Chapter 198

Movement Disorders and Essential Tremor

Nancy McQueen Le, Katie McCube

Definition and Epidemiology

Movement disorders include a variety of neurologic conditions that cause alteration in normal movement or unnatural movements. These can be further categorized as excessive movements or hyperkinesis and decreased amplitude or range of movement or hypokinesis. Additional definitions can be found in Box 198-1.

Box 198-1

Definitions

Akathisia: A sense of inner general restlessness reduced or relieved by moving about.

Asterixis: A brief flap of outstretched limb, transient inhibition of the muscles of posture.¹

Ataxia: An unsteady or swaying motion. Movements may appear irregular or clumsy.

Athetosis: A slow, writhing, continuous, involuntary movement.

Chorea: An involuntary, irregular, nonrhythmic movement that seems to flow from one body part to another. The movements are unpredictable in timing, direction, and body part affected.

Dyskinesia: A general term for any abnormal involuntary movement. Paroxysmal dyskinesias are abnormal movements that occur only at certain times; hypnogenic dyskinesias typically occur during non–rapid eye movement (REM) sleep. Tardive dyskinesia refers to movements induced by dopaminergic agents, most commonly neuroleptics and metoclopramide.

Dystonia: A sustained involuntary muscle contraction that results in twisting movement and posture, often patterned and repetitive.

Myoclonus: Sudden, irregular, involuntary jerking of the muscles.

Myokymia: A fine quivering or rippling of muscles. Common and benign in facial muscles.

Stereotypy: A coordinated movement that repeats continually and identically. Compulsion.

Tics: Sudden, repetitive, nonrhythmic motor movement or vocalization. A habitual spasmodic involuntary muscle contraction.

Tremor: An oscillation, usually rhythmic and regular, affecting various body parts, such as limbs, neck, tongue, chin, or vocal cords. Can be classified as resting, postural, or action or intention tremor.

The most common hyperkinetic movement disorders include essential tremor, restless legs syndrome, dystonia, and Tourette syndrome. Less common are hemifacial spasms, blepharospasm, ataxias, and Huntington disease.¹

The most common hypokinetic movement disorder is Parkinson disease. Less common are progressive supranuclear palsy and multisystem atrophy.¹

Pathophysiology

Voluntary movement requires complex interactions between the pyramidal tracts, cerebellum, and basal ganglia to produce smooth, decisive movement without extraneous muscular contractions.² Many abnormal movements are associated with pathologic alterations within these structures and their connections, whereas others can arise from elsewhere in the central nervous system (CNS), such as the cerebral cortex or the spinal cord. The peripheral nervous system can also give rise to abnormal movements, such as restless leg syndrome.

In some movement disorders, such as Parkinson disease, the underlying complex pathology is becoming better understood, but for many movement disorders much of the cause remains unclear.

Clinical Presentation

The presentation of movement disorders will depend on the underlying cause, so establishing a careful history specific to the patient’s complaint is important (Box 198-2). The primary complaint may not be the abnormal movement, but the functional limitation it imposes on the patient’s activities of daily living. Movement disorders primarily fall into several categories.

Box 198-2

Categories of Movement Disorders³

Insufficient Movement

• Akinetic, hypokinetic, or bradykinetic syndromes

Too Much Movement

• Jerky

• Myoclonus, chorea, and tic disorders

• Nonjerky

• Dystonia and tremor

It is important to ascertain which category the movement disorder falls into by obtaining a careful history. This includes the age at onset, the regions of the body affected, progression of symptoms, the quality of movements and dysfunction, the factors that make symptoms better or worse, and the timing. A family history of movement disorder should be noted as well. A medication, alcohol, and drug history is necessary and should include prescription, over-the-counter, and illicit drug use. Alcohol, drugs, and/or medications can exacerbate or even mask underlying conditions or symptoms.

Physical Examination

The examination should be approached in a systematic fashion. Make note of observations throughout the examination visit. The examination should include a complete neurologic examination and general physical assessment. Subtle findings in movement may differentiate some of the disorders. All aspects of the neurologic examination may provide clues to assist in ruling in or out different movement disorders. A neurologic examination should include evaluation of cognition, cranial nerves, motor function (strength, tone, and coordination), sensor function, deep tendon reflexes (DTRs), and gait. The goal is to define the characteristics of the movement, determine which definition fits, and eliminate those that do not.

First look at obvious features. These include rhythm, duration, and continuity of contractions; type of oscillations (rapid or slow); and amplitude (fine or coarse). Note whether the movements occur at rest or during action and are patterned or random and whether there is a combination of movements. Also evaluate other factors such as speed, force, complexity of the movement, and any associated sensory symptoms.

Diagnostics

Initial diagnostic studies to consider would be basic laboratory studies to rule out medical or metabolic abnormalities. If there is reason to suspect infection or alcohol or drug use, additional focused workup would be warranted. Neurologic imaging, often in conjunction with a neurologic referral, may be warranted if there are specific neurologic findings.