Somatosensory Evoked High Frequency Oscillations in a Homogeneous Population of Drug Naive Migraineurs

Introduction: High band pass filtering of evoked potentials have produced the results of decreased early High frequency oscillations (HFOs) in previous studies of migraine patients. However, in most of these studies, the study population has been heterogeneous. The only study till date which used homogenous drug naive group of patients has actually produced contradictory results to the previous studies showing. Aim: We aimed to clarify the status of HFO amplitudes and latencies in drug-naive newly diagnosed patients. Methods: In the present study, we evaluated the 20 newly diagnosed and drug naive migraine patients using electrophysiological assessments using Somatosensory evoked potentials (SSEPs) and compared their SSEP parameters with those of the healthy age and gender matched normal controls. Median nerve SSEP was obtained by standard protocols. High frequency oscillations were extracted from the broad-band evoked potentials by digitally filtering using high pass filtering at 450Hz-1KHz. Early HFOs were identified when occurred before the N20 peak. Results: No differences were observed in the broad-band SSEPs i.e., N20 amplitudes and latencies. The maximal peak to peak amplitudes in the drug naïve migraineurs in between the attacks for the early HFOs (occurring before the N20 peak) were significantly smaller than the normal controls (p=0.046). The number of negative peaks were also fewer in the migraineurs in a statistically nonsignificant way. Discussion: This is the first HFO study on a homogenous population of migraineurs which shows decreased early HFOs, thus implicating weaker thalamocortical activity and contradicting the results by Lai et al¹.