The term movement disorders refers to a group of neurological conditions affecting the deep part of the brain known as the basal ganglia, resulting in either impaired control of mobility and walking (gait) or abnormal involuntary movements such as shaking (known as tremor).
Movement disorders can either cause a deficiency of movement, resulting in slowness, stiffness and delay of natural movements; or an excess of movement, resulting in abnormal involuntary movements such as tremor, jerking (e.g., myoclonus), tics, twitches, or both. The most well-known movement disorder is Parkinson’s disease, but the most common movement disorder is actually Essential Tremor (ET). Other common movement disorders include dystonia (abnormal muscle tone with inability to relax muscles fully, resulting in abnormal postures) and tic disorders (semi-involuntary movements in response to involuntary urges to move).
Although other neurological conditions may affect mobility, they may not fall into the category of movement disorders if they affect another part of the nervous system other than the basal ganglia, such as muscle or nerve. While other neurological conditions may not be considered movement disorders per se, such as stroke and multiple sclerosis, they may be associated with spasticity (an inability to relax muscles fully) which can be treated by a movement disorders team.