Vertebral artery hypoplasia may contribute to abnormal vestibular evoked myogenic potentials

Congenital vertebral artery hypoplasia (VAH) is an uncommon embryonic variation of the posterior circulation. The clinical relevance and hemodynamic impact of VAH have been under debate. We tried to localize the topographic domain of vertebral artery hypoplasia with vestibular evoked myogenic potential (VEMP) studies. From January 2005 to October 2005, we reviewed the magnetic resonance angiographic records of 250 health check-up outpatients (108 men and 142 women; mean age, 30.8 +/- 14.0 years; range, 25 to 55 years). There were 26 subjects with a hypoplasic VA. We performed a case-control study by recruiting another 26 healthy subjects without hypoplastic VA as a control group. VEMP testing was performed in each subject for comparison. The results revealed that 88.47% of the healthy subjects with a VAH demonstrated abnormal VEMPs either unilaterally or bilaterally, which was statistically higher than control group without a VAH (p=0.019). Given that hypoplasic VA was exclusively right-sided in these patients, the majority of whom had an ipsilateral delayed response or absence of VEMP. We therefore hypothesize that VA hypoplasia might contribute to brain stem lesion or interruption of sacculo-collic reflex.