Hemimasticatory spasm associated with localized scleroderma and facial hemiatrophy

Area of Science:

• Neurology
• Ophthalmology

Background:

• Hemimasticatory spasm is a rare condition characterized by involuntary contractions of the masticatory muscles.
• It is often associated with other neurological or autoimmune conditions.

Observation:

• A 37-year-old woman presented with a 3-year history of right masseter muscle spasms, localized scleroderma, and facial hemiatrophy.
• Electrophysiological studies showed an absent masseter reflex and silent period on the affected side.
• MRI revealed masseter hypertrophy and subcutaneous fatty tissue atrophy.

Findings:

• Needle electromyography indicated abnormal motor unit potentials consistent with hemifacial spasm.
• Focal demyelination of trigeminal nerve motor branches due to deep tissue changes is proposed as the underlying mechanism.
• Local injection of botulinum toxin A successfully resolved the patient's symptoms.

Implications:

• This case highlights a potential mechanism for hemimasticatory spasm involving trigeminal nerve demyelination.
• Botulinum toxin A offers a viable treatment option for managing this debilitating condition.
• Further research into the pathogenesis of hemimasticatory spasm is warranted.