A Rare Potential Compression Can Be Avoided by Lateral Spread Response Recordings During Microvascular Decompression for Hemifacial Spasm.

The authors report a 34-year-old female with hemifacial spasm who was identified as a candidate for microvascular decompression. Lateral spread response (LSR) was not recorded at first because of anatomical shift of neurovascular relationship after drainage of cerebrospinal fluid, but they reappeared only after a piece of shredded gelatin sponge was placed near the posteroinferior cerebellar artery to expand surgical field. As the authors removed the gelatin sponge, the LSRs disappeared instantly. Subsequently, the authors put some soft shredded Teflon between the offending vessel and brainstem. Since then the authors did not find LSRs anymore. Clinical follow-up had been carried out with a questionnaire from 1 week to 3 months postoperatively, and the patient was cured with no complications. This report presented that the gelatin sponge placed in an inappropriate position resulting in compression potentially leading to the opposite effect of treatment. Such kind of excessive operation could be avoided by electrophysiological monitoring.