Tonic seizures are a particular risk factor for drowning in people with epilepsy

Tonic seizures pose a high risk of drowning because expulsion of air from the lungs causes rapid submersion

It is accepted that people with epilepsy should be supervised when swimming. However, there is little or no guidance about special precautions that should be taken for particular types of seizures. During a tonic seizure the muscles of the chest wall contract and much of the air from the lungs may be expelled. If such a seizure occurs while a person is swimming, the average body density may become higher than the density of the water, causing rapid submersion. When the muscles of the chest wall relax, the person will still be submerged, with the result that water, not air, will enter the respiratory tract and the person will not rise to the surface. We present a case of fatal drowning in a 14 year old boy with epilepsy who had seizures with a marked tonic phase. This case raises an important question with regard to safety: should special precautions be taken to minimise the risk of drowning in patients with tonic seizures?