'Reverse crescent pattern' on SPECT brain perfusion scan in chronic subdural hematoma

A SPECT brain perfusion scan was performed on a patient who had symptoms of dementia. The SPECT scan showed marked crescentic medial displacement of the left cerebral hemisphere ('reverse crescent pattern'), and mildly decreased cortical perfusion in the affected hemisphere. Crossed cerebellar diaschisis was not present. On x-ray CT, the underlying abnormality was found to be a unilateral chronic subdural hematoma causing a significant mass effect. A reverse crescent pattern without crossed cerebellar diaschisis on SPECT brain perfusion scan in patients with dementia may suggest the diagnosis of chronic subdural hematoma.