Hemichorea-hemiballismus syndrome

Hemichorea-hemiballismus syndrome (HCHB) describes a rare movement disorder characterized by unilateral hemichorea and hemiballismus.

Epidemiology

The syndrome is thought to be rare, however the exact epidemiology depends on the cause of HCHB.

Clinical presentation

Patient presents with either or both of :

• hemichorea: involuntary, irregular, non-rhythmic movements of one side of the body
• hemiballismus: involuntary, flinging, violent movements of one side of the body

Notably, given hemichorea is the clinically milder movement disorder of the two, some patients are seen to transition from hemiballismus to hemichorea as they recover .

Pathology

The syndrome is thought to be caused by a lesion in the basal ganglia, specifically, the subthalamic nucleus (corpus Luysi) . When this nucleus is damaged, there is reduced excitatory innervation to the internal segment of the globus pallidus, which results in increased inhibitory innervation to the thalamus, which finally leads to increased excitatory innervation to the primary motor cortex . This cascade of events leads to the development of the involuntary movements exhibited in this syndrome .

However, there are many reports, perhaps even a majority of reports, of this syndrome developing in patients with lesions not of the subthalamic nucleus . These are thought to occur in regions of the brain with innervation to the subthalamic nucleus, of which there postulated to be many, however their individual exact roles in the development of this syndrome are yet to be elucidated .

Etiology

There are numerous etiologies potentially affecting the subthalamic nucleus (or other strategic areas) that have been implicated in this syndrome :

• stroke: ischemic or hemorrhagic
• neoplasm
• vascular malformation
• demyelination
• non-ketotic hyperglycemia (when presenting with HCHB, is known as ‘non-ketotic hyperglycemic hemichorea’, or as ‘diabetic striatopathy’, or as ‘chorea, hyperglycemia, basal ganglia syndrome’)
• vasculitis (e.g. due to systemic lupus erythematosus)
• trauma
• infection:
  • tuberculoma
  • cerebral toxoplasmosis

Radiographic features

The specific radiographic features depend on the underlying etiology - please see individual articles.

Treatment and prognosis

The specific treatment and prognosis depend on the underlying etiology - please see individual articles.

Generally, symptomatic relief should be offered to patients significantly affected and who are unlikely to make a rapid recovery . This symptomatic treatment may include medications such as typical neuroleptics or tetrabenazine, or neurosurgical intervention .