Chapter 186: Parkinson’s Disease

Chapter 186: Parkinson’s Disease is a topic covered in the Harrison's Manual of Medicine.

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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 186-1: Clinical Features of Parkinson’s Disease
CARDINAL MOTOR FEATURESOTHER MOTOR FEATURESNONMOTOR FEATURES

Bradykinesia

Rest tremor

Rigidity

Postural instability

Micrographia

Masked facies (hypomimia)

Reduced eye blinking

Drooling

Soft voice (hypophonia)

Dysphagia

Freezing

Anosmia

Sensory disturbances (e.g., pain)

Mood disorders (e.g., depression)

Sleep disturbances (e.g., RBD)

Autonomic disturbances

 Orthostatic hypotension

 Gastrointestinal disturbances

 Genitourinal disturbances

 Sexual dysfunction

Cognitive impairment/Dementia

Abbreviation: RBD, rapid eye movement behavior disorder.
TABLE 186-2: Differential Diagnosis of Parkinsonism

Parkinson’s disease

 Sporadic

 Genetic

Dementia with Lewy bodies

Atypical parkinsonism

 Multiple-system atrophy (MSA)

  Cerebellar type (MSA-c)

  Parkinson type (MSA-p)

Progressive supranuclear palsy

  Parkinsonism

  Richardson variant

Corticobasal syndrome

Frontotemporal dementia

Secondary parkinsonism

 Drug-induced

 Tumor

 Infection

 Vascular

 Normal-pressure hydrocephalus

 Trauma

 Liver failure

 Toxins (e.g., carbon monoxide, manganese, MPTP, cyanide, hexane, methanol, carbon disulfide)

Neurodegenerative disorders and other forms of parkinsonism

 Wilson’s disease

 Huntington’s disease

 Neurodegeneration with brain iron accumulation

 SCA 3 (spinocerebellar ataxia)

 Fragile X–associated ataxia-tremor-parkinsonism

 Prion disease

 X-linked dystonia-parkinsonism

 Alzheimer’s disease with parkinsonism

 Dopa-responsive dystonia

Abbreviation: MPTP, 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine.

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