Paroxysmal dysarthria and ataxia is characterized by abrupt onset of dysarthria and ataxia of unilateral limbs for seconds. We present a 45-year-old female patient with paroxysmal symptoms of dysarthria, right-sided ataxia, and a persistent symptom of upbeating nystagmus. Her brain fluid attenuated inversion recovery (FLAIR) magnetic resonance imaging indicated potential diagnosis of demyelinating disease. The paroxysmal and persistent symptoms have recovered after phenytoin administration. Sodium channel blocker may play a role in reducing the ephaptic transmission in a demyelinated or re-myelinated lesion.