Tongue biting: a case of sporadic geniospasm during sleep.

We report a healthy teenager with involuntary nocturnal tongue biting resulting in recurrent tongue injury. Causes for tongue biting during sleep in children include seizures, bruxism, faciomandibular myoclonia, hypnic myoclonia, and rarely geniospasm, which has been described as a rare inherited movement disorder accompanied with chin quivering. In the absence of family history, we diagnosed our patient with sporadic geniospasm based on polysomnographic findings with good response to clonazepam. Geniospasm should be considered in the differential diagnosis of cases with unexplained tongue injury in sleep.