Stuttering: disappearance and reappearance with acquired brain lesions.

Despite 60 years of study, the brain mechanisms for stuttering are unknown. In an effort to shed light on these mechanisms, we studied two cases in which the fluency of speech changed after brain damage in adulthood. The first, an ambidextrous man, ceased to stutter after a head injury. The second, a converted left-handed man, experienced recurrence of childhood stuttering after a stroke.