Definition

Involuntary movement disorders can be characterized by either too little (hypokinetic) or too much (hyperkinetic) movement. Hypokinetic problems include Parkinson disease and Parkinson-like conditions, such as progressive supranuclear palsy, vascular or trauma-induced parkinsonism, and multisystem atrophy (which encompasses the related disorders of Shy-Drager syndrome, striatonigral degeneration, and olivopontocerebellar degeneration). Hyperkinetic disorders include parkinsonian and nonparkinsonian tremor, tics, Gilles de la Tourette syndrome, dystonia, dyskinesias (including tardive dyskinesias), hemifacial spasm, athetosis, chorea (including Huntington disease), hemiballismus, myoclonus, and asterixis [1].

Essential tremor, the most common movement disorder, is 5 to 10 times more prevalent than Parkinson disease in the general population. Parkinson disease affects 1 million Americans including 1% of those older than 60 years. Idiopathic Parkinson disease constitutes approximately 85% of all the Parkinson-like conditions; neuroleptic-induced Parkinson disease (7%-9%), vascular parkinsonism (3%), multisystem atrophy (2.5%), and progressive supranuclear palsy (1.5%) represent much smaller fractions. Relatively rare, Huntington disease occurs with a frequency in the population as low as 0.004% by some estimates [2,3].

Symptoms

Tremors, the most common form of involuntary movement disorders, are characterized by rhythmic oscillations of a body part. Tremors can be classified as to the situation in which they are most prominent, that is, most pronounced at rest or with movement. Tremors with movement are subdivided into those occurring with maintained posture (postural or static tremor, tested by holding the arms out in front), with movement from point to point (kinetic or intentional tremor, tested by finger to nose pointing), or with only a specific type of movement (task-specific tremor). Tremors that are at their worst at rest are exclusively associated with Parkinson disease or other parkinsonian states (such as those produced by neuroleptics) [2,4].

Parkinsonian patients commonly show a resting tremor, slowness of movement or bradykinesia, and a form of increased muscle tone called rigidity (see Chapter 141 for more details). Other common features are reduction in movements of facial expression resulting in “masked facies,” stooped posture, and reduction of the amplitude of movements (hypometria). Also seen are changes in speech to a soft monotone (hypophonia) and small, less legible handwriting (micrographia). Walking becomes slower, stride length is reduced, and pivoting is replaced with a series of small steps (turning “en bloc”) [5,6]. The nonmotor symptoms associated with Parkinson disease can be equally disabling: fatigue, pain, and neuropsychiatric disturbances, among others [3]. The following syndromes typically are manifested with the listed features in addition to the characteristic symptoms of Parkinson disease (tremor and rigidity) [7].

• Shy-Drager syndrome: autonomic failure with prominent postural hypotension

• Progressive supranuclear palsy: reduction in vertical gaze and slowing of eye movements

• Vascular parkinsonism: early dementia with brisk tendon reflexes

• Multiple head trauma, “parkinsonism pugilistica”: early dementia with brisk tendon reflexes

• Olivopontocerebellar degeneration: prominent intention tremor, imbalance, and ataxia

Tics are sustained nonrhythmic muscle contractions that are rapid and stereotyped, often occurring in the same extremity or body part during times of stress. The muscles of the face and neck are usually involved, with movement of a rotational sort away from the body’s midline. They are commonly familial and often seen in otherwise normal children between the ages of 5 and 10 years and usually disappear by the end of adolescence. Tourette syndrome is characterized by motor and vocal tics lasting for more than 1 year and may involve involuntary use of obscenities and obscene gestures, although such behavior may be mild and transient and occurs only in a minority of afflicted persons [6,8].

Dystonias are slow, sustained contractions of muscles that frequently cause twisting movements or abnormal postures. The disorder resembles athetosis but shows a more sustained static contraction. When rapid movements are involved, they are usually repetitive and continuous. Dystonia often increases with emotional or physical stress, anxiety, pain, or fatigue and disappears with sleep. The dystonias are further classified as focal, segmental, or multifocal on the basis of the distribution of muscles affected. Symptoms of hemifacial spasm usually begin in the orbicularis oculi and later involve other muscles innervated by cranial nerve VII [1,6,9].

Tardive dyskinesia is a condition characterized by involuntary, choreiform movements of the face and tongue associated with chronic neuroleptic medication use. Common movements include chewing, sucking, mouthing, licking, “fly-catching movements,” puckering, and smacking (buccal-lingual-masticatory syndrome). Choreiform movements of the trunk and extremities can also occur along with dystonic movements of the neck and trunk.

Athetosis is characterized by involuntary, slow, writhing, and repetitious movements. They are slower than choreiform movements and less sustained than dystonia. Athetosis may be seen alone or in combination with other movement disorders and itself leads to bizarre but characteristic postures. Any part of the body can be affected, but it is usually the face and distal upper extremities that are involved. Chorea is manifested as nonstereotyped, unpredictable, and jerky movements that interfere with purposeful motion. The movements are rapid, erratic, and complex and can be seen in any or all body parts but usually involve the oral structures, causing abnormal speech and respiratory patterns. Hemiballismus is an uncommon disorder consisting of extremely violent flinging of the arms and legs on one side of the body.

Myoclonus is one of the most common involuntary movement disorders of central nervous system origin. It is characterized by sudden, jerky, irregular contractions of a muscle or groups of muscles. It can be subdivided into stimulus-sensitive myoclonus (reflex myoclonus), appearing with volitional movement, muscle stretch, or superficial stimuli such as touch, and non–stimulus- sensitive myoclonus, which occurs at rest (spontaneous myoclonus). Myoclonic movements can be either irregular or periodic [1,6].

Physical Examination

A complete physical examination is key to ruling out treatable causes of the presenting movement disorder, such as infectious (encephalitis), medication side effect (tardive dyskinesia), genetic (Tourette syndrome), or endocrinologic (tremor-associated thyrotoxicosis).