Dense Cerebellum Sign

This 22 yo female presented unconscious. The non-contrast CT brain shows: subarachnoid high density consistent with acute haemorrhage (arrows); effacement of basal cisterns consistent with descending transtentorial herniation; uncal herniation; and the “dense cerebellum sign” (open arrow). There was also a large haematoma in the right Sylvian fissure (not shown). The findings suggest rupture of a middle cerebral artery aneurysm. The patient did not recover.
The “dense cerebellum sign” is actually a cerebellum of normal density, but it appears dense next to the extremely hypodense supratentorial structures. The sign suggests marked cerebral oedema or infarction affecting the supratentorial brain.
Complications of subarachnoid haemorrhage include hydrocephalus; vasospasm; infarction; rebleeding; and diffuse cerebral swelling with cerebral herniation (as in this case).
Reference: Chapman S, Nakielny R. Aids to Radiological Differential Diagnosis. 4th edition. Saunders 2003.
Credit: Dr Laughlin Dawes
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