A physician initially assesses for<unk>  with a careful medical history and neurological examination. Focus is put on confirming motor symptoms (bradykinesia, rest tremor, etc.) and supporting tests with clinical diagnostic criteria. The finding of Lewy bodies in the midbrain on autopsy is usually considered final proof that the person had<unk> . The clinical course of the illness over time may reveal it is not<unk> , requiring that the clinical presentation be periodically reviewed to confirm the accuracy of the diagnosis. Multiple causes can occur for parkinsonism or diseases that look similar. Stroke, certain medications, and toxins can cause "secondary parkinsonism" and need to be assessed during visit. Parkinson-plus syndromes, such as progressive supranuclear palsy and multiple system atrophy, must also be considered and ruled out appropriately due to different treatment and disease progression (anti-Parkinson's medications are typically less effective at controlling symptoms in Parkinson-plus syndromes). Faster progression rates, early cognitive dysfunction or postural instability, minimal tremor, or symmetry at onset may indicate a Parkinson-plus disease rather than<unk>  itself. Medical organizations have created diagnostic criteria to ease and standardize the diagnostic process, especially in the early stages of the disease. The most widely known criteria come from the UK Queen Square Brain Bank for Neurological Disorders and the U.S. National Institute of Neurological Disorders and Stroke. The Queen Square Brain Bank criteria require slowness of movement (bradykinesia) plus either rigidity, resting tremor, or postural instability. Other possible causes of these symptoms need to be ruled out. Finally, three or more of the following supportive features are required during onset or evolution: unilateral onset, tremor at rest, progression in time, asymmetry of motor symptoms, response to levodopa for at least five years, the clinical course of at least ten years and appearance of dyskinesias induced by the intake of excessive levodopa. Assessment of sudomotor function through electrochemical skin conductance can be helpful in diagnosing dysautonomia. When<unk>  diagnoses are checked by autopsy, movement disorders experts are found on average to be 79.6% accurate at initial assessment and 83.9% accurate after they have refined their diagnoses at follow-up examinations. When clinical diagnoses performed mainly by nonexperts are checked by autopsy, the average accuracy is 73.8%. Overall, 80.6% of<unk>  diagnoses are accurate, and 82.7% of diagnoses using the Brain Bank criteria are accurate. Imaging Computed tomography (CT) scans of people with<unk>  usually appear normal. Magnetic resonance imaging has become more accurate in diagnosis of the disease over time, specifically through iron-sensitive T2* and susceptibility weighted imaging sequences at a magnetic field strength of at least 3T, both of which can demonstrate absence of the characteristic 'swallow tail' imaging pattern in the dorsolateral substantia nigra. In a meta-analysis, absence of this pattern was highly sensitive and specific for the disease. A meta-analysis found that neuromelanin-MRI can discriminate individuals with Parkinson's from healthy subjects. Diffusion MRI has shown potential in distinguishing between<unk>  and Parkinson-plus syndromes, though its diagnostic value is still under investigation. CT and MRI are also used to rule out other diseases that can be secondary causes of parkinsonism, most commonly encephalitis and chronic ischemic insults, as well as less frequent entities such as basal ganglia tumors and hydrocephalus. The metabolic activity of dopamine transporters in the basal ganglia can be directly measured with positron emission tomography and single-photon emission computed tomography scans, with the DaTSCAN being a common proprietary version of this study. It has shown high agreement with clinical diagnoses of<unk> . Reduced dopamine-related activity in the basal ganglia can help exclude drug-induced Parkinsonism. This finding is not entirely specific, however, and can be seen with both<unk>  and Parkinson-plus disorders. In the United States, DaTSCANs are only FDA approved to distinguish<unk>  or Parkinsonian syndromes from essential tremor. Iodine-123-meta-iodobenzylguanidine myocardial scintigraphy can help find denervation of the muscles around the heart, which can support a<unk>  diagnosis. Differential diagnosis Secondary parkinsonism – The multiple causes of parkinsonism can be differentiated between with careful history, physical examination, and appropriate imaging. This topic is further discussed in the causes section here. "Hot Cross Bun" sign that is commonly found in MRI of Multiple System Atrophy. Parkinson-plus syndrome – Multiple diseases can be considered part of the Parkinson's plus group, including corticobasal syndrome, multiple system atrophy, progressive supranuclear palsy, and dementia with lewy bodies. Differential diagnosis can be narrowed down with careful history and physical (especially focused on onset of specific symptoms), progression of the disease, and response to treatment. Some key features between them: * Corticobasal syndrome - levodopa-resistance, myoclonus, dystonia, corticosensory loss, apraxia, and non-fluent aphasia * Multiple system atrophy – levodopa resistance, rapidly progressive, autonomic failure, stridor, present Babinski sign, cerebellar ataxia, and specific MRI findings * Progressive supranuclear palsy – levodopa resistance, restrictive vertical gaze, specific MRI findings, and early and different postural difficulties * Dementia with Lewy bodies – levodopa resistance, cognitive predominance before motor symptoms, and fluctuating cognitive symptoms, (visual hallucinations are very common in this disease, but<unk>  patients also have them) *Essential tremor – This can at first look like parkinsonism, but has key differentiators. In essential tremor, the tremor gets worse with action (whereas in<unk> , it gets better), a lack of other symptoms is common in<unk> , and normal DatSCAN is seen. Other conditions that can have similar presentations to<unk>  include: * Arthritis * Creutzfeldt–Jakob disease * Dystonia * Depression * Fragile X-associated tremor/ataxia syndrome * Frontotemporal dementia and parkinsonism linked to chromosome 17 * Huntington's disease * Idiopathic basal ganglia calcification * Neurodegeneration with brain iron accumulation * Normal-pressure hydrocephalus * Obsessional slowness * Psychogenic parkinsonism * Wilson's disease
Parkinson's disease
Dementia with Lewy bodies
Parkinsonism
Antipsychotic
Parkinson-plus syndrome
Essential tremor
Alzheimer's disease
Progressive supranuclear palsy