Febrile seizures - Diagnosing febrile seizures

Febrile seizures can often be diagnosed from a description of what happened.

Further tests may be needed if the cause of the associated infection isn't clear.

It's unlikely that your doctor will see the seizure, so an account of what happened is useful.

It's useful to know:

• how long the seizure lasted
• what happened – body stiffening, twitching of the face, arms and legs, staring and loss of consciousness
• whether your child recovered within one hour
• whether they've had a seizure before

Tests to identify the source of the infection will only usually be necessary to rule out rarer conditions which can cause similar symptoms, such as meningitis.

A blood or urine sample may be needed to test for signs of infection. It can sometimes be difficult to obtain a urine sample from young children, so it may have to be done in hospital.

Read more about blood tests.

Further tests

Further tests may be carried out in hospital if your child’s symptoms are unusual – for example, if they don't have a high temperature or their seizures don't follow the normal pattern.

Further testing and observation in hospital is also usually recommended if your child is having complex febrile seizures.

Your child may have other tests including an electroencephalogram and lumbar puncture, particularly if they're less than 12 months old.

These two tests are explained below.

Electroencephalogram

An electroencephalogram (EEG) measures your child’s electrical brain activity through electrodes that are placed on their scalp. Unusual patterns of brain activity can sometimes indicate epilepsy.

However, some studies have suggested that an EEG may not be useful in many cases of febrile seizures.

Lumbar puncture

During a lumbar puncture, a small sample of cerebrospinal fluid (CSF) is removed for testing. CSF is a clear fluid that surrounds and protects the brain and spinal cord.

A hollow needle is inserted into the base of the spine to obtain the CSF sample. During the procedure, local anaesthetic will be used to numb your child’s back so that they don't feel any pain.

A lumbar puncture can be used to determine whether your child has an infection of the brain or nervous system.