To the Editor:

This letter is in response to the comments by Dr. Ahmed concerning our recent report on the effectiveness of voluntary hyperventilation (HV) in eliciting seizures in patients with proven epilepsy (1). Dr. Ahmed takes issue with our conclusion that seizures in adults with either generalized and localization-related epilepsy syndromes are relatively resistant to routine HV activation. This is a surprising position, given the fact that in >400 consecutive and unselected patients with proven epilepsy in our series, HV elicited a clinical seizure in only two (i.e., fewer than one half of 1% of the total number). Given these results, we find it difficult to conceive that an objective observer would reach any conclusion other than the one we reached in our study.

As a counterargument, Dr. Ahmed offers his anecdotal experience with HV in eliciting seizures while obtaining ictal single-photon emission computed tomography (SPECT) studies. Unfortunately, the data that Dr. Ahmed presents are imprecise and unpublished. Therefore it is impossible to comment further on his findings. Dr. Ahmed is incorrect in his assertion that routine HV by technologists performing standard EEG is not aimed at provoking a seizure. On the contrary, the point of HV is to attempt to elicit, if not epileptic seizures, at least interictal epileptiform discharges. That is the reason HV for decades has been used in clinical EEG laboratories around the world; it is based on the widespread, but erroneous, belief that HV is an effective provocative maneuver. With the caveat that our results may not apply to children (as we noted in our report), HV performed during routine EEG recordings will rarely be associated with clinical seizures, even in individuals with unequivocal epilepsy.


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