The localizing value of auditory event-related potentials (P300) in patients with medically intractable temporal lobe epilepsy

The localizing value of postictal versus interictal event-related potentials (ERPs) was studied in patients with medically intractable TLE admitted for long-term video EEG monitoring. Ten patients with partial seizures and secondary generalization underwent preictal (upon hospital admission), postictal (6 h after seizure), and interictal (7–48 h after seizure) ERP recordings of an auditory oddball paradigm. Preictal ERPs were compared to postictal and interictal recordings. Intraclass correlations, transformed into z scores, were utilized to analyze amplitude differences between electrodes placed on the hemisphere ipsilateral versus contralateral to the epileptogenic focus. The results showed that in 9 out of 10 patients the ERP amplitude was reduced in postictal compared to preictal recordings for electrodes placed ipsilateral to the epileptogenic focus (P<0.0001). However, there was no difference in amplitude between ipsilateral and contralateral electrodes in preictal and interictal recordings. These findings suggest that postictal ERPs are of localizing value in patients with TLE while interictal ERPs are not.     

Postictal SPECT in Epileptic Versus Nonepileptic Seizures

Despite advances in video-electroencephalogram (EEG) technology, in many patients distinguishing epileptic seizures from nonepileptic seizures (NES) remains a challenge. Reliable methods to make this distinction are needed. In a pilot study, we performed postictal and interictal single photon emission computed tomography (SPECT) in 22 patients undergoing video-EEG monitoring who had altered responsiveness during an episode. Eleven had seizures, defined as episodes associated with EEG seizure patterns or postictal prolactin (PRL) elevations greater than 1.5 times the highest interictal baseline PRL; 11 had NES. Among the 11 seizures, postictal SPECT was abnormal in seven (regions of hypoperfusion in six and hyperperfusion in one) and normal in four. In six cases (55%), the interictal and postictal SPECT changed. Among the 11 NES cases, postictal SPECT was abnormal in three cases (all hypoperfusion abnormalities) and normal in eight cases. In no case did the interictal and postictal SPECT change. This small sample revealed a trend toward greater hypometabolism (postictal versus interictal) on SPECT for epileptic seizures compared to NES (p < 0.12). There were postictal SPECT changes in two of five seizures unassociated with postictal PRL elevation. Prolactin was elevated in two cases unassociated with change on SPECT. Comparision of postictal to interictal SPECT may help distinguish epileptic seizures from NES. Results from SPECT may also help identify epileptic seizures unassociated with PRL elevation.     

Lateralized Postictal EEG Delta Predicts the Side of Seizure Surgery in Temporal Lobe Epilepsy

PURPOSE: The concordance of lateralized EEG postictal polymorphic delta activity (PPDA) to the side of seizure origin in temporal lobe epilepsy (TLE) has received limited study. Our objective was to study the lateralizing value of PPDA in patients with documented TLE. METHODS: A cohort of consecutive adults with TLE, detailed presurgical evaluation before temporal lobectomy, and minimal follow-up of 2 years were included. One author masked the ictal rhythm of presurgical EEGs and randomly presented 20 s of preictal and the postictal EEG to two electroencephalographers who were blind to all clinical data. They independently assigned PPDA to one of three categories: not present, bilateral, or lateralized (defined as newly appearing or an amplitude >50% of the preictal record). RESULTS: Eighty seizures from 29 patients were studied. Fifteen patients had a left, and 14 had a right temporal lobectomy. Twenty-three patients were seizure free or substantially improved (defined as simple partial or nocturnal seizures only). Lateralized PPDA was present in 64% of all EEGs and at least one record from 22 (76%) patients. Lateralized PPDA, when present, was concordant with the side of surgery in 96% of the EEGs. CONCLUSIONS: Lateralized PPDA is highly predictive of the side of ultimate temporal lobectomy, and by inference the side of seizure origin.     

Interictal and postictal language testing accurately lateralizes language dominant temporal lobe complex partial seizures

PURPOSE: Noninvasive tests that accurately localize seizure onset provide great value in the presurgical evaluation of patients with intractable epilepsy. This study examined the diagnostic utility of three expressive language disturbances in lateralizing language-dominant (DOM) temporal lobe complex partial seizures: (1) the postictal language delay (PILD; time taken to correctly read a test phrase out loud immediately following seizures); (2) the production of postictal phonemic paraphasic errors (PostPE); and (3) interictal phonemic paraphasic errors (InterPE). METHODS: All 60 subjects underwent inpatient video/EEG monitoring and had surgically confirmed temporal lobe epilepsy (TLE). We determined the presence and number of PostPE and, PILD times (in s) for 212 seizures, and InterPE on the Boston Naming Test (BNT). Each technique's diagnostic usefulness was evaluated via logistic regression and ROC curve analysis. Sensitivity, specificity, positive predictive value and negative predictive values were computed. RESULTS: PILD, PostPE and InterPE production were equally effective and accurate in lateralizing DOM seizure onset. Patients with DOM TLE had a longer PILD and committed more PostPE and InterPE than those with nondominant (NDOM) TLE. Respective sensitivity and specificity values were as follows: PILD (84%, 86%), PostPE (94%, 64%), and InterPE (97%, 86%). No single predictor was significantly better but a combination model yielded enough incremental utility to collectively outperform each separate predictor model. CONCLUSIONS: Interictal language testing is as accurate as postictal language testing in predicting DOM lateralization of TLE. Clinicians should also attend to the quality of errors produced during interictal and postictal language testing.     

Role of immediate postictal diffusion-weighted MRI in localizing epileptogenic foci of mesial temporal lobe epilepsy and non-lesional neocortical epilepsy.

OBJECTIVE: To determine whether meaningful changes in signal intensity or in the apparent diffusion coefficient of water (ADC) in the ictal onset zone can be detected through immediate postictal and interictal diffusion-weighted magnetic resonance imaging (DWMRI) in patients with localization-related epilepsy. METHOD: In randomly selected 10 medial and lateral temporal lobe epilepsy (TLE) and four extratemporal epilepsy patients, DWMRI was performed immediately after a seizure and during the interictal period. All 14 patients were non-lesional except for hippocampal sclerosis detected on MRI. The mean time interval from seizure onset to postictal DWMRI was 81 min. Regions of interest (ROI) were selected in both the cortex, which was believed to be the ictal onset zone, and the corresponding anatomical region of the contralateral hemisphere in the postictal and interictal DWMRI. The mean ADC measured from all ROIs was compared. Ictal onset zones were determined by ictal electroencephalography (EEG) and seizure semiology. RESULTS: On visual inspection of postictal and interictal DWMRI, signal changes in the ictal onset zone could be identified in only one patient with medial TLE. The mean ADC values from the ictal onset zones were not significantly different from those of the corresponding contralateral regions of the cortices in both postictal and interictal DWMRI. However, the postictal ADC values of the epileptogenic foci of neocortical epilepsy or neocortical temporal portion of TLE without hippocampal sclerosis were decreased compared with interictal ones in whom both interictal and postictal DWMRIs were obtained (P = 0.028). CONCLUSION: Our results demonstrate that water diffusion can change even after a single seizure in non-lesional neocortical epilepsy.     

The expression of interictal, preictal, and postictal facial-wiping behavior in temporal lobe epilepsy: a neuro-ethological analysis and interpretation

By videotape recordings analysis we investigated the frequencies of interictal, preictal, and postictal wiping or rubbing movements targeting the face region (face wiping, FW) in 17 right and 13 left mesial temporal lobe epilepsy (MTLE) patients. Patients' data were compared with FW frequencies obtained in 22 healthy controls listening to a presentation. Results showed that: (1) FW movements were present in both controls and patients; however, the patient groups showed lower interictal and preictal FW rates relative than controls; (2) right and left temporal lobe seizures were followed by a marked increase in the expression of wiping activities directed to the nose as well as to other face regions with respect to the interictal-preictal period; (3) during the first 5min postictal FW was performed preferentially with the hand ipsilateral to the seizure focus; (4) postictal examination of the patient by an observer, especially if of the opposite sex, resulted in a higher incidence of FW acts. After temporal lobe seizures there is an exaggerated expression of movements targeting the face region, and not exclusively directed to the nose. According to an ethological interpretation of the FW behavior as a motor behavior present throughout the phylogenetic scale, from rodents to primates, we suggest the postictal emergence of an innate action pattern modulated by external emotional-cognitive stimuli.     

Neuropsychological characteristics of nonepileptic seizure semiological subgroups

The present study sought to identify neuropsychological characteristics of patients with nonepileptic seizures (NESs) based on seizure semiological subgroups and to make comparisons among NES subgroups and with patients with temporal lobe epilepsy (TLE). A total of 173 patients with NESs and 180 patients with TLE were included in this study. Statistical comparisons were made between a NES four-subgroup model, a NES two-subgroup model, and patients with TLE on neurocognitive measures. A trend toward declining performance was noted across the subjective, catatonic, minor motor, and major motor subgroups, respectively. The nonmotor subgroup showed stronger performance on verbal intelligence, naming, verbal learning, and verbal memory compared with the TLE group. The motor subgroup generally performed equivalently to the patients with TLE. Results indicate that patients with more dramatic seizure semiology appear to have lower neurocognitive functioning at a level comparable to that of patients with TLE. Patients with NESs with the least dramatic semiology appear to have fewer neurocognitive abnormalities.     

Postictal stability of proton magnetic resonance spectroscopy imaging (1H-MRSI) ratios in temporal lobe epilepsy

Interictal proton (1H) MRS is increasingly used for seizure lateralization in patients with temporal lobe epilepsy (TLE). Studies reporting postictal 1H-MRS metabolite changes in patients with TLE are few and contradictory. The authors prospectively performed interictal and postictal proton magnetic resonance spectroscopy imaging (1H-MRSI) studies in seven patients with TLE. The authors found no consistent changes in metabolite peak area ratios between studies, suggesting that 1H-MRS ratios remain stable between interictal and postictal state in TLE.     

Epileptic seizures are preceded by a decrease in synchronization

The exact mechanisms leading to the occurrence of epileptic seizures in humans are still poorly understood. It is widely accepted, however, that the process of seizure generation is closely associated with an abnormal synchronization of neurons. In order to investigate this process, we here measure phase synchronization between different regions of the brain using intracranial EEG recordings. Based on our preliminary finding of a preictal drop in synchronization, we investigate whether this phenomenon can be used as a sensitive and specific criterion to characterize a preseizure state and to distinguish this state from the interictal interval.Applying an automated technique for detecting decreased synchronization to EEG recordings from a group of 18 patients with focal epilepsy comprising a total of 117 h, we observe a characteristic decrease in synchronization prior to 26 out of 32 analyzed seizures at a very high specificity as tested on interictal recordings. The duration of this preictal state is found to range from several minutes up to a few hours. Investigation of the spatial distribution of preictal desynchronization indicates that the process of seizure generation in focal epilepsy is not necessarily confined to the focus itself but may instead involve more distant, even contralateral areas of the brain. Finally, we demonstrate an intrahemispheric asymmetry in the spatial dynamics of preictal desynchronization that is found in the majority of seizures and appears to be an immanent part of the mechanisms underlying the initiation of seizures in humans.     

Spatiotemporal relationship between seizure activity and interictal spikes in temporal lobe epilepsy.

PURPOSE: To analyze the spatio-temporal relationship between seizure propagation and interictal epileptiform discharges (IEDs) in patients with bitemporal epilepsy. METHODS: We investigated 18 adult patients with intractable temporal lobe epilepsy (TLE) who had undergone continuous video-EEG monitoring during presurgical evaluation. Only those patients were selected who had independent IEDs over both temporal lobes. Two authors evaluated the ictal and interictal EEG data independently. RESULTS: We analyzed 52 lateralized seizures of 18 patients. Thirty-one seizures showed ipsilateral seizure spread exclusively, whereas in 21 seizures the contralateral hemisphere was also involved. In lateralized seizures without contralateral propagation, we found that spikes ipsilateral to the seizure onset occurred postictally in a greater ratio than preictally (P<0.001). In lateralized seizures with contralateral propagation, we found no significant changes in the postictal spike distribution. CONCLUSIONS: Our findings showed that the lateralization of IEDs may depend on the brain areas involved by the preceding seizures, suggesting that spikes can be influenced by the seizure activity, and are not independent signs of epileptogenicity.     

Periictal heart rate variability analysis suggests long‐term postictal autonomic disturbance in epilepsy

Background: One of the possible pathomechanisms of sudden death in epilepsy (SUDEP) is a postictal dysregulation of autonomic nervous system. We performed a heart rate variability (HRV) analysis of the periictal state to analyze whether a cardiac autonomic disturbance exists after an epileptic seizure. Methods: We included 31 periictal video–EEG–ECG recordings of 31 patients with epilepsy who had consecutively undergone pre‐surgical evaluation. Nine generalized tonic‐clonic (GTCS), 15 complex partial, and seven simple motor seizures were included. HRV was evaluated by analyzing 5‐min‐long ECG epochs, sampling from baseline, direct preictal, early‐postictal (<15 min after the seizure), and late‐postictal (5–6 h after the seizure) periods. Results: The heart rate was elevated immediately after the seizures, but 5–6 h postictally returned to the baseline level. Time‐domain components of HRV decreased after the seizure and this decrease lasted for 5–6 h. Low‐frequency power decreased in the early‐postictal phase and high‐frequency power of HRV dropped in the late‐postictal phase. GTCS had an impact on short‐term but not on long‐term postictal HRV decrease. Conclusions: We found decreased HRV immediately after the seizures, which lasted at least 5–6 h postictally, indicating a long‐term postictal disturbance of the autonomous nervous system. GTCS were accompanied by a more decreased HRV than other seizures. Our results may have relevance in explaining pathomechanism of SUDEP.     

Spirituality and religion in epilepsy

Revered in some cultures but persecuted by most others, epilepsy patients have, throughout history, been linked with the divine, demonic, and supernatural. Clinical observations during the past 150 years support an association between religious experiences during (ictal), after (postictal), and in between (interictal) seizures. In addition, epileptic seizures may increase, alter, or decrease religious experience especially in a small group of patients with temporal lobe epilepsy (TLE). Literature surveys have revealed that between .4% and 3.1% of partial epilepsy patients had ictal religious experiences; higher frequencies are found in systematic questionnaires versus spontaneous patient reports. Religious premonitory symptoms or auras were reported by 3.9% of epilepsy patients. Among patients with ictal religious experiences, there is a predominance of patients with right TLE. Postictal and interictal religious experiences occur most often in TLE patients with bilateral seizure foci. Postictal religious experiences occurred in 1.3% of all epilepsy patients and 2.2% of TLE patients. Many of the epilepsy-related religious conversion experiences occurred postictally. Interictal religiosity is more controversial with less consensus among studies. Patients with postictal psychosis may also experience interictal hyper-religiosity, supporting a "pathological" increase in interictal religiosity in some patients. Although psychologic and social factors such as stigma may contribute to religious experiences with epilepsy, a neurologic mechanism most likely plays a large role. The limbic system is also often suggested as the critical site of religious experience due to the association with temporal lobe epilepsy and the emotional nature of the experiences. Neocortical areas also may be involved, suggested by the presence of visual and auditory hallucinations, complex ideation during many religious experiences, and the large expanse of temporal neocortex. In contrast to the role of the temporal lobe in evoking religious experiences, alterations in frontal functions may contribute to increased religious interests as a personality trait. The two main forms of religious experience, the ongoing belief pattern and set of convictions (the religion of the everyday man) versus the ecstatic religious experience, may be predominantly localized to the frontal and temporal regions, respectively, of the right hemisphere.     

Hyperorality in epileptic seizures: periictal incomplete Klüver-Bucy syndrome

PURPOSE: To analyze systematically hyperorality associated with epileptic seizures and its relation to the localization of epileptic activity. METHODS: To identify patients with periictal hyperorality, we reviewed video-recordings of 269 patients (aged 6-59 years) who had consecutively undergone presurgical evaluations including ictal video-EEG recordings and high-resolution magnetic resonance imaging (MRI) and had had epilepsy surgery because of intractable frontal (FLE) or temporal lobe epilepsy (TLE). Periictal hyperorality was defined if patients put or unambiguously intended to put nonfood items into their mouths during or after at least one of the reviewed seizures. For the further analysis, we included only patients with periictal hyperorality. We reviewed their medical records and reexamined their ictal video-EEG recordings. RESULTS: We identified eight patients (six women) aged 8-59 years who had hyperorality during or after seizures. Seven patients had TLE, and one patient had frontal lobe epilepsy (FLE). Three of these patients underwent right-sided surgery, whereas five patients had surgery on the left. Three patients exhibited ictal and five showed postictal hyperorality. Interictal EEG suggested bilateral interictal epileptiform discharges (IEDs) in three patients; in two other patients, no IEDs were detected. Ictal EEG suggested bilateral involvement in six cases. Patients with unilateral epileptiform activity had left TLE. CONCLUSIONS: Periictal hyperorality is a rare phenomenon occurring in 3% of the investigated epilepsy population. We suggest that periictal hyperorality is an ictal-postictal mental disturbance, an incomplete Klüver-Bucy syndrome. In most patients, bilateral seizure activity plays an important role in the pathomechanism, but it would appear that left-sided epileptic activity without contralateral involvement also can cause periictal hyperorality.     

Spike frequency is dependent on epilepsy duration and seizure frequency in temporal lobe epilepsy.

OBJECTIVES: We wanted to investigate factors that are associated with frequency of interictal epileptiform discharges by investigating 303 patients with temporal lobe epilepsy (TLE). METHODS: We included all patients who consecutively underwent the adult presurgical evaluation program at our center and who had intractable, medial TLE with complex partial seizures due to unilateral medial temporal lobe lesions. The interictal EEG samples were automatically recorded and stored on computer. The location and frequency of interictal epileptiform discharges were assessed by visual analysis of interictal EEG samples of 2-minute duration every hour. RESULTS: There were 303 patients (aged 16-63) who met the inclusion criteria. The median interictal epileptiform discharge frequency was 15 IED/h, the median seizure frequency was 4 seizures/month. According to univariate analyses, we found that age at monitoring, epilepsy duration, and higher seizure frequency were associated with higher interictal epileptiform discharge frequency. In the logistic regression analysis, we found that higher seizure frequency (p < 0.001) and longer epilepsy duration (p = 0.007) were independently associated with higher spike frequency, while the age at monitoring was not. CONCLUSIONS: Seizure frequency and epilepsy duration (years of patient's life with seizure activity) were independently associated with IED frequency, suggesting that IED are modulated by seizures.     

Postictal breathing pattern distinguishes epileptic from nonepileptic convulsive seizures

PURPOSE: To examine postictal breathing pattern in generalized convulsive nonepileptic seizures (GCNES) and generalized tonic-clonic seizures (GTCS) and evaluate this feature as a discriminating sign. METHODS: We reviewed the postictal breathing pattern seizures in 23 generalized tonic-clonic seizures in 15 consecutive patients with epilepsy and 24 convulsive nonepileptic seizures in 16 consecutive patients with pure psychogenic seizures. We also analyzed 21 frontal lobe hypermotor seizures (FLHS) in 9 patients with frontal lobe epilepsy. RESULTS: The breathing after GTCS was deep with prolonged inspiratory and expiratory phases, regular, and loud (except for two short seizures). The breathing after GCNES was characterized by increased respiratory rate or hyperpnea with short inspiratory and expiratory phases, as can be noted after exercise. The breathing was often irregular, with brief pauses. The altered breathing lasted longer after GTCS. The two groups differed significantly in loudness of postictal respiration, postictal snoring (only with GTCS), respiratory rate (faster for the GCNES group), and duration of altered breathing (longer after GTCS) (p < 0.00001 for all features). FLHS shared postictal breathing features of GCNES, but had other distinguishing features. CONCLUSIONS: The postictal breathing pattern can help differentiate generalized tonic-clonic seizures from nonepileptic psychogenic seizures with generalized motor activity and may be helpful to the practitioner obtaining a seizure history in the clinic setting or witnessing a seizure.     

Eating epilepsy

The clinical and EEG profiles of 13 cases of eating epilepsy are described. Temporal lobe epilepsy (TLE) formed the seizure type in 12 cases. In all but one case, the seizures were precipitated only by eating a heavy meal. In ten cases EEG showed interictal seizure discharges. EEG recordings were obtained from 12 patients during and after eating. In two patients clinical attacks (TLE) could be induced by eating in the laboratory. There was a good response to conventional anticonvulsants in only 3 cases. Alteration of eating habits helped in controlling reflex seizures in 2 cases. Various mechanisms of reflex precipitation of seizures by eating are discussed.     

SPECT in the localisation of extratemporal and temporal seizure foci.

The yield of ictal, postictal, and interictal SPECT was compared in the localisation of seizure foci in 177 patients with partial epilepsy. In 119 patients with known unilateral temporal lobe epilepsy ictal SPECT (97% correct localisation) was superior to postictal SPECT (71% correct), which was better than interictal studies (48% correct). Similarly, in cases of known or suspected extratemporal epilepsy the yield of ictal SPECT studies was high (92%). By contrast, the yield of postictal studies was much lower (46%) and usually only very early postictal studies were diagnostic. Interictal SPECT was of little value. The accuracy of ictal SPECT in localising temporal lobe seizures is now well established. Extratemporal seizures are often brief and difficult to localise. This report shows that ictal SPECT also has a high diagnostic yield in a wide range of extratemporal epilepsies. The brevity of many extratemporal seizures means that true ictal SPECT examinations can be difficult to achieve, but the high diagnostic yield justifies the special organisational effort needed to obtain such studies.     

Postictal nose-rubbing in the diagnosis, lateralization, and localization of seizures

BACKGROUND: Semiology is very useful in the diagnosis and classification of seizures. Some clinical signs occur primarily with specific localization-related epilepsies. OBJECTIVE: To evaluate postictal nose-rubbing as a potential diagnostic sign and a potential lateralizing or localizing indicator. METHODS: We reviewed presurgical prolonged video-EEG results of 50 consecutive patients with right temporal lobe epilepsy (TLE), 50 consecutive patients with left TLE, 50 consecutive patients with frontal lobe epilepsy, 11 consecutive patients with generalized epilepsy, and 100 consecutive patients with nonepileptic events. Videotapes of all events were reviewed independently by two investigators who were blinded to the results of the monitoring. The episodes of nose-rubbing and the hand with which the patient rubbed the nose were recorded. RESULTS: Nose-rubbing occurred in 25 of 50 (50%) right TLE patients and in 21 of 50 (42%) left TLE patients. Approximately 90% of patients rubbed his or her nose with the ipsilateral hand. Nose-rubbing occurred in 5 of 50 (10%) frontal lobe epilepsy patients. Nose-rubbing was not seen in any patient with generalized epilepsy or nonepileptic events. Postictal nose-rubbing did not occur after secondarily generalized seizures. CONCLUSIONS: Nose-rubbing is an easily observed phenomenon, has high interobserver reliability, and provides useful lateralizing information in patients with TLE. It was less frequently seen in extratemporal lobe epilepsy and was not seen after generalized seizures or nonepileptic events.     

Localization of epileptic foci with postictal single photon emission computed tomography

Effective surgical treatment of patients with intractable complex partial seizures depends on accurate preoperative seizure focus localization. We evaluated seizure localization with interictal and immediate postictal single photon emission computed tomographic images of cerebral perfusion using technetium-99m-hexamethyl-propyleneamineoxime (99mTc-HMPAO) in comparison with conventional ictal electroencephalographic (EEG) localization. Thirty-two patients with intractable complex partial seizures were studied. The mean delay from seizure onset to injection was 6.3 +/- 5.3 (SD) minutes. Independent blinded observers assessed the scans for interictal hypoperfusion and postictal focal hyperperfusion. Interictal scans alone were unreliable, indicating the correct localization in 17 patients (53%) and an incorrect site in 3 (9%). When interictal and postictal scans were interpreted together, the focus was correctly localized in 23 patients (72%). There was 1 false-positive study, and 8 patients had inconclusive changes, including 2 with inconclusive depth EEG studies. Postictal hyperperfusion was predominantly mesial temporal and frequently associated with hypoperfusion of lateral temporal cortex. Secondarily generalized seizures tended to show focal hyperperfusion less often than complex partial seizures did (Fisher's exact test p = 0.09). Combined interictal and immediate postictal single photon emission computed tomography with 99mTc-HMPAO is a useful noninvasive technique for independent confirmation of electrographic seizure localization. It may provide a suitable alternative to the use of depth electrode studies for confirmation of surface EEG findings in many patients with complex partial seizures.     

Frontal hemodynamic changes precede EEG onset of temporal lobe seizures

ObjectiveA preictal state exists minutes or hours prior to the clinical seizure. We investigated whether hemodynamic changes preceding temporal lobe seizures were detectable in frontal scalp recordings using near-infrared spectroscopy (NIRS). Patients undergoing video-EEG telemetry (VET) were studied.MethodsA NIRS sensor was placed over the frontal scalp ipsilateral to the patient’s first recorded seizure. Regional cerebral oxygenation (rSO2) was recorded synchronously with VET data and peripheral oxygen saturation (SaO2). Periictal changes in rSO2 were compared with baseline interictal rSO2.ResultsEleven seizures were recorded in six patients. A mean peak preictal increase in rSO2 of 7.1% from the interictal baseline (p < 0.001) occurred at a mean peak latency of 298.9 s before seizure onset. rSO2 then decreased around seizure onset. SaO2 nadir occurred at a mean latency of 62 s following rSO2 nadir. A postictal increase in rSO2 occurred with a mean duration of about 35 min. Periictal rSO2 changes occurred with both ipsi and contralateral temporal lobe seizures.ConclusionWe have shown that preictal changes in cerebral oxygenation occur with a mean peak latency of about 4.98 min before seizure onset.SignificanceNIRS has the potential for providing a noninvasively detected signal of an imminent seizure.