The actual site of excitation of the facial nerve by transcranial magnetic stimulation was investigated in five patients with hemifacial spasm who underwent microvascular decompression. The facial nerve was stimulated preoperatively and intraoperatively by transcranial magnetic stimulation and intraoperatively by electrical stimulation at its root exit zone with a minimum of surgical invasion of the facial nerves. The onset latency of compound muscle action potentials recorded from the nasalis muscle was 5.06 +/- 0.44 ms by magnetic stimulation and 5.08 +/- 0.43 ms by electrical stimulation. The latency difference was 0.06 +/- 0.08 ms. Therefore, transcranial magnetic stimulation was basically the same as electrical stimulation in onset latency. From this study, it appears that the root exit zone of the facial nerves is stimulated by transcranial magnetic stimulation.

Among the surgical procedures used in microvascular decompression surgery, dislocation of the offending vessel with Teflon slings is a useful surgical technique to treat trigeminal neuralgia due to a tortuous vertebral artery.

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Objective:The aim of this study was to identify the etiology of hemifacial spasm (HFS) and trigeminal neuralgia (TN) in patients aged 30 years or younger and to examine the efficacy of microvascular decompression (MVD).Patients and Methods:Between 1996 and 2012, 228 HFS and 190 TN patients underwent MVD at Atsuchi Neurosurgical Hospital. Of these, 7 patients were 30 years of age or younger at the time of treatment (HFS: n = 6, TN: n = 1). Assessments were based on their medical history and on magnetic resonance imaging, magnetic resonance angiography, surgical, and follow-up findings.Results:The age of the 6 HFS patients ranged from 23 to 30 years (mean 27.8 ± 1.8 [standard deviation] years) at the time of surgery; the earliest symptom onset was in an 11-year-old boy. We noted vascular variations in 5 patients, a duplicate posterior inferior cerebellar artery in 2 patients, a short basilar artery in 1 patient, and an aberrant arterial course in 2 patients. At the latest follow-up, 1–69 months after MVD, 5 of the HFS patients were asymptomatic and the 6th had mild residual symptoms. A 23-year-old TN female underwent straightening of the trigeminal nerve by separation of a thickened arachnoid membrane from the nerve and dislocation of a small branch of the superior cerebellar artery from the distal end of the root exit zone. While she continued to experience occasional facial pain 48 months after the operation, she required no medication because surgery yielded significant pain amelioration.Conclusion:Although the pathogenesis of early-onset HFS and TN remains unclear, our findings suggest that vascular variations may be related to the etiology of vascular compression symptoms in patients with HFS or TN. MVD was useful for the treatment of neurovascular compression symptoms in young patients.