36 Chorea
Clinical Vignette
John is a 56-year-old-right-handed architect who developed tick-like movements in his body within the past 3–4 years and was now “fidgety” all the time. His wife reported intellectual changes in her husband; he seemed withdrawn and forgetful, was occasionally inappropriate in his behavior, had difficulties with his job, and had to retire early due to inability to “concentrate.” He had no other past medical history. He was adopted and there was no health information about his parents. Tourette syndrome was diagnosed by his primary care physician.
When seen in movement disorders clinic, he was unable to sit still. He had constant grimacing in his face, motor impersistence in his tongue, and piano-like playing movements in his hands. Brief, jerky choreiform movements were present in his trunk and extremities. His gait appeared very disorganized and unsteady. He had bradykinesia predominantly with testing of his hands. His demeanor was jovial and he had no signs of depression. The movements were not under any voluntary control and he had no urge to do them.
Because of the combination of cognitive decline and generalized chorea, Huntington disease was suspected. His genetic testing revealed 45 CAG repeats in the HD gene. He was treated with low doses of haloperidol 1 mg daily with substantial improvement in chorea. Recently, an addition of tetrabenazine was initiated, with further improvement of involuntary movements. However, his intellectual and behavioral decline continued.
Chorea (from Latin choreus, dance) is an abnormal involuntary movement usually distal in location, brief, nonrhythmic, abrupt, and irregular, that seems to flow from one body part to another. The movements are random, unpredictable in timing, direction, and distribution. Chorea can be partially suppressed; some patients can incorporate these into semipurposeful movements called parakinesia. Motor impersistence, the inability to maintain a sustained contraction, is a typical feature of chorea.
Athetosis and ballism are sometimes confused with chorea. Athetosis is a slow, writhing, continuous set of involuntary movements, usually affecting limbs distally, but it can involve the axial musculature (neck, face, and tongue). If athetosis becomes faster, it sometimes blends with chorea, that is, choreoathetosis. Ballism is large-amplitude, involuntary movements affecting the proximal limbs, causing flinging and flailing limb movements.
Patients with chorea are often initially unaware of these involuntary movements. The chorea is often first interpreted by observers as fidgetiness. The patients are usually frustrated by their own incoordination or clumsiness.
Etiology
Chorea results from disruption of the basal ganglia’s modulation of thalamocortical motor pathways. Multiple pathophysiologic mechanisms may be implicated. These include neuronal degeneration in selective regions, neurotransmitter receptor blockade, other metabolic factors within the basal ganglia, and exceedingly rarely a structural lesion. Chorea is classified into inherited, primarily Huntington disease (HD), immunologic Sydenham chorea, drug-related, structural, and various miscellaneous etiologies (Table 36-1).
| Type of Chorea | |
|---|---|
| Inherited | |
| Metabolic | |
| Immunologic | |
| Drug related | |
| Structural | |
| Miscellaneous | |
Pathophysiology
The putamen, globus pallidus, and subthalamic nuclei are the key pathologic sites related to the development of chorea. Normal movement patterns depend on the presence of a critical physiologic balance between the direct and indirect motor pathways. Healthy individuals have an excitatory glutamate pathway, arising from within the subthalamic nucleus, that excites the globus pallidus interior and the substantia nigra. Concomitantly, these areas then signal the GABA inhibitory pathway within the thalamus. In a simplified model, the excitatory action of the subthalamic nucleus is reduced or lost, leading to a disinhibition of the pallidothalamic pathway.
The major neurodegenerative pathology in HD occurs within the caudate nuclei and the putamen (striatum). These changes primarily affect medium-sized “spiny” neurons
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