Chorea consists of irregular, unpredictable, involuntary muscle jerks that occur in different parts of the body and impair voluntary activity. In some instances, the proximal muscles of the limbs are most severely affected, and because the abnormal movements are then particularly violent, the term ballismus has been used to describe them. Chorea may be hereditary or acquired and may occur as a complication of a number of general medical disorders and of therapy with certain drugs.
Abnormal movements may be slow and writhing in character (athetosis) and, in some instances, are so sustained that they are more properly regarded as abnormal postures (dystonia). Athetosis or dystonia may occur with perinatal brain damage, with focal or generalized cerebral lesions, as an acute complication of certain drugs, as an accompaniment of diverse neurologic disorders, or as an isolated inherited phenomenon of uncertain cause known as idiopathic torsion dystonia or dystonia musculorum deformans. Various genetic loci have been reported depending on the age of onset, mode of inheritance, and response to dopaminergic therapy. The physiologic basis is uncertain, and treatment is unsatisfactory. Patients with dystonia commonly have psychiatric complications, such as depression, that affect the quality of life. These may be secondary to the dystonia or a nonmotor manifestation of the underlying disorder.
Tics are sudden coordinated abnormal movements that tend to occur repetitively, particularly about the face and head, especially in children, and can be suppressed voluntarily for short periods of time. Common tics include repetitive sniffing or shoulder shrugging. Tics may be single or multiple and transient or chronic. Gilles de la Tourette syndrome is characterized by chronic multiple tics; its pharmacologic management is discussed at the end of this chapter.
Many of the movement disorders have been attributed to disturbances of the basal ganglia. The basic circuitry of the basal ganglia involves three interacting neuronal loops that include the cortex and thalamus as well as the basal ganglia themselves (Figure 28–1). However, the precise function of these anatomic
FIGURE 28–1 Functional circuitry between the cortex, basal ganglia, and thalamus. The major neurotransmitters are indicated. In Parkinson’s disease, there is degeneration of the pars compacta of the substantia nigra, leading to overactivity in the indirect pathway (red) and increased glutamatergic activity by the subthalamic nucleus.
structures is not yet fully understood, and it is not possible to relate individual symptoms to involvement at specific sites.
Parkinsonism is characterized by a combination of rigidity, bradykinesia, tremor, and postural instability that can occur for a variety of reasons but is usually idiopathic (Parkinson’s disease or paralysis agitans). Bradykinesia should be present before a diagnosis of Parkinson’s disease is made. Focal dystonic features may be present. Cognitive decline occurs in many patients as the disease advances. Other nonmotor symptoms include affective disorders (anxiety or depression); confusion, cognitive impairment, or personality changes; apathy; fatigue; abnormalities of autonomic function (eg, sphincter or sexual dysfunction, dysphagia and choking, sweating abnormalities, sialorrhea, or disturbances of blood pressure regulation); sleep disorders; and sensory complaints or pain. The disease is incurable, is generally progressive, and leads to increasing disability with time, but pharmacologic treatment may relieve motor symptoms and improve the quality of life for many years.