A seizure can be triggered by repeatedly rubbing a small, well defined area of skin, reports research in the Journal of Neurology, Neurosurgery and Psychiatry.
The phenomenon is described in a series of case studies. None of the reported cases, say the authors, fits the classification of startle epilepsy, which also requires tactile stimulation, but which is triggered by sudden noise.
In one, a 35 year old woman realised at the age of 17 that she could trigger a seizure by repeatedly patting her left shoulder. In another case, a 21 year old woman discovered, by accident, that she could bring on a seizure by rubbing her left leg.
In a third case, a 31 year old man discovered that having his hair cut triggered a seizure when a particular area of his head was rubbed for 10 seconds or more. He had seizures every day, but realised that if he deliberately induced one, the trigger zone no longer worked for several hours, during which time he could resume normal activities, including having his hair cut.
Some people can trigger an seizure by cleaning their teeth, say the researchers, who have seen several such patients, but this is not rub epilepsy, say the authors. This is because each of the cases reported followed a distinct neurological pattern, was mostly left-sided, with contractions down one side of the body only; and none of the individuals lost consciousness without convulsions.
Monica Cooper, Head of BEA's Advice and Information Services commented:
"A seizure triggered by rubbing is an example of reflex epilepsy where a specific stimulus or event provokes an epileptic attack. Photosensitive epilepsy (i.e sensitivity to flashing/flickering lights) is the most common form of reflex epilepsy with 4-5 per cent of all people with epilepsy affected. Stimuli such as rubbing only rarely provokes seizures and will be distinct to the individual affected.
"Other examples of rare stimuli include reading, eating, listening to music and decision making. In such cases the brain is oversensitive to a particular stimulus. The reason for this type of response to an everyday event is generally poorly understood."