Parkinson's disease: diagnosis
Parkinson's disease is seen with increasing frequency after the age of 50. It is a progressive disorder of the central nervous system. This means that certain cells in an area of the brain — substantia nigra — undergo a degenerative process and these cells fail to perform in a normal manner. The basic cause of the cells behaving abnormally remains unknown.
The dysfunction of these cells results in a loss of a neurotransmitter called dopamine, (a chemical which carries impulses from one nerve cell to the next) which results in the clinical symptoms and signs of Parkinson's.
In recent years, people have become so imbued with the idea that there is a definitive test or procedure to establish the exact diagnosis of all illnesses, that doctors are frequently asked to perform such a test in relationship to the diagnosis of Parkinson's disease. While there is no definitive test, there are certain characteristic physical findings which your doctor observes that establish the diagnosis of Parkinson's.
The most common initial problems that people notice before diagnosis are:
- an isolated tremor of one arm or one leg;
- alteration in handwriting;
- difficulty with walking or balance; and
- general slowness in most of the activities of daily living.
In order to make a diagnosis, your doctor will be interested in exploring the following problem areas related to Parkinson's:
- tremor;
- rigidity;
- akinesia; and
- postural imbalance.
Tremor
The tremor which is observed by both patient and physician alike in Parkinson's disease is what is called a resting tremor. This implies that the tremor, which is an involuntary (unintentional) rhythmic movement of the arms, legs, feet and hands, occurs when the person is at rest and there is no activity in the involved limb. It is also quite typical that when the involved limb is actively engaged in a volitional activity, for example, reaching for a glass of water, the tremor will markedly diminish.
Rigidity
Rigidity of the muscles is a common finding in Parkinson's. The particular kind of rigidity which is characteristic of Parkinson's is termed cogwheel rigidity. This simply refers to the fact that when your doctor examines you and moves your limbs about to feel the tone of your muscle, s/he feels (and sometimes you feel or even see) a certain ratchet-like movement which resembles a cogwheel in motion. People rarely complain of rigidity of their muscles, but what they will notice is a feeling of stiffness and occasional discomfort, which may be related to the rigidity of the muscles.
Akinesia and bradykinesia
Akinesia (lack of movement) and bradykinesia (slowness of movement) are terms used to describe the slowness of voluntary movement which is the hallmark of Parkinson's. Akinesia and bradykinesia represent one of the most disabling aspects of the entire disorder. It is bradykinesia which is responsible for the sometimes excruciating slowness with which people with Parkinson's perform the simplest tasks. The difficulty rising from chairs, turning over in bed, getting in or out of cars, dressing, preparing foods, eating and bathing all are intricately interwoven with this problem.
Obviously, this is something which the individual and their partner relate to the doctor and it is also something which is often readily observable by having the person perform various simple tasks during a surgery visit.
Postural imbalance
Postural dysfunction, imbalance or the tendency to fall is also quite characteristically seen in Parkinson's. This is a very important problem since falling can sometimes result in injury. Obviously, the person with Parkinson's and their family will be able to describe whether or not any episodes of imbalance or postural disturbance have occurred in the past and your doctor will be able to test for the presence of this problem by watching you walk, turn and respond to slight postural challenges.
There are many other historical and neurological findings which characterise Parkinson's but these areas are the ones of primary concern when a diagnosis is being made. It should be remembered that, most frequently, an individual will have a combination of these problems or possibly initially only one. The important point to understand and to remember is that the initial diagnosis of Parkinson's involves both the history which you and your partner give to your doctor and the doctor's clinical examination which will focus on these points. This co-operation between patients and doctors is vital because there is no specific laboratory or diagnostic test that can confirm or establish a diagnosis of Parkinson's.
Last Reviewed: 18 July 2002
