How is Parkinson's Disease Diagnosed?
Unfortunately, there is no single test that can diagnose Parkinson’s disease (PD). If PD is suspected, the person should be referred to a neurologist specially trained in movement disorders who can assess for signs and symptoms of the disease. The exam usually involves questions about the person’s history followed by a neurologic exam.
Obtaining a Parkinson's disease diagnosis
During the exam, the neurologist will look for cardinal symptoms of the disease. Facial expressions and features will be assessed. The doctor will look for signs of tremor while the patient is at rest. The doctor may watch how easily the patient stands up from sitting in a chair. The doctor may also stand behind the patient and gently pull back on the patient’s shoulders and look for how easily the patient can regain balance. Good responsiveness to levodopa also helps support the diagnosis of PD. However, taking levodopa may exclude patients from clinical studies that need to recruit recently diagnosed patients who have not yet had treatment (called “de novo”). Participation in a clinical trial should be discussed with the doctor.
PD can be challenging to accurately diagnose, particularly in early stages of the disease, which is why a neurologist trained in movement disorders is critical. Approximately 5-10% of patients with PD are misdiagnosed, as many of the symptoms of PD are similar to other diseases. If the patient thinks that he or she has been misdiagnosed, a second opinion may help.1,2
The importance of early diagnosis
Early detection and diagnosis is important because the treatments for PD are more effective in the early stages of the disease. In addition, physical therapy and exercise, which greatly improve symptoms and delay progression of the disease, are much easier to perform in the early stages.
Current diagnosis is made through the presence of motor symptoms; however, researchers have found that by the time motor symptoms occur, over 60% of all dopamine neurons in the basal ganglia of the brain have been damaged. Non-motor symptoms become apparent in people with PD long before motor symptoms, including sleep disturbances and loss of the sense of smell.3
Active areas of research include looking for markers in the blood, urine, or cerebral spinal fluid that reliably detect PD, called “biomarkers”. In addition, brain imaging tests that have high sensitivity for detecting PD are also being actively researched.4
Diagnosis of PD is generally made using a medical history and a physical exam, or a neurological exam. Imaging tests, such as MRI (magnetic resonance imaging), PET (positron emission tomography) scans, or DaTscans are expensive and are not routinely used.5