Abstracts

Rationale: Neurological consultation is very frequently requested for patients presenting with transient loss of consciousness (T-LOC) for possible seizure as the cause. Even though routine EEG (rEEG) has been shown to have low diagnostic yield for T-LOC, it is still commonly ordered. But is rEEG ordered for patients who actually fulfill the criterion for T-LOC as per latest guidelines published in 2009? Previous literature has shown that older patients are at increased risk of seizures but these patients also have multiple co-morbidities which can lead to T-LOC from a non-epileptic etiology. This leads us to our next question - among the patients who fulfill the criteria for T-LOC, is there any difference in the diagnostic yield of rEEG based on age? Methods: A records review at Stony Brook University Hospital was performed for patients who had a rEEG study done for 20-40 minutes, between 07/01/2010 and 06/30/2012, using portable EEG equipment in the emergency room or inpatient wards, within 24 hours of the hospital visit, to evaluate for etiology of their T-LOC. Patients who had T-LOC rapid in onset, short in duration, with complete spontaneous recovery, with loss of postural tone were included in the study. The inclusion criteria was met by 147 patients. Patients were divided into two groups depending on age: ‹60 years (n=59) and ≥60 years (n=88). Chi-Square test was used to compare the reports between the two groups. Results: rEEG in patients objectively presenting with T-LOC had 6% diagnostic yield of detecting epileptiform discharges. For all patients presenting with T-LOC, 57/147 had abnormal (slowing and/or epileptiform discharges) rEEG studies; 42 patients ≥60 years, and 15 patients ‹60 years. The yield for epileptiform discharges was significantly lower (p‹0.001) for patients ≥ 60 (n=2/42) as compared to ‹60 years (n=7/15). Conclusions: Our study found in patients being evaluated with EEG for T-LOC, a yield of 6% with epileptiform discharges, higher than the 1-2% reported in the literature. This again highlights the importance of detailed history taking to determine the patient selection for the diagnostic test ordered. Based on age, there was a significant difference in the diagnostic yield of rEEG for detecting seizure potential. When presenting with T-LOC, older patients are less likely to have an abnormal EEG with epileptiform discharges than younger patients. This might be related to comorbidities other than seizures as the cause of T-LOC in patients ≥60 years of age. The significance of these findings suggests that there should be a greater index of suspicion for seizure as the etiology in younger patients presenting with T-LOC. Further prospective studies with emphasis on detailed history taking, and a larger sample size, need to be done to verify this finding, and to understand the role of age in obtaining rEEG in patients presenting with T-LOC.