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Introduction

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Paroxysmal movement disorders may be mistaken as seizure activity due to similar clinical characteristics and often overlapping treatment strategies. This chapter reviews the paroxysmal movement disorders, highlighting their key clinical features and emphasizing the differences between episodic movement and seizure disorders. Distinction between these disease entities may lead to more accurate and rapid diagnoses.

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Paroxysmal Dyskinesias

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The paroxysmal dyskinesias are a heterogeneous group of disorders clinically characterized as acute episodes of hyperkinetic involuntary movements. These disorders are rare and can be misdiagnosed as seizures. The episodic nature of these conditions is the primary defining feature, as movements can range from dystonia to choreoathetosis to ballismus. To better understand the paroxysmal dyskinesias, they are often categorized into four main subgroupings: (1) paroxysmal kinesigenic dyskinesia (PKD), (2) paroxysmal nonkinesigenic dyskinesia (PNKD), (3) paroxysmal exertion-induced dyskinesia (PED), and paroxysmal hypnogenic dyskinesia (PHD). Table 21-1 summarizes some of the distinguishing characteristics of these groups.

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Table 21-1Characteristics of Paroxysmal Dyskinesias
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Paroxysmal Kinesigenic Dyskinesia

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Epidemiology

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PKD is a rare condition, and its incidence in the general population is unknown. Symptoms usually manifest before age 20, although patients may present at later stages of adulthood. Older age of onset is associated with symptomatic (secondary) rather than idiopathic (familial and sporadic) etiology. There is a reported 4:1 male predominance.1 In certain cases, PKD co-occurs with infantile convulsions. This rare syndrome is known as infantile convulsions with paroxysmal choreoathetosis (ICCA).2

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Causes or Risk Factors

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Typically, PKD is inherited in an autosomal dominant familial pattern, although some cases occur sporadically. The ICCA syndrome, also inherited in an autosomal dominant pattern, was mapped to chromosome 16 (16p11.2-q11.2). Aside from genetic sources, common symptomatic etiologies are multiple sclerosis, head trauma, and perinatal encephalopathy. Hypoparathyroidism, hyperthyroidism, and diabetes mellitus are less common sources of symptomatic PKD.

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Typical Manifestations

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PKD is provoked by a sudden movement, such as arising from a chair. However, cases similar in character may occur during exercise, from hyperventilation, or after a startle.1 Movements may be preceded by an “auralike” limb sensation....

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