Unveiling Multiple Sclerosis: Acute Hemichorea Masquerading as Sydenham's Chorea

Multiple sclerosis (MS) is a demyelinating disorder of the central nervous system characterized by the dissemination of lesions in time and space. Although tremors are the most commonly reported movement disorder in MS, less frequent manifestations such as paroxysmal tonic spasms, dystonia, chorea, ballism, myoclonus, myokymia, restless leg syndrome, and hemifacial spasms can also occur. Chorea and ballism are particularly rare in MS.

We report the case of a 20-year-old female who presented with a 1-month history of unsteady gait and involuntary movements of the right upper limb. Neurological examination revealed slight deviation of the angle of the mouth, hypertonia of both lower limbs, brisk knee reflexes, and involuntary, rapid, irregular, semi-purposeful movements of the right upper limb. The initial suspicion was Sydenham's chorea due to prolongation of PR interval (220 ms) and the presentation of choreiform movements. However, extensive workup including normal acute rheumatic fever markers, normal metabolic and infectious profiles, and negative autoimmune screenings did not support this diagnosis. Cerebrospinal fluid (CSF) analysis revealed positive oligoclonal bands, and Magnetic resonance imaging (MRI) showed multiple demyelinating plaques in characteristic locations for MS. The patient was diagnosed with MS and treated with steroids and valproate, followed by azathioprine. At 3-month follow-up, the patient showed significant improvement in motor functions, regaining the ability to walk and perform daily activities independently.

Acute unilateral dyskinesia in young patients, especially when other common etiologies are ruled out, should prompt consideration of MS. Detailed evaluation, including neuroimaging and CSF analysis, is crucial for accurate diagnosis and appropriate management.