Prognostic value of lateral spread response during microvascular decompression for hemifacial spasm

Objective This study aimed to investigate the prognostic value of the lateral spread response (LSR) for predicting surgical outcomes following microvascular decompression (MVD) in patients with hemifacial spasm. Methods Seventy-three patients with hemifacial spasm underwent MVD with intraoperative LSR monitoring. Surgical outcomes were evaluated 1 week and 1 year after MVD and correlations between LSR characteristics and surgical outcomes were analyzed. Results The LSR disappeared completely in 61 patients during surgery (Group A; prior to insertion of Teflon felt pledgets in 11, after insertion of pledgets in 50), disappeared partially in nine patients (Group B), and remained unchanged in three patients (Group C). Fifty-five patients showed short-term and 61 patients showed long-term clinical cures during the follow-up period. The short-term and long-term cure rates were significantly higher in Group A than in Group C. There was no correlation between the time of complete LSR disappearance and surgical outcomes. Conclusions Disappearance of the LSR during MVD is correlated with the surgical outcomes. Intraoperative LSR monitoring is a reliable approach for predicting the prognosis of hemifacial spasm following MVD, but the time at which LSR disappears is not a prognostic indicator.