Febrile convulsions are fits or seizures that occur in young children when they have a high temperature. Because the growing brains of little children are more sensitive to fever than the more mature central nervous systems of older children and adults, when normal brain activity is upset a fit can occur.
For parents, a febrile convulsion can be a frightening experience. Suddenly their child is not "quite with it", its limbs start to jerk or twitch and it may have difficulty breathing.
Most seizures last only a few minutes; however it is important to place the child on his or her side, chest down, with the head turned to one side. Do not force anything into the child's mouth and never lie a fitting or unconscious child on their back.
Children can become unwell quite quickly; a high temperature is usually the result of a viral infection which may not be obvious. Other causes include upper respiratory tract infections (especially of the ear and throat), bladder infections or meningitis. Although the fitting may stop quickly, it is important to seek immediate medical help so that more serious causes for the fever can be investigated and ruled out.
Body temperature is controlled by a part of the brain called the hypothalamus. It gets feedback from peripheral nerves which monitor hot and cold in the different body regions as well as from the temperature of the blood. The aim is to keep the core body temperature at 37 degrees Celsius. The body's temperature is actually lower in the mornings - a 6 a.m. nadir - and highest in the late afternoon. The normal 24-hour circadian temperature rhythm usually includes a variation of 0.5 to 1.0 degree Celsius.
The actual substance which causes a fever is called a pyrogen, and the majority of these are either micro organisms themselves or toxins which bacteria or viruses produce as part of infecting the child's body. They enter the bloodstream and influence the temperature regulation centre in the hypothalamus.
Childhood febrile convulsions are particularly common at the onset of the fever and also when the body temperature rises above 40 degrees Celsius. They affect five in 100 children and are strongly age related. Temperature convulsions rarely affect children before six months or after six years of age. The incidence peaks in the second year of life.
Once a child has had one febrile convulsion, the risk of recurrence is raised with a subsequent high temperature. This can be minimised by:
Taking some of the child's clothes off and redressing in light clothing
Keeping the child cool - a fan may be helpful
Giving small drinks of light fluids and encouraging the child to sip frequently
Giving paracetemol syrup every four hours until the temperature settles
Sponging with lukewarm water will usually lower even the most resistant temperature
Doctors may also prescribe an anti-convulsant - diazepam - as a liquid in a tube which parents can give rectally should a further febrile convulsion occur
Parents worry that a febrile convulsion means their child will go on to develop epilepsy later in life. A single temperature-related fit does not usually cause epilepsy, nor is there any subsequent brain damage.
However, if the febrile convulsion is prolonged (lasting longer than 15 minutes) or if the doctor identifies some neurological abnormality after the fit is over, then the risk of developing epilepsy is in the region of 4 per cent. But this still means that the overwhelming majority of children with a history of febrile convulsions never develop epilepsy.
Finally, it is important to emphasise that febrile convulsions, frightening as they are, never cause death or brain damage.
Dr Muiris Houston, Medical Correspondent, can be contacted at mhouston@irish-times.ie or leave messages on tel 01-6707711, ext 8511, but he regrets he cannot reply to individual medical problems.