Journal of Neurology, Neurosurgery, and Psychiatry 1992;55:891-894 891 Postictal switch in blood flow distribution and J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.55.10.891 on 1 October 1992. Downloaded from temporal lobe seizures Mark R Newton, Samuel F Berkovic, Mark C Austin, Christopher C Rowe, W John McKay, Peter F Bladin Abstract ictal studies with PET can be performed only The ictal increase of regional cerebral serendipitously when seizures happen to occur blood flow has yet to be fully utilised in the during the scan. SPECT radionuclides such investigation of focal seizures. Although as o9mTechnetium-hexamethyl propyleneami- single photon emission tomography neoxime (HMPAO) rapidly cross the blood- (SPECT) is being increasingly used in the brain barrier and reside in cerebral tissue for localisation of epileptic foci, the evolution several hours. Isotope can thus be injected and time courses of the peri-ictal perfu- during an observed seizure and the patient can sion changes have yet to be clarified. We then be scanned within the next few hours, performed serial SPECT studies in the with the scan reflecting cerebral blood flow interictal, ictal and immediate postictal (CBF) at the time ofinjection."4These proper- states in 12 patients with refractory tem- ties permit the prospective and serial evalu- poral lobe epilepsy to define the patterns ation of changes in CBF associated with focal and duration of peri-ictal cerebral blood seizures, which typically last less than two flow changes. Visual analysis showed a minutes. constant pattern of unilateral global We previously reported the early postictal increases in temporal lobe perfusion dur- perfusion changes with SPECT, which allowed ing seizures which suddenly switched to a accurate prediction of seizure focus in 69% of pattern of relative mesial temporal (hip- a series of patients with refractory temporal pocampal) hyperperfusion and lateral lobe epilepsy."-3 We have since sought to temporal hypoperfusion in the immediate determine the diagnostic value of ictal and postictal period. Quantitative analysis postictal SPECT scans by examining a series confirmed the visual assessment. Lateral of ictal and postictal paired studies in the same temporal cortex ictal/normal side to side patients with qualitative and quantitative ratios were increased by mean 35-1% (95% image analysis. We found a remarkable differ- confidence interval 21-8% to 48-4%) more ence in the ictal and postictal perfusion in the ictal studies than in the interictal patterns, representing a postictal switch in studies and mesial temporal cortex ratios blood flow distribution. This finding is impor- increased by mean 30-8% (22.4% to tant for clinical diagnosis of seizure localisation 39-2%). In the postictal state, however, and for understanding the pathophysiology of lateral temporal ratios were reduced by temporal lobe epilepsy. mean 7-7% (-15-'8% to 0.4%) compared http://jnnp.bmj.com/ with interictal values, whereas mesial temporal perfusion was man*tained com- Methods pared with the interictal studies. These Twelve patients (mean age 28, (range 16-46) observations provide critical information years; seven women) with intractable unilateral for interpreting scans which can be used temporal lobe epilepsy diagnosed on clinical in the localisation of epileptic foci. This and EEG criteria, and MRI" and neuro- postictal switch in blood flow patterns psychological data were studied (table 1). Peri- on October 4, 2021 by guest. Protected copyright. may reflect the underlying metabolic pro- ictal SPECT is a routine investigation for cesses ofneuronal activation and recovery prospective therapeutic temporal lobectomy in Department of and have implications for understanding our centre,' 1-13 and the 12 patients analysed Neurology, Austin Hospital, Melbourne, the neurobiology of human epileptic were selected because they had undergone Victoria, Australia seizures. paired SPECT studies for both ictal and M R Newton postictal states. S F Berkovic (7 Neurol Neurosurg Psychiatry CC Rowe 1992;55:891-894) An interictal study was performed when the P F Bladin patient had been seizure free for at least 24 Department of hours, with full medication. The 99mTc- Nuclear Medicine, The abnormal synchronised discharge of a HMPAO was injected with the patient in the Austin Hospital neuronal aggregate that characterises focal resting state (supine, eyes closed, and silent M C Austin J epileptic seizures is accompanied by focal with a minimum of background noise). W McKay Patients were Correspondence to: hyperperfusion''and hypermetabolism.67 continuously monitored with Dr Berkovic, Department of Functional imaging with positron emission video recording and EEG for periods of up to Neurology, Austin Hospital, Heidelberg (Melbourne), tomography (PET) and single photon emission two weeks (with reduced medication) and Victoria 3084, Australia computed tomography (SPECT) has shown a underwent 99Tc-HMPAO injection as soon Received 18 June 1991 variety of peri-ictal blood flow patterns., 8-13 as possible after onset of the seizure. SPECT and in revised form 28 August 1991. presumably reflecting the rapid changes of images derived from injections during or up to Accepted 3 September 1991 blood flow accompanying focal seizures. Peri- 30 seconds after the end of a seizure were 892 Newton, Berkovic, Austin, Rowe, McKay, Bladin Table I Localisation data in 12 patients studied with ictal and postictal SPECT* J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.55.10.891 on 1 October 1992. Downloaded from Interictal Ictal Postictal Patient Ictal EEG SPECT SPECT SPECT MRIt Pathlogy I Left temporal discharge$ Not lateralised Left Not lateralised Left HS HS 2 Right hippocampal dischargeS Right Right Right Right HS HS 3 Left hippocampal dischargeS Left Left Left Left HS HS 4 Left temporal dischargell Not lateralised Left Left Left tumour Ganglioglioma 5 Left hippocampal dischargeS Left Left Left Normal Normal 6 Left temporal dischargell Left Left Left Left HS HS 7 Unlocalised. Active Right interictal Not lateralised Right Right Right HS HS 8 Left temporal dischargell Left Left Left Left dysplasia Dysplasia 9 Left temporal dischargell Left Left Not lateralised Left HS HS 10 Right temporal dischargell Not lateralised Right Right Right HS Cortical gliosis¶ 11 Right hippocampal dischargeS Right Right Not lateralised Normal Normal 12 Left temporal dischargell Left Left Left Left HS HS HS = hippocampal sclerosis. *SPECT results derived from blinded visual assessment. Interictal SPECT localised by focal hypoperfusion, ictal SPECT by focal hyperperfusion, and postictal SPECT by mesial hyerperfusion with lateral hyoperfusion. tMRI diagnosis of hippocampal sclerosis was made as previously described and validated.5 $Surface EEG. §Depth EEG. llSphenoidal EEG. ¶Hippocampal tissue not found on pathology specimen. called "ictal studies", as the appearances of showed a pronounced global increase in tem- scans in all cases were consistently similar. All poral lobe blood flow on the epileptogenic side 12 patients underwent an additional injection (figure). This pattern was seen when injections on another occasion more than 30 seconds were given during clinical and EEG ictal after seizure end (postictal study; mean (SD) activity or up to 30 seconds after its cessation delay 1-46 (0-4) min). Exact timing of the and was easily identified in all 12 cases by the injections was made possible by the timer three blinded observers independently (table linked to the video and EEG, which was read 1). Postictal studies showed a switch in dis- on playback of all seizures. The paired seizures tribution of blood flow with hypoperfusion of studied were of a stereotyped pattern and the epileptogenic lobe and hemisphere in all 12 similar length for each patient. Patients were studies and residual hyperperfusion of the scanned within two hours of injection, with a mesial temporal region in seven. The postictal Starcam 400AC gammacamera (General Elec- changes were not always striking. In nine tric, Milwaukee, USA). Data acquisition, patients they were obvious to all three obser- reconstruction, and display methods have been vers but in the three others they were not described previously.'2 sufficiently clear for blinded lateralisation inde- Scans were qualitatively interpreted by three pendent of other data. blinded observers. The blood flow changes Hypoperfusion of the frontal and parietal were quantitated by determining a ratio of cortex was seen ipsilateral to the discharging counts, dividing the number in the epilepto- focus in the ictal studies and persisted into the genic side by that in the normal side, in the postictal period. One patient progressed to following regions of interest; mesial, lateral, hemigeneralisation after his complex partial and posterior temporal regions; lateral frontal seizure. SPECT showed increased perfusion in http://jnnp.bmj.com/ and parietal cortices; basal ganglia; and cere- the contralateral motor cortex in this case, in bellar hemispheres. Three contiguous 3-2 mm addition to the temporal lobe hyperperfusion. transverse slices were summed and regions of Perfusion ratios for all regions of interest in interest were drawn using rectangular boxes. the patients' interictal state did not differ from The volume studied was 4 9 cm3 (5 x 10 x 3 those in the control group, except for the pixels) for all regions except for the cerebellum mesial temporal region where there was a x x (7 7 3 pixels, 4-8 cm3) and basal ganglia significant decrease on the side of the epileptic on October 4, 2021 by guest. Protected copyright. (5 x 5 x 3 pixels, 25 cm3).Normal data were focus (table 2). Quantitative analysis of the obtained from scans of 18 healthy male volun- ictal and postictal studies confirmed the qual- teers where IJR ratios were calculated for the itative interpretation of the images (table 3). same regions of interest. Mean ratios for each region of interest in the ictal, postictal, and interictal patient studies were compared with each other by using paired t tests and with Table 2 Side to side perfusion ratios in the interictal state, * control values by using multiple unpaired t Values are means (SD) tests.