Abstracts

Rationale: Aim Patients are often referred for routine electroencephalogram (EEG) with a diagnosis of migraine or headache not otherwise specified (NOS). This is sometimes the case when a patient presents with atypical symptoms raising the suspicion for a seizure disorder. The aim of obtaining an EEG study is typically to determine if the index event is epileptic in etiology. We decided to review the studies of adult outpatients who were referred to our electroencephalography laboratory with a diagnosis of migraine or headache NOS. Our aim was to determine the diagnostic utility of routine outpatient EEG to document seizure (definite epileptogenic abnormalities on EEG) as the etiology of the index event in patients referred with a diagnosis of migraine and headache NOS. Methods: Methods All routine adult EEG studies with a referring diagnosis of migraine or headache NOS over a 2-year period (1/2007-1/2009) were reviewed by a board certified electroencephalographer (GS) for the presence of epileptiform abnormalities (sharp waves or spike wave discharges). Patient history and reason for study was determined from the referring physician’s history or directly from patient at the time of the study. EEG records of patients who underwent further long-term ambulatory or inpatient video EEG monitoring were reviewed to determine how many met the final diagnosis of seizure. Results: Results A total of 50 patients yielded 50 routine EEG studies (headache NOS n=32, migraine n=18). Overall, there were 37 (74%) normal routine EEG studies and 13 (26%) abnormal routine EEG studies. Of the 13 abnormal studies, 9 (28%) were in the headache NOS group and 4 (22%) were in the migraine group. Eight of the 13 (62%) abnormal EEG studies revealed epileptiform features, while the remaining 5 (38%) abnormal studies exhibited non-specific features (focal or diffuse slowing). One patient with headache NOS and a normal routine EEG underwent further long-term EEG evaluation. This video EEG was normal. Stratifying the data according to age revealed 2/5 (40%) patients above the age of 60 had abnormal routine EEG studies as compared to 6/25 (24%) of patients aged 18 to 40. Conclusions: Conclusion Routine EEG studies are mostly normal in young patients (18-40 years of age) who are referred to the laboratory with a diagnosis of headache NOS or migraine. In patients presenting with atypical features and a history suggestive of a seizure disorder, judicious use of long-term ambulatory or inpatient video-EEG monitoring may increase the diagnostic yield.