How Is Parkinson's Disease Diagnosed?

Medically reviewed by Nicholas R. Metrus, MD

A neurologist (who specializes in the brain and nervous system) can test for Parkinson's disease with a neurological examination and medical history. Symptoms can resemble other conditions, so you may require additional testing to confirm suspected cases.

Parkinson's disease is a neurodegenerative disorder that causes trembling, muscle rigidity, interrupted or slow movements, and postural problems. The disorder primarily affects those older than 60 and increases in severity over time. Parkinson's disease can also impact memory, concentration, sleep quality, mood, and behavior.

Related: How Is Epilepsy Diagnosed?

Diagnostic Criteria

Parkinson's disease diagnosis mostly depends on the neurologist's ability to identify symptoms. Aside from some genetic forms, no blood or imaging tests can diagnose the condition. This disorder has four characteristic or "cardinal" symptoms, the presence of which is often termed Parkinsonism.

These characteristics include:

• Bradykinesia: This is when movements are slow or interrupted, something experienced clinically as fatigue, weakness, or lack of coordination. This issue creates a distinctive shuffling or interrupted gait, characterized by short, unsteady steps. Bradykinesia is seen at onset in 80% of cases and becomes a feature seen in nearly every case.

• Postural issues: Problems maintaining a normal, erect posture are generally associated with more advanced cases. These issues lead to trouble maintaining balance and coordinating movements.

• Rigidity: This is characterized by stiffness and resistance to passive movements of the limbs. Rigidity often occurs first on one side of the body and then eventually moves to the other. About 75% to 90% of people with Parkinson's disease have rigidity.

• Tremors: These are uncontrolled shaking movements that worsen when at rest or during activity. Tremors, usually seen in the hands, tend to be intermittent at first and become more prominent and chronic over time. You may also develop tremors in the lips, legs, jaw, and tongue.

Individual presentations of Parkinson's disease can vary. People must display bradykinesia alongside resting tremors or rigidity to be diagnosed, according to the International Parkinson and Movement Disorder Society (MDS).

Supportive Symptoms and Red Flags

Other neurological disorders can also cause Parkinsonism. There are also supportive criteria for the condition, as well as certain "red flag" signs that may rule out the condition.

Supportive criteria include:

• Cardiac denervation, in which heart rate does not increase with rises in activity, something which is seen by using a form of imaging called Cardiac 123I-metaiodobenzylguanidine (123I-MIBG) scintigraphy

• Decreases in symptoms after taking drugs that increase the neurotransmitter dopamine (dopaminergic drugs), such as Sinemet (levodopa)

• Increases in motor difficulties or interruptions with levodopa therapy as the medication wears off

• Loss of the sense of smell (olfactory loss)

• Tremor in a limb, either immediately observable or detected in a previous evaluation

Several red flags and signs may indicate other issues and that Parkinson's disease is not the diagnosis. These are counterbalanced with supportive symptoms.

The most common red flags are:

• Abnormally low blood pressure upon standing (orthostatic hypotension) within five years of symptom onset

• Absence of common non-motor symptoms of Parkinson's disease, such as insomnia, daytime sleepiness, urinary constipation or incontinence, inability to detect smells, depression, anxiety, or hallucinations within five years of symptom onset

• Early and rapid onset of severe dysphonia (an inability to speak or articulate) and dysphagia (an inability to chew properly)

• Excessive anterocollis (repeated flexing of neck muscles) or flexion of hand or foot muscles within 10 years of symptom onset

• Inspiratory stridor, or a whistling sound when inhaling

• Rapid and early onset of severe urinary retention (also called urinary constipation) or incontinence (leaking urine on accident)

• Recurring falls—more than one a year—within three years of symptom onset

• Very rapid progression of effects on gait, including an inability to walk within five years of symptom onset

Several symptoms outright exclude a Parkinson's diagnosis, such as:

• An inability to look up (supranuclear gaze palsy) or selective reductions in the ability to gaze downward

• Cerebellar abnormalities, such as cerebellar gait, characterized by widened stance; lateral unsteadiness; irregular steps; and difficulties with oculomotor function (movement of the eyes)

• Current or recent treatment with a dopamine-blocking drug (dopamine antagonists)

• Lack of response to levodopa therapy

• Loss of sensation and perception in the body, an inability to imitate actions (ideomotor apraxia), and an inability to express or comprehend written and spoken language (aphasia)

Medical History

An evaluation of your medical history is essential for Parkinson's diagnosis. Neurologists focus on identifying symptom patterns and factors that may increase Parkinson's disease risk.

This generally means discussing:

• A family history of Parkinson's disease

• Any history of exposure to pesticides, chemicals, or other environmental toxins that are risk factors for the condition

• Any non-motor symptoms of Parkinson's disease, such as sleep problems, mental health effects, and others

• Medications you've taken or are currently taking

• Prior history or current status of any diseases or medical conditions

• The intensity and duration of cardinal signs like tremors, bradykinesia, and rigidity

Neurological Exam

The physical examination for Parkinson's disease, or a neurological exam, screens for motor effects of the disease. This assessment tests coordination, strength, and overall ability to move.

A neurological exam involves:

• Assessment for tremors: You'll be observed as you remain still and focus on a specific task to screen for rest tremors, or trembling when you are not moving.

• Checking for rigidity: The extent of any rigidity can be tested by pushing on a wrist or limb and feeling for resistance. This resistance tends to increase during voluntary movement.

• Gait assessment: The neurologist will watch as you walk down a hall or through a door. They can detect postural problems or any effects on motor coordination while walking.

• Observation of spontaneous movements: The neurologist will observe any movement irregularities as you're seated, when you stand up, or while walking.

• Pull test: This is an additional assessment of postural stability. The neurologist will pull you back from behind while you're standing to assess how well you retain balance and stance.

• Tests of repetitive movement: A neurologist may ask you to perform repetitive movements, such as opening and closing a hand and tapping fingers or toes.

Genetic Testing

Genetic testing is generally not a routine part of Parkinson's diagnosis. Genetic testing may help identify rare inherited forms of the disease. Mutations or over-expression of certain genes, such as synuclein alpha (SNCA), parkin (PRKN), and PTEN-induced putative kinase 1 (PINK1) can imply a genetic case.

Screening for Related Conditions

One of the major challenges of diagnosing Parkinson's disease is that it can present similarly to other neurological disorders. Certain medications can cause a similar set of symptoms. Symptoms can also arise as a result of other health conditions, some

thing called secondary Parkinsonism.

Among other possible diagnoses are:

• Corticobasal degeneration: This rare neurodegenerative disorder causes an array of Parkinsonian motor symptoms, such as rigidity, tremors, and lack of coordination.

• Dementia with Lewy bodies: This common form of dementia causes cognitive difficulties, hallucinations, and difficulties remembering and daily functioning. The symptoms also arise due to advanced Parkinson's disease.

• Essential tremor: This affects both sets of hands and feet, face, voice, arms, and abdomen. This type of tremor differentiates from Parkinsonism because it occurs during motion or activity, such as while holding your arms up or writing. It tends to affect one side of the body more than the other, and it is not associated with Parkinson's symptoms like stooped posture or bradykinesia.

• Fahr syndrome: This rare genetic disorder causes Parkinsonism, cognitive impairment, and involuntary muscle contractions, which cause repetitive twisting movements.

• Multiple system atrophy: This is a progressive neurological disorder that impacts motor function and affects autonomic function. Autonomic function includes digestion, blood pressure, and urinary regulation. Earlier phases are often misdiagnosed as Parkinson's disease.

• Progressive supranuclear palsy: Early phases of this condition closely mimic Parkinson's disease symptoms. Therapy with levodopa may yield moderate effects, further complicating diagnosis.

Secondary Parkinson's disease can be caused by:

• Advanced Alzheimer's disease

• Brain lesions caused by hydrocephalus (a buildup of fluids surrounding the brain), tumors, or brain bleed

• Certain infections, including encephalitis, human immunodeficiency virus (HIV), and others

• Certain medications, such as the antipsychotic medications Serpasil (reserpine), Reglan (metoclopramide), and Stemetil (prochlorperazine)

• Exposure to toxins and certain chemicals, including carbon monoxide and manganese

• Head trauma

• Metabolic disorders, such as end-stage kidney disease with diabetes, liver failure, and hypoparathyroidism (insufficient production of parathyroid hormone, which regulates calcium and phosphorous in the body)

• Neurogenetic disorders, such as Wilson disease and degeneration of neurons due to iron accumulation in the brain

A neurologist may use:

• DaTScan: An iodine-based radioactive material is injected into the blood to assist with MRI or X-ray imaging. DaTScan tests can distinguish Parkinson's disease from other neurological disorders, like essential tremor and multiple symptom atrophy.

• Magnetic resonance imaging (MRI): A brain MRI uses magnetic fields and computer-generated radio waves to generate images. This type of imaging may detect alternative causes of Parkinson's disease-like symptoms, such as hydrocephalus or tumor.

• Olfactory tests: A neurologist may test your sense of smell to rule out other neurological disorders. Olfactory loss is a supportive sign of Parkinson's disease.

• Positron emission tomography (PET) scan: This test uses small amounts of radioactive material (radiotracer) injected into the bloodstream. Neurologists measure dopamine levels in the brain using computerized imaging techniques. Dopamine levels can differentiate Parkinson's disease from other neurological disorders.

Related: How Is Multiple Sclerosis Diagnosed?

A Quick Review

Parkinson's disease is a progressive neurological disorder that affects motor function. A neurologist primarily diagnoses Parkinson's disease by conducting a neurological exam and collecting medical history. A neurological exam can test coordination, strength, and movement capability. Imaging and other tests can rule out other conditions that cause similar symptoms.

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