Parkinsonism
Page most recently updated 7 September 2026
This page reviews the differential diagnosis of parkinsonism in the context of presentations with psychiatric symptoms, focusing on conditions in which both may occur together. It begins by defining parkinsonism and outlining initial diagnostic considerations before examining the broader differential diagnosis.
Description
Parkinsonism is a clinical syndrome characterised by bradykinesia accompanied by either rest tremor or rigidity.
● Bradykinesia refers to slowness of movement accompanied by either (1) a progressive reduction in speed or amplitude, or (2) increasing hesitations or interruptions with repetitive movements.
● Rigidity is resistance to passive movement of a relaxed limb that is independent of the speed of passive movement and may have a characteristic “lead-pipe” quality.
● Parkinsonian tremor is typically a rest tremor (i.e., occurring in a relaxed limb) at approximately 4–6 Hz that diminishes or disappears with voluntary movement.
Initial considerations
Parkinson disease (PD) is the most common cause of parkinsonism. Drug-induced parkinsonism is the second most common cause of parkinsonism and, after Parkinson disease, is often the most important initial alternative diagnosis to consider. An additional diagnostic consideration is that other neurodegenerative parkinsonian disorders, including dementia with Lewy bodies (DLB) ➚, progressive supranuclear palsy (PSP) ➚ and multiple system atrophy (MSA) ➚, can closely resemble Parkinson disease early in their course, with their distinguishing clinical features often becoming apparent only as the disorder progresses.
Broader differentials
● From a cognitive lens ➚ perspective
◦ Progressive supranuclear palsy ➚
◦ Alzheimer disease (late stages) ➚
◦ Huntington disease (rigid form)
◦ Frontotemporal dementia with parkinsonism linked to chromosome 17 ➚
◦ Spinocerebellar ataxias (SCAs), particularly SCA2, SCA3 and SCA17
◦ Dentatorubral pallidoluysian atrophy (DRPLA)
◦ Neurodegeneration with brain iron accumulation (NBIA)
● From a lesional lens ➚ perspective
Structural abnormalities that disrupt nigrostriatal pathways ➚ can result in parkinsonism. Examples include traumatic, neoplastic and vascular lesions. Of note, vascular parkinsonism remains a debated clinical entity, partly because basal ganglia infarction often does not result in parkinsonian features.
● Other differentials (including multisystemic conditions ➚ )
● Intrinsic
▪ Endocrine
◦ Pseudohypoparathyroidism
▪ Genetic
(in addition to genetic conditions mentioned above with the cognitive lens)
◦ Primary familial brain calcification (PFBC; formerly referred to as familial idiopathic basal ganglia calcification or Fahr disease)
◦ Neurometabolic disorders
▪ Other
◦ Functional movement disorder
● Extrinsic
▪ Toxic and deficiency states
◦ Drug-induced parkinsonism
First- and second-generation antipsychotics, metoclopramide, prochlorperazine, valproic acid, tetrabenazine, and others
◦ Toxic exposures/poisoning
Carbon monoxide, manganese, carbon disulfide, organic solvents, and others
▪ Infectious
◦ Bacterial
◦ Viral
Human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) ➚
Progressive multifocal leukoencephalopathy (PML)
◦ Parasitic
Toxoplasmosis
◦ Other
Encephalitis lethargica (von Economo encephalitis)
Prion diseases, particularly sporadic and variant Creutzfeldt-Jakob disease (sCJD and vCJD) (parkinsonian features are more commonly seen in sCJD than in vCJD, with ataxia being more prominent in the latter)
Selected references and further reading — Movement lens
Jankovic J, Hallett M, Okun MS, Comella CL, Fahn S. Principles and practice of movement disorders. 3rd ed. Philadelphia: Elsevier; 2021.
Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, editors. Bradley and Daroff's neurology in clinical practice. 8th ed. Philadelphia: Elsevier; 2022.
Campbell WW. DeJong's the neurologic examination. 8th ed. Philadelphia: Wolters Kluwer; 2020.
Arciniegas DB, Yudofsky SC, Hales RE, editors. The American Psychiatric Association Publishing textbook of neuropsychiatry and clinical neurosciences. 6th ed. Washington (DC): American Psychiatric Association Publishing; 2018.
Agrawal N, Faruqui R, Bodani M, editors. Oxford textbook of neuropsychiatry. Oxford: Oxford University Press; 2020.
Dening T, Thomas A, editors. Oxford textbook of old age psychiatry. 3rd ed. Oxford: Oxford University Press; 2021.
Blazer DG, Steffens DC, Busse EW, editors. The American Psychiatric Publishing textbook of geriatric psychiatry. 5th ed. Washington (DC): American Psychiatric Publishing; 2015.