A 59 year-old-man had ataxia and hemiparesis of progressive onset whic
h resolved in a few weeks. CT scan and magnetic resonance imaging show
ed white matter multiple lesions. The cerebrospinal fluid was consiste
nt with an inflammatory disease. The diagnosis of multiple sclerosis w
as evoked. However, the patient had chronic brucellosis and serologica
l rates increased and decreased according to the clinical and radiolog
ical signs. Thus, encephalitis caused by brucellosis was evoked. Tile
mechanism is assumed to be a demyelinating process caused by a deep fo
cus reactivation.