Original ArticleHearing Outcome Following Microvascular Decompression for Hemifacial Spasm: Series of 1434 Cases
Introduction
Hemifacial spasm (HFS) is a motor disorder defined as involuntary, irregular contractions of the ipsilateral facial muscles innervated by cranial nerve VII.1, 2 The symptoms usually start from the periorbital muscles in the early stage, and then spread downward to the ipsilateral facial muscles.3 Neurovascular compression has been generally accepted as the etiology of HFS according to Dandy’s first proposal4; however, there are several hypotheses of the pathogenesis of HFS, including ectopic excitation and ephaptic transmission in cranial nerve VII itself, hyperexcitability of the facial nerve nucleus, and triggering of neurotransmitter release from the sympathetic nerve endings of the offending artery wall.1, 5, 6 These findings support the use of microvascular decompression (MVD) surgery in treating HFS. Indeed, MVD was found to be an effective procedure associated with a low rate of complications.7 Since HFS is not life threatening, it is considered unacceptable to increase undue risk through its treatment. Therefore, efforts to reduce the complications associated with surgical treatment for HFS have been underway for years. The most frequent perioperative complications are cranial nerve palsies resulting from the unavoidable nerve manipulation during the procedure. The incidence of cranial nerve palsy is reported to be 2.8%–22.7% for facial palsy, including both immediate and delayed onset,7, 8, 9, 10, 11 2.3%–21.2% for hearing impairment,7, 8, 10 and 0.44%–9.7% for lower cranial nerve palsy.8, 9, 12 Other related complications include ear fullness, cerebrospinal fluid (CSF) leakage, hemorrhage, infarction, and infection. Although these complications follow mostly transient and mild clinical courses, some can persist and significantly affect patients' quality of life. In particular, hearing is an important element of conversation; therefore, postoperative auditory complications can have a great influence on a patient's daily social interactions.13, 14 Although the incidence has been decreasing because of the development of improved surgical instruments and techniques, there is still a variety of complication rates depending on the institute or surgeons involved. To assess the risk of hearing impairment after MVD, and to identify potential ways to reduce it, we reviewed our own MVD surgical procedures in more than 1000 cases, and we assessed the effectiveness of the efforts to reduce the auditory risk after MVD for HFS.
Section snippets
Materials and Methods
We retrospectively reviewed the medical records of patients with HFS who underwent MVD at our institute from March 2003 to October 2016; all operations were performed by the same surgeon (J.W.C.). Preoperative evaluation routinely included magnetic resonance imaging, magnetic resonance angiography, computed tomography, and electrophysiologic studies such as nerve conduction study and electromyography. Preoperative auditory evaluations included subjective reports of hearing-related symptoms,
Statistical Analysis
Statistical analyses were completed using SPSS version 23 (IBM Corporation, New York, USA). Continuous variables are presented as mean ± standard deviation and categorical variables as frequency (%). Any differences in demographic, clinical characteristics, and intraoperative findings between groups were analyzed with either t tests or Fisher exact tests as appropriate. Multivariate regression test was used to identify any relationship between demographic factors or operation-related factors. P
Results
A total of 1490 patients underwent MVD for intractable HFS. Among them, 1434 patients were included in this study; those not included had missing data or insufficient follow-up (<6 months). Among the participants, there were 1033 women (72.0%) and 401 men (28.0%). The mean age was 51.4 years (range, 19–77 years). MVD was needed for the right side in 718 patients (50.1%) and the left side in 716 patients (49.9%). Intraoperative findings showed that the most common offending vessel was the
Discussions
Hearing impairment after MVD for HFS can occur for the following reasons: stretching of cranial nerve VIII during cerebellar retraction; manipulation of the labyrinthine artery and/or the anterior inferior cerebellar artery; direct trauma to the nerve caused by instruments or nearby coagulation; and new compression of the nerve by the insertion between the offending vessels and the VII–VIII nerve complex after completion of the surgery.15, 16 Recently, several studies suggested that other
Conclusions
MVD is a safe and effective surgical technique with rare permanent complications. The authors report a low incidence rate of hearing impairment, which can be yet improved upon by appropriate preoperative planning and meticulous surgical techniques.
Acknowledgments
The authors thank Eun Jung Kweon for arranging the clinical data.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.