Abstracts

Rationale: EEG has low sensitivity in epilepsy at 25-56%. Specificity is 78-98%. About 50% of patients with epilepsy show Interictal Epileptiform Discharges (IEDs) in the first test (1). The incidence of IEDs in healthy population is 0.5 % (2). This study is designed to assess the EEG diagnostic value in patients with syncope, a very common symptom presenting among veterans, given the advanced age of patient population. EEG is frequently requested to rule out seizures as the leading cause of syncope. Methods: A survey on outpatient EEG demographics was conducted blindly from results. Included referral reasons were syncope, loss of consciousness, unresponsiveness, blacking out, passing out and collapsing spells without association with seizure-like activity. All inpatient EEGs and other referral reasons (episodic focal deficits, non-epileptic events and new-recurrent seizures) were excluded. A total of 639 EEGs read by an epileptologist and board certified neurophysiologist from Sep-09 to Jun-12 were researched. A total of 141 (22.06%) EEGs were selected. EEGs were classified as normal vs abnormal and as having (IEDs) or not. Results: From 141 EEGs with syncope, 103 (73.04%) were normal and 38 (26.95%) were abnormal. The presence of (IEDs) was found only in 3 (2.12%) EEGs from different patients. From the 38 abnormal EEGs, 2 (5.26%) had focal slowing alone, 19 (50%) had diffuse slowing and 14 (36.48%) had both. In order to calculate the EEG sensitivity and specificity in this cohort, we eliminated repeated EEGs from same patients. 23/134 patients were found to have new or known diagnosis of seizures and 111 patients didn't. (IEDs) were found in 1/23 and 2/111 patients. Focal slowing was found in 5/23 and 10/111 patients. In veterans with syncope, the EEG sensitivity to capture (IEDs), specific markers for seizures, was only 4%. The specificity, however, was 98%. The positive predictive value (PPV) was 33% and the negative predictive value (NPV) was 85%. However, after combining focal slowing and IEDs, the sensitivity was 26%, specificity was 89%, (PPV) was 33% and (NPV) was 85%. Conclusions: Our data were harmonious with other results (3) in concluding that EEG has a very low diagnostic value in screening whether seizure is the cause of syncope. The EEG sensitivity in syncope for capturing (IEDs) is low at 4% and remains low at 26% despite combining IEDs with focal slowing if the later is considered a seizure marker in certain population. In veterans, however, there is a high incidence of focal slowing due to the advanced age. Nevertheless, the EEG provides a good probability of excluding the diagnosis of seizures as a leading cause of syncope given the reasonable high (NPV). References: 1)S J M Smith. EEG in the diagnosis, classification, and management of patients with epilepsy. J Neurol Neurosurg Psychiatry 2005 2)Gregory RP, et al. EEG epileptiform abnormalities in candidates for aircrew training. Electroencephalogr Clin Neurophysiol1993 3)Dantas FG, et al. The role of EEG in patients with syncope. Department of Physiotherapy, State University of Paraiba, Brazil, J Clin Neurophysiol. 2012 Feb