11th August 2024

Other causes of parkinsonism

Drug-induced parkinsonism

Drug-induced parkinsonism is the second most common cause of parkinsonism after idiopathic Parkinson’s disease. There are a range of different medications that have been identified as triggers including calcium channel blockers, tetrabenazine and metoclopramide, but most commonly it is due to antipsychotic medications resulting in iatrogenic inhibition of dopamine. It is normally more rapid in onset and symmetrical given the drug will affect both sides of the brain equally, with tremor a less prominent feature compared to idiopathic Parkinson’s disease. DaT imaging can help differentiate drug-induced parkinsonism from idiopathic PD or Parkinson’s plus syndromes, as it will normally be negative in drug-induced parkinsonism. Treatment involves stopping the offending drug if possible and/or using antimuscarinics such as procyclidine, benztropine or trihexyphenidyl (benzhexol).

Vascular parkinsonism

Vascular parkinsonism is a clinical syndrome secondary to vascular insults to the basal ganglia. The predominant feature is gait disturbance known as lower body parkinsonism, along with dementia, pyramidal signs and incontinence. Symptoms are normally symmetrical and progress in a stepwise manner. MRI imaging in these patients will typically show significant small vessel disease or basal ganglia lacunar infarcts. This group of patients have minimal response to dopamine therapy if at all. Treatment involves managing vascular risk factors to reduce the risk of disease progression.