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Related Experiment Videos

Cryptogenic hemifacial spasm. A neurophysiological study.

G Roth1, M R Magistris, P Pinelli

  • 1Electromyographic Unit, University Hospital, Geneva, Switzerland.

Electromyography and Clinical Neurophysiology
|October 1, 1990
PubMed
Summary
This summary is machine-generated.

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This study investigates hemifacial spasm (HFS), suggesting abnormal nerve axon connections (ephapses) and facial nucleus hyperexcitability contribute to the condition. Findings indicate ephaptic transmission and F-responses play key roles in HFS.

Area of Science:

  • Neuroscience
  • Neurology
  • Clinical Electrophysiology

Background:

  • The underlying cause of hemifacial spasm (HFS) remains debated, with theories including axono-axonal ephaptic transmission and abnormal facial nucleus hyperexcitability.
  • Delayed responses (DRs) are a key neurophysiological marker in HFS, characterized by indirect pathways and long latencies.
  • DRs can manifest as distant responses in unrelated muscles or direct responses in stimulated muscles.

Purpose of the Study:

  • To investigate the neurophysiological mechanisms of cryptogenic hemifacial spasm (HFS).
  • To differentiate between ephaptic transmission and facial nucleus hyperexcitability as causes of HFS.
  • To analyze the characteristics of delayed responses (DRs) in HFS patients.

Main Methods:

  • Studied 99 single all-or-none delayed responses (DRs) from 24 patients with cryptogenic HFS.

Related Experiment Videos

  • Utilized threshold stimulation of facial nerve branches or trunk.
  • Employed a collision technique with paired stimuli to analyze double discharges (DDs) and F-responses.

    • Main Results:

    • Eighty-eight distant DRs were analyzed, with 54 frequently showing double or multiple discharges (3-7 ms interval).
    • Collision testing revealed back-waves in 12/20 DDs, indicating proximal ectopic re-excitation or alpha cell back-firing (F-response).
    • F-waves were more prevalent in HFS patients compared to controls or other facial pathologies.
    • Eleven DRs in stimulated muscles showed characteristics suggesting interconnected axons via ephapses and potential alpha cell involvement.

    Conclusions:

    • Findings support the hypothesis that hemifacial spasm (HFS) involves interconnected axons via uni- and bidirectional ephapses.
    • Self-sustained repetitive firing, driven by re-excitations at ephapse sites and cellular levels (F-responses), contributes to HFS.
    • Modulation of alpha cell excitability influences the severity of HFS phenomena.