Dissecting aneurysm of the middle cerebral artery associated with subarachnoid haemorrhage.

A 73-year-old male with known hypertension presented with subarachnoid haemorrhage due to a ruptured dissecting aneurysm of the middle cerebral artery. Angiography showed a dilatation with proximal and distal narrowing of the right middle cerebral artery. Conservative treatment resulted in almost complete resolution of the angiographic abnormalities 6 months later. Dissecting aneurysms of the middle cerebral artery with haemorrhagic manifestations are extremely rare and are not generally recognized as a cause of subarachnoid haemorrhage. If angiography fails to demonstrate a saccular aneurysm in a patient with subarachnoid haemorrhage, a ruptured dissecting aneurysm may be a possible cause. Repeat angiography should be performed for definitive diagnosis. More knowledge about the natural course is essential before determining whether surgical treatment is always necessary.