How is it assessed?
The diagnosis of epilepsy is almost entirely based on a history of what has happened and any eyewitness accounts. An Electroencephalogram (EEG) and other scans can help but do not in themselves give a diagnosis. In ninety percent of cases, the EEG is normal because seizures are intermittent and sometimes hospitalisation is necessary for monitoring and observation. An accurate description of seizure might give clues as to whether the seizure was a partial seizure with secondary generalization versus a primary generalized seizure.
When evaluating a child who has experienced a first seizure, the clinician needs to address the following -:
- An identifiable aetiology (cause) to the seizure
- The most appropriate therapy
- The prognosis
Differential diagnosis
Many disorders can mimic seizures in children and should be considered in the differential diagnosis of first seizure in a child. The most common non-epileptic disorders include the following -:
- Syncope or breath-holding spells
- Migraine
- Benign paroxysmal vertigo
- Staring spells
- Movement disorders including tics, benign myoclonus, and dyskinesias
- Sleep disorders such as night terrors
- Febrile seizures - These are convulsions brought on by a high fever, typically above 38.5° C in the absence of central nervous system infection and affect 2-5% of children in the first 6 years of life with peak incidence between 18 months and 4 years. 3-6% of patients with febrile seizures will develop afebrile seizures or epilepsy. Children prone to febrile seizures are not considered to have epilepsy, (since epilepsy is characterized by recurrent seizures that are not triggered by fever.)
If the description is consistent with a seizure a number of tests may be important in helping to confirm the diagnosis of epilepsy, including the following -:
Electroencephalogram (EEG)
This test records electrical activity in the brain. Some types of seizures produce characteristic EEG patterns but a normal recording does not rule out epilepsy. Not all abnormalities detected by an EEG are related to epilepsy. If a characteristic seizure pattern is detected then further investigation may not be necessary.
N.B. It is important to note that some patients with unequivocal epilepsy will have persistently normal or non- epileptic EEG’s.
Brain Scan (usually MRI or CT)
This is useful to identify any structural abnormality of the brain.
A Magnetic Resonance Image (MRI) scan is more sensitive and specific than Computerised Tomography (CT) for detecting small brain lesions and abnormalities, which may be a relevant cause of epilepsy).
Blood tests
These would be necessary to rule out any underlying pathology and to identify other possible causes of the seizure or event, though any metabolic disturbance is likely to have already been recognized. Blood levels of medications are also monitored.
Video-telemetry
Video-telemetry combines continuous EEG and video recording and is valuable in the specialist assessment of difficult cases of episodes of disturbed consciousness.
It is possible for all of these tests to be negative and yet for the diagnosis of epilepsy to be established.
