Parkinson's disease. Diagnosis and the initiation of therapy.

Parkinson's disease (PD) is the most common cause of parkinsonism. Parkinsonism is characterized by resting tremor, bradykinesia, rigidity and gait impairment. There is no specific diagnostic test for PD and it is important for clinicians to understand the clinical signs which help to distinguish PD from parkinsonism. It is equally important to be aware of the clinical signs which can be an indication that the diagnosis is not PD. These so-called Parkinson-plus syndromes include progressive supranuclear palsy (PSP), multiple systems atrophy (MSA), corticobasal degeneration (CBD), vascular parkinsonism (VP) and parkinsonism with dementia (Lewy body dementia, LBD). The differential diagnosis of parkinsonism will be discussed. Initiating pharmacologic therapy for PD must take into consideration the degree of dysfunction the patient is experiencing, the question of neuroprotection, the degree of motor response required, and the potential complications of long-term treatment. Neuropro-tective trials of coenzyme Q10 (CoQ), vitamin C, vitamin E, monoamine oxidase B inhibitors (MAO-I) and dopamine agonists do not support the use of any of these drugs for a neuroprotective effect. There is recent supportive evidence that levodopa may have a neuroprotective effect. Either dopamine agonists or levodopa may be initiated. Dopamine agonists are associated with fewer motor fluctuations and dyskinesias, while levodopa is associated with better motor performance. Initiation of therapy should be tailored to individual patients with the emphasis on symptom control, with the hope that new approaches to treatment of PD (including neuroprotection) will be forthcoming.