Asano S, Hara T. Hyperventilation-stage electroencephalography in lateral temporal lobe epilepsy. Background: To observe spike activity in electroencephalograms (EEGs), patients with symptomatic partial epilepsy are rarely monitored during the hyperventilation stages. Case: A 38-year-old woman suffered from a ruptured arteriovenous malformation in the left temporal lobe. One and a half years later, the patient experienced her first generalized convulsion. EEG showed small spikes in the posterior of the left temporal lobe, which was observed during the hyperventilation and posthyperventilation stages. Because the location of the spikes correlated with the site of the lesion as observed from radiographic findings, she was diagnosed with lateral temporal lobe epilepsy. Drug treatment resulted in no further convulsive episodes and the patient has since returned to work. Conclusion: EEG recordings during hyperventilation should be regarded as an effective technique in analyzing epilepsy because of its ease and cost-effectiveness compared with other methods such as single-photon emission computed tomography.