Aphasia due to simple partial status epilepticus is rare. We report a case of prolonged mixed aphasia without clouding of consciousness in a patient with an old history (10 years) of multiple sclerosis (MS). We found a clear clinical-EEG correlation with a continuous epileptic pattern in the shape of periodic lateralized epileptiform discharges (PLEDs). Clinical, laboratory and neuroradiological data ruled out possible etiological conditions other than MS and suggested that the development of new subcortical demyelinating lesions might play a critical role in seizure production. These findings, besides the role of PLEDs as an intrinsic feature of the status epilepticus condition, are discussed in relation to the literature.