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A 68-year-old man presented with 3 years of progressive painful lower extremity weakness. He had urinary retention. Neurological examination showed spastic paraparesis (Medical Research Council grades 1 to 3, worst at ankles and thighs). Reflexes were diffusely reduced with bilateral Babinski signs. There was symmetric loss of vibration and pain detection extending to the umbilicus and hands. He required 2-person assistance to stand and walk. A large cervicothoracic syrinx was seen on magnetic resonance imaging (MRI) in association with cervical stenosis. Despite cervical decompression fusion at C5-C6, he continued to worsen. Repeated MRI with contrast identified enlargement and enhancement of all roots. Electromyography and nerve conductions identified an axonal predominant chronic-active polyradiculopathy C5-T1 and L2-S1 with fibrillations extending to paraspinal muscles. Cerebrospinal fluid (CSF) protein was elevated at 102 mg/dL, and an inflammatory myelopolyradiculopathy with syrinx was postulated, with no other explanation found. He did not respond to weekly intravenous immunoglobulin (IVIG) and intravenous (IV) methylprednisolone, which were discontinued after 6 months.
In referral, we noted that the syrinx was associated with thoracolumbar flow voids, raising the possibility of a spinal dural arteriovenous fistula (SDAVF) (Figure). Spinal angiogram confirmed the SDAVF, arising from the left L1 lumbar artery, which was treated by transarterial embolization (Figure). Three months after the procedure, he had normal power and near-normal gait, with resumption of outdoor hiking. Babinski signs and urinary retention persisted, but reflexes returned, and sensation improved. Repeated MRI of the spine showed the cervicothoracic syrinx resolved, and all roots had normalized: no longer enlarged or enhancing (Figure).
Syringomyelia is the result of an expansion of CSF in the spinal cord. It has been most commonly recognized in association with Chiari malformation-type 1 (CM-1), but also in spinal cord tumors, trauma, ischemia, infection, and inflammatory arachnoiditis.
In our case, once the SDAVF was embolized, the spinal root and central canal congestion resolved, leading to the dramatic clinical and radiographic improvements (Figure). Our patient still has urinary retention, and like CM-1 patients status post-foramen magnum decompression, some extent of myelomalacia is predicted in chronic disease. There are only 2 other cases reported in the literature of SDAVF associated with syrinx, and polyradicular features were not highlighted.
We believe that our patient, and possibly others with SDAVF and syringomyelia, may have a significant clinical polyradicular component responsive to embolization.
This case highlights that idiopathic syringomyelia should not be diagnosed without serious consideration of SDAVF. Lower-extremity weakness, episodes of acute worsening, sensory level, or sphincter dysfunction should raise the possibility of SDAVF. A decision to move to spinal angiogram can be assisted by observation of venous congestion on routine MRI as witnessed by flow voids on T2 imaging most commonly seen on sagittal images (Figure). Early diagnosis may help prevent permanent myelomalacia, polyradicular injury, and poor prognosis.