Parkinsonism, or paralysis agitans, is a progressive disease of insidious onset usually occurring in the second half of life. Degenerative changes in the basal ganglia (see BASAL GANGLION) lead to a deficiency in the NEUROTRANSMITTER, DOPAMINE – or in other neurotransmitters – and it is this deficiency that is responsible for most cases.
The clinical picture is characterised by TREMOR, rigidity and poverty of spontaneous movements. The loss of natural play of expression in the face produces a mask-like expression. Rigidity of the larynx, tongue and lips produces a flat, expressionless voice. The most common symptom is tremor, often affecting one hand, spreading to the leg on the same side, then to the other limbs. It is more pronounced in resting limbs and is exaggerated by excitement, stopping during sleep. It may interfere with eating and dressing. Limb rigidity leads to an increasing tendency to stoop. The patient has a shuffling walk with a peculiar running gait (‘festination’).
Several drugs are used to keep the condition under control. None is curative, all have side-effects, and finding the most suitable one for any individual depends largely on understanding cooperation between family doctor and patient. Dopaminergic and antimuscarinic (see ANTIMUSCARINE) drugs are used in treatment. Levodopa, a precursor of dopamine, is a long-used example of the former; it produces spectacular improvement in one-fifth and moderate improvement in two-fifths of patients. Benzhexol hydrochloride is one of several antimuscarinic drugs used in Parkinson's disease; selegiline is one of the MONOAMINE OXIDASE INHIBITORS (MAOIS) used in severe parkinsonism in conjunction with levodopa to reduce ‘end-of-dose’ deterioration. Adverse effects include HYPOTENSION, nausea and vomiting, confusion, and agitation. Some drugs used to treat other disorders produce Parkinsonian side-effects. Some patients are amenable to surgical treatment, including deep brain stimulation – the implantation of electrodes into particular parts of the brain, connected to a pulse generator under the skin. Sending electrical impulses to the electrodes may alleviate symptoms. Experimental surgery includes producing irreversible brain lesions, infusing chemicals into the basal ganglia and implanting brain tissue.