Iatrogenic parkinsonism in Huntington's chorea

Area of Science:

• Neuroscience
• Pharmacology
• Clinical Neurology

Background:

• Huntington's Chorea is a progressive neurodegenerative disorder.
• Tetrabenazine is a commonly used treatment for chorea associated with Huntington's disease.
• Concurrent use of antipsychotics with tetrabenazine has been reported as safe in previous literature.

Observation:

• A 63-year-old woman with a 19-year history of Huntington's Chorea, successfully treated with tetrabenazine for 9 years, developed acute parkinsonism.
• The patient received two doses of chlorpromazine for a vascular headache during a hospital admission.
• Within hours of chlorpromazine administration, she became mute, rigid, and unable to move or swallow.

Findings:

• The patient was diagnosed with severe drug-induced parkinsonism.
• Intramuscular benztropine mesylate led to a dramatic and immediate improvement in symptoms.
• Discontinuation of both chlorpromazine and tetrabenazine resulted in complete resolution of parkinsonian symptoms.
• Restarting tetrabenazine alone after 48 hours controlled her Huntington's Chorea without recurrence of parkinsonism.

Implications:

• This case suggests caution is warranted when co-administering chlorpromazine (an antipsychotic) with tetrabenazine, even in patients who have previously tolerated them separately.
• Early recognition and treatment with anticholinergic agents like benztropine mesylate are crucial for managing drug-induced parkinsonism.
• Further research may be needed to elucidate the specific mechanisms underlying this adverse drug interaction and to refine treatment guidelines for Huntington's Chorea patients on combined therapies.