Diagnosis

It is difficult to diagnose Parkinson's in early stages. The disease is primarily diagnosed by its symptoms, and studies indicate that doctors make an incorrect initial diagnosis of Parkinson's disease in 8 - 35% of cases. Even neurologists have difficulties in correctly identifying the disease.

Medical and Personal History

A medical and personal history should include any relevant symptoms as well as any medications taken, and information on exposure to environmental toxins.

Diagnosing by Symptoms

Early Symptoms. Early treatment may help slow progression, so an early diagnosis of Parkinson's is highly desirable. Early symptoms are often mild however, so Parkinson's disease can be missed, particularly in young adults. Repeated assessment of symptoms over time is important for improving the accuracy of diagnosis. Too often a younger person with Parkinson's may be diagnosed with mental illness, because the doctor associates the disease only with older people.

Parkinson's may be suspected in patients with the following symptoms:

• Slowness and difficulty of movement. These are usually the first symptoms. The patient will be asked to walk and to get out of a chair, preferably a deep one. Early gait disturbance, however, often indicates a disease other than Parkinson's disease.
• A tremor when their limb is relaxed. (As many as 25% of patients, however, will not have a tremor.)
• Symptoms on one side of the body.

Later Symptoms. In later stages of Parkinson's disease, the symptoms are usually unmistakable, and the problem can often be diagnosed using simple physical tests and a medical and personal history.

Smell Test

The loss of smell is associated with loss of dopamine receptors in the brain. “Scratch and sniff” smell tests can help a doctor diagnose Parkinson’s disease. Smell tests can help differentiate Parkinson’s disease from other conditions with similar symptoms. Some patients with a very similar condition called multiple system atrophy will have a good initial response to levodopa, but it is not usually sustained.

Drug Challenge Test

Levodopa and apomorphine can confirm a diagnosis of Parkinson’s disease. If patients’ symptoms improve when they take these drugs, they likely have Parkinson’s, ruling out other neurological diseases.

Imaging Tests

According to 2006 guidelines from the American Academy of Neurology, there is not enough evidence to recommend for or against the use of imaging techniques such as computerized tomography (CT), magnetic resonance imaging (MRI), or positron-emission tomographic (PET) to diagnose PD.

Ruling out Causes of Parkinsonism and Diseases that Mimic Parkinson's Disease

When symptoms resemble Parkinson's disease but have an identifiable cause, the syndrome is known as parkinsonism. People who have parkinsonism, but not Parkinson's disease, often have additional neurologic symptoms. A number of conditions can also have similar or some of these symptoms.

Other Neurologic Conditions. Many medical conditions may cause symptoms of Parkinson's disease:

• Hardening of the arteries (arteriosclerosis) in the brain can cause multiple small strokes, which can produce loss of motor control.

Click the icon to see an image of plaque in an artery.

• Alzheimer's disease can be very similar. In one study 23% of people with Alzheimer's also met the criteria for Parkinson's disease. The two diseases often coexist, and research suggests that Alzheimer's and Parkinson's disease may sometimes share a common biologic origin, the accumulation of the protein alpha synuclein and Lewy bodies in the brain.
• Lewy bodies variant (LBV), also called dementia with Lewy bodies, is a separate disease from both Alzheimer's and Parkinson's disease. It has similar symptoms to both but is marked by early dementia.
• Encephalitis caused by influenza has been known to cause parkinsonism.
• Primary progressive freezing gait is a progression condition, in which freezing gait occurs at the onset. Other Parkinson-like features, such as slow movement, often develop. Although very similar to PD, this condition does not respond to L-dopa or other PD medications.
• Essential tremor, unlike the tremor of Parkinson's disease, often occurs in the head and voice and is usually worse during motion, as opposed to rest.
• Progressive supranuclear palsy has similar symptoms, but involves less tremor and earlier rigidity, and it tends to affect both sides of the body symmetrically. Magnetic resonance imaging scans that measure parts of the midbrain may be a reliable method for distinguishing between PD and progressive supranuclear palsy.
• Multiple system atrophy (previously called Shy-Drager syndrome) is a degenerative nerve disease that also affects movement and blood pressure and has many of the symptoms of Parkinson's disease. Some research suggests that a trial using the drug apomorphine may help differentiate between the two.
• Other problems that may mimic Parkinson's disease include Wilson's disease, thyroid abnormalities, hydrocephalus, tumors, having the fragile X trait (but not the full disorder), and a number of degenerative neurologic diseases.

Drugs. Certain drugs or medications account for about 4% of all cases of parkinsonism. According to some studies, patients who experience drug-induced parkinsonism may actually be at an increased risk of developing Parkinson's disease later in life. A number of drugs can cause these symptoms, including antipsychotic and antiseizure drugs. Anyone with parkinsonism should discuss their medications with their doctor.

Tests for Depression and Dementia

The American Academy of Neurology (AAN) recommends the Beck Depression Inventory or the Hamilton Depression Rating Scale to screen for depression in patients with Parkinson’s disease. The AAN recommends the MMSE and CAMCOG tests to screen for dementia. During these tests, the patient answers a series of questions.