Artery supply and surrounding neurovascular relationships of hypoglossal nerve root: surgical anatomy of its cisternal segment

Objective To study artery supply and adjacent neurovascular relationships of the hypoglossal nerve root of its cisternal segment. [Method] The length, number, arrangements and artery supply of hypoglossal nerve rootlets and the relationship between the nerve root and its surrounding vessels were observed on 25 brain stems. [Results] The number of the hypoglossal nerve rootlet is about 5; the length is about 10 mm. The rootlets emerged as two bundles (72%), three bundles (10%), or fan-shaped distribution (18%). The major blood supplies of the cisternal segments of the hypoglossal nerve root were from anterolateral medullary arteries, lateral medullary artery and lateral pontomedullar artery. These arteries arise from vertebral artery, anterior spinal artery, posterior inferior cerebellar artery, basilar artery or their perforating branches. The ventral surface of hypoglossal nerve root was crossed by the vertebral artery (90%), Occasionally, vertebral artery ran between upper and lower bundles or coursed dorsal surface of hypoglossal nerve root. About 50% posterior inferior cerebellar artery ran through upper and lower bundles, then ran upward behind the rootlets of hypoglossal nerve. About 74% of the rootlets of hypoglossal nerve were contacted with vertebral artery, 20% contacting with posterior cerebellar, and 18% were compressed by vertebral artery. [Conclusions] The blood supplies of the cisternal segments of the hypoglossal nerves were from several vessels, which mainly arised from the vertebral artery and its branches; rootlets of hypoglossal nerve were contacted or compressed by vertebral artery.