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55 y.o. with headache.

Findings

T2 GRE reveals diffuse coating of the surface of the intracranial contents with hypointense material.

T2 FSE demonstrates the same abnormality, however, less conspicuously.

Differential Diagnosis

MRI sequence artifact

Normal surface vascularity

Neurocutaneous melanosis

Meningioangiomatosis

Superficial siderosis

Superficial Siderosis

Caused by recurrent SAH.

Results in hemosiderin deposition on the surface of the brain, brainstem, and cranial nerve leptomeninges.

Age: all

M:F = 3:1

Typical presentation includes profound B SNHL and ataxia.

Deaf if unrecognized. 25% ultimately become non-ambulatory.

There is often a pre-sympomatic phase which averages ~15 years.

Superficial Siderosis

Bilateral sensorineural hearing loss is present in 95% of cases.

Other symptoms include:

Ataxia (88%)

Bilateral hemiparesis

Hyperreflexia,

Bladder incontinence,

Anosmia (CN I particularly angered),

Dementia, and

Headache

Superficial Siderosis: CT

Cerebral and pronounced cerebellar atrophy.

Subtle hyperdensity over the brain surface. CT is relatively insensitive to hemosiderin deposition.

No enhancement.

Superficial Siderosis: MRI

T1: +/- surface hyperintensity.

T1 w/ GAD: No enhancement.

FLAIR: Hypointense borders.

T2: Less easily appreciated than T2 GRE. Look for dark, thick CN 7/8 complexes.

Surface hypointensities.

T2 GRE: Most sensitive to hemosiderin.

“Blooming.”

MRI findings do not correlate with severity of disease.

Superficial Siderosis: Pathology

Cytotoxic hemosiderin stains the underlying tissues. (Xanthochromic CSF).

Hydroxyl radical production from Fe is one proposed mechanism of cytotoxicity.

Consider the hemosiderin sensitive microglia who accompany the myelin of CN VIII.

Hemosiderin stains the meninges and sub-pial tissues up to a depth of 3 mm.

Thickening of the leptomeninges.

Cerebellar folia: Loss of Purkinjie cells.

Superficial Siderosis

Which of the following etiologies can result in superficial siderosis?

A Treated childhood cerebellar neoplasm

B Traumatic nerve root avulsion

C Aneurysm

D AVM

E Neoplasm