Hydrosyringomyelia and Diastematomyelia Detected by MRI in Myelomeningocele Galen N. Breningstall, MD*, Stephen M. Marker, MDi, and David E. Tubman, MD*
Magnetic resonance imaging of the spine in 45 patients with myelomeningocele revealed hydrosyringomyelia in 24 and diastematomyelia in two. No patient at initial imaging manifested symptoms referable to hydrosyringomyelia; both patients with diastematomyelia had flaccid lower extremities. One patient developed an upper extremity monoparesis which resolved with syringoperitoneal shunt placement; no other patient manifested symptoms or required surgery. Ventriculoperitoneal shunt malfunction produced reversible distention of the syrinx in another patient who remained asymptomatic. Breningstall GN, Marker SM, Tubman DE. Hydrosyringomyelia and diastematomyelia detected by MRI in myelomeningocele. Pediatr Neurol 1992;8:267-7 1.
had MRI
of the spine
performed
(44 complete
spine
and I limited
cer-
vical). The spine was evaluated using sagittal and axial Tt-weighted sequences with either a I .O or I.5 T magnet MRI (Siemens). Eleven patients had repeat studies performed. Most frequently pentobarbital sedation was employed at a dosage of 5 mg/kg intramuscularly. The youngest patients and patients with vocal cord paralysis or other respiratory difficulty had imaging performed under general anesthesia. The 4 patients who did not have MRI studies were younger than 18 months of age. None of the patients had symptoms suggesting the presence of hydrosyringomyelia at initial study. One patient, to be described further below, subsequently became symptomatic with the subacute development of right upper extremity monoparesis. Another patient experienced striking enlargement of the syrinx concurrent with shunt malfunction, although no symptoms of cord compression occurred.
Results Hydrosyringomyelia was present in 24 patients (54%). In 4 patients, the syrinx extended from the cervical through
Introduction Hydrosyringomyelia refers to the often asymmetric accumulation of fluid in the enlarged central canal of the spinal cord with the cavitation lined by both ependymal and glial tissue [ 11. The association between myelodysplasia and hydrosyringomyelia was reported by Tumbull in 1933 [2]. Myelodysplasia with the Chiari type 2 malformation is the most common cause of hydrosyringomyelia in childhood [3]. Magnetic resonance imaging (MRI) of the spinal cord provides a means of noninvasively detecting the presence of hydrosyringomyelia in patients with myelodysplasia. We utilized MRI of the spinal cord to define the incidence and character of hydrosyringomyelia in patients with myelodysplasia attending a spina bifida clinic. Diastematomyelia was also detected in some patients. Methods Several patients attending a spina bifida clinic were discovered to have rather large hydrosytingomyelic cavities when MRI of the spine was performed for other reasons. Because neither the natural history nor the prevalence of such prominent lesions was known, an effort was made to obtain an MRI of the spine in all clinic patients with myelomeningocele. Forty-five of 49 patients examined at a spina bifida clinic
From the Department of Pediatrics (*Neurology and ‘Infectious Disease); Park Nicollet Medical Center; *Consulting Radiologists; Abbott Northwestern Hospital; Minneapolis, Minnesota.
Figure I. Patient 3, age 5 years, experienced multiple congenital anomalies. including exstrophy of the bladder, lipomeningocele, omphalocele. and impetforate anus. The syrinx extended through the entire cord.
Communications should be addressed to: Dr. Breningstall; Pediatric Subspecialties; Park Nicollet Medical Center; 910 East 26th Street; Suite 325; Minneapolis, MN 55404. Received January 22, 1992; accepted April 15, 1992.
Breningstall
et al: Myelomeningocele
267
Figure 2. Patient I& age 3 years. A large syrinx extending from C7Te, expanding the spinal cord and the spinal canal in this region. A Chiari type 2 malformation is present.
Figure T4-L7, syrinx.
the lumbar cord (Fig 1). Six syrinxes extended from the cervical or thoracic region at least 5 spinal segments caudally (Figs 2,3). There were 2 large thoracolumbar syrinxes (Fig 4). Twelve syrinxes were l-4 spinal segments in length. One additional patient had a questionable cervical syrinx. In Patient 16, a repeat MRI during intermittent shunt malfunction with symptoms of obtundation and
autonomic instability revealed enlargement of the syrinx (Figs 5,6). In the patient treated with a syringoperitoneal shunt (Patient 8) there was a slight decrease in the size of the hydrosyringomyelia after shunting. Otherwise, repeat studies, when performed, demonstrated no significant alteration in the appearance of the hydrosyringomyelia. Midthoracic diastematomyelia accompanied a
Figure 3. Patient 8, age 6 weeks, A syrinx extends from focal dilatation visualized from C7-T5 and Te-TIO (only illustrated).
Figure 5. Patient was an additional present.
268
PEDIATRIC
NEUROLOGY
Vol. 8 No. 4
C7-TIO with the former
4. Patient 14. age 7 years. widening the thoracic cord.
fitensive Sepiations
syrinx extending from are observed in the
16, age 5 years. A syrinx extena!sj?om C7-T4 There syrinx at Ttt-TQ. A Chiari type 2 malformation is
Discussion Hydromyelia is a pathologic condition characterized by an accumulation of fluid in the enlarged central canal of the spinal cord. The term, syringomyelia, implies the accumulation of fluid in cavities within the parenchyma of the spinal cord. Hydrosyringomyelia is an amalgam of hydromyelia and syringomyelia, implying a pathogenesis involving the distension of the central canal with eventual rupture into the substance of the spinal cord [3]. In one pathology series, serial sectioning of the spinal cord in patients with myelomeningocele demonstrated communication of all syringomyelic cavities with the central canal at some point [4]. It has been suggested that hydrosyringomyelia may be a conduit for cerebral ventricular decompression in certain patients [5]. The majority of our patients had functional ventriculoperitoneal shunts at initial study. The patients who did not have ventriculoperitoneal
Figure 6. After esperieaciq inrrrmirrmt ~~en/riclcloperitoneal shunr maljrncrion with obtrmdation and bradvcardia. Patient 16 also demonstrated ealargemerrt of the syrinx depicted in Figure 5.
syrinx in one patient (Fig 7). One of the patients who did not have a syrinx had a partial dorsal diastematomyelia (Fig 8). The findings of the patients with hydrosyringomyelia and diastematomyelia are described in detail in Table I. Figure 8. Patient 5, age 3 months. Partial dorsal diastematomyelia 1141 is present in the lower cervical and apper thoracic region.
Figure 7. Patient 1, age 6 years. In this patient diastematomyelia extends from Tr-Tit. The fibrous septum has diminished signal intensity centrally, suggesting ossification.
shunts in place at study had no evidence of obstructive hydrocephalus. The syrinx, which enlarged coincident with intermittent shunt malfunction, returned to basal dimensions after shunt revision. Gardner observed that hydrocephalomyelia, dilatation of the cerebral ventricles and the spinal central canal, is present in the embryo prior to the opening of the foramina of the fourth ventricle [6,7]. The association of myelomeningocele and hydrosyringomyelia then was attributed to preservation of the embryonal state of hydrocephalomyelia due to inadequate permeability of the foramina of the fourth ventricle. Patients with hydrosyringomyelia may have had earlier focal distention and rupture of the central canal during a state of hydrocephalomyelia which then persisted after resolution of the hydrocephalomyelia. At surgery for hydrosyringomyelia, in many patients, the foramen of Magendie was bridged by a membrane representing an unperforated rhombic roof [7]. The Chiari mal-
Breningstall
et al: Myelomeningocele
269
Table 1. Myelomeningocele aging summary Pt. NoJAge at Imaging
patients
with
bydrosyringomyelia
VP Shunt
and diastematomyelia:
Diastematomyelia
Syrinx
Lower Extremity Function
+
2J7&8yrS
-
L2.3
-
Quadriceps, dorsiflexion on right
315 & 6 yrs
-
Holocord
-
Quadriceps
43 mos
-I-
Tiny
-
Quadriceps
513 mos
+
6/15 mos
+
syrinx
LI-2
-
Midthoracic
and im-
l/6 yrs
715 days
Small midthoracic and hemicord below fibrous septum
Clinical
Partial dorsal
Flaccid
Flaccid
+/- Cervical
-
Quadriceps
LI
-
Plantarflexion
8/6wks& 21 mos
+
C7-TIO
-
Dorsiflexion
916 mos
+
Small syrinx upper cervical cord
-
Dorsiflexion
lo/7 mos .
+
Small syrinx
-
Right hip flexion
Iv3
+
Syrinx
-
Dorsiflexion
yrs
-
Holocord
-
Dorsiflexion
13R mos & 3Yrs
-
TIZ-L2
-
Quadriceps
1416 & 7 yrs
+
T4-L2
-
Quadriceps
15R yrs
+
cd4
-
Dorsiflexion
1615 & 6 yrs
+
C7-T4,
-
Right hip flexion
l7/8 mos
+
T~-LI
-
Quadriceps
18/10 mos & 3Yrs
+
C7-T.5
-
Quadriceps
19/9 & 11 yrs
+
Holocord
-
Flaccid
2018 mos
+
Tiny syrinx cervicothoracic cord
-
Dorsiflexion
21/4 mos
+
‘M-2
-
Dorsiflexion
2U5 mos
-
c3-4,
-
Dorsiflexion
2312 yrs
+
‘ho,
-
Phmtatflexion
24/3 mos
+
LI-L3-l
-
Quadriceps
2513 mos
+
Holocord
-
Dorsiflexion
26/12 mos
+
TII-L3
-
Quadriceps
wks
1214&5
Tta
Ttt-12
TII-12
x2,7YrS
c7-8 TII-L1
formation associated with myelomeningocele would further compromise fourth ventricular fluid egress, as well as conceal the unperforated rhombic roof. A thickened dural
270
PEDIATRIC
NEDROLOGY
Vol. 8 No. 4
band compressing the dural sac and the underlying neural tissue is frequently identified under the arch of Cl [3,8]. Observed associations between compensated hydroceph-
alus and hydrosyringomyelia as well as radioisotopic ventriculography studies in patients with myelodysplasia and hydrosyringomyelia have supported a relationship between hydrosyringomyelia and disordered ventricular hydrodynamics [5]. The sequential imaging of our patient with shunt malfunction and syrinx also supports this relationship. In those patients with hydrosyringomyelia and a functioning shunt, it has been proposed that a secondary aqueductal block precludes the shunt managing effectively the cerebrospinal fluid (CSF) produced by the choroid plexus of the fourth ventricle [3]. Gardner speculated that the foramina of the fourth ventricle in patients with hydrosyringomyelia were not competent to equalize pulse pressures generated by the choroid plexus, although the foramina may be competent to equalize mean pressures [7]. According to this theory, the formation of a syrinx is a process of hydrodissection comparable to that which is responsible for developing the subarachnoid space in the embryo. Alternately, it has been proposed that defective intracranial drainage partially obstructs the free flow of CSF from the cranium into distensible spinal subarachnoid spaces. This creates a craniospinal pressure dissociation which draws fluid into the syrinx [9]. The features of hydrosyringomyelia explained by these theories and criticisms of these theories have been outlined previously [ 101. The pathologic association of hydrosyringomyelia with myelomeningocele has long been known. Keiller invariably found hydromyelia at autopsy of patients with myelomeningocele [ 111. Cameron reported that 20 of 22 patients with myelomeningocele accompanied by a typical Chiari malformation had associated hydromyelia [12]. A more recent pathology series of 100 patients revealed hydrosyringomyelia in 43 [4]. These reports, however, anteceded contemporary early management of hydrocephalus in patients with myelomeningocele. In a recent series, 13 of 40 patients (33%) with myelomeningocele had hydrosyringomy,elia detected by MFU [ 131. Two of these 13 were reported to be symptomatic, without further specification. Two additional patients, both with asymmetric lower extremity dysfunction, had diastematomyelia. In our patients, even impressive cystic abnormality was generally asymptomatic. Patient 3, who became symptomatic, experienced multiple congenital anomalies including exstrophy of the bladder, lipomeningocele, omphalocele, and irnperforate anus. This patient had a holocord syrinx. When the patient experienced a subacute right upper extremity monoparesis at 6 years of age, a SytigOperitoneal shunt was placed. There was gradual recovery of right upper extremity function. Imaging subsequent to syringoperitoneal shunting disclosed a decrease in the dimensions of the lumbar portion of the syrinx. This was the only one of our patients with hydrosyringomyelia to receive surgical treatment for the syrinx. Treatments employed by others for symptomatic patients have included
ventriculoperitoneal shunt placement, posterior fossa decompression, with (Gardner procedure) or without plugging of the obex, and shunting of the hydrosyringomyelic cavity [3,8]. Both the patient with the midthoracic diastematomyelia and the patient with partial dorsal diastematomyelia in the lower cervical and upper thoracic region had flaccid lower extremities. Hydrosyringomyelia is an anomaly frequently associated with myelomeningocele; diastematomyelia is occasionally associated with myelomeningocele. Impressive cystic abnormality of the spinal cord has been generally asymptomatic in our experience. Diastematomyelia, conversely, was associated with paraplegia. Although the observation period has been relatively short, with one exception our patients have been asymptomatic. The natural history of hydrosyringomyelia associated with myelodysplasia remains to be defined.
The authorsthank Barbara Bergeronfor assistance in preparingthe
manuscript.
References [l] Eggers C. HamerJ. Hydrosyringomyelia in childhood - Clinical aspects, pathogenesis and therapy.Neuropaediahie 1979;10:87-99. [2] ‘liwnbull FA. Syringomyeliccomplicationsof spina bifida. Brain1933;56:304-17. [31 Hoffman HJ, Neil1J, CroneKR, HendrickEB,HumphreysRP. Hydrosyringomyelia and its management in childhood. Neurosurgery 1987;21:347-51.
[4] Emery JL, Lendon RG. The local cord lesion in neurospinal dysraphism (meningomyelocele). J Path01 1973;110:83-96.
[S] Hall PV,KalsbecJE,WellmanHN, BatnitzkyS, CampbellRJ+ Lewis S. Clinicalradioisotopeinvestigationsin hydrosyringomyelia and myelodysplasia. J Neurosurg 1976;45:188-94. [6] Gardner WJ. Anatomic abnormalities common to myelomeningocele of infancy and syringomyelia of adulthood suggest a common origin. Cleve Clin Q 1959;26:118-33. [7] Gardner WJ. Hydrodynamic mechanism of syringomyelia: Its relationship to myelocele. J Neurol Neurosurg Psychiatry 1965;28: 247-59. [8] Park TS, Cail WS, Maggio WM. Mitchell DC. Progressive spasticity and scoliosis in children with myelomeningocele. Radiological investigation and surgical treatment. J Neurosurg 1985;62:367-75. [9] Williams B. On the pathogenesis of syringomyelia: A review. J R Sot Med 1980;73:798-806. [lo] Cahan LD, Bentson JR. Considerations in the diagnosis and treatment of syringomyelia and the Chiari malformation. J Neurosurg 1982;57:24-31. [11] Keiller VH. A contribution to the anatomy of spina biida. Brain 1922;45:31-103. 1121
Cameron
AH. The Arnold-Chiariand other neuroanatomical
malformations associated with spina bifida. J Path01 Bacterial 1957;73: 195-211. [13] Azhmdlah PC, Smit LIviE, Riemeld-Kol E, Valk J. Malformations of the spinal cord in 53 patients with spina bifida studied by magnetic resonance imaging. Childs Nerv Syst 1991;7:63-6. [14] Wolf AL, Tubman DE, Seljeskog EL. Diastematomyelia of the cervical spinal cord with tethering in an adult. Neurosurgery 1987;21: 94-8.
Breningstall et al: Myelomeningocele
271
Magnetic resonance imaging of the spine in 45 patients with myelomeningocele revealed hydrosyringomyelia in 24 and diastematomyelia in two. No patient at initial imaging manifested symptoms referable to hydrosyringomyelia; both patients with diastematomyelia had flaccid lower extremities. One patient developed an upper extremity monoparesis which resolved with syringoperitoneal shunt placement; no other patient manifested symptoms or required surgery. Ventriculoperitoneal shunt malfunction produced reversible distention of the syrinx in another patient who remained asymptomatic. Breningstall GN, Marker SM, Tubman DE. Hydrosyringomyelia and diastematomyelia detected by MRI in myelomeningocele. Pediatr Neurol 1992;8:267-7 1.
had MRI
of the spine
performed
(44 complete
spine
and I limited
cer-
vical). The spine was evaluated using sagittal and axial Tt-weighted sequences with either a I .O or I.5 T magnet MRI (Siemens). Eleven patients had repeat studies performed. Most frequently pentobarbital sedation was employed at a dosage of 5 mg/kg intramuscularly. The youngest patients and patients with vocal cord paralysis or other respiratory difficulty had imaging performed under general anesthesia. The 4 patients who did not have MRI studies were younger than 18 months of age. None of the patients had symptoms suggesting the presence of hydrosyringomyelia at initial study. One patient, to be described further below, subsequently became symptomatic with the subacute development of right upper extremity monoparesis. Another patient experienced striking enlargement of the syrinx concurrent with shunt malfunction, although no symptoms of cord compression occurred.
Results Hydrosyringomyelia was present in 24 patients (54%). In 4 patients, the syrinx extended from the cervical through
Introduction Hydrosyringomyelia refers to the often asymmetric accumulation of fluid in the enlarged central canal of the spinal cord with the cavitation lined by both ependymal and glial tissue [ 11. The association between myelodysplasia and hydrosyringomyelia was reported by Tumbull in 1933 [2]. Myelodysplasia with the Chiari type 2 malformation is the most common cause of hydrosyringomyelia in childhood [3]. Magnetic resonance imaging (MRI) of the spinal cord provides a means of noninvasively detecting the presence of hydrosyringomyelia in patients with myelodysplasia. We utilized MRI of the spinal cord to define the incidence and character of hydrosyringomyelia in patients with myelodysplasia attending a spina bifida clinic. Diastematomyelia was also detected in some patients. Methods Several patients attending a spina bifida clinic were discovered to have rather large hydrosytingomyelic cavities when MRI of the spine was performed for other reasons. Because neither the natural history nor the prevalence of such prominent lesions was known, an effort was made to obtain an MRI of the spine in all clinic patients with myelomeningocele. Forty-five of 49 patients examined at a spina bifida clinic
From the Department of Pediatrics (*Neurology and ‘Infectious Disease); Park Nicollet Medical Center; *Consulting Radiologists; Abbott Northwestern Hospital; Minneapolis, Minnesota.
Figure I. Patient 3, age 5 years, experienced multiple congenital anomalies. including exstrophy of the bladder, lipomeningocele, omphalocele. and impetforate anus. The syrinx extended through the entire cord.
Communications should be addressed to: Dr. Breningstall; Pediatric Subspecialties; Park Nicollet Medical Center; 910 East 26th Street; Suite 325; Minneapolis, MN 55404. Received January 22, 1992; accepted April 15, 1992.
Breningstall
et al: Myelomeningocele
267
Figure 2. Patient I& age 3 years. A large syrinx extending from C7Te, expanding the spinal cord and the spinal canal in this region. A Chiari type 2 malformation is present.
Figure T4-L7, syrinx.
the lumbar cord (Fig 1). Six syrinxes extended from the cervical or thoracic region at least 5 spinal segments caudally (Figs 2,3). There were 2 large thoracolumbar syrinxes (Fig 4). Twelve syrinxes were l-4 spinal segments in length. One additional patient had a questionable cervical syrinx. In Patient 16, a repeat MRI during intermittent shunt malfunction with symptoms of obtundation and
autonomic instability revealed enlargement of the syrinx (Figs 5,6). In the patient treated with a syringoperitoneal shunt (Patient 8) there was a slight decrease in the size of the hydrosyringomyelia after shunting. Otherwise, repeat studies, when performed, demonstrated no significant alteration in the appearance of the hydrosyringomyelia. Midthoracic diastematomyelia accompanied a
Figure 3. Patient 8, age 6 weeks, A syrinx extends from focal dilatation visualized from C7-T5 and Te-TIO (only illustrated).
Figure 5. Patient was an additional present.
268
PEDIATRIC
NEUROLOGY
Vol. 8 No. 4
C7-TIO with the former
4. Patient 14. age 7 years. widening the thoracic cord.
fitensive Sepiations
syrinx extending from are observed in the
16, age 5 years. A syrinx extena!sj?om C7-T4 There syrinx at Ttt-TQ. A Chiari type 2 malformation is
Discussion Hydromyelia is a pathologic condition characterized by an accumulation of fluid in the enlarged central canal of the spinal cord. The term, syringomyelia, implies the accumulation of fluid in cavities within the parenchyma of the spinal cord. Hydrosyringomyelia is an amalgam of hydromyelia and syringomyelia, implying a pathogenesis involving the distension of the central canal with eventual rupture into the substance of the spinal cord [3]. In one pathology series, serial sectioning of the spinal cord in patients with myelomeningocele demonstrated communication of all syringomyelic cavities with the central canal at some point [4]. It has been suggested that hydrosyringomyelia may be a conduit for cerebral ventricular decompression in certain patients [5]. The majority of our patients had functional ventriculoperitoneal shunts at initial study. The patients who did not have ventriculoperitoneal
Figure 6. After esperieaciq inrrrmirrmt ~~en/riclcloperitoneal shunr maljrncrion with obtrmdation and bradvcardia. Patient 16 also demonstrated ealargemerrt of the syrinx depicted in Figure 5.
syrinx in one patient (Fig 7). One of the patients who did not have a syrinx had a partial dorsal diastematomyelia (Fig 8). The findings of the patients with hydrosyringomyelia and diastematomyelia are described in detail in Table I. Figure 8. Patient 5, age 3 months. Partial dorsal diastematomyelia 1141 is present in the lower cervical and apper thoracic region.
Figure 7. Patient 1, age 6 years. In this patient diastematomyelia extends from Tr-Tit. The fibrous septum has diminished signal intensity centrally, suggesting ossification.
shunts in place at study had no evidence of obstructive hydrocephalus. The syrinx, which enlarged coincident with intermittent shunt malfunction, returned to basal dimensions after shunt revision. Gardner observed that hydrocephalomyelia, dilatation of the cerebral ventricles and the spinal central canal, is present in the embryo prior to the opening of the foramina of the fourth ventricle [6,7]. The association of myelomeningocele and hydrosyringomyelia then was attributed to preservation of the embryonal state of hydrocephalomyelia due to inadequate permeability of the foramina of the fourth ventricle. Patients with hydrosyringomyelia may have had earlier focal distention and rupture of the central canal during a state of hydrocephalomyelia which then persisted after resolution of the hydrocephalomyelia. At surgery for hydrosyringomyelia, in many patients, the foramen of Magendie was bridged by a membrane representing an unperforated rhombic roof [7]. The Chiari mal-
Breningstall
et al: Myelomeningocele
269
Table 1. Myelomeningocele aging summary Pt. NoJAge at Imaging
patients
with
bydrosyringomyelia
VP Shunt
and diastematomyelia:
Diastematomyelia
Syrinx
Lower Extremity Function
+
2J7&8yrS
-
L2.3
-
Quadriceps, dorsiflexion on right
315 & 6 yrs
-
Holocord
-
Quadriceps
43 mos
-I-
Tiny
-
Quadriceps
513 mos
+
6/15 mos
+
syrinx
LI-2
-
Midthoracic
and im-
l/6 yrs
715 days
Small midthoracic and hemicord below fibrous septum
Clinical
Partial dorsal
Flaccid
Flaccid
+/- Cervical
-
Quadriceps
LI
-
Plantarflexion
8/6wks& 21 mos
+
C7-TIO
-
Dorsiflexion
916 mos
+
Small syrinx upper cervical cord
-
Dorsiflexion
lo/7 mos .
+
Small syrinx
-
Right hip flexion
Iv3
+
Syrinx
-
Dorsiflexion
yrs
-
Holocord
-
Dorsiflexion
13R mos & 3Yrs
-
TIZ-L2
-
Quadriceps
1416 & 7 yrs
+
T4-L2
-
Quadriceps
15R yrs
+
cd4
-
Dorsiflexion
1615 & 6 yrs
+
C7-T4,
-
Right hip flexion
l7/8 mos
+
T~-LI
-
Quadriceps
18/10 mos & 3Yrs
+
C7-T.5
-
Quadriceps
19/9 & 11 yrs
+
Holocord
-
Flaccid
2018 mos
+
Tiny syrinx cervicothoracic cord
-
Dorsiflexion
21/4 mos
+
‘M-2
-
Dorsiflexion
2U5 mos
-
c3-4,
-
Dorsiflexion
2312 yrs
+
‘ho,
-
Phmtatflexion
24/3 mos
+
LI-L3-l
-
Quadriceps
2513 mos
+
Holocord
-
Dorsiflexion
26/12 mos
+
TII-L3
-
Quadriceps
wks
1214&5
Tta
Ttt-12
TII-12
x2,7YrS
c7-8 TII-L1
formation associated with myelomeningocele would further compromise fourth ventricular fluid egress, as well as conceal the unperforated rhombic roof. A thickened dural
270
PEDIATRIC
NEDROLOGY
Vol. 8 No. 4
band compressing the dural sac and the underlying neural tissue is frequently identified under the arch of Cl [3,8]. Observed associations between compensated hydroceph-
alus and hydrosyringomyelia as well as radioisotopic ventriculography studies in patients with myelodysplasia and hydrosyringomyelia have supported a relationship between hydrosyringomyelia and disordered ventricular hydrodynamics [5]. The sequential imaging of our patient with shunt malfunction and syrinx also supports this relationship. In those patients with hydrosyringomyelia and a functioning shunt, it has been proposed that a secondary aqueductal block precludes the shunt managing effectively the cerebrospinal fluid (CSF) produced by the choroid plexus of the fourth ventricle [3]. Gardner speculated that the foramina of the fourth ventricle in patients with hydrosyringomyelia were not competent to equalize pulse pressures generated by the choroid plexus, although the foramina may be competent to equalize mean pressures [7]. According to this theory, the formation of a syrinx is a process of hydrodissection comparable to that which is responsible for developing the subarachnoid space in the embryo. Alternately, it has been proposed that defective intracranial drainage partially obstructs the free flow of CSF from the cranium into distensible spinal subarachnoid spaces. This creates a craniospinal pressure dissociation which draws fluid into the syrinx [9]. The features of hydrosyringomyelia explained by these theories and criticisms of these theories have been outlined previously [ 101. The pathologic association of hydrosyringomyelia with myelomeningocele has long been known. Keiller invariably found hydromyelia at autopsy of patients with myelomeningocele [ 111. Cameron reported that 20 of 22 patients with myelomeningocele accompanied by a typical Chiari malformation had associated hydromyelia [12]. A more recent pathology series of 100 patients revealed hydrosyringomyelia in 43 [4]. These reports, however, anteceded contemporary early management of hydrocephalus in patients with myelomeningocele. In a recent series, 13 of 40 patients (33%) with myelomeningocele had hydrosyringomy,elia detected by MFU [ 131. Two of these 13 were reported to be symptomatic, without further specification. Two additional patients, both with asymmetric lower extremity dysfunction, had diastematomyelia. In our patients, even impressive cystic abnormality was generally asymptomatic. Patient 3, who became symptomatic, experienced multiple congenital anomalies including exstrophy of the bladder, lipomeningocele, omphalocele, and irnperforate anus. This patient had a holocord syrinx. When the patient experienced a subacute right upper extremity monoparesis at 6 years of age, a SytigOperitoneal shunt was placed. There was gradual recovery of right upper extremity function. Imaging subsequent to syringoperitoneal shunting disclosed a decrease in the dimensions of the lumbar portion of the syrinx. This was the only one of our patients with hydrosyringomyelia to receive surgical treatment for the syrinx. Treatments employed by others for symptomatic patients have included
ventriculoperitoneal shunt placement, posterior fossa decompression, with (Gardner procedure) or without plugging of the obex, and shunting of the hydrosyringomyelic cavity [3,8]. Both the patient with the midthoracic diastematomyelia and the patient with partial dorsal diastematomyelia in the lower cervical and upper thoracic region had flaccid lower extremities. Hydrosyringomyelia is an anomaly frequently associated with myelomeningocele; diastematomyelia is occasionally associated with myelomeningocele. Impressive cystic abnormality of the spinal cord has been generally asymptomatic in our experience. Diastematomyelia, conversely, was associated with paraplegia. Although the observation period has been relatively short, with one exception our patients have been asymptomatic. The natural history of hydrosyringomyelia associated with myelodysplasia remains to be defined.
The authorsthank Barbara Bergeronfor assistance in preparingthe
manuscript.
References [l] Eggers C. HamerJ. Hydrosyringomyelia in childhood - Clinical aspects, pathogenesis and therapy.Neuropaediahie 1979;10:87-99. [2] ‘liwnbull FA. Syringomyeliccomplicationsof spina bifida. Brain1933;56:304-17. [31 Hoffman HJ, Neil1J, CroneKR, HendrickEB,HumphreysRP. Hydrosyringomyelia and its management in childhood. Neurosurgery 1987;21:347-51.
[4] Emery JL, Lendon RG. The local cord lesion in neurospinal dysraphism (meningomyelocele). J Path01 1973;110:83-96.
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