Parkinson disease is a progressive disease that commences between the ages of 45 and 55 years. It is also known as paralysis agitans and results from neuronal degradation of that area of substantia nigra that sends dopamine-secreting nerve fibers to the caudate nucleus and the putamen. This disease affects millions of people in the world.
The exact cause of this disease is unknown. However, the dopamine secreted in the caudate nucleus and the putamen is of the inhibitory type of transmitters and therefore the destruction of these dopaminergic neurons in the substantia nigra of these patients theoretically allow the caudate nucleus and the putamen to become overactive and cause a continuous output to excitatory signals to the corticospinal motor system. These signals can then excite many or all of the muscles of the body and thus leading to rigidity. Also, the degeneration of the neurons of the substantia nigra that send their axon to the corpus striatum results in the reduction in the release of the neurotransmitter dopamine within the corpus striatum. This further leads to hypersensitivity of the dopamine receptors in the postsynaptic neurons in the striatum.
Signs and Symptoms
- Tremors: These result from alternate contraction of agonists and antagonists. These are slow and occur most frequently when the person is at rest. They disappear during sleep. They should be distinguished from the cerebellar disease which occurs when purposeful movement is attempted means intention tremors.
- Rigidity: It is present equally in all opposing muscles groups. If tremors are absent, the rigidity is felt as resistance to passive movement and is referred to as plastic rigidity. In case tremors are present, the muscle resistance is overcome as a series of jerks and it is called cogwheel rigidity.
- Bradykinesia: Here there is a difficulty in initiating and performing new movements and these are slow, the face becomes expressionless and the voice becomes slurred and unmodulated. There is lost of swinging of the arms.
- Postural disturbances: The patient of this disease stands with a stoop and his arms are flexed. He walks by taking shorts steps and often is unable to stop. In fact, he may break into a shuffling run to maintain his balance.
- Normal Muscle Power: There is no loss of muscle power and no loss of sensibility as well. Because corticospinal tracts are normal, the superficial abdominal reflexes are normal and there is no Babinski response too. The deep tendon reflexes are normal as well.
Three types of this disease are present for which causes are also known. These are
- Postencephalitic Parkinsonism: It is due to viral encephalitis which damages the basal nuclei. Its outbreak occurred in 1916-1917.
- Iatrogenic Parkinsonism: This is due to the side effect of neuroleptics drugs e.g. phenothiazine. Meperidine analogues and carbon monoxide poisoning, as well as manganese, can produce the symptoms of parkinsonism
- Atherosclerotic Parkinsonism: This disease occurs in an elderly patient which are suffering from hypertension.
Treatment* with L-Dopa: Administration of L-dopa to these patients usually ameliorates many of the symptoms especially the rigidity and akinesia.
Treatment* with L-deprenyl: This drug inhibits monoamine oxidase which is responsible for uptake of dopamine and its destruction.
Treatment* With Transplant Fetal Dopamine Cells: This gives short-term success by transplanting dopamine secreting cells into the caudate nuclei and putamen.