Syringomyelia




Clinical Presentation


The patient is a 73-year-old woman with a history of old fracture of the T12 vertebra secondary to prior motor vehicle accident. Patient was treated at the time of the fracture with thoracolumbar laminectomy and posterior fusion. The patient complains of progressive low back pain, lower extremity weakness, numbness, and pain. She has no bladder or bowel dysfunction. Upon examination, lower thoracic kyphosis is evident. She has mild to moderate motor weakness in both lower extremities proximally.




Imaging Presentation


Magnetic resonance (MR) imaging obtained reveals kyphotic deformity of the spine at the T11-12 level and an old compression fracture of the T12 vertebral body with retropulsion of the T12 vertebral body impinging upon the ventral cord surface. Spinal cord syringomyelia extends from the T10 to the T12 level ( Figs. 76-1 and 76-2 ) .




Figure 76-1


Post-traumatic Syringomyelia.

Old T12 compression fracture with resulting kyphotic deformity at the T11-12 level viewed on sagittal T2-weighted image A , T1-weighted image B, and contrast enhanced image C . There has been retropulsion of the posterosuperior vertebral body margin which impinges upon the ventral aspect of the thecal sac and spinal cord at the T1 2 level. A T2 hyperintense and T1 hypointense syrinx cavity ( arrows ) extends from the T12 level superiorly to mid T10 level. The substance of the cord is very thin posterior to the syringomyelic cavity ( arrows ). There is no abnormal contrast enhancement of the spinal cord as shown on image C .



Figure 76-2


Post-traumatic Sringomyelia.

Same patient as in Figure 76-1 . Axial T2-weighted image A , and T1-weighted image B reveal a T1 hypointense and T2 hyperintense syrinx ( arrow in images A and B ) within the cord at the T11 level. Note marked thinning of posterior spinal cord substance posterior to the syrinx cavity.




Discussion


Hydromyelia (sometimes called primary cord syrinx ) refers to dilation of the ependymal-lined central canal of the spinal cord. Syringomyelia (or secondary cord syrinx ) is the term used to indicate a glial-lined cavity in the cord parenchyma without involvement of the central canal of the cord. The term syringohydromyelia encompasses both syringomyelia and hydromyelia and is used to include both cavitations occurring in the cord parenchyma and/or dilation of the central canal or an unspecified cavity in the cord. If the syrinx extends into the brainstem, this is referred to as syringobulbia .


Hydromyelia usually manifests in younger patients and is often associated with a developmental anomaly such as Chiari type 1 malformation, Chiari type 2 malformation (also called Arnold-Chiari malformation ), meningomyelocele, diastematomyelia, tethered cord, congenital scoliosis, basilar invagination, or hydrocephalus. In approximately 50% of patients with Chiari type 1 malformation, a hydromyelic cavity develops in the spinal cord. The hydromyelia may be of variable size, configuration, and length ( Figs. 76-3 and 76-4 ) . The hydromyelia may extend over a few vertebral levels or may extend the entire length of the spinal cord. Posterior fossa tumors can also cause dilation of the central canal of the spinal cord by obstruction of the obex or altered cerebrospinal fluid (CSF) flow dynamics near the foramen magnum region. Hydromyelia is believed to be due to interference in CSF flow in the spinal cord secondary to a mass, adhesions, or obstructing process in the posterior fossa interfering with CSF flow at the obex, foramen magnum, or C2-3 level. One theory suggests that when an obstructing or partially obstructing process exists at or near the foramen magnum level, caudal motion of the spinal cord, cerebellar tonsils, and brainstem, generates a piston-like effect that results in pulse-pressure abnormalities that drive the CSF downward into the central canal forming the hydromyelic cavity, assuming the central canal still communicates with the fourth ventricle. If the central canal does not communicate with the fourth ventricle, it is possible that exaggerated spinal pulse pressures may lead to increased transmedullary pressure gradients between the spinal subarachnoid space and the extracellular space within the cord, forcing CSF into the spinal cord via perivascular spaces and eventually leading to cord cavitation.




Figure 76-3


Chiari Type 1 Malformation with Hydromyelia.

Sagittal TI-weighted MRI shows malformed, inferiorly pointed cerebellar tonsil ( T ). A moderated sized “unilocular” intramedullary hydromyelic cavity ( arrow ) causes fusiform enlargement of the spinal cord.



Figure 76-4


Chiari Type 1 Malformation with Hydromyelia.

Sagittal T2-weighted MR image A , T1-weighted image B , and contrast enhanced fat saturated image C . The cerebellar tonsils ( T ) are pointed inferiorly and are low lying, extending inferiorly to the level of the posterior arch of C1. A large T1 hypointense, T2 hyperintense “mulitlocular-appearing” or “haustrated” hydromyelic intramedullary cavity ( arrows in images A and B ) causes diffuse enlargement of the spinal cord. Heterogeneous flow artifacts are noted in the cavity on T2-weighted image A . No abnormal contrast enhancement is visible in the spinal cord tissue adjacent to the intramedullary cavity.


Syringomyelia is widely believed to be an acquired condition that is often idiopathic, but can be seen following trauma, spinal cord infarction, cord infection, noninfectious myelitis, arachnoiditis, or scoliosis, or can be associated with intramedullary tumors such as hemangioblastoma or ependymoma ( Figs. 76-5 and 76-6 ) . In these cases, the syrinx may form because of actual destruction of the cord parenchyma by the trauma, infection, or tumor. Alternatively, the syrinx cavity may form secondarily by underlying pathologic process interfering with the blood supply of the cord resulting in degeneration of spinal cord tissue and eventual cavitation. Uncommonly, a syrinx may develop adjacent to a large spondylitic ridge or large herniated disc compressing the spinal cord. However, in such cases, it is not known whether the cord compression is responsible for the syrinx formation or merely is a coexistent finding ( Figs. 76-7, 76-8, and 76-9 ) .




Figure 76-5


Ependymoma Aassociated with Spinal Cord Syringomyelia.

On sagittal contrast enhanced fat-saturated T1-weighted MR image A , the intramedullary ependymoma ( E ) is located within the spinal cord from C7 to T2 level. Syringomyelia is demonstrated in the mid-thoracic lower-thoracic spinal cord ( arrows ) on sagittal T2-weighted image B , the full extent of the syrinx cavity ( arrows ) below the ependymoma ( E ) is defined to better advantage.



Figure 76-6


Ependymoma Associated with Spinal Cord Syringomyelia.

Same patient as in Figure 76-5 . Sagittal T2-weighted MRI of the cervical spinal cord. A multiloculated syrinx cavity ( short arrows ) extends above the intramedullary ependymoma ( E ). The superior extent ( SE ) of the syrinx is at the C2 level. There is a vague region of T2 hyperintensity, likely representing cord edema and/or myelomalacia, in the spinal cord adjacent to the syrinx and also in the lower portion of the medulla. The region above the syrinx is considered a “pre-syrinx” zone ( PS ), where additional cord cavitation may eventually occur.



Figure 76-7


Herniated Disc Causing Cord Compression and Coexistent Syringomyelia.

On sagittal T2-weighted MRI, a herniated disc at the T11-12 level causes cord compression ( long arrow ). A small diameter syrinx ( short arrows ) is located within the cord from T6 to T8 level.

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Aug 25, 2019 | Posted by in NEUROLOGICAL IMAGING | Comments Off on Syringomyelia
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