A movement disorder, or dyskinesia, is a neurological condition that limits a patient’s ability to control movement. Depending on the condition and the area of the brain affected, the movements may either be exaggerated or occur beyond the patient’s control. Conversely, some movement disorders are characterized by slowed movement or the inability to move.

Voluntary movements – those that a person consciously thinks about and controls – require complex processes. Movement begins with nerve signals that are processed in multiple parts of the brain. The signals then travel through the spinal cord to motor neurons, the nerve cells that signal muscles. The motor neurons send neurotransmitters to muscle fibers that cause contraction or relaxation. In addition to voluntary movements, there are also reflexes and internal muscle movements, such as those that involve circulation and breathing. They are controlled by different aspects of the nervous system, but may also be impacted by movement disorders.

Any condition that disrupts the communication process between the nerves and muscles and causes problems with movement may be considered a movement disorder. These conditions include head injury, stroke, infection, genetic defects and nerve degeneration in the brain. The severity of the disorder is likely linked to the degree of damage to the nerve cells (neurons). It may also reflect which section or sections of the brain are affected.

Many movement disorders involve damage or disease to the basal ganglia, which is located deep within the brain and is integral to many aspects of movement. Other movement disorders may result from damage or disease to the cortex, brain stem or cerebellum, each of which are also associated with aspects of movement. For example, Parkinson’s disease involves the destruction of cells within a small region of the brain stem known as the substantia nigra. These cells produce and release a neurotransmitter called dopamine, which controls movement and balance in the body. Dopamine is vital to proper central nervous system functioning and helps electrochemical signals move from one neuron to another. A sharp decline in dopamine production results in most of the symptoms of Parkinson’s disease.