# Lateral Spread Response in Hemifacial Spasm: Physiological Mechanisms, Intraoperative Utility, and Prognostic Significance

## TL;DR

This paper reviews the lateral spread response in hemifacial spasm, focusing on its physiological basis and role in surgical outcomes.

## Contribution

The paper provides a comprehensive review of the lateral spread response's physiological mechanisms and intraoperative significance in hemifacial spasm surgery.

## Key findings

- Lateral spread response is a key electrophysiological marker during hemifacial spasm surgery.
- Its disappearance indicates successful microvascular decompression.
- More research is needed to fully understand its physiological origin.

## Abstract

Facial nerve compression by blood vessels near the brainstem can cause hemifacial spasm (HFS). There are two treatment options for this condition: botulinum toxin and surgical microvascular decompression (MVD). During microvascular decompression, the facial nerve is separated from the offending vessel, and intraoperative neuromonitoring in these patients demonstrates abnormal muscle response (AMR), which is known as the lateral spread response (LSR). Though the disappearance of lateral spread response is a hallmark of successful microvascular decompression, little information is available about its physiological origin and diagnostic utility. In the present review, we have attempted to address the aforementioned caveats about lateral spread response with an emphasis on the intraoperative utility and diagnostic role of this electrophysiological phenomenon.