The utility of facial nerve amplitude and latency ratios in predicting postoperative facial nerve function after vestibular schwannoma surgery

Turel, Mazda K; Babu, K. Srinivasa; Singh, Gautam; Chacko, Ari G

doi:10.4103/0028-3886.132373

Cited by 6 publications

(7 citation statements)

References 16 publications

(19 reference statements)

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“…The existence of a high P/D amplitude ratio with poor postoperative FN outcome has been previously reported and was mainly attributed to the presence of an injury at the REZ with an intact distal nerve. 14 Based on our findings, another reason for this situation is peripheral volume conduction to the FN-innervated muscles, and a clue to this condition is a CMAP latency of < 6 ms.…”

Section: Discussionmentioning

confidence: 55%

“…10 During the last few decades, numerous triggered EMG measurement criteria have been devised and refined to predict postoperative FN outcomes. [11][12][13][14][15][16][17] Typically, many studies have resorted to FN stimulation at the end of surgery, using the minimum threshold required to elicit a compound muscle action potential (CMAP). Several reports have indicated that a FN response at a threshold of less than 0.05 mA is a reliable but not infallible predictor of good short-term and long-term FN function.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Latency Variations on the Predictive Value of Facial Nerve Proximal-to-Distal Amplitude Ratio during Vestibular Schwannoma Surgery

Ashram

Zohdy

Garzón-Muvdi

2023

J Neurol Surg B Skull Base

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Introduction This study highlights the relation between compound muscle action potential (CMAP) latency variations and the predictive value of facial nerve (FN) proximal-to-distal (P/D) amplitude ratio measured at the end of vestibular schwannoma resection. Methods Forty-eight patients underwent FN stimulation at the brainstem (proximal) and internal acoustic meatus (distal) using a current intensity of 2 mA. The proximal latency and the P/D amplitude ratio were assessed. House–Brackmann grades I & II indicated good FN function, and grades III to VI were considered fair/poor function. A P/D amplitude ratio > 0.6 was used as a cutoff to indicate a good FN function, while a ratio of ≤ 0.6 indicated a fair/poor FN function. Results The P/D amplitude ratio was measured for all patients, and the calculated sensitivity (SE), specificity (SP), positive predictive value (PPV), and negative predictive value (NPV) were 85.2, 85.7, 88.5, and 81.8%, respectively. The CMAPs from the mentalis muscle were then classified based on their proximal latency into group I (< 6 ms), group II (6–8 ms), and group III (> 8 ms). The SE, SP, PPV, and NPV became 90.5, 90.9, 95, and 83.3%, respectively, in group II. In group I, SE and NPV increased, whereas SP and PPV decreased. While in group III, SP and PPV increased, whereas SE and NPV decreased. Conclusion At a latency between 6 and 8 ms, the P/D amplitude ratio was predictive of outcomes with high SE and SP. When latency was < 6 ms or > 8 ms, the same predictive ability was not observed. Knowing the strengths and limitations is important for understanding the predictive value of the P/D amplitude ratio.

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Section: Discussionmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Impact of Latency Variations on the Predictive Value of Facial Nerve Proximal-to-Distal Amplitude Ratio during Vestibular Schwannoma Surgery

Ashram

Zohdy

Garzón-Muvdi

2023

J Neurol Surg B Skull Base

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“…A positive response after tumor removal should be considered a good predictor of function, and its absence does not always predict poor facial outcomes. 18 VS affect people in the age group of 45 to 64 years without any gender difference. In Turel et al series, the mean age of patients was 41.8 years for tumors between 4 and 5 cm; and 34.8 years for tumors larger than 5 cm.…”

Section: Discussionmentioning

confidence: 97%

“…A positive response after tumor removal should be considered a good predictor of function, and its absence does not always predict poor facial outcomes. 18…”

Section: Discussionmentioning

confidence: 99%

Is Preoperative Facial Palsy a Deterrent to Facial Nerve Preservation after Gross-Total Removal of Giant Vestibular Schwannomas?

Sahana

Kumar

Rathore

et al. 2022

Indian Journal of Neurosurgery

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Background Although rare in small vestibular schwannomas, preoperative facial nerve paresis is often present in giant schwannomas. Preserving facial nerve function in these cases remains a herculean task. This study evaluates the facial functions after complete tumor removal and whether preoperative facial nerve involvement affects postoperative functional status. Methods This retrospective study from January 2014 to August 2021 excluded nongiant tumors (< 4 cm), neurofibromatosis type 2 cases, incomplete removals, redo surgeries, deaths, and cases done without nerve monitoring. These were grouped into preoperative facial palsy present (PFP) and no preoperative facial palsy (NFP). Facial nerve functions were assessed on first postoperative day, at the time of discharge, and at last follow-up and dichotomized into two groups: nondisfiguring (House–Brackmann [HB] grades I–III) and disfiguring (HB grades IV–VI). The cohort outcomes of patients with nondisfiguring PFP (HB grades I–III) were also analyzed. Results There were 88 cases (PFP, n = 57; NFP, n = 31). Facial nerve was preserved anatomically in 62 (70.45%) patients (PFP, n = 38; NFP, n = 24) without any statistical difference (p = 0.29). Statistically significant disfiguring facial outcomes (HB IV, V, VI) were seen in patients with preoperative facial palsy (p = 0.01); however, a comparison of facial functions in patients with only nondisfiguring PFP with those in NFP group did not show the statistical difference (p = 0.12). Conclusions Facial nerve palsy present before surgery does not seem to be a deterrent to intraoperative preservation of facial nerve during complete removal of giant vestibular schwannomas. Patients with nondisfiguring facial palsies have postoperative facial functions comparable to those without facial palsy.

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“…In this situation the CMAPs recorded from the muscles supplied by the facial nerve are not purely due to facial nerve stimulation but are likely to have contributions from the peripheral volume conducted responses; a condition that can be suspected if the latencies of the CMAPs are shorter than those of the usual proximal facial nerve stimulation and are associated with a simultaneous trigeminal nerve stimulation response. This problem may be one of the reasons why predictive methods for assessment of the facial nerve functional integrity show variability among different studies [5,19,21]. It is therefore critical to analyze facial nerve EMG data within context of the trigeminal nerve data for more accurate analysis.…”

Section: Discussionmentioning

confidence: 99%

Value of intraoperative monitoring of the trigeminal nerve in detection of a superiorly displaced facial nerve during surgery for large vestibular schwannomas

et al. 2021

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ObjectiveTo investigate the role of trigeminal and facial nerve monitoring in the early identi cation of a superiorly displaced facial nerve. Patients and MethodsThis prospective study included 24 patients operated for removal of large vestibular schwannomas (VS). Electromyographic (EMG) events recorded after mapping the superior surface of the tumor were evaluated by analyzing the latencies of the responses from the masseter and facial nerve innervated muscles. ResultsThe latency of the recorded compound muscle action potential (CMAP) from the masseter muscle was 3.6 ±0.5 msec, and of the simultaneously recorded volume conducted responses from the frontalis, o.oculi, nasalis, o.oris and mentalis muscles were 4.6 ±0.9, 4.1 ±0.7, 3.9 ±0.4, 4.3 ±0.8 and 4.5 ±0.6 msec respectively after trigeminal nerve stimulation in 24 (100%) patients. In 6 (25%) patients, the mean latency of CMAP on the masseter was 3.6 ±0.5 msec, and the latencies of the CMAP from the frontalis, nasalis, o.oris and mentalis muscles were longer than those of the volume conduced responses (p=0.002; p=0.001; p< 0.001; and p=0.015 respectively) indicating stimulation of both nerves (trigemino-facial EMG response). All patients with this response were later con rmed anatomically to have an AS displaced facial nerve. ConclusionUnderstanding the trigemino-facial EMG response is of value in identifying an AS displaced facial nerve; in preventing electrophysiological confusion between the trigeminal and the facial nerves; and in detecting the presence of volume conducted contributions in the measured facial nerve CMAP at the end of surgery.

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The utility of facial nerve amplitude and latency ratios in predicting postoperative facial nerve function after vestibular schwannoma surgery

Cited by 6 publications

References 16 publications

Impact of Latency Variations on the Predictive Value of Facial Nerve Proximal-to-Distal Amplitude Ratio during Vestibular Schwannoma Surgery

Impact of Latency Variations on the Predictive Value of Facial Nerve Proximal-to-Distal Amplitude Ratio during Vestibular Schwannoma Surgery

Is Preoperative Facial Palsy a Deterrent to Facial Nerve Preservation after Gross-Total Removal of Giant Vestibular Schwannomas?

Value of intraoperative monitoring of the trigeminal nerve in detection of a superiorly displaced facial nerve during surgery for large vestibular schwannomas

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