Cortical superficial siderosis

Last revised by Rohit Sharma on 3 Mar 2024

Cortical superficial siderosis (cSS) refers to deposition of hemosiderin along the leptomeninges and subpial surfaces, localized to the cortical sulci, as a sequela of convexal subarachnoid hemorrhage.

Cortical superficial siderosis is a supratentorial pathology and should not be confused with superficial siderosis of the central nervous system, which is largely an infratentorial pathology and has a different aetiopathogenesis with different clinicoradiological stigmata.

Cortical superficial siderosis is often asymptomatic, but if is present over regions of eloquent cortex can result in transient focal neurological episodes or symptoms, which are often referred to as “amyloid spells” when occurring in the setting of cerebral amyloid angiopathy 1-4. Please see the article on cerebral amyloid angiopathy for a further discussion of this clinical presentation.

Cortical superficial siderosis can be the chronic sequela of any cause of convexal subarachnoid hemorrhage, however, in an older demographic the most common cause is cerebral amyloid angiopathy 1-3. In patients with cerebral amyloid angiopathy, presence of cortical superficial siderosis is a marker of increased risk of intracerebral hemorrhage 5.

Causes of isolated cortical superficial siderosis are those that cause convexal subarachnoid hemorrhage, including having a past history of 1-3,6:

Additionally, extensive superficial siderosis of the central nervous system can also result in radiographic appearances of cortical superficial siderosis 1.

Cortical superficial siderosis is not appreciable on CT brain 2.

MRI brain is the modality of choice for assessment of cortical superficial siderosis 1-3. There are characteristically asymmetric bi-curvilinear regions of low signal (blooming artifact) seen on susceptibility-sensitive sequences (e.g. GRE, SWI) following the contour of cortical gyri, often resembling 'tram tracks' 1-3. There is no accompanying hyperintensity in the convexal subarachnoid space on FLAIR, differentiating it from acute convexal subarachnoid hemorrhage.

The severity of cortical superficial siderosis can be quantified 3:

  • focal: if 1-3 sulci have cortical superficial siderosis

  • diffuse: if >3 sulci have cortical superficial siderosis

MRI brain may also provide demonstrate features of the underlying cause of cortical superficial siderosis, for example, the concurrent presence of lobar cerebral microhemorrhages may suggest underlying cerebral amyloid angiopathy 1,2.

Management of the underlying condition is paramount, if possible. In patients who are symptomatic with transient focal neurological episodes or symptoms, antiseizure medications and migraine prophylactics (e.g. levetiracetam, sodium valproate) have been anecdotally trialed with varying benefits 4.

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