Decreased cerebral blood flow during seizures with ictal SPECT injections

Increased regional cerebral blood flow (rCBF) at the epileptogenic site has been consistently reported for single photon emission computed tomography (SPECT) injections made during seizure activity, and the increased rCBF has been shown to remain elevated at the epileptogenic site in some cases, eve n when SPECT injections are made after seizure termination (postictal). A s ustained increase in rCBF after seizure cessation was recently confirmed, b ut for no more than 100 s from seizure onset [Avery, R.A., Spencer, S.S., S panaki, M.V., Corsi, M., Seibyl, J.P., Zubal, I.G., 1999. Effect of injecti on time on postictal SPET perfusion changes in medically refractory epileps y. fur. J. Nucl. Med. 26, 830-836]. In the current study, it is examined wh ether ictal SPECT injections demonstrate a similar change in rCBF around 10 0 s from seizure onset. Twenty-one patients with medically refractory epile psy and a known area of seizure onset receiving ictal and interictal Tc-99m -Hexamethyl-propyleneamineoxime (HMPAO) SPECT scans were studied. The resul ts of SPECT subtraction analysis which visualize increased and decreased rC BF were compared to seizure duration and HMPAO injection time. Five patient s received ictal SPECT injections (during ongoing seizure activity) more th an 90 a after seizure onset and demonstrated decreased rCBF. Two of these p atients also demonstrated areas of increased rCBF. Decreased rCBF was local ized to the epileptogenic lobe in four of the five patients. By examining i ctal SPECT injections made 90 s after seizure onset, evidence was found tha t reduced rCBF may exist during ictus. The change in rCBF around 90 s is al so observed in postictal injections, suggesting a common metabolic mechanis m may be responsible. (C) 2000 Elsevier Science B.V. All rights reserved.