Every body movement, from raising a hand to smiling, involves a complex interaction between the central nervous system (brain and spinal cord), nerves, and muscles. Damage to or malfunction of any of these components may result in a movement disorder.
Different types of movement disorders can develop, depending on the nature and location of the damage or malfunction, as in the following:
Damage to the parts of the brain that control voluntary (intended) movement or the connections between the brain and spinal cord: Weakness or paralysis of the muscles involved in voluntary movements and exaggerated reflexes
Damage to the basal ganglia (collections of nerve cells located at the base of the cerebrum, deep within the brain): Involuntary (unintended) or decreased movements, but not weakness or changes in reflexes
The basal ganglia help initiate and smooth out voluntary muscle movements, suppress involuntary movements, and coordinate changes in posture.
The cerebellum coordinates the body’s movements, helps the limbs move smoothly and accurately, and helps maintain balance.
Some movement disorders, such as hiccups Hiccups Hiccups are repeated involuntary spasms of the diaphragm, followed by quick, noisy closings of the glottis. The diaphragm is the muscle that separates the chest from the abdomen and that is... read more , are temporary, usually causing little inconvenience. Others, such as Parkinson disease Parkinson Disease (PD) Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more , are serious and progressive, impairing the ability to speak, use the hands, walk, and maintain balance when standing.
Locating the Basal Ganglia
The basal ganglia are collections of nerve cells located deep within the brain. They include the following:
The basal ganglia help initiate and smooth out muscle movements, suppress involuntary movements, and coordinate changes in posture.
Classifying movement disorders often helps doctors identify the cause.
Movement disorders are commonly classified as those that cause
Decreased or slow movement
The most common disorder that decreases and/or slows movement is
Disorders that increase movement include
Akathisia (inability to sit still)
Restless leg syndrome Periodic Limb Movement Disorder (PLMD) and Restless Legs Syndrome (RLS) Periodic limb movement disorder involves repetitive movements of the arms, legs, or both during sleep. Restless legs syndrome involves an irresistible urge to move and usually abnormal sensations... read more
Stereotypies (stereotypic movements)
Stereotypies are repetitive, rhythmic movements. They occur in children with autism spectrum disorders Autism Spectrum Disorders Autism spectrum disorders are conditions in which people have difficulty developing normal social relationships, use language abnormally or not at all, and show restricted or repetitive behaviors... read more , intellectual disability Intellectual Disability Intellectual disability is significantly below average intellectual functioning present from birth or early infancy, causing limitations in the ability to conduct normal activities of daily... read more , or encephalitis Encephalitis Encephalitis is inflammation of the brain that occurs when a virus directly infects the brain or when a virus, vaccine, or something else triggers inflammation. The spinal cord may also be involved... read more , as well as in children without these conditions. These movements can usually be stopped by distracting the child—for example, by calling the child's name.
Coordination problems are sometimes classified as disorders that increase movement. They are often caused by malfunction of the cerebellum, resulting in tremor and problems with balance and walking.
In some disorders, movement is increased and decreased. For example, Parkinson disease causes tremors—increased unintended (involuntary) movements—and slow intended (voluntary) movements.
Disorders that increase movement can be
Rhythmic, which are primarily tremors (although tremors are sometimes irregular, as occurs in dystonia Dystonias Dystonias are involuntary muscle contractions, which may be long-lasting (sustained) or come and go (intermittent). Dystonias may force people into abnormal positions—for example, causing the... read more )
Nonrhythmic, which may involve slow or rapid movements and/or a sustained position
Some rapid, nonrhythmic movements, such as tics Tourette Syndrome and Other Tic Disorders in Children and Adolescents Tics are rapid, purposeless, repetitive but not rhythmic, involuntary movements (muscle or motor tics) or involuntary, abrupt, often repetitive sounds and/or words (vocal tics). They can be... read more , can be temporarily stopped (suppressed). Others, such as hemiballismus, chorea, and myoclonus, may be difficult to suppress or impossible to suppress completely.