Parkinson's disease is a progressive neurodegenerative disorder that is common, age-related and chronic.

It is caused by loss or degeneration of dopaminergic neurons in the substantia nigra of the midbrain.

Onset of symptoms and progression of the disease is gradual.

Motor signs and symptoms include resting tremor, rigidity, bradykinesia and postural instability.

Parkinson's disease dementia indicates loss of intellectual functions including memory, significant deterioration in the ability to carry out day-to-day activities and changes in social behavior are often noted.

Differential Diagnosis

Red Flags
  • Potential signs that would indicate alternate pathology although with low specificity
  • Gait impairment that has rapid progression within 5 years onset
  • Absence of motor symptoms progression or signs for ≥5 years
  • Presence of early bulbar dysfunction within the first 5 years
  • Presence of inspiratory respiratory dysfunction
  • Presence of severe autonomic failure in the initial 5 years of the disease
  • Fall that is recurrent or more than once a year due to impaired balance within 3 years of onset
  • Presence of disproportionate anterocollis or contractures of hand or feet within the first 10 years
  • Despite 5 years duration of the disease there is absence of any common nonmotor features of Parkinson’s disease
  • Presence of pyramidal weakness or clear pathologic hyperreflexia
  • Presence of bilateral symmetric parkinsonism with no side predominance
Absolute Exclusion Criteria
  • Presence of unequivocal unequivocal abnormalities of the cerebellum eg cerebellar gait, limb ataxia or cerebellar oculomotor
  • Presence of downward vertical supranuclear gaze palsy or selective slowing of downward vertical saccades
  • In the initial 5 years of the disease there is a diagnosis of probable behavioral variant frontotemporal dementia or primary progressive aphasia
  • For >3 years parkinsonian features are restricted to the lower limbs
  • Presence of current or within the past year treatment of dopamine receptor blocker or a dopamine-depleting agent in a dose and time-course consistent with drug-induced parkinsonism
  • There is no observable response to high-dose Levodopa despite at least moderate severity of disease
  • Presence of unequivocal cortical sensory loss, clear limb ideomotor apraxia or progressive aphasia
  • Neuroimaging shows normal function of the presynaptic dopaminergic system
  • There is a documentation of the presence of an alternative condition known to produce parkinsonism and can be connected to the patient’s symptoms
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