Causes, pathology, radiological findings and clinical consequences of superficial siderosis

Abstract

Learning Objectives: 1 To improve knowledge of causes, pathology, diagnosis and clinical presentation of superficial siderosis. 2 To outline the radiological findings of superficial siderosis using case examples. Background: Superficial siderosis (SS-CNS) is a rare condition of the central nervous system characterized by deposition of haemosiderin into the sub-pial layers of the brain and spinal cord secondary to chronic or intermittent haemorrhage into the subarachnoid space.(1,2) Advances in MRI have led to increased rates of detection.(3) Causes of SS-CNS include: trauma, tumours, vascular malformations, intradural surgery and nerve root injury.(1,4-7) Spontaneous intracranial hypotension has also been found to cause SS-CNS.(8) However, approximately 30% of patients diagnosed with SS-CNS do not have an identifiable source of bleeding.(8) Haemosiderin, a byproduct of haemoglobin breakdown, has a predilection for the cerebellum, frontal and temporal cortex, brainstem, spinal cord, nerve roots and cranial nerves I, II and VIII.(3,5) Patients primarily present with gait ataxia, sensorineural hearing loss, pyramidal dysfunction and cognitive decline.(9) Symptoms are progressive, and diagnosis is often made years after disease onset.(9) Imaging Findings: Magnetic resonance imaging (MRI) is the preferred imaging modality. The classic imaging finding is a rim of hypointensity along the contours of the brain and spinal cord on T2 weighted MRI, often in association with cerebellar and spinal cord atrophy.(10) Hypointensities are more prominent on T2∗ and on susceptibility weighted images (SWI). Within the spine, cavities may be seen, indicative of a possible dural tear.(10) Case 1: 68 year old male patient with insidious and progressive ataxia, sensorineural hearing loss, anosmia and cervical myelopathy. MRI shows siderosis of the cerebellum, bilateral cerebral hemispheres, bilateral cranial nerve VIII and the upper spinal cord. There is anterior epidural fluid collection of the upper cervical spine, without evidence of dural tear. Case 2: 54 year old female patient with a history of resection of cerebral metastatic melanoma. MRI shows superficial siderosis over the occipital cortex, thought to be from leptomeningeal haemorrhagic metastases. Case 3: 67 year old male patient with a history of subarachnoid haemorrhage secondary to ruptured cerebral aneurysm, with MRI findings of parafalcine superficial siderosis. Conclusion: SS-CNS is an uncommon condition, diagnosed increasingly frequently due to advances in imaging techniques. It should be suspected in patients with progressive neurological symptoms, particularly gait ataxia and sensorineural hearing loss.L618976996 <br />