Unusual Presentation of Skull Base Carotid Artery Aneurysm Causing Multiple Lower Cranial Nerve Palsies

Introduction: Extracranial carotid artery dissections and pseudoaneurysms are much more common than intracranial ones, and often extend to the level of the foramen lacerum. Involvement of cranial nerve XII from extracranial dissection and pseudoaneurysm is frequent, followed by IX, X, XI, V, VII, VI, III (in order of frequency). These aneurysms have a myriad of clinical presentations, and may result in thrombosis, embolization, compression of adjacent structures, and rupture. We report a case of extracranial carotid artery dissection with a unique clinical course of evolving radiographic findings from a tongue mass to a later-diagnosed pseudoaneurysm.

Case Report: A 51-year-old man presented with a 4-week history of voice changes, left-sided tongue enlargement, and decreased mobility of his tongue. Examination revealed asymmetric enlargement of the left base of tongue and lingual tonsil. Flexible laryngoscopy established a new diagnosis of left-sided true vocal fold immobility. The patient was evaluated with CT scan, which revealed a low-density and asymmetric fullness of the left tongue base and palatine tonsil, suggestive of possible denervation injury. CT angiogram established the diagnosis of dissection of the distal left internal carotid artery at the skull base with a mural thrombus and pseudoaneurysm. Per recommendations of the neurovascular team, the patient was treated with aspirin, underwent injection augmentation for improvement in voice quality, and has been followed with serial CT angiogram. The patient’s tongue swelling and mobility have improved over time as has the CTA appearance.

Discussion: We believe the clinical presentation in our case is attributable to thrombus and pseudoaneurysm causing compression of the left hypoglossal and vagus nerves at the point where they exit the skull base. The asymmetric enlargement of the left tongue was the result of denervation injury causing ipsilateral atrophy. Dissection of the internal carotid artery rarely presents as isolated lower cranial nerve palsy, having been reported in only 6% of ICA dissections. Although the precise mechanism causing cranial neuropathies has not been elucidated, it is postulated that ICA extraluminal wall hematoma can cause direct mass effect on the cranial nerves.

Conclusion: Unilateral tongue enlargement associated with cranial neuropathies warrants thorough investigation. Extracranial carotid pathology is an important consideration in the diagnostic evaluation.