Endoscopic Microvascular Decompression for Hemifacial Spasm: A Technical Case Report Demonstrating the Benefits of the Angled Endoscope and Intraoperative Neuromonitoring

A 57-year-old female with eight years of hemifacial spasm (HFS) underwent endoscopic microvascular decompression (MVD) of the facial nerve. Baseline stimulation of the zygomatic branch of the facial nerve activated at 1.2 mA. Lateral spread response (LSR) to the buccal and mandibular branches was observed at 2.2 mA. A straight endoscope was used to enter the cerebellopontine angle, allowing for visualization of the vestibulocochlear and facial nerve. Neurovascular compression was not clearly identified. A 30-degree endoscope was directed medially/inferiorly and compression at the root entry zone was identified and decompressed. Subsequent LSR to the buccal/mandibular branches was seen at 3.2 mA/3.6 mA, respectively. Additional vascular compression was suspected given persistent LSR. The 30-degree endoscope was directed laterally. Compression was seen at the porus acustics and decompressed. Subsequent LSR to the buccal/mandibular branches was not observed until 9.8 mA, indicating good decompression. The patient tolerated the procedure well with complete resolution of her symptoms and remains spasm-free as of three months post-procedure without a hearing deficit. The 30-degree endoscope enabled visualization of pathology that was not easily seen at 0-degree. Additionally, LSR indicated persistent nerve compression following root entry zone decompression. Subsequent distal decompression resulted in greater LSR reduction. This case report suggests that MVD for HFS may yield better results with both proximal and distal decompression of the seventh nerve, and this type of decompression can benefit from endoscopic visualization.