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

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.

An Artificial Neural Network Model for Predicting Postoperative Facial Nerve Outcomes After Vestibular Schwannoma Surgery.

BACKGROUND AND OBJECTIVES: The emergence of machine learning models has significantly improved the accuracy of surgical outcome predictions. This study aims to develop and validate an artificial neural network (ANN) model for predicting facial nerve (FN) outcomes after vestibular schwannoma (VS) surgery using the proximal-to-distal amplitude ratio (P/D) along with clinical variables. METHODS: This retrospective study included 71 patients who underwent VS resection between 2018 and 2022. At the end of surgery, the FN was stimulated at the brainstem (proximal) and internal acoustic meatus (distal) and the P/D was calculated. Postoperative FN function was assessed using the House-Brackmann grading system at discharge (short-term) and after 9-12 months (long-term). House-Brackmann grades I-II were considered good outcome, whereas grades III-VI were considered fair/poor. An ANN model was constructed, and the performance of the model was evaluated using the area under the ROC curve for internal validation and accuracy, sensitivity, specificity, and positive and negative predictive values for external validation. RESULTS: The short-term FN outcome was grades I-II in 57.7% and grades III-VI in 42.3% of patients. Initially, a model using P/D had an area under the curve of 0.906 (internal validation) and an accuracy of 89.1% (95% CI: 68.3%-98.8%) (external validation) for predicting good vs fair/poor short-term FN outcomes. The model was then refined to include only muscles with a P/D with a proximal latency between 6 and 8 ms. This improved the accuracy to 100% (95% CI: 79%-100%). Integrating clinical variables (patient's age, tumor size, and preoperative HB grade) in addition to P/D into the model did not significantly improve the predative value. A model was then created to predict the long-term FN outcome using P/D with latencies between 6 and 8 ms and had an accuracy of 90.9% (95% CI: 58.7%-99.8%). CONCLUSION: ANN models incorporating P/D can be a valuable tool for predicting FN outcomes after VS surgery. Refining the model to include P/D with latencies between 6 and 8 ms further improves the model's prediction. A user-friendly interface is provided to facilitate the implementation of this model.

Patterns of Visual Task-based Functional MRI Activation in Chronic Posterior Cerebral Artery Stroke Patients.

PURPOSE: Stroke is a principal cause of disability worldwide. In motor stroke, the tools for stratification and prognostication are plentiful. Conversely, in stroke causing mainly visual and cognitive problems, there is still no gold standard modality to use. The purpose of this study was to explore the fMRI recruitment pattern in chronic posterior cerebral artery (PCA) stroke patients and to investigate fMRI as a biomarker of disability in these patients. METHODS: The study included 10 chronic PCA stroke patients and another 10 age-matched volunteer controls. The clinical presentation, cognitive state, and performance in visual perceptual skills battery (TVPS-3) were determined for both patients and control groups. Task-based fMRI scans were acquired while performing a passive visual task. Individual and group analyses of the fMRI scans as well as correlation analysis with the clinical and behavioral data were done. RESULTS: At the level of behavioral assessment there was non-selective global impairment in all visual skills subtests. On visual task-based fMRI, patients recruited more brain areas than controls. These activations were present in the ipsilesional side distributed in the ipsilesional cerebellum, dorsolateral prefrontal cortex mainly Brodmann area (BA) 9, superior parietal lobule (somatosensory associative cortex, BA 7), superior temporal gyrus (BA 22), supramarginal gyrus (BA 40), and contralesional associative visual cortex (BA 19). Spearman's rank correlation was computed to assess the relationship between the TVPS scores and the numbers of fMRI neuronal clusters in each patient above the main control activations, there was a negative correlation between the two variables, r(10) = -0.85, p ≤ 0.001. CONCLUSION: In chronic PCA stroke patients with residual visual impairments, the brain attempts to recruit more neighboring and distant functional areas for executing the impaired visual skill. This intense recruitment pattern in poorly recovering patients appears to be a sign of failed compensation. Consequently, fMRI has the potential for clinically relevant prognostic assessment in patients surviving PCA stroke; however, as this study included no longitudinal data, this potential should be further investigated in longitudinal imaging studies, with a larger cohort, and multiple time points.

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

The aim of this study was to investigate the role of trigeminal and facial nerve monitoring in the early identification of a superiorly (anterior and superior (AS)) displaced facial nerve. This prospective study included 24 patients operated for removal of large vestibular schwannomas (VS). The latencies of the electromyographic (EMG) events recorded from the trigeminal and facial nerve innervated muscles after mapping the superior surface of the tumor were analyzed. The mean latency of the recorded compound muscle action potential (CMAP) from the masseter muscle was 3.6 ± 0.5 ms and of the peripherally transmitted responses by volume conduction from the frontalis, o. oculi, nasalis, o. oris, and mentalis muscles was 4.6 ± 0.9, 4.1 ± 0.7, 3.9 ± 0.4, 4.3 ± 0.8, and 4.5 ± 0.6 ms, respectively, after trigeminal nerve stimulation in 24 (100%) patients (pattern I response). In 6 (25%) patients, the mean latency of CMAP on the masseter was 3.3 ± 0.3 ms, and the latencies of the CMAP from the frontalis, o. oculi, nasalis, o. oris, and mentalis muscles were 6.5 ± 1.3, 5.0 ± 1.5, 7.5 ± 1.3, 7.4 ± 0.6, and 7.0 ± 1.5 ms, respectively, longer than those of the peripherally transmitted responses (p = 0.002, p = 0.001, p < 0.001, and p = 0.015, respectively) indicating simultaneous stimulation of both nerves (pattern II response). All patients with this response were later confirmed to have an AS-displaced facial nerve. Recognizing the response resulting from simultaneous stimulation of both the facial and trigeminal nerves is important to help early identification of an AS-displaced facial nerve before it is visible in the surgical field and to avoid misleading information by confusing this pattern for a pure trigeminal nerve response.

Pattern and Rate of Functional Recovery After Surgery for Cervical Spondylotic Myelopathy: Egyptian Prospective Study.

OBJECTIVE: To study pattern and rate of neurological functional recovery after surgery for cervical spondylotic myelopathy (CSM). METHODS: This prospective study comprised 25 patients with CSM who underwent surgical decompression at our institution. Upper limb, lower limb, and sphincter functions were assessed using the modified Japanese Orthopaedic Association score (mJOA). Assessment was done before the operation and at 1 month, 3 months, and 1 year after surgery. RESULTS: The mJOA score did not significantly increase at 1 month after surgery (P = 0.051); however, increase in mJOA score was statistically significant at 3 and 1 year after surgery (P < 0.001 and P < 0.001, respectively). Upper limb motor dysfunction improved in 65% of patients, lower limb motor dysfunction improved in 52% of patients, upper limb sensory dysfunction improved in 48% of patients, and sphincter dysfunction improved in 14.2% of patients. There was a significant positive correlation between preoperative and postoperative mJOA score at 1 month, 3 months, and 1 year after surgery. CONCLUSIONS: Minimal improvement occurred in the first month after CSM surgery to reach a peak at 3 months after surgery and steady improvement up to 1 year after surgery. Upper limbs recovered better and earlier than lower limbs and sphincter function. Preoperative severity of CSM is one of the main predictors of postoperative neurological outcome.

Multichannel facial nerve monitoring: value in detection of mechanically elicited electromyographic activity and prediction of postoperative outcome.

OBJECTIVE: To determine the value of using a multichannel facial nerve (FN) monitoring setup in detecting mechanically elicited EMG activity during vestibular schwannoma (VS) surgery. STUDY DESIGN: Prospective study. SETTING: Tertiary referral center. PATIENTS AND METHODS: This study was conducted on 42 patients operated for VS removal. The FN was monitored using a 5-channel setup with electrodes inserted in mentalis, o.oris, nasalis, o.oculi, and frontalis. The number of channels activated simultaneously in response to a particular event was recorded together with the amplitude of response on each muscle. EMG activity occurring simultaneously on all 5 channels was referred to as "all-channels activity." Postoperative FN function was assessed immediately and 1 year postoperatively using the House-Brackmann classification. RESULTS: The 5-channel setup detected a significantly higher number of mechanically elicited EMG activity than would have been possible using a 2-channel setup. The number and amplitude of EMG activity detected on the mentalis muscle was significantly higher compared with other muscles. Patients with higher percentage of events in which the mentalis fired while o.oris and o.oculi did not were more likely to develop a better long-term outcome. Positive correlation was found between the number of all-channels activity and postoperative outcome (p < 0.001). CONCLUSION: The use of a multichannel setup allowed earlier and efficient detection of mechanically elicited EMG activity. Including the mentalis muscle significantly increased the detection rate, which tended to reflect as improvement in the long-term outcome. The occurrence of all-channels activity should be considered a prompt warning sign.

Surgery for traumatic facial nerve paralysis: does intraoperative monitoring have a role?

The use of intraoperative facial nerve (FN) monitoring during surgical decompression of the FN is underscored because surgery is indicated when the FN shows more than 90 % axonal degeneration. The present study proposes including intraoperative monitoring to facilitate decision taking and provide prognostication with more accuracy. This prospective study was conducted on ten patients presenting with complete FN paralysis due to temporal bone fracture. They were referred after variable time intervals for FN exploration and decompression. Intraoperative supramaximal electric stimulation (2-3 mA) of the FN was attempted in all patients both proximal and distal to the site of injury. Postoperative FN function was assessed using House-Brackmann (HB) scale. All patients had follow-up period ranging from 7 to 42 months. Three different patterns of neurophysiological responses were characterized. Responses were recorded proximal and distal to the lesion in five patients (pattern 1); only distal to the lesion in two patients (pattern 2); and neither proximal nor distal to the lesion in three patients (pattern 3). Sporadic, mechanically elicited EMG activity was recorded in eight out of ten patients. Patients with pattern 1 had favorable prognosis with postoperative function ranging between grade I and III. Pattern 3 patients showing no mechanically elicited activity had poor prognosis. Intraoperative monitoring affects decision taking during surgery for traumatic FN paralysis and provides prognostication with sufficient accuracy. The detection of mechanically elicited EMG activity is an additional sign predicting favorable outcome. However, absence of responses did not alter surgeon decision when the nerve was found evidently intact.

First branchial cleft anomalies: presentation, variability and safe surgical management.

First branchial cleft (FBC) anomalies are uncommon. The aim of this retrospective clinical study is to describe our experience in dealing with these sporadically reported lesions. Eighteen cases presenting with various FBC anomalies managed surgically during an 8-year period at a tertiary referral medical institution were included. Ten were males (56 %) and eight females (44 %) with age range 3-18 years. Anomaly was right-sided in 12 cases (67 %). None were bilateral. Nine patients (50 %) had prior abscess incision and drainage procedures ranging from 1 to 9 times. Two also had previous unsuccessful surgical excisions. Clinical presentations included discharging tract openings in external auditory canal/conchal bowl (n = 9), periauricular (n = 6), or upper neck (n = 4); cystic postauricular, parotid or upper neck swellings (n = 5); and eczematous scars (n = 9). Three distinct anatomical types were encountered: sinuses (n = 7), fistulas (n = 6), and cysts (n = 5). Complete surgical excision required superficial parotidectomy in 11 patients (61 %). Anomaly was deep to facial nerve (FN) in three cases (17 %), in-between its branches in two (11 %) and superficial (but sometimes adherent to the nerve) in remaining cases (72 %). Continuous intraoperative electrophysiological FN monitoring was used in all cases. Two cases had postoperative temporary lower FN paresis that recovered within 2 months. No further anomaly manifestation was observed after 49.8 months' mean postoperative follow-up (range 10-107 months). This study has shown that awareness of different presentations and readiness to identify and protect FN during surgery is essential for successful management of FBC anomalies. Intraoperative electrophysiological FN monitoring can help in that respect.

Intraoperative electrophysiologic identification of the nervus intermedius.

OBJECTIVE: Although enormous attention has been directed to the localization and preservation of the facial nerve in acoustic neuroma surgery, the nervus intermedius has largely been ignored. In this article, we describe a method for intraoperative electrophysiologic identification of the nervus intermedius. STUDY DESIGN: Retrospective case review. SETTING: University hospital (tertiary care center). PATIENTS: Thirty-three patients who underwent intraoperative facial nerve monitoring for various cerebellopontine angle procedures. Recording electrodes were placed in the orbicularis oculi and orbicularis oris muscles. A constant-voltage stimulator was used to stimulate both the facial nerve and the nervus intermedius. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Electrophysiologic response after stimulation of the nervus intermedius. RESULTS: Stimulation of the nervus intermedius produced long-latency, low-amplitude response recorded only on the orbicularis oris channel. The response had a mean threshold 0.4 V, a mean latency of 11.1 ms, and a mean amplitude of 11.1 microV, all significantly different from responses to stimulation the facial nerve. CONCLUSION: Knowledge of electrophysiologic features of nervus intermedius stimulation can help protect the facial nerve during cerebellopontine angle surgery. The surgeon must recognize that stimulation of the nervus intermedius can cause electromyographic activity in the facial nerve monitoring channels, but the main trunk of the facial nerve may lie in entirely different location in the cerebellopontine angle.