Document resource
Deriving normative values presents a challenge because of the barriers to recruiting healthy participants. The eNorms method has been used to extract normal values from mixed healthy/unhealthy datasets. eNorms was applied to peak alpha frequency in clinical EEG and compared them to values from the literature.Six studies were identified recording the alpha frequency in healthy participants, encompassing 965 participants (total). The peak alpha frequency weighted average was 9.65Hz with a pooled standard deviation (SD) of 1.04.Alpha peaks were extracted from an independent reportedly normal clinical EEG dataset of 1096 patients. Each EEG’s median alpha peak frequency was extracted across all leads (mean=9.93Hz (95% CI [9.87,10.00]), SD=1.02 (95% CI [0.97, 1.05]))).Applying eNorms provided an estimated mean of 9.66-9.69Hz and an eNorms estimated SD of 0.3. The latter is less than a third of the pooled SD from the literature.This is the first application of eNorms to EEG with successful extraction of the mean alpha frequency; however, it underestimated the SD. Hence, a significant, but perhaps not insurmountable, challenge was identified with applying eNorms. Potential explanations include distributions of EEG frequency data containing overlapping peaks, for which adjustment is required.rohan.kandasamy@nhs.net