Borrelia burgdorferi (Bb) can cause a large number of neurological symptoms. Although extrapyramidal disturbances are rare (representing less than 2% of all neurological complications), diffuse choreic dyskinesias have been described during the course of mild encephalitis. The data published in the literature suggest that there are clinical and neurological analogies between neuroborreliosis and multiple sclerosis (MS). The presence of specific anti-Bb antibodies in cerebrospinal fluid is a discriminating factor that allows a diagnosis of neuroborreliosis to be made. We describe the case of a patient with Lyme disease, characterised by widespread chorea and behavioural disturbances. Emphasis is placed on the atypical onset and evolution, the difficulties encountered in formulating a diagnosis, and the uncertainties concerning the pathophysiology and clinical/neuroradiological correlations of the disease.