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Parkinsonism is defined by the presence of the cardinal symptoms of bradykinesia, rigidity, tremor, and postural instability. The most common cause of parkinsonism is idiopathic Parkinson's disease (PD) but a number of cases are due to secondary parkinsonism for which there are multiple causes. This chapter will review parkinsonism resulting from infectious causes1 and exposure to various toxins and drugs.2

There are several potential infectious causes of parkinsonism (Table 23–1).39 This chapter reviews postencephalitic parkinsonism as well as other infectious causes of parkinsonism, including acquired immune deficiency syndrome (AIDS), syphilis, fungal and parasitic infections, and Creutzfeldt–Jakob disease.

Table 23–1. Potential Infectious Causes of Parkinsonism

Postencephalitic Parkinsonism

“Postencephalitic parkinsonism,” “von Economo's disease,” and “encephalitis lethargica” are multiple terms used to describe a form of parkinsonism, which occurs after a bout of encephalitis. In 1917, von Economo9 described this condition, which became an epidemic during World War I. Postencephalitic parkinsonism accounted for the majority of the cases of parkinsonism from 1920 to 1930 and for one-half of the cases seen during the 1930s.10 The incidence of postencephalitic parkinsonism was significantly reduced over time, and by the late 1960s, it represented less than 1% of the cases of parkinsonism. There have been no new cases in the recent literature.

Clinical Features

Initial symptoms were consistent with a viral infection, including influenza and pharyngeal symptoms with fever followed by a variety of neurological symptoms.11 The majority of patients had ophthalmoplegia in combination with a persistent pathological somnolence lasting for days to weeks in which arousal was brief and often required vigorous stimulation.12 Signs of cortical dysfunction, like aphasia, convulsions, psychosis, and sensory disturbances were rare. Clinical, laboratory, and pathological features were consistent with a viral infection. Elevated cerebrospinal fluid protein with lymphocytic pleocytosis was seen in about one-half of patients. No specific virus was ever identified and the encephalitis was not contagious.1315

The initial symptoms generally lasted for several weeks, and mortality was as high as 40%. A large percentage of patients who survived had delayed symptoms with the most common including central respiratory irregularities, oculogyric crises, and parkinsonism.16,17 Oculogyric crisis consisted most commonly of upward deviation of the eyes although downward deviations and convergence rarely occurred.18 Most attacks lasted minutes to hours and disappeared during sleep. Oculogyric crisis occurred in approximately 20% of parkinsonian patients.19 In some patients with oculogyric crisis, symptoms similar to Meige's syndrome or other forms of dystonia ...

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