Unilateral hypoglossal nerve palsy due to aneurysm of the stump of persistent hypoglossal artery.

A 47 year old woman presented two weeks before admission with a severe right sided headache followed by pain in her right ear and right scalp which was tender to touch, and mild dysphagia. On examination she had a right hypoglossal nerve palsy (figure A), the remainder of the neurological and general examination was normal. Brain CT (figure B) showed a soft tissue density mass lying medial to the right styloid process adjacent to the anterior arch of the atlas and anterior to the right hypoglossal canal. Carotid angiography (figure C) showed an aneurysm which arose from the stump of a persistent hypoglossal artery just outside the skull base. A persistent trigeminal artery of large calibre was also present. Her symptoms gradually resolved and subsequent angiography showed a clotted aneurysm and no further treatment was required. The persistent primitive hypoglossal artery first described by Batie in l899 is one of the three anastomotic channels (primitive trigeminal artery, acoustic artery, and hypoglossal artery) between the internal carotid and the basilar artery. To our knowledge there is no documented similar case and the cause should be added to the list of aetiological diagnoses of isolated hypoglossal nerve.