BNC is a relatively uncommon type of epilepsy that happens in babies and infants. The seizures, or convulsions, usually start between three and 10 days after the baby has been born. Because most start on the fifth day of life, they used to be called ‘fifth day fits’. The seizures affect girls and boys equally.
There are two types of BNC:
- benign familial neonatal convulsions
- benign idiopathic or sporadic neonatal convulsions.
In the first type, benign familial neonatal convulsions, someone else in the family must have had similar convulsions and this is usually one of the baby’s parents. It may be hard for the parents to know whether they had convulsions as a baby, because they won’t remember this themselves! Therefore, if possible, it is important to ask the baby’s grandparents if they can remember whether the baby’s parents had convulsions or ‘fits’ at the same age. A genetic fault that causes benign familial neonatal convulsions has been found in some genes, which are part of chromosome number 8 and also chromosome number 20.
In the second type, benign idiopathic or sporadic neonatal convulsions, there is no history of convulsions at a similar age in other members of the family.
The seizures can appear in different forms.
- An arm or leg stiffens and then jerks rhythmically (called a clonic seizure).
- The head turns to one side and then jerks a few times. This can be followed by a clonic seizure affecting either the right or left side of the body.
- Both arms or both legs, or all four limbs, jerk at the same time.
- There are repeated cycling or punching movements of the legs or arms.
- Rarely, the whole body goes stiff and then all four limbs jerk (called a ‘tonic-clonic’ seizure).
Most seizures last less than two minutes. The seizures are more likely to happen when the baby is sleepy or has just woken from sleep. The babies are otherwise normal and will have been feeding and behaving normally before the seizures started. Their birth will usually have been normal.
Benign neonatal convulsions (BNC) are diagnosed when the doctor takes a careful history of when the seizures started and a careful family history. Seizures that start on the fifth day after birth in otherwise normal babies are important clues as to the correct diagnosis. Results of tests such as blood tests, electroencephalogram (EEG) and brain scan (computed tomography [CT] or magnetic resonance imaging [MRI]) are usually normal.
There are other causes for seizures and other epilepsy syndromes that might also start at the same age. These can include low levels of glucose, calcium or magnesium in the blood, infections or abnormalities in the brain. Because of this, it is often important for the doctor to perform some more tests to rule out these other causes. These may include a lumbar puncture test to look for an infection such as meningitis or encephalitis, and more detailed brain scans.
Blood tests can also be done to look for the genetic fault with benign familial neonatal convulsions. No genetic fault has yet been confirmed in benign idiopathic or sporadic neonatal convulsions.
Treatment is not always necessary because the seizures may only happen for a few weeks. However, sometimes medication is prescribed, particularly if the seizures continue to happen. Commonly used anti-epileptic drugs (AEDs) include carbamazepine (Tegretol), sodium valproate (Epilim) or far less commonly, phenytoin (Epanutin) or phenobarbital. The AED is usually given for six or occasionally 12 months and then slowly discontinued.
In most babies, the seizures usually stop after a few days, weeks, or, rarely, months. About ten per cent of children (one in 10) who have benign familial neonatal convulsions may start having other types of seizures in late childhood or, more commonly, in adulthood. However, the risk is much lower in benign idiopathic or sporadic neonatal convulsions, with perhaps only one - two per cent of children (one - two in 100) developing epilepsy in adulthood. If this happens, the seizures are usually controlled with AEDs. Babies feed normally, behave normally and develop normally. They usually don’t have learning difficulties or need extra care/support in the future.
Babies who have benign familial neonatal convulsions or benign idiopathic or sporadic neonatal convulsions can be given the full range of immunisations, including mumps, measles and rubella.
- Contact a Family, 209-211 City Road, London, EC1V 1JN, telephone 0808 808 3555, www.cafamily.org.uk
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Epilepsy Action would like to thank:
• Dr Richard Appleton, and Dr Rachel Kneen, consultant paediatric neurologists at Alder Hey Children’s Hospital, Liverpool, UK and
• Dr Stewart Macleod, consultant paediatric neurologist at Royal Hospital for Sick Children, Glasgow, UK.
They have kindly prepared the information on this page. It is based on their own research, experience and expertise.