Diagnosis of Parkinson's Disease

Levodopa is a molecule from which dopamine is synthesized in the brain. It is the gold standard treatment for Parkinson’s disease, and it also can be used to aid in diagnosis. A neurologist recommends a sufficient dose of levodopa to see whether it has any effect on a patient’s symptoms. If symptoms alleviate after levodopa administration, a diagnosis of Parkinson’s disease is confirmed.

A trained clinician will perform motor examination tasks to help determine whether a patient’s symptoms are related to Parkinson’s disease or another disorder. There are four main symptoms of Parkinson’s that a doctor will look for during a motor exam: tremor, rigidity, bradykinesia or akinesia, and postural instability.

Real-time quaking-induced conversion (RT-QuIC), also called protein misfolding cyclic amplification, is a diagnostic method that can help in the early detection of Parkinson’s disease by identifying the formation of abnormal clusters of the protein alpha-synuclein. These protein clumps are a hallmark of many neurodegenerative diseases including Parkinson’s.

A smell test is a simple, sensitive but nonspecific test that is still under development for the diagnosis of Parkinson’s prior to the appearance of motor symptoms. Loss of smell (also called olfactory dysfunction or hyposmia) is one of the most common and best characterized non-motor symptoms of Parkinson’s. Studies suggest that patients may lose their sense of smell up to 10 years before other symptoms appear.

After an initial assessment of symptoms, a physician may use imaging tests to confirm a diagnosis of Parkinson’s disease or atypical parkinsonism (Parkinson’s-like disorders that do not respond to treatment with levodopa). Imaging tests can help physicians distinguish between these diseases and other neurological disorders, the early stages of which may resemble Parkinson’s disease.