"Triple cross" of the hypoglossal nerve and its microsurgical impact to entrapment disorders.
OBJECTIVE
Cadaveric dissections were performed to review the intracranial and extracranial course of the hypoglossal nerve. The neurological significance of a newly defined "triple cross" of the hypoglossal nerve is discussed.


METHODS
10 cadaveric heads (left and right; 20 sides) were dissected using microsurgical techniques.


RESULTS
In the cisternal segment of hypoglossal nerve, the diameter of the rostral trunk amounted to 155-680 microm (mean 435 microm), and the caudal trunk to 210-820 microm (mean 482 microm). The roots formed three trunks in 20% of the hypoglossal nerves and two trunks in the rest. As a first cross, the anterior medullary segment of the vertebral artery crossed the hypoglossal nerve roots in 14 of 20 sides (70%). As a rare variation, the vertebral artery extended medial to the nerve (25%) or between its roots (5%). The second cross was found between the descendens hypoglossus and the occipital artery (75%), sternocleidomastoid artery and vein complex (15%) and external carotid artery (10%). The third cross was shown in the submandibular triangle between the lingual hypoglossus and its drainage vein; vena committans nervus hypoglossus.


CONCLUSIONS
Throughout its way, the hypoglossal nerve passes over vascular structures in three crossing points which may serve as a probable cause of hypoglossal nerve entrapment disorders.
Bademci
G
G
Department of Neurosurgery, University of Kirikkale, Kirikkale, Turkey. bademci70@yahoo.com
Batay
F
F
Yaşargil
M G
MG
D000328:Adult; D001808:Blood Vessels / Q000033:anatomy & histology*; D002342:Carotid Artery, External / Q000033:anatomy & histology; D019299:Decompression, Surgical / Q000379:methods / Q000592:standards; D004210:Dissection / Q000379:methods*; D006801:Humans; D007002:Hypoglossal Nerve / Q000033:anatomy & histology* / Q000601:surgery; D020437:Hypoglossal Nerve Diseases / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D007431:Intraoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D007601:Jugular Veins / Q000033:anatomy & histology; D008866:Microsurgery / Q000379:methods / Q000592:standards; D009408:Nerve Compression Syndromes / Q000503:physiopathology* / Q000601:surgery; D019635:Neurosurgical Procedures / Q000379:methods / Q000592:standards; D014059:Tongue / Q000294:innervation; D014711:Vertebral Artery / Q000033:anatomy & histology