The Neuroradiology Journal 19: 367-374, 2006
www. centauro. it
MRI Evaluation of Diastematomyelia and Associated Abnormalities M. EMMANOUILIDOU, S. CHONDROMATIDOU, F. GOUTSARIDOU, P. PAPAPOSTOLOU, A. BINTOUDI, N. SIOUGGARIS, D. SIDIROPOULOS, I. ECONOMOU, I. TSITOURIDIS Radiology Department, Papageorgiou General Hospital; Thessaloniki, Greece. Radiology Department, AHEPA University Hospital; Thessaloniki, Greece
Key words: diastematomyelia, MRI
SUMMARY – Fourteen children were studied with a 1Tesla scanner to assess the role of magnetic resonance (MR) imaging in the recognition and evaluation of diastematomyelia and associated abnormalities. With MRI divided spinal cord was well imaged in its entire craniocaudal extent. Fibrous bands or bony septum when it contained a marrow cavity, were also well depicted. Direct visualization of the spinal cord itself is probably the most rewarding feature of MR imaging compared with other more conventional techniques. MR imaging demonstrated associated syringohydromyelia, segmentation anomalies, scoliosis, low position of the conus medularis and intradural lipoma that they were not detected with other radiologic studies.
Introduction
Methods and Materials
Diastematomyelia signifies a sagittal clefting of the spinal cord, conus medullaris, and/or filum terminale into two, not necessarily symmetric hemicords. Diastematomyelia is often part of a more complex dysraphic picture, and longitudinal assessment of the entire spinal column is necessary for proper surgical management. Diastematomyelia is typically sporadic but few cases have been familiar. Most cases are seen in association with other anomalies of the vertebral column such as spina bifida, kyphoscoliosis, butterfly vertebra and hemivertebra. Associated conditions like tethered cord, inclusion dermoid, lipoma, syringohydromyelia and chiari malformation have been described in the literature. Intramedullary tumors with diastematomyelia have rarely been described. MRI generally allows adequate analysis of the spinal deformities and is the technique of choice for dysraphism requiring full elucidation. However, bony malformations and bony septum between the two hemicords can be further evaluated by computed tomography. Depending on whether the diastematomyelia is isolated, with the skin intact or is in association with more serious neural tube defects, prenatal diagnosis of this condition is possible 1,2.
Since 2000 we have evaluated fourteen children in our department, ten females and four males, of mean age between two months and three years old. Examinations were performed using a 1 Tesla Siemens Expert Plus scanner. Using the sagittal midline T2 weighted image as a guide, axial and coronal T2 weighted images were then obtained at appropriate levels. Axial T1 weighted images were also obtained before and after gadolinium injection. Four of the fourteen cases also underwent additional CT-examinations and 3-D reconstructions to confirm and elucidate the appearance of the bony septum between the two hemicords. Results A high level of contrast between the spinal cord and surrounding structures was achieved with the MRI technique used. In general, axial images demonstrated the split cord as two separate, intermediate signal intensity structures in the spinal canal. Sagittal and coronal images, obtained at several different levels, were able to delineate the entire 367
MRI Evaluation of Diastematomyelia and Associated Abnormalities
M. Emmanouilidou
Figure 1 Sagittal and axial T1WI images reveal an intradural lipoma that tethers the conus medullaris. CT and CT-3D reconstruction images delineate the divided spinal cord and bony septum arising from posterior aspect of vertebral body. Segmentation anomalies at the level of diastematomyelia are also well seen.
368
www. centauro. it
The Neuroradiology Journal 19: 367-374, 2006
Figure 2 Axial and Sagittal T1WI and T2WI images at the level of thoracolumbar spine. The bony septum lies between the two hemicords. The conus medullaris lies in a lower position than normally.
369
MRI Evaluation of Diastematomyelia and Associated Abnormalities
M. Emmanouilidou
Figure 3 Computed tomography images in a 15-day-old infant. The spinal column is divided by a bony septum.
Figure 4 Sagittal T2WI and T1WI and axial T1WI reveal diastematomyelia and segmentation anomalies at the lumbar region. The conus medullaris is tethered in a lower position. CT images clearly delineate the presence of the bony septum between the two hemicords.
370
www. centauro. it
The Neuroradiology Journal 19: 367-374, 2006
Figure 5 Sagittal T2WI images reveal the low position of the conus medullaris. Axial T1WI images provide direct imaging of the two asymmetric hemicords.
extent of the divided cord. In four of the fourteen cases we observed separate dural sacs for each hemicord and a bone of fibrocartilaginous spur was found between the two dural tubes. This bony or fibrocartilaginous septum was further elucidated by CT examination. In the remaining ten cases the two hemicords were contained in a single dural sac. Syringohydromyelia and low conus medullaris position was found in four patients Two patients had scoliosis and segmentation anomalies such as hemivertebrae and butterfly vertebrae associated in one patient with intradural lipoma.
In the majority of the cases the diastematomyelia was located at the thoracolumbar spine and the spinal canal was dilated at the levels of diastematomyelia. In the majority of the cases the two hemicords were symmetric. Only in one case was one hemicord thinner than the other. Discussion Diastematomyelia is a rare form of spinal dysraphism characterized by a sagittal cleft of the spinal cord. This condition is the result of 371
MRI Evaluation of Diastematomyelia and Associated Abnormalities
M. Emmanouilidou
Figure 6 Sagittal and coronal T2WI showing an intradural lipoma that tethers the conus medullaris in a lower position. Axial T1WI showing the two hemicords in a single dural sac. Over the level of diastematomyelia an area of syringomyelia is clearly seen.
the presence of an osseous, cartilaginous or fibrous septum producing a complete or incomplete sagittal division of the spinal cord into two hemicords. It may be isolated or associated with other dysraphic anomalies 1,2. Diastematomyelia is a dysraphic state of unknown or undeterminated etiology. There are multiple theories of embryonic origin of diastematomyelia. The most noteworthy seem to be the following two 3,4. If the canal of Kovalevsky or an accessory canal persists (or there is a midline adhesion between the ectoderm and endoderm), the notochordal cells might deviate left or rightward around the adhesion or to both sides of the adhesion. As a result, 372
the notochord could develop with a focal left sided or right sided notch or a central “donut hole”. These alterations would create a local unilateral vertebral agenesis with contralateral hemivertebra and the paired hemicords of diastematomyelia 3. Dias and Walker proposed that diastematomyelia could be the consequence of an abnormally wide primitive streak. In such case the prospective notochordal cells could begin to ingress more laterally than normal. Because of the distance between them, the two streams of notochordal cells could not merge into the single normal notochordal process but would persist instead as two separate notochordal
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processes. The laterally displaced somitic tissue would then form an abnormally widened spinal canal with multiple concurrent vertebral anomalies. In such a case the tissue situated between the separated hemicords would be composed of pluriportential primitive cells explaining the diverse fibrous, cartilage or bone tissue 4. Most cases of diastematomyelia occur in females 80%-94% in some series 4. Clinically, patients usually present in childhood at one of three age ranges: 0 to 2 years (20%), 4 to 8 years 40, or 12 to 13 years (17%). Cutaneus nevi overlie the site of diastematomyelia in 45% to 85% of cases. The most characteristic of these is nevus pilosus, a large patch of long silky hairs 2,6. In children the common presenting symptoms are musculoskeletal deformities, including asymmetric lower extremities, neurologic deficits, including weakness, reduced sensation, incontinence of bladder and bowel and scoliosis 2. In adults, sensorimotor changes and pain are the most common complaints 7. Diastematomyelia affects the lumbosacral spine (45%), thoracic spine (31%) and thoracolumbar spine in 12%. The cervical spine is rarely affected. Diastematomyelia may extend widely over multiple segments in continuity. “Double” diastematomyelia at two separate sites has been described in literature but is a very rare condition. In diastematomyelia the conus medullaris is usually low in position. The two hemicords are narrower than normal and nearly always reunite distally into a reformed cord below the cleft 8,9. The two hemicords are asymmetric in 30% of cases. When the hemicords are asymmetric, one hemicord may give rise to three or four nerve roots and the other hemicord only one root. Accessory nerve roots may also be present. In the slight majority of diastematomyelia
The Neuroradiology Journal 19: 367-374, 2006
the two hemicords are enveloped together in a single dural sac. In these cases there is no bone spur but fibrous bands may join the two hemicords to the midline. Therefore, surgical intervention may be required to release the hemicords from adhesions or aberrant nerve roots, even though no bone spur is present. In the remaing cases the meninges are also cleft so that each hemicord is contained in its own dural sac. In nearly all cases with cleft meninges a bone spur forms in the interdural cleft between the two dural tubes. The spur forms in cartilage from one or several ossification centers that mature with age. Depending on age, one may see no bone, or several small bone fragments separated by cartilage. Concurrent lesions seen with diastematomyelia include: segmentation anomalies, hemivertebrae and butterfly vertebrae, scoliosis and kyphosis. Klippel-Feil-syndrome, chiari malformation, dermal sinus, teratomas and syringohydromyelia. Horseshoe kidneys are found in 10% of cases 10,11. Patients with untreated diastematomyelia usually show deterioration. The longer the delay in surgery the greater the likelihood of progressive neurologic symptoms. In the series of Russel et Al. immediate postoperative improvement was seen in 88% 12. Conclusion MR imaging is an exciting technique for the evaluation of spinal dysraphism. It is noninvasive, yet offers excellent tissue discrimination in several phases. The entire extent of the divided spinal cord in cases of diastematomyelia can be demonstrated consistently in only a few selected MR images. Visualization of associated abnormalities is another advantage and in fact these are better seen in exquisite detail on MR images.
373
MRI Evaluation of Diastematomyelia and Associated Abnormalities
M. Emmanouilidou
References 1. Han J, Benson J, Kaufman B, Rekate H, Alfioli R. Demonstration of Diastematomyelia and associated abnormalities with MR Imaging. Am J Neuroradiol 6: 215-219, 1985. 2 Harwood-Nash DC, Mc Hugh K. Diastematomyelia in 172 children: the impact of modern neuroradiology. Pediatr Neurosurg 16: 247-251, 1990-1991. 3 Rilliet B, Berney J, Schowing J: Pathogenesis of diastematomyelia: can a surgical model in the chick embryo give some clues about the human malformation? Child Nerve Syt 8: 310-316, 1992. 4 Pang D, Dias MS, Ahab- Bamada M: Split cord malformation. Part I. A Unified theory of embryogenesis for double spinal cord malformations. Neurosurgery 31: 451-480, 1992. 5 Balsi S, Caglark, Eryilmaz M: Diastematomyelia in two sisters. Am J Med Genet 86: 180-182, 1999. 6 Pang D: Split cord malformation. Part II. Clinical syndrome. Neurosurgery 31: 481-500, 1992. 7 Russel NA, Benoit BG, Joaquin AJ: Diastematomyelia in adults. A review. Pediatr Neurosurg 16: 252-257, 1990-1991. 8 Herman TE, Siegel MJ: Cervical and basicranial diastematomyelia. Am J Radiol 154: 806-808, 1990. 9 Pfeifer JD: Basicranial Diastematomyelia. Clin Neuropathol 10: 232-236, 1991. 10 Ugarte N, Conzalez-Crussi F, Sotelo-Avila C: Diastematomyelia associated with teratoma. J Neurosurg 53: 720-725, 1980. 11 Hader NJ, Steinbok KP, Poskitt K: Intramedullary spi-
374
nal teratoma and Diastematomyelia. Case report and review of the literature. Pediatr Neurosurg 26: 17-24, 1997. 12 Miller AW, Guille JT, Bowen JR: Evaluation and treatment of diastematomyelia. J Bone Joint Surg Am 75A: 1308-1317, 1993.
I. Tsitouridis, M.D, PhD Radiology Department Papageorgiou General Hospital Ring Road, Nea Efkarpia 56403 Thessaloniki - Greece Tel: +30 2310 693319 Fax: +30 2310 693320 E-mail: [email protected]
www. centauro. it
MRI Evaluation of Diastematomyelia and Associated Abnormalities M. EMMANOUILIDOU, S. CHONDROMATIDOU, F. GOUTSARIDOU, P. PAPAPOSTOLOU, A. BINTOUDI, N. SIOUGGARIS, D. SIDIROPOULOS, I. ECONOMOU, I. TSITOURIDIS Radiology Department, Papageorgiou General Hospital; Thessaloniki, Greece. Radiology Department, AHEPA University Hospital; Thessaloniki, Greece
Key words: diastematomyelia, MRI
SUMMARY – Fourteen children were studied with a 1Tesla scanner to assess the role of magnetic resonance (MR) imaging in the recognition and evaluation of diastematomyelia and associated abnormalities. With MRI divided spinal cord was well imaged in its entire craniocaudal extent. Fibrous bands or bony septum when it contained a marrow cavity, were also well depicted. Direct visualization of the spinal cord itself is probably the most rewarding feature of MR imaging compared with other more conventional techniques. MR imaging demonstrated associated syringohydromyelia, segmentation anomalies, scoliosis, low position of the conus medularis and intradural lipoma that they were not detected with other radiologic studies.
Introduction
Methods and Materials
Diastematomyelia signifies a sagittal clefting of the spinal cord, conus medullaris, and/or filum terminale into two, not necessarily symmetric hemicords. Diastematomyelia is often part of a more complex dysraphic picture, and longitudinal assessment of the entire spinal column is necessary for proper surgical management. Diastematomyelia is typically sporadic but few cases have been familiar. Most cases are seen in association with other anomalies of the vertebral column such as spina bifida, kyphoscoliosis, butterfly vertebra and hemivertebra. Associated conditions like tethered cord, inclusion dermoid, lipoma, syringohydromyelia and chiari malformation have been described in the literature. Intramedullary tumors with diastematomyelia have rarely been described. MRI generally allows adequate analysis of the spinal deformities and is the technique of choice for dysraphism requiring full elucidation. However, bony malformations and bony septum between the two hemicords can be further evaluated by computed tomography. Depending on whether the diastematomyelia is isolated, with the skin intact or is in association with more serious neural tube defects, prenatal diagnosis of this condition is possible 1,2.
Since 2000 we have evaluated fourteen children in our department, ten females and four males, of mean age between two months and three years old. Examinations were performed using a 1 Tesla Siemens Expert Plus scanner. Using the sagittal midline T2 weighted image as a guide, axial and coronal T2 weighted images were then obtained at appropriate levels. Axial T1 weighted images were also obtained before and after gadolinium injection. Four of the fourteen cases also underwent additional CT-examinations and 3-D reconstructions to confirm and elucidate the appearance of the bony septum between the two hemicords. Results A high level of contrast between the spinal cord and surrounding structures was achieved with the MRI technique used. In general, axial images demonstrated the split cord as two separate, intermediate signal intensity structures in the spinal canal. Sagittal and coronal images, obtained at several different levels, were able to delineate the entire 367
MRI Evaluation of Diastematomyelia and Associated Abnormalities
M. Emmanouilidou
Figure 1 Sagittal and axial T1WI images reveal an intradural lipoma that tethers the conus medullaris. CT and CT-3D reconstruction images delineate the divided spinal cord and bony septum arising from posterior aspect of vertebral body. Segmentation anomalies at the level of diastematomyelia are also well seen.
368
www. centauro. it
The Neuroradiology Journal 19: 367-374, 2006
Figure 2 Axial and Sagittal T1WI and T2WI images at the level of thoracolumbar spine. The bony septum lies between the two hemicords. The conus medullaris lies in a lower position than normally.
369
MRI Evaluation of Diastematomyelia and Associated Abnormalities
M. Emmanouilidou
Figure 3 Computed tomography images in a 15-day-old infant. The spinal column is divided by a bony septum.
Figure 4 Sagittal T2WI and T1WI and axial T1WI reveal diastematomyelia and segmentation anomalies at the lumbar region. The conus medullaris is tethered in a lower position. CT images clearly delineate the presence of the bony septum between the two hemicords.
370
www. centauro. it
The Neuroradiology Journal 19: 367-374, 2006
Figure 5 Sagittal T2WI images reveal the low position of the conus medullaris. Axial T1WI images provide direct imaging of the two asymmetric hemicords.
extent of the divided cord. In four of the fourteen cases we observed separate dural sacs for each hemicord and a bone of fibrocartilaginous spur was found between the two dural tubes. This bony or fibrocartilaginous septum was further elucidated by CT examination. In the remaining ten cases the two hemicords were contained in a single dural sac. Syringohydromyelia and low conus medullaris position was found in four patients Two patients had scoliosis and segmentation anomalies such as hemivertebrae and butterfly vertebrae associated in one patient with intradural lipoma.
In the majority of the cases the diastematomyelia was located at the thoracolumbar spine and the spinal canal was dilated at the levels of diastematomyelia. In the majority of the cases the two hemicords were symmetric. Only in one case was one hemicord thinner than the other. Discussion Diastematomyelia is a rare form of spinal dysraphism characterized by a sagittal cleft of the spinal cord. This condition is the result of 371
MRI Evaluation of Diastematomyelia and Associated Abnormalities
M. Emmanouilidou
Figure 6 Sagittal and coronal T2WI showing an intradural lipoma that tethers the conus medullaris in a lower position. Axial T1WI showing the two hemicords in a single dural sac. Over the level of diastematomyelia an area of syringomyelia is clearly seen.
the presence of an osseous, cartilaginous or fibrous septum producing a complete or incomplete sagittal division of the spinal cord into two hemicords. It may be isolated or associated with other dysraphic anomalies 1,2. Diastematomyelia is a dysraphic state of unknown or undeterminated etiology. There are multiple theories of embryonic origin of diastematomyelia. The most noteworthy seem to be the following two 3,4. If the canal of Kovalevsky or an accessory canal persists (or there is a midline adhesion between the ectoderm and endoderm), the notochordal cells might deviate left or rightward around the adhesion or to both sides of the adhesion. As a result, 372
the notochord could develop with a focal left sided or right sided notch or a central “donut hole”. These alterations would create a local unilateral vertebral agenesis with contralateral hemivertebra and the paired hemicords of diastematomyelia 3. Dias and Walker proposed that diastematomyelia could be the consequence of an abnormally wide primitive streak. In such case the prospective notochordal cells could begin to ingress more laterally than normal. Because of the distance between them, the two streams of notochordal cells could not merge into the single normal notochordal process but would persist instead as two separate notochordal
www. centauro. it
processes. The laterally displaced somitic tissue would then form an abnormally widened spinal canal with multiple concurrent vertebral anomalies. In such a case the tissue situated between the separated hemicords would be composed of pluriportential primitive cells explaining the diverse fibrous, cartilage or bone tissue 4. Most cases of diastematomyelia occur in females 80%-94% in some series 4. Clinically, patients usually present in childhood at one of three age ranges: 0 to 2 years (20%), 4 to 8 years 40, or 12 to 13 years (17%). Cutaneus nevi overlie the site of diastematomyelia in 45% to 85% of cases. The most characteristic of these is nevus pilosus, a large patch of long silky hairs 2,6. In children the common presenting symptoms are musculoskeletal deformities, including asymmetric lower extremities, neurologic deficits, including weakness, reduced sensation, incontinence of bladder and bowel and scoliosis 2. In adults, sensorimotor changes and pain are the most common complaints 7. Diastematomyelia affects the lumbosacral spine (45%), thoracic spine (31%) and thoracolumbar spine in 12%. The cervical spine is rarely affected. Diastematomyelia may extend widely over multiple segments in continuity. “Double” diastematomyelia at two separate sites has been described in literature but is a very rare condition. In diastematomyelia the conus medullaris is usually low in position. The two hemicords are narrower than normal and nearly always reunite distally into a reformed cord below the cleft 8,9. The two hemicords are asymmetric in 30% of cases. When the hemicords are asymmetric, one hemicord may give rise to three or four nerve roots and the other hemicord only one root. Accessory nerve roots may also be present. In the slight majority of diastematomyelia
The Neuroradiology Journal 19: 367-374, 2006
the two hemicords are enveloped together in a single dural sac. In these cases there is no bone spur but fibrous bands may join the two hemicords to the midline. Therefore, surgical intervention may be required to release the hemicords from adhesions or aberrant nerve roots, even though no bone spur is present. In the remaing cases the meninges are also cleft so that each hemicord is contained in its own dural sac. In nearly all cases with cleft meninges a bone spur forms in the interdural cleft between the two dural tubes. The spur forms in cartilage from one or several ossification centers that mature with age. Depending on age, one may see no bone, or several small bone fragments separated by cartilage. Concurrent lesions seen with diastematomyelia include: segmentation anomalies, hemivertebrae and butterfly vertebrae, scoliosis and kyphosis. Klippel-Feil-syndrome, chiari malformation, dermal sinus, teratomas and syringohydromyelia. Horseshoe kidneys are found in 10% of cases 10,11. Patients with untreated diastematomyelia usually show deterioration. The longer the delay in surgery the greater the likelihood of progressive neurologic symptoms. In the series of Russel et Al. immediate postoperative improvement was seen in 88% 12. Conclusion MR imaging is an exciting technique for the evaluation of spinal dysraphism. It is noninvasive, yet offers excellent tissue discrimination in several phases. The entire extent of the divided spinal cord in cases of diastematomyelia can be demonstrated consistently in only a few selected MR images. Visualization of associated abnormalities is another advantage and in fact these are better seen in exquisite detail on MR images.
373
MRI Evaluation of Diastematomyelia and Associated Abnormalities
M. Emmanouilidou
References 1. Han J, Benson J, Kaufman B, Rekate H, Alfioli R. Demonstration of Diastematomyelia and associated abnormalities with MR Imaging. Am J Neuroradiol 6: 215-219, 1985. 2 Harwood-Nash DC, Mc Hugh K. Diastematomyelia in 172 children: the impact of modern neuroradiology. Pediatr Neurosurg 16: 247-251, 1990-1991. 3 Rilliet B, Berney J, Schowing J: Pathogenesis of diastematomyelia: can a surgical model in the chick embryo give some clues about the human malformation? Child Nerve Syt 8: 310-316, 1992. 4 Pang D, Dias MS, Ahab- Bamada M: Split cord malformation. Part I. A Unified theory of embryogenesis for double spinal cord malformations. Neurosurgery 31: 451-480, 1992. 5 Balsi S, Caglark, Eryilmaz M: Diastematomyelia in two sisters. Am J Med Genet 86: 180-182, 1999. 6 Pang D: Split cord malformation. Part II. Clinical syndrome. Neurosurgery 31: 481-500, 1992. 7 Russel NA, Benoit BG, Joaquin AJ: Diastematomyelia in adults. A review. Pediatr Neurosurg 16: 252-257, 1990-1991. 8 Herman TE, Siegel MJ: Cervical and basicranial diastematomyelia. Am J Radiol 154: 806-808, 1990. 9 Pfeifer JD: Basicranial Diastematomyelia. Clin Neuropathol 10: 232-236, 1991. 10 Ugarte N, Conzalez-Crussi F, Sotelo-Avila C: Diastematomyelia associated with teratoma. J Neurosurg 53: 720-725, 1980. 11 Hader NJ, Steinbok KP, Poskitt K: Intramedullary spi-
374
nal teratoma and Diastematomyelia. Case report and review of the literature. Pediatr Neurosurg 26: 17-24, 1997. 12 Miller AW, Guille JT, Bowen JR: Evaluation and treatment of diastematomyelia. J Bone Joint Surg Am 75A: 1308-1317, 1993.
I. Tsitouridis, M.D, PhD Radiology Department Papageorgiou General Hospital Ring Road, Nea Efkarpia 56403 Thessaloniki - Greece Tel: +30 2310 693319 Fax: +30 2310 693320 E-mail: [email protected]
