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EEG and epilepsy
  1. C D FERRIE
  1. Yorkshire Regional Paediatric Neurology Service
  2. Leeds Teaching Hospitals NHS Trust
  3. Room 14B, Clarendon Wing
  4. Leeds General Infirmary
  5. Leeds LS2 9NS, UK

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    Editor,—We welcome the debate on the timing of EEG examinations.1 The practice of delaying the EEG until after a second seizure began when epilepsy syndromes were unrecognised. The EEG was then of little help in predicting prognosis or guiding treatment, but has been transformed by the recognition of epilepsy syndromes. Although some of these syndromes may be difficult to diagnose,2 others—for example, benign childhood epilepsy with centrotemporal spikes, and juvenile myoclonic epilepsy, have easily recognised clinical and EEG features.3 It may not be possible to predict seizure recurrence in a child who has had a nocturnal tonic clonic seizure, but if the EEG shows centrotemporal spikes, we can reassure the family that if recurrent seizures occur, they will almost certainly remit and the cognitive outcome will be good. Similarly, a child presenting with a tonic clonic seizure whose EEG shows generalised multiple spike and wave discharges and photosensitivity, can be advised on the likelihood of seizure recurrence, and specific measures to reduce seizure frequency. These are common clinical situations and the advice is specific and practical. Why delay giving it?

    A further argument about how to define epilepsy is often used to delay EEG examinations. If epilepsy is a condition where a person experiences recurrent epileptic seizures,2 it can be argued that a person who has had a single seizure is not epileptic and, therefore, does not need an EEG. However, the clinical usefulness of this definition should not be overemphasised. Epilepsy is a symptom of a number of different conditions whose only common feature is an increased susceptibility to seizures. This can be shown by the occurrence of recurrent seizures or characteristic EEG abnormalities. In the future, a specific gene or ion channel defect may be the strongest predictor of a decreased threshold. An EEG should not be used to diagnose epilepsy, but its role lies in helping to diagnose which type of epilepsy the patient has.

    A third argument for delaying EEG examinations is the quality of EEG services. It is undoubtedly dangerous to rely on a poorly performed and incorrectly interpreted EEG. Is it safer to rely on such an EEG after a second seizure? This is an argument for improving services rather than an argument against adopting best practice.

    There are few circumstances in which an EEG would be not appropriate when a child is considered to have had an epileptic seizure.

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