Primary hemifacial spasm: a neurophysiological study.

Area of Science:

• Neurology
• Neurophysiology

Background:

• Primary hemifacial spasm (HFS) is a neurological disorder characterized by involuntary contractions of facial muscles.
• Understanding the underlying neurophysiological mechanisms of HFS is crucial for diagnosis and treatment.

Purpose of the Study:

• To evaluate blink reflex abnormalities in patients with primary hemifacial spasm.
• To compare reflex responses in HFS patients with a healthy control group.

Main Methods:

• Evaluated 53 primary hemifacial spasm cases and a control group.
• Utilized percutaneous electrical stimulation of the supraorbital nerve (trigemino-facial reflex) and facial nerve (facio-facial reflex).
• Assessed R2 response latency for shortened (hyperactivity) or delayed (hypoactivity) patterns.

Main Results:

• Abnormal blink reflex responses were observed in 36 out of 53 HFS cases.
• Common findings included facial nerve impairment (delayed R2, facio-facial reflex) and trigeminal-facial hyperactivity (shortened R2, trigemino-facial reflex).
• Five cases exhibited hyperactivity in both reflex pathways.

Conclusions:

• Results indicate a high prevalence of hyperexcitability, likely in the facial nucleus, co-occurring with peripheral facial nerve involvement in primary hemifacial spasm.
• Blink reflex testing provides valuable insights into the pathophysiology of HFS.