Parkinson Disease

Key Features

Essentials of Diagnosis

• Any combination of tremor, rigidity, bradykinesia, and progressive postural instability ("parkinsonism")

• Cognitive impairment is sometimes prominent

General Considerations

• Risk factors

  • Age

  • Family history

  • Male sex

  • Ongoing herbicide/pesticide exposure

  • Significant prior head trauma

• Dopamine depletion due to degeneration of the dopaminergic nigrostriatal system leads to an imbalance of dopamine and acetylcholine

• Exposure to toxins and certain medications can lead to parkinsonism

  • Manganese dust

  • Carbon disulfide

  • Severe carbon monoxide poisoning

  • 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) (a recreational drug)

  • Neuroleptic drugs

  • Reserpine

  • Metoclopramide

• Postencephalitic parkinsonism is becoming increasingly rare

• Only rarely is hemiparkinsonism the presenting feature of a space-occupying lesion

Demographics

• Common disorder that occurs in all ethnic groups, with an approximately equal sex distribution

• The most common variety, idiopathic Parkinson disease, usually begins in people between ages 45 and 65 years

• May rarely occur on a familial basis

Clinical Findings

Symptoms and Signs

• Cardinal features

  • Tremor

  • Rigidity

  • Bradykinesia

  • Postural instability

• Nonmotor manifestations include

  • Affective disorders (depression, anxiety, and apathy)

  • Psychosis

  • Cognitive changes

  • Fatigue

  • Sleep disorders

  • Anosmia

  • Autonomic disturbances

  • Sensory complaints or pain

  • Seborrheic dermatitis

• Dementia or mild cognitive impairment will eventually develop in many patients

• Tremor

  • Four to six cycles per second

  • Most conspicuous at rest

  • Enhanced by stress

  • Often less severe during voluntary activity

  • Commonly confined to one limb or to one side for months or years before becoming more generalized

  • May be present about mouth and lips

  • May be absent in some patients

• Rigidity causes the flexed posture

• Bradykinesia is the most disabling symptom, ie, a slowness of voluntary movement and a reduction in automatic movements such as swinging of the arms while walking

• The face

  • Relatively immobile with widened palpebral fissures

  • Infrequent blinking

  • Fixity of facial expression

  • Seborrhea of scalp and face

• Mild blepharoclonus

• Repetitive tapping (about twice per second) over the bridge of the nose producing a sustained blink response (Myerson sign)

• Other findings

  • Saliva drooling from the mouth

  • Soft and poorly modulated voice

  • Variable rest tremor and rigidity in some or all of the limbs

  • Slowness of voluntary movements

  • Impairment of fine or rapidly alternating movements

  • Micrographia

• Typically no muscle weakness and no alteration in the tendon reflexes or plantar responses

• Difficulty rising from a sitting position and beginning to walk

• Gait

  • Small shuffling steps and a loss of the normal automatic arm swing

  • There may be unsteadiness on turning, difficulty in stopping, and a tendency to fall

Differential Diagnosis

• Essential tremor

• Depression

• Wilson disease

• Huntington disease

• Normal-pressure hydrocephalus

• Multisystem atrophy (previously called Shy-Drager syndrome)

• Progressive supranuclear palsy

• Corticobasal ganglionic degeneration

• Diffuse Lewy body disease

• Creutzfeldt-Jakob disease

• Drugs causing parkinsonism

  • Antipsychotic agents

  • Reserpine

  • Metoclopramide

  • MPTP

Diagnosis