Hemifacial Spasm Does Occur at Rest
Hemifacial spasm is characterized by involuntary contractions that occur both at rest and during movement, distinguishing it from other facial movement disorders. 1, 2
Clinical Characteristics of Hemifacial Spasm
Hemifacial spasm presents as involuntary, paroxysmal contractions of muscles innervated by the facial nerve that are persistent and can occur at any time, including during rest. 1, 2 The condition is characterized by:
- Brief or persistent involuntary contractions that are unilateral, intermittent, and irregular, affecting muscles on one side of the face 2, 3
- Tonic or clonic contractions that typically begin in the lower eyelid and progress to involve the cheek and perioral region 3, 4
- Continuous nature that can interfere with daily activities including reading and driving, as well as causing involuntary eye closure 1, 3
Distinguishing Features from Bell's Palsy Grading
The House-Brackmann grading system for facial nerve function explicitly addresses hemifacial spasm in its assessment criteria, confirming that hemifacial spasm can be present at rest. 5 Specifically:
- Grade 2 (Mild dysfunction) notes "no synkinesis, contracture, or hemifacial spasm" at rest with normal symmetry 5
- Grade 3 (Moderate dysfunction) describes "noticeable but not severe synkinesis, contracture, and/or hemifacial spasm" even with normal symmetry and tone at rest 5
- Grade 4 (Moderately severe dysfunction) includes patients with "synkinesis, mass action, and/or hemifacial spasm severe enough to interfere with function" despite normal symmetry and tone at rest 5
This grading system demonstrates that hemifacial spasm is assessed as a feature that can be present even when the face appears symmetric at rest, confirming that the spasms themselves occur during rest periods. 5
Pathophysiology Supporting Rest Occurrence
The underlying mechanism explains why spasms occur at rest:
- Vascular compression of the facial nerve at the root exit zone causes ephaptic transmission and hyperexcitability of the facial nerve, leading to spontaneous muscle contractions independent of voluntary movement 6, 2
- The pulsatile compression creates continuous irritation that triggers involuntary contractions regardless of facial muscle activity 6
- This differs fundamentally from voluntary movement disorders, as the pathology creates autonomous nerve firing 2, 4
Clinical Implications
Understanding that hemifacial spasm occurs at rest is critical for:
- Differential diagnosis: Distinguishing hemifacial spasm from facial tics or voluntary movements that only occur with activity 4
- Impact assessment: Recognizing that patients experience symptoms continuously, including during social situations and sleep, affecting quality of life 1, 3
- Treatment planning: Both botulinum toxin injections and microvascular decompression target the underlying pathology that causes spontaneous contractions, not just movement-related symptoms 7, 2