Diagnosis of Parkinson's Disease
The diagnosis of Parkinson’s disease is not easy. Many early symptoms can be put down to other conditions such as arthritis and general age related problems. Likewise Parkinson’s is often diagnosed when in fact the problem turns out to be something else.
It is currently believed that as many as 40% of people with the disease remain undiagnosed and about 25% are misdiagnosed one way or another.
The problem is that there is no definitive test for Parkinson’s but an early diagnosis is crucial because it determines the type of treatment a person will get and the success of that treatment.
An accurate diagnosis tends to be down to the experience and skill of individual physicians in evaluating and pinpointing the illness rather than sophisticated tests at their disposal (although certain tests do play a significant part).
Generally speaking, Parkinson’s is suspected if at least two of the three major symptoms are present: tremors while resting, stiffness and slowness of movement.
The main tools used to make a diagnosis:
Medical history/neurological examination
Physicians take a detailed medical history including information about all symptoms experienced (even minor ones which to the patient may be insignificant but to the doctor very important). The doctor will be looking to rule out other causes of the symptoms. The patient is asked to perform a whole range of movements including sitting, standing, walking and turning, giving the doctor the opportunity to assess balance and coordination. Neurological tests are carried out to assess reflexes, strength and coordination. Family members may be asked how they see the patient’s symptoms.
If Parkinson’s disease is suspected the physician will refer the patient on to a neurologist, ideally one specializing in the illness.
Motor physiology tests
These tests are very useful for confirming a diagnosis and are also a good benchmark against which to base treatment. The tests measure the force and speed with which certain tasks are performed. They can involve reaching out for objects and copying certain shapes.
Computed topography scans (known as CT or CAT scans) and magnetic resonance imaging (MRI) can’t confirm a diagnosis of Parkinson’s because the brain changes in the disease are microscopic. But they’re useful in ruling out other conditions such as a brain tumor or stroke, which can produce similar symptoms.
One of the newest diagnostic tools, still very much at the experimental stage, is a positron emission tomography scan (PET). The scan uses 18-flurodopa (a form of the Parkinson’s treatment drug, levodopa) to measure dopamine neurons in the substantia nigra area of the brain. The symptoms of Parkinson’s are caused by loss of the dopamine neuron. 18-flurodopa is injected into the patient and then the brain is scanned. The scan is very sensitive to the dopamine cells and many people with Parkinson’s will have an abnormal PET scan.
It is also a useful tool for monitoring how quickly the disease progresses, though it still isn’t widely available.