital anomalies. Although Chiari malformations have been reported with leptomyelolipoma in as many as 7% of some series, 53 they are generally considered to be rare in these patients.12,14,56 At the 15-mm stage of fetal development, the cord is a structure extending to the lower end of the sacrum. 64 The process of tube closure and formation of the vertebral column by mesodermal investment of the spinal cord must be altered early in order to account for the partial dorsal myeloschisis53 and the presence of spina bifida (identified in 85% of our patients). It is the developmental process to this point which must give rise to leptomyelolipoma. Alvord, et al.,2 proposed that these abnormalities arise from a clone of lipomatous cells that has escaped normal controls. The presence of ependyma, neuroglia, smooth and striated muscle, and other elements in leptomyelolipomas supports this contention.48'52'61,71 In the case of leptomyelolipomas, the conus is tethered and compressed by the lipoma and is unable to undergo its normal ascent. 9,7j With progressive lengthening of the vertebral axis, greater traction is placed upon the cord, producing the low-lying conus medullaris. Leptomyelolipomas produce neurological impairment by traction, compression, and direct transmission of force. Patients frequently become symptomatic during growth spurts. Childbirth, sexual intercourse, and bending during exercise have all been implicated in the precipitation of symptoms. 54 Although adipose tissue in leptomyelolipomas does not undergo mitotic activity, the tumor does change in size, depending on the nutritional status of the individual. Patients may experience neurological deterioration with weight gain. Coexisting conditions which narrow the spinal canal will also increase the compressive effect of the lipomatous mass and exacerbate symptoms. 54 Transient paralysis due to a blow on the back is caused by the direct transmission of force to the lipoma 362
FlG. 1. Supine abdominal radiograph showing spina bifida at multiple sacral levels (large arrow) and a scoliosis convex to the right. The interpedicular distances in the lumbar spine and sacrum are increased (small arrow).
by a water-hammer effect?2 Hilal and Keim 29 and others 61'75 demonstrated that tension on the conus caused impaired blood flow with resultant ischemia and spinal cord damage.
Evaluation of Cases Clinical Studies. Leptomyelolipoma can produce both upper and lower motor neuron deficits, mimicking a myriad of urological and orthopedic problems. Urinary tract infections may be the first symptom of the disease, along with the onset of an orthopedic foot deformity. Apparently neurologically intact patients may have abnormal electromyographic (EMG) studies, 56and EMG examination of the perineum and lower extremities is advisable in all patients. The presence of neurogenic bladder and other urological abnormalities is reported in between 21% and 64% of patients. 12'18,32,56Intravenous pyelograms with cystometry and EMG evaluation of urethral and rectal sphincters are particularly important in younger patients. 45 Somatosensory evoked potentials (SSEP) monitoring may help to measure baseline neurological function. Neuroradiographic Studies. Plain radiographs may offer details of bone in cases of spina bifida (seen in 100% of patients in many series 4,37,43,62)and other spinal abnormalities (Fig. 1). Although in the past the neuroradiographic mainstay has been metrizamide myelography followed by computerized tomography (CT) J. Neurosurg. / Volume 73/September, 1990
Leptomyelolipoma
FIG. 3. Sagittal T~-weighted magnetic resonance image showing a lipoma with high signal intensity (arrow) within the spinal canal, extending pc~.'eriorly into the subcutaneous soft tissues through a neural arch defect. FIG. 2. Axial computerized tomography scans in two patients. Upper: Scan obtained through the midlumbar spine showing a lipoma, which is located posteriorly within the spinal canal (arrow). Lower." Scan obtained through the lower lumbar spine showing fatty tissue (arrow) which surrounds a cord-like structure (arrowhead) extending through a neural arch defect.
scanning, 8'12'18'25'32'39'42'43'45'53'56'59'62'63this has been replaced by magnetic resonance (MR) imaging. M a l i s 48'49 and Carem, et al., 17 do not suggest myelography for fear of traumatizing the low-lying conus or an undiagnosed Chiari malformation. The use of CT scanning with contrast enhancement allows delineation of nerve root emergence and the lipoma-cord relationship (Fig. 2 upper) in a complementary fashion to the studies obtained by MR imaging. Other abnormalities, such as diplomyelia, thickened ilium, diastematomyelia, dermoid cyst, and terminal hydromyelia may also be diagnosed by CT 1'23'32'35'39'56'59(Fig. 2 lower). The usefulness of MR studies in visualizing cord lesions is well d o c u m e n t e d . 6,39,44,6~ On T~-weighted spin-echo images, the lipoma shows a high signal intensity, the cord an intermediate intensity, and the cerebrospinal fluid (CSF) a low intensity (Fig. 3). On T2-weighted images, the lipoma and cord show inter-
J. Neurosurg. / Volume 73/September, 1990
mediate intensity, the lipoma being of equal or slightly lower intensity than the cord. In general, CSF shows high intensity on Tz-weighted images. Axial images demonstrate a low-intensity band between the lipoma and the spinal cord. On sagittal images, the band is cephalad and anterior to the lipoma, separating it from the cord (Fig. 4 left). The lowintensity band has been likened to a halo, 3~but is more accurately described as a chemical shift artifact. 72 It has a characteristic appearance and occurs Perpendicular to the direction of the frequency-encoding gradient and the interface of tissues with different chemical-shift properties. The greater the magnetic field, the greater is the intensity of this artifact? 9,72 With leptomyelolipomas, this phenomenon is particularly fortuitous in providing exact demarcation at the lipoma-cord interface. This line assists in demonstrating the relationship of the nerve roots to this interface (Fig. 4 right). Magnetic resonance imaging is particularly adept at revealing the presence of terminal hydromyelia, and allows for evaluation of the paraspinal structures; MR imaging is now the diagnostic method of choice for leptomyelolipoma.
Surgical Indications All patients with leptomyelolipoma should undergo surgical correction. If the neoplasm is asymptomatic, 363
M. J. Harrison, et al.
FIG. 4. Sagittal T~-weighted magnetic resonance images. Left: A lipoma with high signal intensity (large arrow) is seen in the posterior spinal canal and a syringohydromyelia with low signal intensity (small arrow) is shown in the distal spinal cord. Right: In another patient, a lipoma (arrow) is seen lying anterior to a meningocele (arrowhead), which extends through a neural arch defect.
the goal is to prevent the onset of neurological symptoms. If it is symptomatic, the goal is to halt progression and alleviate deficits where possible. Bassett,~~ recognizing the progressive nature of the disease, advocated early prophylactic surgery. Others have recommended surgical repair only after the onset of neurological deficit 65 or for the repair of cosmetic deformity alone, s~ Malis 48 and others ~8,43 have observed that superficial removal of the mass leads to intense arachnoidal scarfing with escalated neurological deterioration and the need for a more dangerous second exploration often resulting in a poor outcome. It has been advocated that surgery be delayed until 1 year of age in asymptomatic infants to allow technically easier removal. A sudden neurological deterioration has been described; four of these patients were under 6 months of age. 56 It is our belief that all patients with leptomyelolipoma should undergo surgical correction as early as possible. Only rarely do neonates demonstrate severe abnormalities. This situation has been encountered by other investigators, 18'56 and is probably due to congenitally absent or malformed nerve roots. Many reports describe a neurological deficit increasing with age. Although neurologically intact patients aged in their 50's have been reported, this is rare?'~l'46 Our oldest patient without a deficit was 25 years old.
If the mass is not situated in the midline, it will deviate and rotate the cord toward the lipoma (Fig. 5). There is a small dural defect through which the lipoma passes. The dura and pia arachnoid fuse to the interface of the
Anatomical Considerations Leptomyelolipomas have been classified into four types, as follows. 18'45,62
Type 1 (Dorsal Type). In Type 1, the lipomatous mass inserts itself directly into the dorsum of the cord. 364
FIG. 5. Coronal T~-weighted magnetic resonance image showing a lipoma on the left side of the lumbar spine (large arrow). The distal spinal cord is pulled to that side (small
arrow).
J. Neurosurg. / Volume 73/September, 1990
Leptomyelolipoma lipoma and cord, but the sensory nerve roots emerge anterior to the interface and none of the nerve roots run through the lipoma. The nerves that emerge at this level are shorter than normal and demonstrate abnormal angulation.
Type 2 (Caudal Type). Type 2 lipoma traverses a defect in the most distal part of the dural sac. There is no fusion of the leptomeninges to the lipoma-cord interface. The lipoma extends cephalad through the subarachnoid space to engulf the tip of the conus. The rootlets run within the fibrous fatty mass, usually in the anterolateral regions. The filum terminale may not be identifiable. 62 Type 3 (Transitional Type). In Type 3, the lipomacord interface resembles the dorsal lipoma superiorly, then extends around the conus inferiorly to resemble the caudal type. The leptomeninges fuse with the cord at the lipoma-cord interface and attach to the exiting nerve roots. Type 4 (Filar Type). Type 4 is relatively rare 22"5~'62 and is not discussed by many authors. 18,32.45,56It consists of a short thick filum terminale widened by infiltrating fat and fibrous tissue. The fat may extend into the conus medullaris. Although the conus is tethered, the nerve roots have a normal configuration. Surgical Approach In the management of our patients we followed the protocol established by Malis. 48'49Monitoring of SSEP's was employed throughout positioning and the surgical procedure. The procedure was performed with the patient in the lateral oblique position and the side of greatest lipomatous involvement upward, allowing free movement of the thorax and abdomen without compression. The SSEP and sphincteric E M G findings were used to avoid damage to functional neural elements. 12,18,32,45,48,49.59 An omega-shaped flap was created so that the base lay inferiorly over the natal cleft, as previously depicted by Rosenblum, et al. 59The vascularity from the lumbar and gluteal arteries was incorporated into the flap. The flap design prevented urinary and fecal contamination of the wound, particularly in younger patients. A margin of adipose tissue was left adherent to the skin to prevent vascular compromise. Amputation of the lip o m a at the point where it penetrated the lumbosacral fascia defect allowed reflection of the flap inferiorly. A laminectomy above the lipomatous insertion was needed to visualize the cephalic extent of the dural dehiscence and the transitional area between the lipoma and normal cord. When the laminae were exposed, a vascular fibrous band might be seen bridging the gap between the laminae of the most superior bifid arches. 2~ If present, this band produced kinking of the herniating meningocele and cord in a configuration Malis has likened to a hairpin turn. 48 This band should be tested for neural function prior to its division.
J. Neurosurg. / Volume 73/September, 1990
The remainder of the procedure entailed untethering the conus from lipomatous, leptomeningeal, and dural attachments, 18'45 and debulking the lipomatous mass with decompression of the conus. The filum terminale was severed as it was shortened and acted as a further tethering agent, with occasional lipomatous infiltration. 59 Reconstruction of the dural canal with a watertight closure provided ample space for CSF to flow around the cord, preventing adhesions with retethering. Reapproximation of muscle mass and lumbosacral fascia was performed over the canal to avoid future trauma to the repaired region. If the dura was deficient, we preferred to use tensor fascia lata for reconstruction of the dural tube. If the canal was too tight, increases in the size of the residual adipose tissue might produce compression and neurological symptoms during periods of weight gain. A watertight closure will prevent accumulation of CSF in the subcutaneous s p a c e . 32'36'59 Conclusions
Leptomyelolipomas are c o m m o n dysraphic lesions produced by aberrant neural tube closure during early embryological development. They may be associated with anomalies in other organ systems. The abnormal spinal development produces four discrete anatomical configurations of the lipoma-spinal cord interface. In our experience the natural history of the disease is that of progressive neurological deterioration with deficits arising during periods of rapid growth and weight gain. Deficits are produced by traction, compression, and direct transmission of force to the cord. Although improvement is c o m m o n with surgical correction, only a minority of patients are cured and few will regain full function after deficits appear. In view of the recent advances in neuroimaging, intraoperative monitoring, and microsurgical techniques, early surgery is recommended for all patients. Acknowledgment
The authors thank Ms. Gloria Minet-Johnson for her assistance in the preparation of this manuscript. References
1. Altman N, Harwood-Nash DC, Fitz CR, et al: Evaluation of the infant spine by direct sagittal computed tomography. AJNR 6:65-69, 1985 2. Alvord EC Jr, Shaw CM, Sumi SM: Central nervous system developmental abnormalities, in Thompson RA, Green JR (eds): Pediatric Neurology and Neurosurgery. New York: Spectrum, 1978, pp 97-166 3. Anderson FM: Occult spinal dysraphism. Diagnosis and management. J Pediatr 73:163-177, 1968 4. Anderson FM: Occult spinal dysraphism. A series of 73 cases. Pediatrics 55:826-835, 1975 5. Balagura S: Late neurological dysfunction in adult lumbosacral lipoma with tethered cord. Neurosurgery 15: 724-726, 1984 6. Barnes PD, Lester PD, Yamanashi WS, et al: MRI in infants and children with spinal dysraphism. AJR 147: 339-346, 1986 365
M. J. Harrison, et al. 7. Barry A, Patten BM, Stewart BH: Possible factors in the development of the Arnold-Chairi malformation. J Neurosurg 14:285-301, 1957 8. Barry FB, Harwood-Nash DC, Fitz CR, et al: Metrizamide in pediatric myelography. Radiology 124:409-418, 1977 9. Barson AJ: The vertebral level of termination of the spinal cord during normal and abnormal development. J Anat 106:489-497, 1970 10. Bassett RC: The neurologic deficit associated with lipomas of the cauda equina. Ann Surg 131:109-116, 1950 11. Bourque PR, D'Alton JG, Russell NA, et al: Congenital lumbosacral lipoma causing primary enuresis in an adult (case report). Can Med Assoe J 135:1007-1008, 1986 12. Bruce DA, Schut L: Spinal lipomas in infancy and childhood. Childs Brain 5:192-203, 1979 13. Burrows FGO: Some aspects of occult spinal dysraphism: a study of 90 cases. Br J Radiol 41:496-507, 1968 14. Cameron AH: The Arnold-Chiari and other neuro-anatomicat malformations associated with spina bifida. J Pathol Bacteriol 73:195-211, 1957 15. Cameron AH: Malformations of the neuro-spinal axis, urogenital tract, and foregut in spina bifida attributable to disturbances of the blastopore. J Pathol Bacteriol 73: 213-221, t957 16. Cameron AH: The spinal cord lesion in spina bifida cystica. Lancet 2:171, 1956 17. Caram PC, Scarcella G, Carton CA: Intradural lipomas of the spinal cord with particular emphasis on the "intramedullary" lipomas. J Neurosurg 14:28-41, 1957 18. Chapman PH: Congenital intraspinal lipomas. Anatomic considerations and surgical treatment. ChUds Brain 9: 37-47, 1982 19. de Jonge MC, Kornelis JA, van Berg JW, et al: The evaluation of functional disorders of the urinary tract in children with spina bifida. Dev Med Child Neurol 20 (Suppl):51-56, 1969 20. Dubowitz V, Lorber J, Zachary" RB: Lipoma of the cauda equina. Arch Dis Child 40:207-213, 1965 21. Ehni G, Lore JG: Intraspinai lipomas. Report of cases, review of the literature, and clinical and pathologic study. Arch Neurol Psychiatry 53:1-28, 1945 22. Emery JL, Lendon RG: Lipomas of the cauda equina and other fatty tumours related to neurospinal dysraphism. Dev Meal Child Neurol 20 (Suppl):62-70, 1969 23. Fitz CR, Harwood-Nash DC: The tethered conus. AJ R 125:515-523, 1975 24. Giuffre R: Intradural spinal lipomas. Review of literature (99 cases) and report of an additional case. Aeta Neurochit 14:69-95, 1966 25. Gold LHA, Kieffer SA, Peterson HO: Lipomatous invasion of the spinal cord associated with spinal dysraphism: myelographic evaluation. AJR 107:479-485, 1969 26. Gowers WR: Myo-lipoma of spinal cord. Trans Pathol Soc Lond 27:19-22, 1876 27. Hall DE, Udvarhelyi GB, Altman J: Lumbosacral skin lesions as markers of occult spinal dysraphism. JAMA 246:2606-2608, 1981 28. Hamby WB: Tumors in the spinal canal in childhood II. Analysis of the literature of a subsequent decade (1933-1942); report of a case of meningitis due to an intramedullary epidermoid communicating with a dermal sinus. J Neuropathol Exp Neurol 3:397-412, 1944 29. Hilal SK, Keim HA: Selective spinal angiography in adolescent scoliosis. Radiology 102:349-359, 1972 30. Hircak H, Williams RD, Moon KL Jr, ct al: Nuclear magnetic resonance imaging of the kidney: renal masses. Radiology 147:765-772, 1983 31. Hoffman H J, Hendrick EB, Humphreys RP: The tethered 366
32.
33. 34. 35. 36.
37. 38. 39. 40. 41. 42.
43. 44. 45. 46. 47. 48. 49. 50. 51.
52. 53.
54.
spinal cord: its protean manifestations, diagnosis and surgical correction. Childs Brain 2:145-155, 1976 Hoffman HJ, Taecholarn C, Hendrick EB, et al: Management of lipomyelomeningoceles. Experience at the Hospital for Sick Children, Toronto. J Neurosnrg 62:1-8, 1985 Johnson A: Fatty tumour connected with the interior of the spinal canal of the sacrum. Trans Pathol Soc Lond 8: 28-29, 1857 Johnson A: Fatty turnout from the sacrum of a child, connected with the spinal membranes. Trans Pathoi Soc Lond 8:16-18, 1857 Kaiser MC, Pettersson H, Harwood-Nash DC, et al: Direct coronal CT of the spine in infants and children. AJNR 2:465-466, 1981 Kallen B: Early embryogenesis of the central nervous system with special reference to closure defects (Casey Holter Memorial Lecture). Dev Med Child Neurol 16 (Suppl):44-53, 1968 Kaplan JO, Quencer RM: The occult tethered conus syndrome in the adult. Radiology 137:387-391, 1980 Kieck DF, De Villiers JC: Subcutaneous lumbosacral lipomas. S Afr Med J 49:1563-1566, 1975 Komiyama M, Hakuba A, Inoue Y, et al: Magnetic resonance imaging: lumbosacral lipoma. Surg Neurol 28: 259-264, 1987 Kunimoto K: The development and reduction of the tail and of the caudal end of the spinal cord in the human embryo. Contrib Embryol 8:161-198, 1918 Langman J: Medical Embryology, ed 4. Baltimore: Williams & Wilkins, 1981, pp 50-56 Lapras CL, Pater JD, Huppert J, et al: Syndrome de traction du cone terminal ou syndrome de la m6elle attachee. Lipomes lombo-sacres. Rev Neurol 141: 207-215, 1985 Lassman LP, James CCM: Lumbosacral lipomas: critical survey of 26 cases submitted to laminectomy. J Neural Neurosurg Psychiatry 30:174-181, 1967 Lee BCP, Zimmerman RD, Manning J J, et al" MR imaging of syringomyelia and hydromyelia. AJNR 6:1-8, 1985 Lhowe D, Ehrlich MG, Chapman PH, et al: Congenital intraspinal lipomas. Clinical presentation and response to treatment. J Pediatr Orthop 7:53t-537, 1987 Loeser JD, Lewin RJ: Lumbosacral lipoma in the adult. Case report. J Neurosnrg 29:405-409, 1968 Luce EA, Walsh J: Wound closure of the myelomeningocele defect. Piast Reconstr Surg 75:389-393, 1985 Malis LI: Intramedullary spinal cord tumors. Clin Neurosurg 25:512-539, 1978 Malis LI: Spinal cord tumors, in Davidoff RA (ed): Handbook of the Spinal Cord. Basel: Marcel Dekker, 1986, Vol 5, pp 319-370 Matson DD: Neurosurgery of Infancy and Childhood, ed 2. Springfield, II1:Charles C Thomas, 1969, p 46 McLendon RE, Oakes W J, Heinz ER, et ai: Adipose tissue in the filum terminale: a computed tomographic fnding that may indicate tethering of the spinal cord. Neurosurgery 22:873-876, 1988 Mickle JP, McLennan JE: Malignant teratoma arising within a lipomeningocele. Case report. J Neurosurg 43: 761-763, 1975 Naidich TP, McLone DG, Mutluer S: A new understanding of dorsal dysraphism with lipoma (lipomyeloschisis): radiologic evaluation and surgical correction. AJNR 4: 103-116, 1983 Pang D, Wilberger JE Jr: Tethered cord syndrome in adults. J Neurosurg 57:32-47, 1982
J. Neurosurg. / Volume 73/September, 1990
Leptomyelolipoma 55. Patten BM: Embryological stages in establishing myeloschisis with spina bifida. Am J Anat 25:1-11, 1953 56. Pierre-Kahn A, Lacombe J, Pichon J, et al: Intra-spinal lipomas with spina bifida. Prognosis and treatment in 73 cases. J Neurosurg 65:756-761, 1986 57. Ramirez OM, Ramasastry SS, Granick MS, et al: A new surgical approach to closure of large lumbo-sacral meningomyelocele defects. Plast Reeonstr Surg 80:799-809, 1987 58. Rogers HM, Long DM, Chou SN, et al: Lipomas of the spinal cord and cauda equina. J Neurosurg 34:349-354, 1971 59. Rosenblum BR, Harrison M J, Rothman AS: Lumbosacral lipomas. Contemp Neurosurg 10 (17): 1-8, 1988 60. Rosenthal DI, Scott JA, Mankin H J, et al: Sacrococcygeal chordoma: magnetic resonance imaging and computed tomography. AJR 145:143-147, 1985 61. Rosenthal M, LaManna J, Yamada S, et al: Oxidative metabolism, extracellular potassium and sustained potential shifts in cat spinal cord in situ. Brain Res 162: 113-127, 1979 62. Sato K, Shimoji T, Sumie H, et al: Surgically confirmed myelographic classification of congenital intraspinal lipoma in the lumbosacral region. Childs Nerv Syst 1: 3-11, 1985 63. Skalpe IO: Lumbar myelography with Comray Meglumin 282. Report of 100 investigations with special reference to the adverse effects. Acta Neurol Scand 47:569-578, 1971 64. Streeter GL: Factors involved in the formation of the filum terminale. Am J Anat 25:1-11, 1919 65. Swanson HS, Barnett JC Jr: Intradural lipomas in children. Pediatrics 29:911-926, 1962 66. Thomas JE, Miller RH: Lipomatous tumors of the spinal canal. A study of their clinical range. Mayo Clin Proc 48: 393-400, 1973 67. Till K: Spinal dysraphism. A study of congenital malfor-
J. Neurosurg. / Volume 73/September, 1990
68. 69. 70. 71. 72. 73. 74. 75. 76.
mations of the lower back. J Bone Joint Surg (Br) 51: 415-422, 1969 Traill MR, Runge VM, Wolpert SM: Dysraphism: MRI strategies. MRI Decisions 2:2-9, 1988 van Hoytema G J, van den Berg R: Embryological studies of the posterior fossa in connection with Arnold-Chiari malformation. J Anat 106:489-497, 1970 Villarejo FJ, Blazquez MG, Gutierrez-Diaz JA: Intraspinal lipomas in children. Childs Brain 2:361-370, 1976 Walsh JW, Markesbery WR: Histological features of congenital lipomas of the lower spinal canal. J Neurosurg 52:564-569, 1980 Weinreb JC, Brateman L, Babcock EE, et al: Chemical shift artifact in clinical magnetic resonance images at 0.35 T. AJR 145:183-185, 1985 Willis RA: The Borderland of Embryology and Pathology, London: Butterworths, 1962, pp 147-163 and 364 Wood BP, Harwood-Nash DC, Berger P, et al: Intradural spinal lipoma of the cervical cord. AJR 145:174-176, 1985 Yamada S, Zinke DE, Sanders D: Pathophysiology of "tethered cord syndrome." J Neurosurg 54:494-503, 1981 Yashon D, Beatty RA: Tethering of the conus medullaris within the sacrum. J Neurol Neurosurg Psychiatry" 29: 244-250, 1966
Manuscript received September 14, 1989. Accepted in final form January 23, 1990. Address reprint requests to: Michael J. Harrison, M.D., c/o Bruce R. Rosenblum, M.D., 1160 Fifth Avenue, Suite 106, New York, New York 10029.
367
