Proposal for best practice in the use of video-EEG when psychogenic non-epileptic seizures are a possible diagnosis.

The gold-standard for the diagnosis of psychogenic non-epileptic seizures (PNES) is capturing an attack with typical semiology and lack of epileptic ictal discharges on video-EEG. Despite the importance of this diagnostic test, lack of standardisation has resulted in a wide variety of protocols and reporting practices. The goal of this review is to provide an overview of research findings on the diagnostic video-EEG procedure, in both the adult and paediatric literature. We discuss how uncertainties about the ethical use of suggestion can be resolved, and consider what constitutes best clinical practice. We stress the importance of ictal observation and assessment and consider how diagnostically useful information is best obtained. We also discuss the optimal format of video-EEG reports; and of highlighting features with high sensitivity and specificity to reduce the risk of miscommunication. We suggest that over-interpretation of the interictal EEG, and the failure to recognise differences between typical epileptic and nonepileptic seizure manifestations are the greatest pitfalls in neurophysiological assessment of patients with PNES. Meanwhile, under-recognition of semiological pointers towards frontal lobe seizures and of the absence of epileptiform ictal EEG patterns during some epileptic seizure types (especially some seizures not associated with loss of awareness), may lead to erroneous PNES diagnoses. We propose that a standardised approach to the video-EEG examination and the subsequent written report will facilitate a clear communication of its import, improving diagnostic certainty and thereby promoting appropriate patient management.

Photic stimulation during electroencephalography: Efficacy and safety in an unselected cohort of patients referred to UK neurophysiology departments.

PURPOSE: To determine efficacy and safety of photic stimulation (PS) during electroencephalography (EEG) in a large group of adult and paediatric patients. METHODS: A prospective multicentre National Service Evaluation was performed organised by the joint audit committee of the two UK professional organisations (Association of Neurophysiological Scientists and British Society for Clinical Neurophysiology). Questionnaires about every EEG performed in the two-month study period were completed contemporaneously by physiologists at the time of the recording-reporting. The occurrence during PS of photoparoxysmal responses (PPRs), seizures and psychogenic non-epileptic attacks was noted from the EEG trace and contemporary clinical observation backed up by the video that was synchronised with the EEG. 5383 patients investigated with EEG and PS, mostly for possible epilepsy, were included in the study. RESULTS: Seventy nine patients (1.5%) had a generalised PPR elicited by PS having had no generalised epileptiform discharges previously in the EEG. Thirty nine patients (0.7%) had seizures provoked by PS including two (0.04%) who had a generalised tonic clonic seizure (GTCS). Forty nine patients (0.9%) had non-epileptic attacks provoked by PS. Thus PS yielded potentially useful information (PPRs, seizures or non-epileptic attacks) in 167/5383 (3.1%) of patients. In a subset of 122/5383 (2.3%), PS provided the only useful information captured within the EEG. CONCLUSION: PS contributes to the diagnosis of epilepsy and non-epileptic attack disorder in 3.1% of patients. It is a safe technique which produces GTCSs in only 0.04% patients. We conclude that PS is a moderately useful activation technique in diagnostic EEG, where the potential benefits out-weigh the risks; this information may assist the informed consent process.

Hyperventilation during electroencephalography: safety and efficacy.

PURPOSE: To determine safety and efficacy of hyperventilation (HV) during electroencephalography (EEG). METHODS: We report the findings of a prospective multicentre National Service Evaluation of the occurrence of adverse events, seizures and interictal epileptiform discharges seen in association with HV during EEG, in a relatively unselected, largely out patient population of 3475 being investigated predominantly for possible epileptic seizures. RESULTS: Adverse events occurred rarely, and there were no reported significant cerebrovascular, cardiovascular or respiratory events. Of the 3170 patients suspected of 'epilepsy or possible epilepsy' 69 patients (2.2%) had seizures provoked by HV, but only one (0.03%) had a generalised tonic clonic seizure. The elicitation or increase of interictal epileptiform discharges (IEDs) was seen in 387 (12.2%) of the total 3170 patients with suspected epilepsy who hyperventilated. Furthermore 31 patients (0.9%) had psychogenic non-epileptic seizures. CONCLUSION: HV is rarely associated with adverse events, but contributes to the diagnosis and classification of seizure disorders in an appreciable proportion of patients with epilepsy and non-epileptic attacks. These findings confirm that HV in selected patients is a valid activation technique in diagnostic EEG, where the potential benefits out weigh the risks, and also provide information that may assist the informed consent process.