Hearing outcomes after loss of brainstem auditory evoked potentials during microvascular decompression

Usefulness of intraoperative monitoring in microvascular decompression for hemifacial spasm: a systematic review and meta-analysis

OBJECTIVE

To review the diagnostic accuracy and possible added value of Brainstem Auditory Evoked Potentials (BAEP) monitoring and Lateral Spread Response (LSR) monitoring in microvascular decompression surgery for hemifacial spasms.

METHODS

For this systematic review we followed the PRISMA guidelines. We searched different databases and bibliographies of articles. We included studies on BAEP and LSR monitoring that reported data on hearing outcome or efficacy. Selected studies were assessed for bias using the MINORS tool.

RESULTS

64 articles were selected for qualitative synthesis, 42 met inclusion criteria for meta-analysis. The overall incidence of hearing loss was 3.4%. For BAEP monitoring AUC and pooled OR with 95% confidence interval were 0.911 (0.753-0.933) and 7.99 (3.85-16.60) respectively. Short-term data on LSR monitoring showed an overall spasm relief rate of 89% with pooled OR, sensitivity and specificity with a 95% confidence interval of 8.80 (4.82-16.08), 0.911 (0.863-0.943) and 0.451 (0.342-0.564) respectively. Long-term data on LSR monitoring showed an overall spasm relief rate of 95% with pooled OR, sensitivity and specificity with a 95% confidence interval of 4.06 (2.15-7.64), 0.871 (0.817-0.911) and 0.39 (0.294-0.495) respectively.

CONCLUSION

The alarm criteria, a wave V latency prolongation of 1ms or a wave V amplitude decrement of 50%, proposed by the 'American Clinical Neurophysiology Society' are a sensitive predictor for postoperative hearing loss. Other BAEP wave changes, for example, complete loss of wave V, are more specific but correspond to irreversible damage and are therefore not useful as warning criteria. LSR monitoring has high diagnostic accuracy at short-term follow-up. At long-term follow-up, diagnostic accuracy decreases because most patients get spasm relief regardless of their LSR status. LSR persistence after surgery has a good long-term outcome, as long as an extensive exploration of the facial nerve has been performed.

Predictive values of maximum changes of brainstem auditory evoked potentials during microvascular decompression for hemifacial spasm

BACKGROUND

Brainstem auditory evoked potentials (BAEPs) have been widely monitored to prevent hearing loss (HL) during microvascular decompression (MVD) for hemifacial spasm (HFS); however, their predictive value is still unclear. The aim of this study is to investigate the predictive values of the maximum changes in BAEPs and define the best warning indicator and a cutoff value (CV) during HFS-MVD.

METHODS

The clinical data of 93 HFS-MVD patients were retrospectively analysed. The maximum change rates of the latency and amplitude of waves I, III, and V and the interpeak latencies (IPLs) I-III, I-V, and III-V, when BAEPs change most during MVD, were defined. Pure tone audiometry was performed to evaluate hearing loss (HL). Logistic regression, propensity score, receiver operating curve (ROC), and area under the curve (AUC) were used to identify the predictive value of relevant indexes and to determine the CV (with the largest Youden index) of the best index at different levels of HL.

RESULTS

The AUCs of BAEPs for predicting HL were 0.98, 0.92, and 0.84 for 50 dB, 30 dB, and 10 dB, respectively. The amplitude of wave V (AwV) was the best single predictive index at all three HL levels. The CV of AwV was 55% (50 dB), 46% (30 dB), and 34% (10 dB). At 50 dB HL, the predictive value of IPLs I-V (AUC 0.89 with CV 0.6 ms) was better than that of LwV (AUC 0.82 with CV 1 ms).

CONCLUSION

BAEPs can predict HL well. AwV is the best single predictive index of all BAEPs. The reduction of AwV by 34% (watching), 46% (reporting), and 55% (warning) can be used as a sliding-scale warning sign. In addition, IPLs I-V (> 0.6 ms) and LwV (> 1 ms) should also be observed and reported during MVD.

Quantitative study of the correlation between cerebellar retraction factors and hearing loss following microvascular decompression for hemifacial spasm

BACKGROUND

This prospective study quantitatively measured the cerebellar retraction factors, including retraction distance, depth and duration, and evaluated their potential relationship to the development of hearing loss after microvascular decompression (MVD) for hemifacial spasm (HFS).

METHODS

One hundred ten patients with primary HFS who underwent MVD in our department were included into this study. The cerebellar retraction factors were quantitatively measured on preoperative MR and timed during MVD. Associations of cerebellar retraction and other factors to postoperative hearing loss were analyzed.

RESULTS

Eleven (10%) patients developed hearing loss after MVD. Compared with the group without hearing loss, the cerebellar retraction distance, depth and duration of the group with hearing loss were significantly greater (p < 0.05). Multivariate regression analysis showed that greater cerebellar retraction depth and longer retraction duration were significantly associated with a higher incidence of postoperative hearing impairment (p < 0.05).

CONCLUSION

This study strongly suggested a correlation between the cerebellar retraction factors, especially retraction depth and duration, and possibility of hearing loss following MVD for HFS.

Operative Complications of Microvascular Decompression for Hemifacial Spasm: Experience of 1548 Cases

BACKGROUND

Although microvascular decompression (MVD) surgery is considered the gold standard treatment for hemifacial spasm, there are some MVD-related complications.

METHODS

We retrospectively reviewed 1548 patients with hemifacial spasm who underwent retromastoid suboccipital craniectomy with MVD from January 2009 to June 2013. All patients were followed for >2 years.

RESULTS

Excellent and good results were 92.5% and 4.2%, respectively. Postoperative complications were recorded in 16.09% (n = 249). There was no MVD-related mortality. After MVD surgery, the most frequent complications were occipital sensory disturbance (7.3%), facial nerve palsy (9.7%), and hearing impairment (3.5%). Other complications were as follows: cerebrospinal fluid leakage (n = 24), poor healing wound (n = 14), lower cranial nerve palsy (n = 12), wound infection (n = 4), and hemorrhage (n = 2).

CONCLUSIONS

MVD operation is a safe treatment for hemifacial spasm. Facial nerve palsy is the most common MVD-related complication; preservation of the lesser occipital nerve during MVD surgery can decrease the rate of occipital sensory disturbance. Permanent or serious complications are comparatively rare in MVD surgery.

Correlation Between Cerebellar Retraction and Hearing Loss After Microvascular Decompression for Hemifacial Spasm: A Prospective Study

BACKGROUND

This study prospectively investigated the relationship between cerebellar retraction factors measured on preoperative magnetic resonance and the development of postoperative hearing loss and evaluated their potential role in predicting the possibility of hearing loss after microvascular decompression (MVD) for hemifacial spasm (HFS).

METHODS

The study included 110 patients clinically diagnosed with primary HFS who underwent MVD in our department. The cerebellar retraction factors were quantitatively measured on preoperative magnetic resonance. Associations of cerebellar retraction and other risk factors with postoperative hearing loss were analyzed.

RESULTS

Eleven patients (10%) developed nonserviceable hearing loss after MVD. Compared with the group without hearing loss, the cerebellar retraction distance and depth of the group with hearing loss were significantly greater (P < 0.05). Multivariate logistic regression analysis showed that greater cerebellar retraction depth was significantly associated with the higher incidence of postoperative hearing loss (P < 0.05).

CONCLUSIONS

The results in this study strongly suggested the correlation between the cerebellar retraction depth and the possibility of hearing loss after MVD for HFS. In addition, cerebellar retraction depth could be considered as a useful tool to predict the risk of post-MVD hearing loss.