Merck Manual

Please confirm that you are a health care professional

honeypot link

Overview of Movement and Cerebellar Disorders


Hector A. Gonzalez-Usigli

, MD, HE UMAE Centro Médico Nacional de Occidente

Last full review/revision May 2020| Content last modified May 2020
Click here for Patient Education
Topic Resources

Voluntary movement requires complex interaction of the corticospinal (pyramidal) tracts, basal ganglia, and cerebellum (the center for motor coordination) to ensure smooth, purposeful movement without extraneous muscular contractions.

The pyramidal tracts pass through the medullary pyramids to connect the cerebral cortex to lower motor centers of the brain stem and spinal cord.

The basal ganglia (caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra) form the extrapyramidal system. They are located deep in the forebrain and rostral midbrain. The basal ganglia direct their output mainly through the thalamus to the cerebral cortex (see figure Basal ganglia).

Most neural lesions that cause movement disorders occur in the extrapyramidal system; thus, movement disorders are sometimes called extrapyramidal disorders.

Basal ganglia

Basal ganglia

Classification of Movement and Cerebellar Disorders

Movement disorders are commonly classified as those with

  • Decreased or slow movement (hypokinetic disorders)

  • Increased movement (hyperkinetic disorders)

The classic and most common hypokinetic disorder is

Hyperkinetic disorders refer to

However, this classification does not account for overlap between categories (eg, tremors that occur in Parkinson disease).

Cerebellar disorders are sometimes considered hyperkinetic disorders.

Hyperkinetic disorders

  • Rhythmic

  • Nonrhythmic

Rhythmic disorders are primarily tremors—regular alternating or oscillatory movements, which can occur mainly at rest, while maintaining a position, and/or during attempted movement. However, in some cases, a tremor, though rhythmic, is irregular, as occurs when tremor is associated with dystonic disorders.

Nonrhythmic hyperkinetic disorders can be

  • Slow (eg, athetosis)

  • Sustained (eg, dystonias)

  • Rapid (eg, myoclonus, chorea, tics, hemiballismus)

Rapid nonrhythmic hyperkinetic disorders may be

  • Suppressible (eg, tics)

  • Nonsuppressible (eg, hemiballismus, chorea, myoclonus)

Athetosis and chorea may occur together as choreoathetosis. Chorea is the most characteristic movement disorder in Huntington disease.

Multiple motor and phonatory tics are the defining feature of Tourette syndrome.

Classification of common hyperkinetic disorders

Classification of common hyperkinetic disorders

Hyperkinetic Disorders

Abnormal Movement



Drugs (eg, cocaine, amphetamines, antipsychotics)

Movements are nonrhythmic, slow, writhing, and sinuous (snakelike), primarily in distal muscles; alternating postures of the proximal limbs often blend continuously to produce a flowing stream of movement.

Athetosis has features of dystonia and chorea and often occurs with chorea as choreoathetosis.

Huntington disease, hyperthyroidism, hypoparathyroidism, paraneoplastic syndromes, systemic lupus erythematosus (SLE) affecting the CNS, other autoimmune disorders, rheumatic fever, tumors or infarcts of the caudate nucleus or putamen

Pregnancy, often in women who had rheumatic fever

Drugs that can cause chorea (eg, levodopa, phenytoin, cocaine, oral contraceptives)

Drugs that can cause tardive dyskinesia (eg, antipsychotics)

Movements are nonrhythmic, jerky, rapid, and nonsuppressible, primarily in distal muscles or the face.

Sometimes abnormal movements are incorporated into semipurposeful acts that mask the involuntary movements.

Chorea often occurs with athetosis as choreoathetosis.


Primary (idiopathic)

Degenerative or metabolic disorders (eg, Wilson disease, neurodegeneration with brain iron accumulation [NBIA] such as PKAN due to a PANK2 mutation [previously, Hallervorden-Spatz disease], various lipidoses, multiple sclerosis, cerebral palsy, stroke, brain hypoxia)

Drugs that block dopamine receptors, most often antipsychotics (eg, phenothiazines, thioxanthenes, butyrophenones) or antiemetics

Sustained or intermittent muscle contractions often distort body posture or cause twisting, repetitive movements.

Lesions (most often due to stroke) in the contralateral subthalamic nucleus or in connecting afferent or efferent pathways

Movements are nonrhythmic, rapid, nonsuppressible, violent, and flinging.

Various causes (eg, degeneration of the basal ganglia, dementias, epileptic syndromes, metabolic disturbances, physical and hypoxic encephalopathies, toxic encephalopathies, viral encephalopathies, certain drugs such as levodopa, lithium, and MAO inhibitors)

Very rapid and jerky, nonsuppressible, shocklike twitches occur; they may be focal, segmental, or generalized.


Secondary: Huntington disease, neuroacanthocytosis, PKAN, infections, stroke, drugs (eg, methylphenidate, cocaine, amphetamines, dopamine antagonists [which can cause tardive dyskinesias])

Movements are nonrhythmic, stereotypical, rapid, and repetitive; characteristically, patients have an urge to do them and feel brief relief after doing them.

Tics can be suppressed only for brief periods and with conscious effort.

Tics may be motor or phonatory; they may be simple (eg, eye blinking, growling, clearing the throat) or complex (eg, shoulder shrugging, arm swinging, shouting words or sentences, including obscenities).

Essential tremor

Wilson disease

Certain drugs (eg, lithium, valproate, olanzapine, other typical and atypical antipsychotics—see table Some Causes of Parkinsonism)

Endocrine, metabolic, and toxic disorders (eg, anoxic encephalopathy, hepatic encephalopathy,, hypoglycemia, hyperparathyroidism, hyperglycemia, hyperthyroidism, hypocalcemia, uremia, heavy metal toxicity)


Movements are regular, mostly rhythmic, and oscillatory.

CNS = central nervous system; MAO = monoamine oxidase; PKAN = pantothenate kinase‒associated neurodegeneration.

Drugs Mentioned In This Article

Drug Name Select Trade
No US brand name
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Test your knowledge

Vascular Dementia
Dementia is chronic and global deterioration of cognition. Delirium also involves disturbances in cognition. Which of the following characteristics best differentiates delirium from dementia?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID