Reexamining the added value of intermittent photic stimulation and hyperventilation in routine EEG practice.

OBJECTIVE

Investigate the added value of hyperventilation (HV) and intermittent photic stimulation (IPS) to the routine electroencephalogram (EEG).

METHOD: This is a retrospective review of 1,172 successive EEGs. The records with evidence of epileptogenic activity were identified and further analyzed to identify if the activation techniques could trigger the expression of epileptic activity not seen otherwise in the nonactivated tracing.

RESULTS

Activation procedures provided additional information in 9.5% of the abnormal EEG files. They helped establish the diagnosis of an epileptic disorder or further characterize the epileptic syndrome. This occurred exclusively in the younger age group (age <36 years), and predominantly in women.

CONCLUSION

IPS and HV are easy to perform and remain important adjuncts to routine EEG. They may trigger the expression of epileptogenic activity in an otherwise uneventful EEG. Whereas their diagnostic value was obvious in the younger age group, we found no evidence to support their usefulness in the middle-age and elderly groups.