The role of functional neurosurgery in Parkinson's disease.

Parkinson’s disease is the most common parkinsonian syndrome among a group of primary degenerative brain disorders that manifest parkinsonian signs and symptoms. First described by Sir James Parkinson almost 200 years ago [1], it is believed to affect 0.5–1% of the population above the age of 60. The cardinal motor phenomena include rest tremor, increased muscle tone (rigidity), bradykinesia and hypokinesia, as well as abnormal postural reflexes and locomotion. Over the last decade, increased attention was focused on the non-motor manifestations of PD, such as cognitive changes, affective disorders (particularly depression), autonomic dysfunction (e.g., constipation, orthostatic hypotension), sleep problems, and sensory disturbances. In general, PD is still diagnosed clinically, but a definite diagnosis can be established only at autopsy with demonstration of eosinophilic cytoplasmatic inclusion bodies (Lewy bodies) in the substantia nigra. The differential diagnosis of PD is shared mainly with multisystem atrophy and vascular parkinsonism, as well as with a long list of other rare parkinsonian syndromes. On clinical grounds, it is sometimes extremely difficult to make the diagnosis, and 10–20% of patients are misdiagnosed even by movement disorders specialists. Pathologically, PD is a degenerative disease of brainstem nuclei, mainly of the pars compacta in the substantia nigra where the dopaminergic cell bodies are located. As a result, the nigrostriatal dopaminergic pathway also degenerates progressively causing hypoactive dopaminergic transmission in the basal ganglia. The cause of the rather selective nigral dopaminergic cell loss in PD is unknown. Certainly, loss of dopamine in the caudate and putamen nuclei of the basal ganglia causes perturbations in other neurotransmitter systems within these nuclei and beyond. Extensive neurophysiological and anatomical research over the last 15 years has indicated that the basal ganglia are only one component of large complex circuits that also involve parts of the cortex and thalamus [2]. Conse-