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), myoclonus (lightning fast jerks), restless legs syndrome, and tic disorders (semi-involuntary movements in response to involuntary urges to move). Gait disorders are often multifactorial in cause; a detailed evaluation by a movement disorders specialist to find treatable causes is the first step in management.
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.