Intraoperative auditory steady-state monitoring during surgery in the cerebellopontine angle for estimation of postoperative hearing classes

Audiological Characteristics of Vestibular Schwannoma Patients With Normal Pure-Tone Audiometry

OBJECTIVE

To investigate the audiological characteristics of vestibular schwannoma (VS) patients with normal pure-tone audiometry (PTA) results.

STUDY DESIGN

A retrospective study.

SETTING

Forty-two VS patients with normal PTA results from October 2016 to October 2022 were included.

METHODS

Normal PTA was defined when the hearing threshold is ≤25 dB hearing loss (HL) in each test frequency and the PTA is ≤25 dB HL. Results of multiple audiological tests such as the auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), multiple auditory steady-state responses threshold (ASSR), and speech discrimination score were retrospectively reviewed. Demographic data of these patients were also been collected.

RESULTS

According to our results, the ABR and average ASSR threshold of the affected side were statistically significantly higher in VS patients with normal PTA. ABR waveforms on the affected side also showed more abnormalities. The DPOAE pass rates of the affected side were lower than the unaffected side while the amplitude and signal-to-noise ratio rate was also lower. In addition, we used magnetic resonance imaging 3-dimensional reconstruction images to measure the volume of tumors in these patients. We also found that higher ABR threshold means lager tumor size in patients with normal PTA.

CONCLUSION

VS patients with normal PTA result cannot be assumed to have no impairment of hearing function. ABR, DPOAE, and ASSR results showed the characteristic changes in the affect ear. ABR threshold has the highest sensitivity for hearing abnormalities and is strong relative with tumor size in patients with normal PTA.

Steady-State Cortico-Cortical Evoked Potential

PURPOSE

The present study evaluated the utility of the steady-state responses of cortico-cortical evoked potentials (SSCCEPs) and compared them with the responses of conventional CCEPs.

METHODS

Eleven patients with medically intractable focal epilepsy who underwent the implantation of subdural electrodes or stereoelectroencephalography were enrolled. Conventional CCEPs were obtained by averaging responses to alternating 1-Hz electrical stimuli, and 5-Hz stimuli were delivered for recording SSCCEPs. The distribution of SSCCEPs was assessed by a frequency analysis of fast Fourier transform and compared with conventional CCEPs.

RESULTS

Steady-state responses of cortico-cortical evoked potentials were successfully recorded in areas consistent with conventional CCEPs in all patients. However, SSCCEPs were more easily disturbed by the 5-Hz stimulation, and small responses had difficulty generating SSCCEPs.

CONCLUSIONS

Steady-state responses of cortico-cortical evoked potentials may be a useful alternative to conventional CCEPs.

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.

Electrophysiological predictors of hearing deterioration based on AEP monitoring during petroclival meningioma resection

The objective of this study was to calculate the risk of postsurgical hearing deterioration as a function of changes in the amplitude and latency of the most stable components (waves III and V) of the auditory evoked potential (AEP) during petroclival meningioma resection surgery. We retrospectively analyzed intraoperative AEP monitoring results and pre- and postsurgical hearing status in 40 consecutive patients who were surgically treated for petroclival meningiomas. Statistical analyses were conducted to identify the most sensitive and specific way to predict hearing dysfunction after surgery. Patients' mean age was 59 ± 10 years, and 31 (77.5%) were women. Twelve (30%) patients presented with clinically detectable hearing impairment preoperatively. At the first postoperative assessment, four of those 12 patients reported subjective improvement, and eight reported hearing deterioration. Of those eight, four remained stable and four recovered hearing by the last assessment. Wave III latency reached its highest specificity (100%) and sensitivity (71.43%) at x = 143%. Wave V latency, on the other hand, reached its highest sensitivity (71%) and specificity (93%) at x = 124%. Finally, wave V amplitude reached its highest sensitivity (100%) and specificity (79%) at x = 74%. Intraoperative alterations of wave III latency and wave V amplitude seem to be highly sensitive and specific at predicting the risk of auditory dysfunction in patients undergoing petroclival meningioma resection and should be used to determine maximum resection with preservation of function.

[Intraoperative monitoring of cochlear nerve function during cerebello-pontine angle surgery]

BACKGROUND

Surgical procedures in the cerebello-pontine angle (CPA), e. g. for vestibular schwannoma, have an increased risk for damage to the cochlear nerve. Consequently, hearing deterioration up to complete deafness may result with severe impact on quality of life. Methods for intraoperative monitoring of function may minimize such risks.

OBJECTIVE

Review of current methods for intraoperative monitoring of the cochelar nerve and summary of new developments.

MATERIALS AND METHODS

Analysis and summary of literature, discussion of new methods.

RESULTS

Early auditory evoked potentials using click stimuli remain the standard method for intraoperative monitoring of cochlear nerve function. Amplitude and latency changes indicate a risk of postoperative hearing deterioration; however demonstrate only limited further differentiation of hearing quality. As novel methods, near-field recordings may allow faster feedback and auditory steady state responses potentially enable frequency specific testing.

CONCLUSIONS

Intraoperative monitoring of the cochlear nerve is an integral component of CPA surgery. It enables detection of potential nerve damage and thus contributes to avoiding postoperative functional deficits. Development and implementation of novel and additional approaches may further improve its clinical value.

Evaluation of the prognostic value of multimodal intraoperative monitoring in posterior fossa surgery patients with cerebellopontine angle tumors

The aim of this study was to compare the outcomes of four intraoperative monitoring approaches in order to compare their prognostic value in surgical complications of the facial nerve. This quasi-experimental study was conducted on 25 patients with Cerebellopontine Angle (CPA) tumors, who were hospitalized in the Valiasr Hospital, affiliated to the Arak University of Medical Sciences, Arak, Iran. The degree of the facial nerve paralysis was assessed based on the House-Brackmann (HB) facial nerve grading system. The Orbicularis oris and Oculi muscles were evaluated by electromyography (EMG) before and after the surgery. Monitoring the facial nerve was performed by the EMG, Facial Nerve Antidromic Potentials (FNAPs), Transcranial Electrical Stimulation (TES), and Brainstem Auditory Evoked Potentials (BAEPs) methods. The mean HB score was 0.36.6±5.83, indicating that the function of the facial muscle was abnormal in all the patients pre-surgery. The comparison of the four monitoring approaches six months after surgery showed that the predictive value of facial nerve TES was higher than the other approaches (P<0.005). Furthemroe, 4% of the patients showed normal function in the facial muscle after the surgery. In addition, 8%, 56%, and 32% of the patients had mild abnormalities, moderate to severe paralysis in the facial muscles, and severe facial nerve dysfunction, respectively. In summary, 36% of the patients showed a mild abnormalities in the follow-up period, and full recovery was observed in 28% of the cases. In conclusion, the transcranial motor evoked potential (TCMEP) is a useful method for monitoring the facial nerve during the surgery along with the continuous EMG recordings.