Monday 27 May 2013

Superficial Siderosis MRI Brain

A known case of Sellar Supra sellar mass with right para sellar component causing encasement of right ICA on MRI. Here are his Axial T2*GRE images. 
Axial T2 *GRE images of brain reveals low signal intensity hemosiderin staining along tentorium, sylvian fissures and hemispheric cortical sulci suggestive of Superficial siderosis, not at all obvious on any other parenchymal sequences implies to highest sensitivity of GRE to blood degradation product.

Superficial Siderosis

A rare condition characterised by abnormal hemosiderin staining of sub arachonid space, may be diffuse or focal, commonly overlying cerebral and cerebellar convexity, basal cisterns, ventral surface of brain stem on T2*GRE, results from excessive and repetitive subarachonid bleed.
An associated staining along cranial nerves particularly i, ii and viii CNs.
May see an associated atrophy of cerebellar hemispheres and vermis, lepto meningeal thickening with enhancement.
CT usually normal may show faint hyperdense layering.
Differential diagnosis is none, it has a pathognomonic appearace on T2*GRE.

Superficial siderosis is not a final diagnosis but an important finding indicating a remote or recurrent intra cranial bleed in subarachnoid space. Further imaging evaluation should be directed towards source of bleeding like MR Angiography to rule out aneurysm or any other vascular malformation.
The issue is cause of bleed. In ~25% cases cause in not found.

Clinically common symptoms are ataxia, hearing loss, anosmia, dementia; in long standing cases adjacent brain parenchymal atrophy ensues with altered cognition.
Treatment directed towards finding and removing cause of bleeding. Iron chelating agents.

Reference: Teaching atlas of brain imaging: By Nancy J. Fischbein, William P. Dillon, A. James Barkovich : Dural and lepto meningeal processes, Case 65, page  231.

To see other cases of Superficial Siderosis :
Case 1: Click here
Case 2: Click here

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