title: Feasibility of eliciting the H reflex in the masseter muscle in patients under general anesthesia.
abstract: OBJECTIVE
  To explore the feasibility of eliciting the brainstem H reflex in the masseter muscle in patients under general anesthesia.
  
  
  METHODS
  We electrically stimulated the masseteric nerve, a branch of the trigeminal nerve, and recorded ipsilateral masseteric and temporalis muscle responses. We tested eight patients who presented with trigeminal neuralgia; one patient had a temporal bone tumor and one patient had a brainstem arteriovenous malformation. All responses were elicited when patients were under general anesthesia and before the initiation of surgery.
  
  
  RESULTS
  The H reflex in the masseter muscle was reliably elicited in 70% of the patients. The reflexes met the usual criteria for the H reflex because they were elicited below the threshold of the direct M response, and their amplitudes decreased when the M response increased with stronger stimuli. The mean onset latencies of the masseter H reflex and the M response were 5.4±1.3ms and 2.6±0.6ms, respectively.
  
  
  CONCLUSIONS
  In the present study, we provide evidence of the feasibility of eliciting the H reflex in the masseter muscles of patients under general anesthesia.
  
  
  CONCLUSIONS
  The H reflex of the masseter muscle may represent a new method available for intraoperative monitoring. Specifically, this method may be important for the monitoring of brainstem functional integrity, particularly in the midbrain and mid-pons, in addition to the trigeminal nerve path.
authors.affiliation: Department of Intraoperative Neurophysiology, Mount Sinai West Hospital, New York, NY, USA. Electronic address: su1969july@outlook.com.
authors.forename: Sedat
authors.initials: S
authors.lastname: Ulkatan
authors.affiliation: Department of Intraoperative Neurophysiology, Mount Sinai West Hospital, New York, NY, USA.
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Jaramillo
authors.affiliation: Department of Intraoperative Neurophysiology, Mount Sinai West Hospital, New York, NY, USA.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Téllez
authors.affiliation: Department of Neurosurgery, Mount Sinai West Hospital, New York, NY, USA.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Goodman
authors.affiliation: Department of Intraoperative Neurophysiology, Mount Sinai West Hospital, New York, NY, USA.
authors.forename: Vedran
authors.initials: V
authors.lastname: Deletis
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General / Q000379:methods*; D018681:Anesthetics, General / Q000008:administration & dosage; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology; D002648:Child; D005240:Feasibility Studies; D005260:Female; D006181:H-Reflex / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods*; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects / Q000502:physiology*; D008875:Middle Aged
chemical_list: D018681:Anesthetics, General
keywords: Anesthesia; Brainstem; H reflex; Intraoperative monitoring; Masseter; Trigeminal