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Diagnosis and differential diagnosis of Parkinson disease

Kelvin L Chou, MD
Section Editor
Howard I Hurtig, MD
Deputy Editor
John F Dashe, MD, PhD


Parkinson disease (PD) is a chronic, progressive neurodegenerative disorder characterized by any combination of four cardinal signs: bradykinesia, rest tremor, rigidity, and postural instability (present in later stages of disease). An accurate diagnosis of PD rests on the clinician's ability to recognize its characteristic signs and associated symptoms, especially in the early stages. Correct diagnosis is fundamental to the appropriate therapy of PD, even though the same menu of antiparkinson drugs is used to treat all of the various parkinsonian syndromes.

This topic will review the diagnosis and differential diagnosis of PD. Other aspects of PD are discussed separately. (See "Etiology and pathogenesis of Parkinson disease" and "Clinical manifestations of Parkinson disease" and "Pharmacologic treatment of Parkinson disease" and "Nonpharmacologic management of Parkinson disease" and "Motor fluctuations and dyskinesia in Parkinson disease" and "Surgical treatment of Parkinson disease".)


The practical diagnosis of PD during life is based upon clinical impression from history and neurologic examination. At a minimum, bradykinesia plus either tremor or rigidity must be present in order to consider the diagnosis of idiopathic PD [1,2]. In addition, an unequivocal, beneficial response to dopaminergic therapy is an important supportive feature of the diagnosis, while the absence of an observable response to high-dose levodopa therapy (>1000 mg daily) in patients with at least a moderate severity of parkinsonism makes the diagnosis of PD extremely unlikely. Other clinical features that are supportive of the diagnosis are unilateral onset, presence of a rest tremor, and a persistent asymmetry throughout the course of the disease, with the side of onset most affected [3]. (See "Clinical manifestations of Parkinson disease".)

Postural instability is also a feature of PD but usually does not appear until later in the course of the disease. Thus, patients with parkinsonian signs who exhibit postural instability early in the course of the illness most likely have another parkinsonian syndrome.

There are no physiologic tests or blood tests for confirming the diagnosis of PD, and neurodiagnostic testing with computerized imaging is almost always unrevealing. The true "gold standard" for diagnosis is neuropathologic examination.


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Literature review current through: Sep 2016. | This topic last updated: May 26, 2016.
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