Abstract
Objective
Intraoperative neuromonitoring (IONM) using lateral spread response (LSR) has been
mostly studied as a tool in optimizing the benefits of microvascular decompression
(MVD) in cases of hemifacial spasm (HFS). Although evidence suggests its utility as
a prognostic marker, our experience with the same remains otherwise. The significance
of the time of disappearance of LSR is also less studied as a factor determining the
outcome. This is a pilot study involving a series of patients operated on for HFS
using MVD. The prime objectives of the study are: (1) to review LSR in HFS as a prognosticator
of outcome and (2) to study the significance of time of disappearance of LSR and its
correlation with outcome.
Materials and Methods
Patients operated on for HFS with MVD under IONM guidance, between August 2022 and
June 2024, were observed in the postoperative period in three phases—immediate, early,
and late. The outcomes were divided into—complete, partial or no improvement, and
recurrence. The results were studied against the corresponding findings of LSR in
those cases.
Results
A total of six patients were studied. Of these, three were males and three were females.
Intraoperatively, all the patients showed complete loss of LSR after separating the
compressing vessel from affected facial nerve. In the immediate postoperative phase,
two out of six patients had incomplete improvement in symptoms which later improved
in one of the patients in early postoperative phase. The remaining one patient who
had partial improvement of symptoms had increased symptoms within 3 months of follow-up.
Conclusion
Although LSR monitoring indicates adequate facial nerve decompression, in our experience,
LSR disappearance was not congruent with the absence of symptoms in postoperative
phase of HFS. The time of disappearance of the LSR waveform intraoperatively has a
significant role in determining the outcome.
Keywords
lateral spread response - hemifacial spasm - microvascular decompression
