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

Abstract

To the Editor: We read with great interest the article by Thirumala et al1 titled “The Utility of intraoperative Lateral Spread Recording in Microvascular Decompression for Hemifacial Spasm: A Systematic Review and Meta-Analysis,” which was recently published in Neurosurgery. The authors reported that the intraoperative lateral spread response (LSR) has a high specificity and moderate sensitivity in predicting the spasm-free status following microvascular decompression. Their analysis revealed that intraoperative LSR disappearance or persistence could predict the patient's outcome at discharge, 3 mo postoperatively, and 1 yr postoperatively: approximately 90% of the patients with LSR disappearance would be asymptomatic, and approximately 40% of the patients with LSR persistence would remain symptomatic. We appreciate the attempt by Thirumala et al1 to clarify the correlation between intraoperative LSR findings and the outcome of microvascular decompression. Their analysis will broaden the extent of perception of LSR. We would like to make some noteworthy points regarding the interpretation of intraoperative LSR findings. Due to the complexity and inhomogeneity of the surgical procedure, we often face unusual circumstances in our practice. In a considerable number of cases, LSR disappears even before we decompress the conflicting zone.2 This may be because cerebrospinal fluid drainage or adjacent structure manipulation changes the position of the relevant structures. We cannot rely on the adequacy of the surgical procedure for LSR disappearance in these cases. It also seems impossible to predict the clinical outcome from LSR disappearance in these cases. In contrast, some patients show delayed LSR disappearance, which does not coincide with neurovascular decompression, even after the end of the operation.3 Although the mechanism underlying this phenomenon is not completely understood yet, previous electrophysiological studies suggest that it is because LSR is related not only to neurovascular conflict but also to secondary neural injury.4-6 We cannot notice LSR disappearance when it occurs after the end of surgery or after LSR monitoring. An experienced surgeon who completes the procedure in less time or a team that stops monitoring LSR after the main procedure would miss the LSR disappearance easily. Lastly, we need to examine whether intraoperative LSR disappearance is sustained. A study reported that intraoperatively disappeared LSR had reappeared at the postoperative follow-up.7 Although the reappearance of LSR does not affect the interpretation of results of the study by Thirumala et al,1 intraoperative LSR findings have a limited impact on the prediction of patients' long-term clinical outcome. We think that it is better to consider these aspects of LSR when planning research because the main independent variable in the study was the disappearance or persistence of LSR. Further studies with a more systematized structure and electrophysiologically oriented techniques could expand our knowledge, the neurosurgical personnel to improve the outcome and quality of life of patients with hemifacial spasm. Disclosures The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.