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Nonspecific Abnormal EEG Patterns during Hyperventilation Test on the Electroencephalogram of Normal and Epileptic Patients

Srinivasulu Naidu S, Shashikala KT, and Srinivasa R.

Hyperventilation (HV) is being used as a activation/provocative test in clinical EEG laboratories to enhance preexisting abnormalities and / or induce abnormal findings in an otherwise normal electroencephalogram(EEG).The present work was done to compare the incidence of focal or generalized slowing, patterns of uncertain significance using activation methods on the EEG of normal young and adult subjects and the age matched epileptic subjects and also to quantify Changes in different seizure categories like Absent, Focal and Generalized. EEGs were recorded using hyperventilation test as activation procedures in 50 patients, who were proven cases of epilepsy with different seizure categories and compared with 50 age and sex matched normal subjects. Effects of hyperventilation test on EEG were recorded and changes were analyzed statistically. Hyperventilation test showed positive association in activation of non epileptiform background slowing. (P=0.487), even though statistically not very significant. Effect of activation was seen maximally in patients of generalized seizures especially in GTCS (75%).This work suggests that Hyperventilation test provoke Nonspecific Abnormal EEG Patterns in EEGs Of epileptic patients and normal subjects and hence increase the yield of EEG recordings.