Predicting Early Loss of Lateral Spread Response before Decompression in Hemifacial Spasm Surgery

Recent studies have shown the evocation of lateral spread response (LSR) due to the compression of the facial nerve in hemifacial spasm (HFS). Intraoperative monitoring (IOM) of LSR could help locate neurovascular conflicts and confirm adequate micro-vascular decompression (MVD) while treatment of hemifacial spasm (HFS). However, studies on early LSR loss before decompression in HFS surgery are sparse, indicating the need to understand various perceptions on it. Therefore, we retrospectively analyzed 50 adult HFS patients who underwent MVD during the period of September 2018–June 2021. We employed IOM combining traditional LSR (tLSR) and dual LSR (dLSR). One patient was excluded owing to the lack of LSR induction throughout the surgery, while 49 were divided into groups A (n = 14) and B (n = 35), designated as with or without early LSR loss groups, respectively, and offending vessels were analyzed. The mean age of group A patients was significantly younger (47.8 ± 8.6) than that of group B (53.9 ± 10.6) (p = 0.0393). The significant predominating offending vessel in group A was the anterior inferior cerebellar artery (AICA, 78.57%). However, group B included those with AICA (28.57%), posterior inferior cerebellar artery (PICA, 22.86%), vertebral artery (VA) involved (25.71%), and combined AICA and PICA (22.86%). Group B exhibited poorer clinical outcomes with more complications. Conclusively, early LSR loss might occur in the younger population, possibly due to the AICA offending vessel. The compression severity of offending vessels may determine the occurrence of early LSR loss.

The novel prognostic value of postoperative follow-up lateral spread response after microvascular decompression for hemifacial spasm

OBJECTIVE The lateral spread response (LSR) is an aberrant electrophysiological response in which a stimulus on one branch of the facial nerve spills over to other branches of the nerve, which can be captured by electrodes near each branch. The authors performed this study to evaluate the prognostic value of the follow-up LSR with a sufficient time interval from intraoperative LSR (IO-LSR) after microvascular decompression (MVD) for hemifacial spasm (HFS), excluding the interference of various intraoperative situations. METHODS A total of 247 patients treated with MVD for HFS between June 2011 and March 2019 were enrolled in this study. The IO-LSR was routinely evaluated in all patients. The LSR was checked again on postoperative day (POD) 2 after surgery (POD2-LSR). A total of 228 patients (92.3%) were considered cured at the last clinical follow-up. RESULTS The IO-LSR disappeared in 189 patients (76.5%), and among them, 181 patients (95.8%) were cured 1 year after surgery. The POD2-LSR disappeared in 193 patients (78.1%), and 185 patients (95.9%) among them were cured. Among the 189 patients in which the IO-LSR disappeared, the POD2-LSR reappeared in 26 patients (13.8%). In contrast, the POD2-LSR disappeared in 30 (51.7%) of 58 patients for whom the IO-LSR continued at the end of surgery. When classified into groups according to the status of the IO-LSR and POD2-LSR, in the group of patients in whom both LSRs disappeared, the cure rate was 98.2%, which was significantly higher than that of the other 3 groups (p < 0.05, Cochran-Armitage trend test). The use of both LSRs was found to be significantly associated with better predictability (p < 0.05, McNemar’s test). CONCLUSIONS Postoperative follow-up LSR examination may be beneficial in predicting clinical outcomes after MVD for HFS, especially when considered together with IO-LSR.

Hemifacial Spam: Endoscopic Assistance in Facial Nerve Decompression With Lateral Spread Response Corroboration: 2-Dimensional Operative Video

This video depicts the case of a 48-yr-old female with 3 yr of progressive left hemifacial spasm (HFS) refractory to medication. Magnetic resonance imaging showed a large anterior inferior cerebellar artery (AICA) and also a labyrinthine artery loop around the facial nerve (FN) root exit zone. A large bony eminence was also noted in the superior and lateral aspects of the porous acousticus (PA). She preferred surgery if “cure” was possible in lieu of Botox injections. A left retro sigmoid craniotomy was performed with brainstem auditory evoked responses (BAERs) and FN monitoring along with lateral spread response (LSR) assessment. The large bony prominence was drilled in its lateral aspect. Despite this, visualization was still limited and therefore we utilized a 30-degree-angled endoscope to observe the vessels caudal and cranial to the FN. This view prompted us to then drill further at the PA to decompress the FN as well as mobilize the labyrinthine artery away from the nerve. The LSR showed a dramatic improvement when FN decompression was accomplished, and then a further improvement with arterial mobilization and Teflon pledget placement. The BAERS remained at baseline throughout. FN function and hearing were intact on postoperative clinical assessment. Her symptomatic improvement was recorded at 12 mo after surgery. This video illustrates a more complex case of microvascular decompression with skull base concepts and techniques. The patient provided consent for the procedure and use of her images and operative video for publication.

The Utility of Intraoperative Lateral Spread Recording in Microvascular Decompression for Hemifacial Spasm: A Systematic Review and Meta-Analysis

BACKGROUND Microvascular decompression (MVD) is the surgical treatment of choice for hemifacial spasm (HFS). During MVD, monitoring of the abnormal lateral spread response (LSR), an evoked response to facial nerve stimulation, has been traditionally used to monitor adequacy of cranial nerve (CN) VII decompression. OBJECTIVE To assess the utility of LSR monitoring in predicting spasm-free status after MVD postoperatively. METHODS We searched PubMed, Web of Science, and Embase for relevant publications. We included studies reporting on intraoperative LSR monitoring during MVD for HFS and spasm-free status following the procedure. Sensitivity of LSR, specificity, diagnostic odds ratio, and positive predictive value were calculated. RESULTS From 148 studies, 26 studies with 7479 patients were ultimately included in this meta-analysis. The final intraoperative LSR status predicted the clinical outcome of MVD with the following specificities and sensitivities: 89% (0.83- 0.93) and 40% (0.30- 0.51) at discharge, 90% (0.84-0.94) and 41% (0.29-0.53) at 3 mo, 89% (0.83-0.93) and 40% (0.30-0.51) at 1 yr. When LSR persisted after MVD, the probability (95% CI) for HFS persistence was 47.8% (0.33-0.63) at discharge, 40.8% (0.23-0.61) at 3 mo, and 24.4% (0.13-0.41) at 1 yr. However, when LSR resolved, the probability for HFS persistence was 7.3% at discharge, 4.2% at 3 mo, and 4.0% at 1 yr. CONCLUSION Intraoperative LSR monitoring has high specificity but modest sensitivity in predicting the spasm-free status following MVD. Persistence of LSR carries high risk for immediate and long-term facial spasm persistence. Therefore, adequacy of decompression should be thoroughly investigated before closing in cases where intraoperative LSR persists.