Movement disorder

A movement disorder is a neurological condition that causes either too much involuntary movement or too little voluntary movement, arising from problems in the brain's motor circuits.

Hypokinetic disorders, of which Parkinson's disease is the main example, produce slowness, rigidity, tremor at rest and reduced facial expression. Hyperkinetic disorders include essential tremor, dystonia (sustained twisting postures), chorea as in Huntington's disease, tics as in Tourette syndrome, myoclonus, and the dyskinesia that can develop after years of levodopa therapy. Most involve the basal ganglia and cerebellum, and the endocannabinoid system is unusually dense in those regions.

Neurologists diagnose movement disorders by observing the movement's speed, pattern, triggers and response to medication, supported by family history and, in some cases, genetic testing or brain imaging. Rating scales such as the Unified Parkinson's Disease Rating Scale track progression. Cannabinoids have been studied in animal models and small trials for Parkinson's symptoms, Huntington's chorea, Tourette tics and dyskinesia, with mixed and inconclusive results, and no cannabinoid has an approved use for any movement disorder.