Subarachnoid haemorrhage in the elderly: a necropsy study of the association with cerebral amyloid angiopathy.

To clarify the contribution of cerebral amyloid angiopathy (CAA) to subarachnoid haemorrhage (SAH) in the elderly, relationships between SAH and CAA were investigated in 997 necropsy cases aged 60 years or older. Primary SAH (bleeding from subarachnoid vessels) was found in 15 cases (1.5%). There was no case in which primary SAH was clearly attributed to CAA. Secondary SAH [secondary rupture of intracerebral haemorrhage (ICH) through the cortex to the subarachnoid space] was found in 23 patients (2.3%). In 11 (48%) of them, ICH with secondary SAH was associated with CAA. The results indicated that primary SAH is rarely related to CAA, however, CAA is the most frequent cause of ICH accompanying secondary SAH in the elderly.