Role of arterioles in management of microvascular decompression in patients with hemifacial spasm

Although microvascular decompression (MVD) is accepted as an effective therapy for hemifacial spasm (HFS), some operations fail. While performing MVD, many surgeons focus on the large arteries but ignore the arterioles. Failure to identify involved arterioles may account for unsuccessful MVD. We aimed to refine the MVD surgery and improve post-operative outcomes by proper management of involved arterioles. Clinical data were collected from 69 consecutive patients who underwent MVD. Intraoperative electromyography (EMG) was employed for each MVD. Each operation was reviewed with a focus on the involved arterioles. All patients were followed up for between nine and 12 months. An abnormal muscle response (AMR) wave was identified by EMG in all patients before decompression, but vanished in most patients as soon as the involved arteries were removed from the cranial nerve (CN). However, in nine of 69 patients, the AMR did not immediately disappear. Further dissection and exploration of the entire CN VII identified an arteriole in contact with, or in some patients embedded in, the nerve. Once the arteriole was isolated from the CN, the AMR disappeared. After surgery, spasms ceased in all patients and no recurrence was found up to the one-year follow-up. To achieve a positive post-operative outcome, exploration of the entire CN VII is necessary, with a focus on the small arterioles. AMR can be a good adjuvant to identify the involved arterioles.