The risk of such seizures is probably zero for people without epilepsy.
The three patients all had reflex epilepsy, in which seizures can be provoked by specific stimuli instead of happening spontaneously.
What's more, all three patients had a lesion in the same brain area, according to brain scans using magnetic resonance imaging (MRI).
Researchers including Wendyl D'Souza of Australia's University of Melbourne describe the cases in Neurology.
One patient was a 31-year-old woman with reflex epilepsy. She tended to have seizures when she brushed her teeth vigorously. She reported an aura described as a "numb feeling in her head."
Another patient was a 33-year-old man with reflex epilepsy in whom brushing teeth triggered tongue tingling, jaw tightening, salivating, and occasional twitching on the right side of his face for 60-90 seconds. He was most likely to have seizures while brushing his right lower teeth. But he also had seizures while eating potato chips.
The third patient was a 42-year-old man who had cramping in his tongue and left jaw when brushing his teeth or, occasionally, when eating.
The rhythmic action of brushing teeth might stimulate the brain area that triggered the seizures, note D'Souza and colleagues.
Brushing teeth, with its persistent rhythm, is probably more likely to stimulate that brain area than chewing, according to the researchers.
By Miranda Hitti
Reviewed by Louise Chang
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