Parkinson's Disease

Differential Diagnosis

There are a number of factors useful in separating an atypical form of parkinsonism from idiopathic Parkinson's disease. Patients with early-onset or rapidly progressive dementia coupled with parkinsonian features are more likely to have diffuse Lewy body disease (also called Lewy body dementia) or Alzheimer's disease. In addition, a history of a rapidly progressive course should trigger the clinician to look for other parkinsonian syndromes. The presence of supranuclear gaze palsy, especially a downgaze palsy, suggests progressive supranuclear palsy (PSP), a parkinsonism-plus syndrome.

Evidence of upper motor neuron involvement, such as Babinski's sign and pathological hyperreflexia, suggests corticospinal pathway involvement. Patients exhibiting cerebellar signs such as dysmetria, ataxia, nystagmus, titubation, or gait ataxia need to be evaluated further for cerebellar diseases. Patients with early onset of urinary incontinence should be evaluated for normal pressure hydrocephalus or other possible symptomatic or secondary causes of parkinsonism.

Early symptomatic postural hypotension is rare in PD, and suggests the possibility of multiple system atrophy.

Differential Diagnosis of PD

Common Misdiagnoses	Distinguishing features
Essential tremor (ET)	Tremor (action/postural) is the only or predominant feature; no response to PD drugs
Progressive supranuclear palsy (PSP)	Supranuclear downgaze palsy; square-wave jerks; upright posture; pseudobulbar affect; early gait instability; dysphagia
Multiple system atrophy (MSA)	Autonomic disturbance, cerebellar signs, relative absence of tremor; early gait instability; dysphagia
Corticobasal degeneration (CBD)	Limb apraxia; cortical sensory abnormalities; coarse unilateral tremor; early dementia
Diffuse Lewy body dementia (LBD)	Early dementia; psychosis; agitation
Alzheimer's disease	Dementia is the primary symptom
Drug-induced parkinsonism	Exposure to dopamine-blocking drugs; lack of rest tremor and asymmetry
Vascular parkinsonism	History of chronic hypertension; stepwise progression (if any); unilateral; imaging

Other Disorders
Wilson's disease
Huntington's disease
DRPLA
SCA-3
Metabolic disorder
Structural lesion
Hydrocephalus
Infectious encephalitis