A previously healthy 10-year-old boy presented with acute onset of abnormal involuntary right-sided movements, predominantly affecting the upper extremity. These movements were continuous and undulating, exacerbated by fatigue and stress, and ceased during sleep. There was no history of fever, prior trauma, or toxic exposures. Personal and family history were negative for neurologic disease.

At admission, vital signs including blood pressure were normal. Neurological examination revealed right hemichorea with low muscle tone and increased ipsilateral stretch reflexes, positive right Babinski sign, and subtly hemiplegic gait.

Lumbar puncture was performed with normal opening pressure. Isoelectric focusing was positive for increased IgG fraction. Plasma IgG was normal.

Laboratory testing of folic acid, thyroid hormone, vitamin B12, collagen, and thrombophilia profile were all normal.

Visual and auditory evoked potentials were normal. ECG and transthoracic echocardiogram were normal.

Doppler US of the neck was normal.

Brain MRI ( Fig. 71.1 ) showed a T2-hyperintense lesion in the left thalamocapsular junction with restricted diffusion. Additional T2-hyperintense, T1-hypointense lesions were noted in the periventricular and subcortical white matter, without enhancement.

Multiple sclerosis. Brain MRI, axial FLAIR shows (A) hyperintensities in the left thalamocapsular junction and (B) bilateral periventricular and subcortical white matter. FLAIR , Fluid-attenuated inversion recovery.

Spine MRI ( Fig. 71.2 ) showed multifocal T2-hyper­intense signal abnormalities in the spinal cord.

Multiple sclerosis. Thoracic spine MRI, (C) axial and (D) sagittal STIR show multifocal T2-hyperintense signal abnormalities in the thoracic cord, largest at T6 ( arrow ). STIR , Short-tau inversion recovery.

The patient received methylprednisolone pulse therapy and improved completely by the time of discharge. However, he experienced two relapses over the next 3 years.

Acute-onset chorea has a broad clinical differential diagnosis including inflammatory, ischemic, metabolic, and genetic.

Sydenham (rheumatic) chorea following group A streptococcus infection is the most frequent cause of acquired chorea in children. It is more often bilateral than unilateral but never presents pyramidal signs.

Systemic lupus erythematosus can be associated with chorea in 7% of patients and is associated with the presence of antiphospholipid antibodies. Again, symptoms are more commonly bilateral than unilateral.

Hyperglycemia can cause bilateral chorea, hemichorea-hemiballismus, and/or severe partial seizures. This is more common in older adults with type 2 diabetes and nonketotic hyperglycemia. Cases in children with type 1 diabetes are rare, as they tend to present earlier with hyperglycemia, glycosuria, and ketoacidosis.

Several genetic conditions are associated with chorea, including benign hereditary chorea, Huntington disease, Rett disease, spinocerebellar ataxia, and neurodegeneration with brain iron accumulation (NBIA). In each of these disorders, additional neurologic features are present.