How is Parkinson’s disease diagnosed?

Parkinson’s disease (PD) is not always simple to diagnose, as every case of PD is unique and, as a neurological disorder, the symptoms are similar to many other disorders of the brain. However, an experienced neurologist should be able to make an accurate diagnosis. When making a diagnosis of PD, the doctor listens to the person’s own experience of their condition, and carefully observes the symptoms during a physical examination.

The main symptoms of PD are slowness of movement, stiffness, and sometimes tremor and loss of balance, and it is the particular combination of these symptoms that may lead the doctor to make a diagnosis of PD. The first signs of PD may be noticed as difficulty with delicate movements such as those required for writing, sewing, shaving, etc. In addition, non-movement related symptoms are being increasingly recognised for their potential in assisting with the early diagnosis of PD.

Although PD affects the brain, a brain scan is not usually able to positively identify PD and the changes that it produces in the brain. However, CT or MRI scans (which produce pictures of different sections of the brain) can be used to eliminate other disorders, which may be causing the symptoms. If the scan looks normal, then it is possible – but not definite – that the symptoms are caused by PD.

Similarly, types of brain scan called PET and SPECT, which can visualise dopamine in the brain, may be used to support a diagnosis of PD and eliminate other causes – but again, these scans cannot prove that a person has PD. For this reason, diagnosis usually relies upon description/observation of symptoms, and a physical examination. In addition, there may be some extra tests such as X-rays and blood tests, which can help to show that the symptoms are not being caused by any other disorders.

If a person does have PD, then progress will be assessed at regular intervals based on the doctor’s clinical impression, and sometimes by using one or more rating scales. These scales involve the doctor testing and observing the person’s actions, and marking this down as a score. One of the most commonly used scales is the Unified Parkinson’s Disease Rating Scale (UPDRS), which scores performance in all areas of movement and daily function.

This sort of rating helps the doctor to monitor the progress of the person with PD, and to deliver the most appropriate type of treatment. Other scales that are used to help assess PD are the Hoehn & Yahr scale, which classes PD as being at one of five stages, and the Schwab & England scale, which rates the individual on their level of independence. A description of each of these scales can be found in the glossary section of this website.