Superficial siderosis (SS) of the CNS results from chronic hemorrhage into the subarachnoid space with hemosiderin deposition in the subpial layers.1,2 The clinical presentation includes progressive ataxia and deafness. Some patients have a history of trauma or intradural surgery. Despite extensive investigations, a cause of bleeding is frequently elusive.
An extra-arachnoid, intraspinal, or intracranial CSF collection, often longitudinally extensive, is sometimes identified in spinal neuroimaging in SS.1–6 A dynamic CT myelogram can identify the dural defect connecting the intrathecal space with the fluid-filled collection.4 The precise mechanism of bleeding is unknown. Rarely CSF hypovolemia accompanies SS.6 Increased CSF RBC count may be seen in CSF hypovolemia.7 These observations have led to the suggestion that repairing the dural defect may halt bleeding and prevent deficit progression.6 Clinical confirmation of this hypothesis is lacking.
We describe a patient with SS and CSF hypovolemia due to a CSF leak. Repair of the leak was accompanied by clinical improvement and resolution of neuroimaging and CSF abnormalities.
Case report.
A 64-year-old man was evaluated for a 3-year history of progressive imbalance and 10-year history of decreased hearing. His history was remarkable for childhood poliomyelitis. Over the years he had multiple horse riding-related falls. Twenty years earlier he had a C4-C7 laminectomy for right upper limb weakness. On examination, he had mild proximal right upper limb weakness. Deficits related to his polio included mild, right greater than left, lower limb weakness and wasting. He had difficulty with the heel-shin and finger-nose tests. Upper limb rapid alternating movements were irregular. His gait was ataxic with marked difficulty on tandem gait.
Brain MRI showed cerebellar atrophy and a confluent T2-hypointensity along the cerebellar surface (figure, A). The hypointensity was typical of that seen due to hemosiderin deposition in SS. Mild dural thickening and pachymeningeal enhancement similar to that seen in CSF hypovolemia was present (figure, B). Spine MRI revealed an intraspinal fluid collection ventral to the cord from C3 to T11 (figure, C and D). Postoperative findings related to the cervical laminectomy and incidental mid-thoracic degenerative disc disease were present. Cerebral angiogram and intracranial MRA were unremarkable except for segments of luminal irregularities.
Figure Brain MRI (A, B, G), spine MRI (C, D, H), and CT myelogram (E, F) before (A–F) and after (G, H) treatment
(A) Axial T2-weighted brain MRI shows hypointensity due to hemosiderin deposition along the cerebellar folia. (B) Axial T1-weighted brain MRI with contrast shows dural thickening and enhancement suggesting CSF hypovolemia. (C, D) Sagittal T2-weighted spine MRI shows a longitudinally extensive intraspinal fluid-filled cavity ventral to the cord from C3 to T11. The inset in (D) shows the cavity on an axial mid-thoracic cut. (E) Dynamic CT myelogram shows leakage of contrast (arrow); the dotted arrow points to intrathecal contrast. (F) Dynamic CT myelogram shows calcified disc protrusion immediately caudal to the dural defect shown in (E); the dotted arrow points to intrathecal contrast. (G) Axial T1-weighted MRI with contrast 6 months after surgery shows absence of dural thickening and pachymeningeal enhancement. (H) Sagittal T2-weighted thoracic spine MRI shows resolution of the intraspinal fluid-filled collection.
CSF study showed xanthochromia with a protein count of 65 mg/dL. CSF erythrocyte count was 462/μL and leukocyte count was 2 cells/μL. The opening pressure was reduced to 4 mm water. CT myelogram demonstrated free communication between the ventral fluid collection and thecal sac. The point of communication could not be identified because of rapid opacification of the fluid-filled space with contrast. Dynamic CT myelogram demonstrated egress of contrast (figure, E) adjacent to a calcified disc protrusion (figure, F) at T7-8.
Eight months later, a T5-7 laminectomy was done. The underlying dura was reflected to permit cord exploration. The dura, nerve roots, and cord appeared normal at this level. A dural defect or bleeding source was not identified. Free fat graft was placed in the epidural space at T7-8 and a sealant (DuraSeal) was injected into the epidural space through the lateral gutters on the right at T6-7.
At 6 months follow-up, the patient reported improvement in his balance and illustrated this by stating that he was able to resume dancing. His neurologic examination was unchanged other than slight improvement in tandem gait. A head MRI showed resolution of the dural thickening and enhancement (figure, G). The thoracic spine MRI showed resolution of the large ventral epidural CSF collection (figure, H). CSF study showed 1 leukocyte/μL, 1 erythrocyte/μL, and protein count of 56 mg/dL. The opening pressure was normal at 186 mm water.
Discussion.
Some patients with SS have dural defects similar to those encountered in CSF hypovolemia syndromes due to a CSF leak. Both disorders may have increase in CSF erythrocyte count and intraspinal fluid collection of variable longitudinal extent. The increased CSF erythrocyte count could be due to the intradural vascular engorgement that accompanies CSF hypotension.7
Our patient’s postoperative clinical improvement was accompanied by resolution of abnormalities on MRI and normalization of the CSF analysis, including normalization of the opening pressure. The abnormalities related to hemosiderin deposition persisted. The mechanical (fat graft) and chemical (sealant: DuraSeal) sealing at the site of leak suggested by the CT myelogram were the likely reason for the improvement. The absence of a visible dural defect at surgery may point to the defect being small. It is also possible that the leak was intermittent and positional. The calcified disc protrusion could have caused the dural defect.
This is the only report that details the clinical outcome in SS where the dural leak associated with a longitudinal intraspinal fluid collection has been repaired.
Footnotes
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Disclosure: The authors report no disclosures.
Received July 22, 2008. Accepted in final form September 24, 2008.
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