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CLINICAL FEATURES

Parkinsonism is a general term used to define a syndrome of bradykinesia (slowness of voluntary movements) with rigidity and/or tremor (Table 186-1); it has a wide differential diagnosis (Table 186-2). Parkinson’s disease (PD) is idiopathic parkinsonism without evidence of more widespread neurologic involvement. PD afflicts >1 million individuals in the United States. Mean age of onset is about 60 years; course progressive over 10–25 years. Tremor (“pill rolling” of hands) at rest (4–6 Hz). Presentation with tremor confined to one limb or one side of body is common. Other findings: rigidity (“cogwheeling”—increased ratchet-like resistance to passive limb movements), bradykinesia, fixed expressionless face (facial masking) with reduced frequency of blinking, hypophonic voice, drooling, impaired rapid alternating movements, micrographia (small handwriting), reduced arm swing, and flexed “stooped” posture with walking, shuffling gait, difficulty initiating or stopping walking, en-bloc turning (multiple small steps required to turn), retropulsion (tendency to fall backwards). Nonmotor aspects of PD include depression and anxiety, cognitive impairment, sleep disturbances, sensation of inner restlessness, loss of smell (anosmia), and disturbances of autonomic function. Normal muscular strength, deep tendon reflexes, and sensory examination. Diagnosis based on history and examination; neuroimaging, EEG, and CSF studies usually normal for age.

TABLE 186-1Clinical Features of Parkinson’s Disease
TABLE 186-2Differential Diagnosis of Parkinsonism

PATHOPHYSIOLOGY

Most PD cases occur sporadically. Degeneration of pigmented pars compacta neurons of the substantia nigra in the midbrain resulting in lack of dopaminergic input to striatum; accumulation of cytoplasmic intraneural inclusion granules (Lewy bodies). Cause of cell death is unknown, but may result from generation of free radicals and oxidative stress, inflammation, or mitochondrial dysfunction; no environmental factor has yet been conclusively determined to cause typical PD. Genetic forms of parkinsonism exist (5−15% of cases); most common are mutations in ...

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