Definition

Movement disorders refer to a collection of CNS conditions that result in abnormal movements, limb postures, or skeletal muscle tone. A number of movement disorders result from damage to the basal ganglia or its connections (leading to the term “extrapyramidal” disease or disorder), although pathology to the cerebellum, cerebral cortex, and peripheral nervous system is also involved. 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.

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.

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).

Parkinsonian patients commonly show a resting tremor, slowness of movement or bradykinesia, and a form of increased muscle tone called rigidity (see Chapter 142 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”). The non-motor symptoms associated with Parkinson disease can be equally disabling: fatigue, pain, and neuropsychiatric disturbances, among others. The following syndromes typically are manifested with the listed features in addition to the characteristic symptoms of Parkinson disease (tremor and rigidity):

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  Shy-Drager syndrome: autonomic failure with prominent postural hypotension

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

  
  
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  Vascular parkinsonism: early dementia with brisk tendon reflexes

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

  
  
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  Olivopontocerebellar degeneration: prominent intention tremor, imbalance, and ataxia

Tics are sustained non-rhythmic 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.

Dystonias are sustained or intermittent contractions of muscles that frequently cause abnormal, involuntary movements and/or postures. The movements are typically described as twisting or patterned. The disorder resembles athetosis, but shows a more sustained static contraction. When rapid movements are involved, they are usually repetitive and continuous. Dystonias are often initiated or made worse by voluntary action and often increase with emotional or physical stress, anxiety, pain, or fatigue. Symptoms quite often disappear with sleep. Dystonia can be classified on the basis of the distribution of the muscles affected. Generally, they are classified as: focal (affecting an isolated body part), segmental (affecting adjacent body areas), or multifocal (affecting two or more noncontiguous areas). Hemidystonia affects the arm and leg muscles on the same side of the body. Generalized dystonia affects most or all of the body. Cervical dystonia is the most common form of focal dystonia (see Chapter 5 ). Dystonias can also be classified as syndromes based on the pattern of distribution. For example, symptoms of hemifacial spasm usually begin in the orbicularis oculi and later involve other muscles innervated by cranial nerve VII.

Chorea is manifested as nonstereotyped, unpredictable, and jerky movements that interfere with purposeful motion. The movements are rapid, erratic, and complex. They can be seen in any or all body parts, but usually involve the oral structures, causing abnormal speech and respiratory patterns. 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.

Ataxia is the loss of the ability to perform coordinated voluntary movement. Ataxia is a primary clinical presentation of cerebellar disease or damage to the pathways connecting to the cerebellum.

Ballismus is an uncommon disorder consisting of large amplitude movements of the proximal limb muscles, which result in flinging or flailing of the arms and legs. Hemiballismus is the term used when symptoms are localized to one side of the body (most common presentation).

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.

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).

A good neurologic examination of patients thought to have a movement disorder helps identify an underlying causative condition, such as stroke (e.g., cerebrovascular-based Parkinson disease, hemiballismus, or ataxia), tumor, brain trauma, or even peripheral nerve injury–associated focal dystonias. Other aspects of physical examination focus on characterization of the type of abnormal movements by detailing of their body distribution (limb, trunk, head, face, or widespread), their quality (tremor, writhing, explosive, rigidity), their frequency (rapid and repetitive or slow and sustained), and their general quantity or lack thereof (hyperactive or hypoactive).

For instance, essential tremor (senile tremor) is usually rapid and fine and occurs when the patient is asked to hold the arms outstretched, whereas parkinsonian tremor decreases with voluntary movement. Intention (cerebellar) tremor is slow and broad, occurring at the end of a purposeful motion, as when the patient executes a finger-to-nose task. In addition to tests of cerebellar function, tests for upper motor neuron syndrome (hyperreflexia, spasticity, presence of Babinski sign) may assist the examiner in distinguishing movement disorders more commonly associated with stroke or brain injury.