Movement Disorders and Neurodegenerative Disease
Questions here separate idiopathic Parkinson disease from its mimics and test drug choices in tremor, dystonia and chorea.
Parkinson disease
Diagnosis requires bradykinesia plus rest tremor or rigidity, with asymmetric onset and a good levodopa response. Levodopa with a decarboxylase inhibitor is the most effective symptomatic therapy; motor fluctuations are managed with dose fractionation, dopamine agonists, MAO-B inhibitors or device-aided therapy.
Red flags for atypical parkinsonism
- Early falls, vertical supraspinal gaze palsy and backward falls suggest progressive supranuclear palsy.
- Prominent dysautonomia with cerebellar signs suggests multiple system atrophy.
- Early dementia with visual hallucinations and REM sleep behaviour disorder suggests dementia with Lewy bodies.
- Asymmetric rigidity with apraxia and alien limb suggests corticobasal syndrome.
Tremor and other hyperkinesias
Essential tremor is bilateral postural and kinetic, alcohol responsive, with no rest component; propranolol and primidone are first line. Huntington disease is autosomal dominant with CAG expansion, chorea, cognitive decline and psychiatric features. Focal dystonia such as cervical dystonia or blepharospasm responds to botulinum toxin. Always check ceruloplasmin and copper in young-onset parkinsonism to exclude Wilson disease.
Worked example
A 68-year-old has 18 months of right hand rest tremor, micrographia and right arm rigidity with an excellent levodopa response, initially diagnosed as Parkinson disease. Two years later he has recurrent falls and cannot look down. The vertical gaze palsy and early falls change the diagnosis to progressive supranuclear palsy, and levodopa should not be escalated indefinitely.
Traps
Calling essential tremor Parkinson disease; missing drug-induced parkinsonism from antipsychotics or metoclopramide; stopping levodopa abruptly, which can precipitate a neuroleptic malignant-like syndrome.