Learning from EMG: semi-automated grading of facial nerve function

The current grading of facial nerve function is based on subjective impression with the established assessment scale of House and Brackmann (HB). Especially for research a more objective method is needed to lower the interobserver variability to a minimum. We developed a semi-automated grading system based on (facial) surface EMG-data measuring the facial nerve function of 28 patients with vestibular schwannoma surgery. The sEMG was recorded preoperatively, postoperatively and after 3–12 months. In addition, the HB grade was determined. After manual selection and preprocessing, the data were subjected to machine learning classificators (Logistic regression, SVM and KNN). Lateralization indices were calculated and multivariant machine learning analysis was performed according to three scenarios [differentiation of normal (1) and slight (2) vs. impaired facial nerve function and classification of HB 1-3 (3)]. The calculated AUC for each scenario showed overall good differentiation capability with a median AUC of 0.72 for scenario 1, 0.91 for scenario 2 and multiclass AUC of 0.74 for scenario 3. This study approach using sEMG and machine learning shows feasibility regarding facial nerve grading in perioperative VS-surgery setting. sEMG may be a viable alternative to House Brackmann regarding objective evaluation of facial function especially for research purposes.

The Offprint of an Abnormal Pre-Parotidectomy Electrodiagnostic Finding in a Normally Functioning Facial Nerve: Correlation with Intraoperative Findings, Histology and Postoperative Facial Nerve Function

The aim of this study was to search for associations between an electrodiagnostically abnormal but clinically normal facial nerve before parotidectomy and the intraoperative findings, as well as the postoperative facial nerve function. The records of all patients treated for parotid tumors between 2002 and 2021 with a preoperative House–Brackmann score of grade I but an abnormal electrophysiologic finding were studied retrospectively. A total of 285 patients were included in this study, and 222 patients had a benign lesion (77.9%), whereas 63 cases had a malignant tumor (22.1%). Electroneurographic facial nerve involvement was associated with nerve displacement in 185 cases (64.9%) and infiltration in 17 cases (6%). In 83 cases (29.1%), no tumor–nerve interface could be detected intraoperatively. An electroneurographic signal was absent despite supramaximal stimulation in 6/17 cases with nerve infiltration and in 17/268 cases without nerve infiltration (p < 0.001). The electrophysiologic involvement of a normal facial nerve is not pathognomonic for a malignancy (22%), but it presents a rather rare (~6%) sign of a “true” nerve infiltration and could also appear in tumors without any contact with the facial nerve (~29%). Of our cases, two thirds of those with an anatomic nerve preservation and facial palsy had already directly and postoperatively recovered to a major extent in the midterm.

An Evidence-Based Vestibular Schwannoma Surgical Outcome Grading Scale for Large-to-Giant Vestibular Schwannomas

Objectives: The objective of this study was to determine the relationship between facial nerve function and extent of resection (EOR) as outcomes in the surgical management of large vestibular schwannoma (VS) (≥ 2.5 cm maximal) and evaluate use of a new grading system that incorporates both outcomes.Methods: We conducted a systematic review of the electronic databases using different MeSH terms from 1990 to 2021. 5,623 patients from 56 studies were found appropriate for inclusion in the study. Surgical approach was reported in 5,144 patients, including translabyrinthine approach (TL) in 43.3% (n=2,225), retrosigmoid (RS) approach in 56.3% (n=2,899), retrolabyrinthine (RL) approach in 0.3% (n=16), and extended translabyrinthine (EX) approach in 0.1% (n=4). The proposed VS Grading System defines outcomes of gross total resection (GTR), near total resection (NTR) and subtotal resection (STR) with good facial nerve function [House-Brackmann (HB) Grade I-II] as Classes A, B and C respectively. Those with poor facial nerve outcome (HB III-VI) are graded as Classes D, E and F, respectively. Results:. As expected, patients with STR had a higher likelihood of better facial nerve outcomes (HB I-II) compared to NTR [Odds Ratio (OR): 7.30, 95%CI: 2.45-12.1, p=0.004] and GTR (OR: 9.61, 95%CI: 3.61-15.6, p=0.002), while NTR had better facial nerve outcome than GTR (OR: 1.5, 95%CI: 1.14-4.6, p<0.0001). A Class A result, representing the best possible outcome, was obtained in 55.8% of TL vs. 49.4% undergoing RS approach. Conclusion: Complete surgical resection with preservation of facial nerve function is the gold standard for large VS.

Complete Facial Paralysis Caused by Stabbing With a Car Key at the Stylomastoid Foramen

Non-iatrogenic traumatic facial paralysis is most common in intratemporal facial nerve injury caused by temporal bone fracture, followed by intraparotid facial nerve branch injury. Facial paralysis caused by injury to the extratemporal trunk of the facial nerve is extremely rare. We present a case of a 60-year-old man suffering from immediate complete left peripheral facial paralysis due to blunt transection of extratemporal trunk of facial nerve by stabbing with a car key. There was a facial nerve defect about 1 cm in length. The great auricular nerve was grafted to repair the facial nerve. Over 12 months, his facial nerve function improved to a House–Brackmann III/VI.

Vestibular schwannoma manifesting with hemifacial spasm in a young woman: clinical considerations and tumor removal with hearing preservation. 2-Dimensional operative video

Hemifacial spasm (HFS) is a rare presentation of vestibular schwannoma. The authors present their experience with a 27-year-old woman who presented with normal hearing and HFS, which was the single neurological manifestation of an 18-mm vestibular schwannoma. In this challenging situation, the treatment goals were maximal tumor removal with preservation of hearing and facial nerve function and cure of the HFS. The authors achieved these goals, performing complete tumor removal via a retrosigmoid approach, assisted with neurophysiological monitoring and a 45°-angle QEVO endoscope. In the video, they explain the clinical, radiological, and surgical considerations and demonstrate the surgical technique. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID2099

Retrosigmoid approach for giant cystic vestibular schwannoma: subperineural dissection technique for facial nerve preservation

In this illustrative video, the authors demonstrate retrosigmoid resection of a giant cystic vestibular schwannoma using the subperineural dissection technique to preserve facial nerve function. This thin layer of perineurium arising from the vestibular nerves is used as a protective buffer to shield the facial and cochlear nerves from direct microdissection trauma. A near-total resection was achieved, and the patient had an immediate postoperative House-Brackmann grade I facial nerve function. The operative nuances and pearls of technique for safe cranial nerve and brainstem dissection, as well as the intraoperative decision and technique to leave the least amount of residual adherent tumor, are demonstrated. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID21128

Defining clinically significant tumor size in vestibular schwannoma to inform timing of microsurgery during wait-and-scan management: moving beyond minimum detectable growth

OBJECTIVE Detection of vestibular schwannoma (VS) growth during observation leads to definitive treatment at most centers globally. Although ≥ 2 mm represents an established benchmark of tumor growth on serial MRI studies, 2 mm of linear tumor growth is unlikely to significantly alter microsurgical outcomes. The objective of the current work was to ascertain where the magnitude of change in clinical outcome is the greatest based on size. METHODS A single-institution retrospective review of a consecutive series of patients with sporadic VS who underwent microsurgical resection between January 2000 and May 2020 was performed. Preoperative tumor size cutpoints were defined in 1-mm increments and used to identify optimal size thresholds for three primary outcomes: 1) the ability to achieve gross-total resection (GTR); 2) maintenance of normal House-Brackmann (HB) grade I facial nerve function; and 3) preservation of serviceable hearing (American Academy of Otolaryngology–Head and Neck Surgery class A/B). Optimal size thresholds were obtained by maximizing c-indices from logistic regression models. RESULTS Of 603 patients meeting inclusion criteria, 502 (83%) had tumors with cerebellopontine angle (CPA) extension. CPA tumor size was significantly associated with achieving GTR, postoperative HB grade I facial nerve function, and maintenance of serviceable hearing (all p < 0.001). The optimal tumor size threshold to distinguish between GTR and less than GTR was 17 mm of CPA extension (c-index 0.73). In the immediate postoperative period, the size threshold between HB grade I and HB grade > I was 17 mm of CPA extension (c-index 0.65). At the most recent evaluation, the size threshold between HB grade I and HB grade > I was 23 mm (c-index 0.68) and between class A/B and C/D hearing was 18 mm (c-index 0.68). Tumors within 3 mm of the 17-mm CPA threshold displayed similarly strong c-indices. Among purely intracanalicular tumors, linear size was not found to portend worse outcomes for all measures. CONCLUSIONS The probability of incurring less optimal microsurgical outcomes begins to significantly increase at 14–20 mm of CPA extension. Although many factors ultimately influence decision-making, when considering timing of microsurgical resection, using a size threshold range as depicted in this study offers an evidence-based approach that moves beyond reflexively recommending treatment for all tumors after detecting ≥ 2 mm of tumor growth on serial MRI studies.

Effect of Penetration Electroacupuncture Combined with Intermediate Frequency Electrotherapy, Facial Acupoint Massage, and Cervical Reduction on Facial Nerve Function and Curative Effect of Senile Refractory Facial Paralysis

Objective. This study aimed to explore the curative effects on senile refractory facial paralysis treated by penetration electroacupuncture combined with intermediate frequency electrotherapy, facial acupoint massage, and cervical reduction on facial nerve. Methods. 106 elderly patients with intractable facial paralysis that were retrospectively analyzed were all admitted from January 2019 to June 2020. The 106 patients were evenly divided into 2 groups according to the treatment method. The control group was treated with penetration electroacupuncture, while the observation group was treated with penetration electroacupuncture plus intermediate frequency electrotherapy + facial acupoint massage + cervical reduction treatment. Then, House–Brackmann (H-B) facial nerve function evaluation, RPA score, TCM syndrome score, disease remission rate, and incidence of adverse events were evaluated and compared between the two groups. Results. After 4 weeks of treatment, the H-B facial nerve function grading in the observation group was better than that in the control group ( P < 0.05). And the disease remission rate after 1 week, 2 weeks, and 4 weeks of treatment was higher than that in the control group ( P < 0.05). Meanwhile, the TCM syndrome score and RPA score after 2 weeks and 4 weeks of treatment were better than that in the control group ( P < 0.05). Conclusion. For the elderly patients with refractory facial paralysis, the application of the combined treatment that penetration electroacupuncture + medium frequency electrotherapy + facial acupoint massage + cervical adjustment can significantly improve the facial nerve function and reduce various diseases, and the effect of this combined treatment plan is more significant than that of penetration electroacupuncture treatment.