[Completely thrombosed large aneurysm of the distal middle cerebral artery: a case report].

A 19 year old male was admitted for evaluation after a seizure. Physical and neurological examination was normal. CT demonstrated an enlarged, high density mass in the right parietal lobe. MRI showed a homogeneous high intensity T1 weighted mass, surrounded by a low intensity T2 weighted rim in the right parietal lobe. Angiography did not show any abnormal findings. A diagnosis of cavernous angioma with primary bleeding in the subcortical region of the right parietal lobe was made after radiological examination. Histological examination showed a completely thrombosed aneurysm. The mechanism of the complete thrombosis and the growth of this large aneurysm and the shortcomings of radiological examination are discussed.