Superficial siderosis.

BACKGROUND

Superficial siderosis (SS) of the CNS is caused by repeated slow hemorrhage into the subarachnoid space with resultant hemosiderin deposition in the subpial layers of the brain and spinal cord. Despite extensive investigations, the cause of bleeding is frequently undetermined.

OBJECTIVES

To review the clinical and imaging features of 30 consecutive patients with SS and provide insights into the underlying causes of subarachnoid bleeding in this disabling disorder.

METHODS

The authors reviewed the medical records of 30 consecutive patients with clinical and MRI evidence of SS.

RESULTS

The commonest neurologic manifestations included gait ataxia and hearing impairment. A clinical history of subarachnoid hemorrhage was relatively rare. Possible predisposing conditions were identified on history in 22 patients, the commonest being a prior trauma (15 patients). In addition to the characteristic MRI findings of SS, 18 patients had abnormalities on MRI possibly related to chronic bleeding. The most common of these was the presence of a fluid-filled collection in the spinal canal seen in 14 patients.

CONCLUSIONS

A history of prior subarachnoid hemorrhage is often absent in patients with superficial siderosis (SS). A past history of trauma is common. Prior intradural surgery may be an additional risk factor. Xanthochromia or the presence of red blood cells in the CSF is a common finding. Only rarely does angiography demonstrate the bleeding source. The presence of a fluid-filled collection in the spinal canal is a common finding on MRI and is likely related to the SS. With longitudinally extensive cavities, a dynamic CT myelogram may help localize the defect and direct the site of laminectomy. Surgical repair of a dural defect, if present, should be considered. Surgical correction of bleeding should be documented by CSF examination months after surgery. Friable vessels in the dural defect are a possible source of the chronic bleeding.