Pitfalls in diagnosis: Acute hypodense posterior fossa subarachnoid haemorrhage on computed tomography scan – An unusual entity

Abstract

Acute subarachnoid haemorrhage (SAH) generally appears hyperdense on computed tomography (CT) scan. However, in some rare circumstances, it may appear hypodense which can pose a diagnostic problem and compromise patient care. We report the case of a 32-year-old man who had presented with acute posterior fossa SAH. A cranial CT scan revealed a hypodense posterior fossa lesion mimicking cerebellar infarct. Surgical intervention confirmed that it was an acute bleed in the subarachnoid space. Treating physicians should be cautious in interpreting CT images as that can sometimes be misleading leading to misdiagnosis and incorrect treatment choices.