Early in the disease process, it may be difficult to know whether symptoms indicate Parkinson disease or a disease or syndrome with similar symptoms. A neurologist that is also board-certified in movement disorders like PD (also called a movement disorder specialist, or MDS) has received training in evaluating symptoms, and is an important part of a suspected PD patient's medical team.
Some conditions that could potentially be mistaken for Parkinson's include:
- Medication-induced Parkinsonism. Medications which can cause Parkinsonism include anti-psychotics or drugs to treat major depression. Sometimes anti-nausea medications can also cause Parkinsonism. Unlike Parkinson disease, medication-induced symptoms typically occur on both sides of the body simultaneously. These symptoms usually resolve within weeks or months of discontinuing the medication.
- Essential tremor. Essential tremor is a common neurologic movement disorder, and is a chronic condition characterized by involuntary, rhythmic tremor of a body part, usually the hands, arms, head, or lips. The tremors associated with essential tremor are action tremors, and occur when the body part is in motion. Parkinson tremors are normally rest tremors, and occur when the body part is not being used.
- Progressive Supranuclear Palsy (PSP), Multiple System Atrophy (MSA) or other Parkinson’s Plus (P+) Syndromes Early onset of imbalance, frequent falls, rigidity of the trunk, and (eventually) eye-movement problems characterize P+. Symptoms usually begin after age 50 and progress more rapidly than with Parkinson’s disease.
- Normal Pressure Hydrocephalus (NPH). NPH is indicated by three primary symptoms: gait problems, urinary incontinence, and dementia. Experienced movement-disorder neurologists can easily distinguish NPH from PD sometimes with the aid of an imaging test such as an MRI.
- Space-Occupying Brain Defects. These include non-malignant and malignant brain tumors, which can cause a wide variety of symptoms which can be similar to PD. They can normally be ruled out with brain imaging techniques such as MRI or CAT scans or other diagnostic tests.
- Strokes. Caused by interruptions in blood flow to parts of the brain which cause damage and death of brain tissue and can create symptoms similar to Parkinsonism. Imaging studies such as SPECT scans which evaluate blood flow in the brain can be helpful in diagnosis.
- Wilson’s Disease. Wilson’s disease is caused by an excess of copper in the body and bloodstream, which causes difficulty in movement and tremors similar to Parkinson’s disease. It can also cause a light-colored ring around the iris in the eye. Urine tests for excess copper are helpful for diagnosing this disease
- Lyme Disease. Symptoms of late-stage Lyme disease, which is caused by the bite of infected blacklegged ticks, are similar to some of the symptoms of Parkinson disease, and can occur months or years after the initial infection. The most common symptoms are muscle and joint pain. Other symptoms may include abnormal muscle movement, muscle weakness, numbness and tingling, and speech problems.