Peri-ictal Period Research Articles

Monitoring peri-ictal changes in heart rate variability, oxygen saturation and blood pressure in epilepsy monitoring unit

PurposeThe peri-ictal autonomic disturbances have been studied as predictors of seizure outcome and as markers of seizure onset. We studied the changes in heart rate (HR), HRV, oxygen saturation and blood pressure (BP) in the peri-ictal period in patients with drug-resistant localization-related epilepsy. MethodologyNinety one subjects undergoing video-EEG monitoring, underwent continuous HR, SpO2, BP and Lead II ECG monitoring. The changes during the preictal, ictal and postictal periods were analyzed for 57 seizures in 42 patients with artifact-free recordings and correlated with VEEG ictal onset and MRI characteristics. ResultsIctal tachycardia was noted in 15 (26.3%) seizures, of which, 60% had temporal lobe onset. HR increased by an average of 20.1% from pre-ictal to ictal phases (p=0.04). Ictal bradycardia was noted in one event with right temporal seizure onset. Heart rate variability (HRV) analysis of the preictal, ictal and postictal phases showed an increase in the sympathetic and decrease in parasympathetic activity during the ictus with relatively preserved total power. Ictal oxygen desaturation (84.1%±3.5%) was noticed in 10 (17.5%) seizures. Ictal hypertension was observed in 15 (26.3%); ictal hypotension was noted in 5 (8.7%) seizures. Both the systolic BP and diastolic BPs increased from the pre-ictal to ictal phase (p=0.01). ConclusionsPeri-ictal dysautonomia can present in variable patterns and can be measured and compared over different modalities such as BP, HR and HRV. Though degree of tachycardia and increase in BP were higher during extratemporal onset of seizures, a fall in variability was noted in seizures of temporal lobe origin. Oxygen desaturation is not an uncommon event during the peri-ictal period in localization related epilepsy.

Épilepsie : pour une sémiologie neuropsychiatrique de la dépression

The prevalence of psychiatric disorders is significantly higher among patients with epilepsy than the general population. Moreover, the profile of depressive disorder is often atypical in patients with epilepsy. Data from human and animal studies have tended to point towards a bidirectional link in the pathophysiological basis of both epilepsy and depressive syndrome. Depressive symptoms in epilepsy can be divided into those occurring in the peri-ictal period (pre-ictal, ictal and post-ictal), and those occurring in the inter-ictal period. Peri-ictal depressive disorders are particularly associated with temporal lobe epilepsies. These include: (i) peri-ictal dysphoria, (symptoms occur in the 24hour period preceding a seizure); (ii) ictal depression, (symptoms develop during the seizure); (iii) post-ictal depression, (symptoms occur in the 72hours following the seizure). The inter-ictal depressive disorders are not temporally related to seizures. The best characterized of these is “inter-ictal dysphoric disorder”. This includes labile depressive symptoms (depressed mood, anergia, pain, insomnia), labile affective symptoms (panic-like symptoms and anxiety), and supposedly “specific” symptoms (paroxysmal irritability and instable-euphoric moods). Standard psychiatric classification may be inadequate to describe some of the atypical profiles seen in this patient population. Depression in patients with epilepsy is therefore under-diagnosed, and yet contributes to poorer quality of life, epilepsy outcome and risk of suicide. It is recommended that an appropriate screening tool be used to detect signs of major depression, the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E). Clinicians should recognize the characteristics of peri-ictal and inter-ictal depressive syndromes.

Autonomic changes following generalized tonic clonic seizures: An analysis of adult and pediatric patients with epilepsy

ObjectiveSudden unexpected death in epilepsy (SUDEP) is the most common cause of mortality directly related to epilepsy. Its incidence is higher in adult patients and its pathophysiology remains poorly understood, but likely involves autonomic dysregulation following generalized tonic clonic seizures (GTCS). In the current study, we aimed to analyze post-ictal autonomic changes following GTCS in adult and pediatric patients. MethodsPatients admitted to the epilepsy monitoring unit were prospectively recruited, and wore an electrodermal activity (EDA) wrist sensor that continuously measured sympathetic activity while being monitored with EEG and EKG electrodes. Peri-ictal EDA parameters were assessed as a measure of sympathetic activity. Peri-ictal parasympathetic activity was determined through the high frequency component (HF) analysis of heart rate variability (HRV). The duration of post-ictal generalized EEG suppression (PGES) was also documented. ResultsTwenty patients with GTCS were included in the study on whom 30 GTCS were recorded. PGES duration strongly correlated with age (r=0.62, p=0.004) and measures of the EDA response. After controlling for PGES duration, we found pediatric patients had greater sympathetic activation measured as log rising portion of the area under the curve of the EDA response (β=+0.67, p=0.034) and a higher degree of vagal suppression measured as maximal percentage change of HF power (β=−12.65, p=0.0036). ConclusionSympathetic activity can be measured in the peri-ictal period, and directly correlates with PGES duration. Age is a significant determinant of the sympathetic and parasympathetic response following a GTCS; given the same PGES duration, pediatric patients demonstrate stronger sympathetic activation and higher vagal suppression. However, the increase in PGES duration with age and the associated autonomic dysregulation may provide clues as to why there is a variable vulnerability to SUDEP across age groups.

Cardiac and autonomic mechanisms contributing to SUDEP.

Sudden unexpected death in epilepsy is likely caused by a cascade of events affecting the vegetative nervous system leading to cardiorespiratory failure and death. Multiple genetic, electrophysiological, neurochemical, and pharmacological cardiac alterations have been associated with epilepsy, which can affect autonomic regulation of the heart and predispose patients to sudden unexpected death in epilepsy. These cardiac and autonomic changes are more frequently seen in patients with longstanding and medication refractory epilepsy and may be a prerequisite for sudden unexpected death in epilepsy. Cardiac changes are also observed within the immediate periictal period in patients with and without preexisting cardiac pathology and could be the tipping point in the cascade of events compromising autonomic, respiratory, and cardiac function during an epileptic convulsion. Better understanding if and how these cardiac alterations can make a particular individual with epilepsy more susceptible to sudden unexpected death in epilepsy will hopefully lead us to more effective preventative strategies.

P904: Normalization of EEG power spectrum in patients with migraine during peri-ictal periods

P904: Normalization of EEG power spectrum in patients with migraine during peri-ictal periods

S63: High frequency activity in the peri-ictal period

S63: High frequency activity in the peri-ictal period

Peri-ictal broadband electrocorticographic activities between 1 and 700 Hz and seizure onset zones in 18 patients

ObjectiveWe investigated the relationship between locations of broadband peri-ictal electrocorticographic activities determined by a semi-automatic detection method and seizure onset zones in medically intractable epilepsy patients. MethodsWe included 18 patients. Peri-ictal periods (−15 to +5s from the ictal onset) were divided into 4 periods of 5s duration each in bandwidth from 1 to 700Hz divided into 11 bins. Thereafter, we calculated the mean overlapping percentage of the maximum amplitude activity electrodes with the seizure onset zone in the total number of seizures in each patient. Significance was considered at an adjusted p-value of 0.05. ResultsBy the maximum amplitude method with the Bonferroni correction, only high-frequency activities (>60Hz) during −5 to 0s from the ictal onset were significantly related to seizure onset zones. In post hoc analyses, bands in 60–139Hz and 4–7Hz were significantly related to seizure onset zones in the Bonferroni correction. However, after the less conservative Benjamini–Yekutieli correction and with the epileptogenicity index, other bands and periods after −10s from the ictal onset were also related with seizure onset zones. SignificanceDetailed bands, timings and analytic methods of peri-ictal activities with high relationships to seizure onset zones were identified.

Cerebral perfusion alterations in epileptic patients during peri-ictal and post-ictal phase: PASL vs DSC-MRI

Non-invasive pulsed arterial spin labeling (PASL) MRI is a method to study brain perfusion that does not require the administration of a contrast agent, which makes it a valuable diagnostic tool as it reduces cost and side effects. The purpose of the present study was to establish the viability of PASL as an alternative to dynamic susceptibility contrast (DSC-MRI) and other perfusion imaging methods in characterizing changes in perfusion patterns caused by seizures in epileptic patients. We evaluated 19 patients with PASL. Of these, the 9 affected by high-frequency seizures were observed during the peri-ictal period (within 5hours since the last seizure), while the 10 patients affected by low-frequency seizures were observed in the post-ictal period. For comparison, 17/19 patients were also evaluated with DSC-MRI and CBF/CBV. PASL imaging showed focal vascular changes, which allowed the classification of patients in three categories: 8 patients characterized by increased perfusion, 4 patients with normal perfusion and 7 patients with decreased perfusion. PASL perfusion imaging findings were comparable to those obtained by DSC-MRI. Since PASL is a) sensitive to vascular alterations induced by epileptic seizures, b) comparable to DSC-MRI for detecting perfusion asymmetries, c) potentially capable of detecting time-related perfusion changes, it can be recommended for repeated evaluations, to identify the epileptic focus, and in follow-up and/or therapy-response assessment.

Central apnea at complex partial seizure onset

Sudden Unexpected Death in Epilepsy (SUDEP) is the most common cause of epilepsy related mortality in treatment resistant epilepsy. Most SUDEPs occur after one or more seizure(s) during sleep. Nocturnal seizures may go unrecognized. Respiratory depression in the peri-ictal period is one of the primary potential causes of SUDEP. Ictal and postictal apnea is often overlooked because it is not routinely assessed, but appears common and has been a recent focus of SUDEP research. We report a 37 year-old man who had central apnea as the initial manifestation of partial complex seizures associated with oxygen desaturation. This important pathophysiological consequence of a nocturnal complex seizure was identified by respiratory monitoring during a combined video EEG and sleep study. Diagnostic and therapeutic implications are discussed.

Peri-ictal urinary dysfunction in patients with epilepsy: a cross-sectional study.

To evaluate the prevalence of peri-ictal urinary symptoms and their association with seizure type in patients with epilepsy. A total of 115 patients with epilepsy were recruited consecutively from neurology clinic between January 2006 and January 2008. Peri-ictal period was defined as the period ranging from 2 minutes prior to seizure attack up to 48 hours after it, and post-ictal period was the time up to 48 hours after regaining consciousness. Peri-ictal urinary complaints were gathered with interview and data were analyzed using Pearson's Chi-square, Fisher's Exact test, and independent sample t test. The study population consisted of 57 (49.5%) men and 58 (50.4%) women, with the mean age of 26.83 ± 10.01 years. The frequency of at least one urinary symptom in studied patients was 39.1%. Incontinence, frequency, urgency, retention, and hesitancy were reported by 28 (24.3%), 14 (12.2%), 19 (16.5%), 10 (8.7%), and 8 (7%) patients, respectively. Women expressed more symptoms than men and a higher frequency of peri-ictal retention. Although overall urinary complaints were more frequent in patients with partial seizures, there was a higher frequency of urgency in patients with partial seizure (P = .037). Furthermore, apart from retention, there was no significant correlation between peri-ictal urinary symptoms and the patients' age. Our findings suggest that peri-ictal urologic dysfunction is a common problem among patients with epilepsy and post-ictal urinary retention might also be considered as a post-ictal deficit (Todd's deficit).

Takotsubo syndrome triggered by an epileptic seizure may be the cause of abnormal cardiac repolarization seen in patients with epilepsy

To the Editors: I read with great interest the excellent review article published recently by Surges et al. in Epilepsia (Surges et al., 2010). The authors reviewed the abnormal cardiac repolarization in patients with epilepsy and discussed the potential role of pathologic cardiac repolarization in sudden unexpected death in epilepsy (SUDEP). They have appropriately described in detail the role of QTc prolongation, QTc shortening, and QT dispersion in causing cardiac arrhythmias. They also have pointed out in the article that SUDEP is probably caused by periictal cardiorespiratory alterations such as central apnea, bradyarrhythmia, and neurogenic pulmonary edema. However, one important increasingly recognized cardiac disease entity, which can be triggered by an epileptic seizure and may be a potential cause of abnormal cardiac repolarization resulting in QTc prolongation in periictal period, was not mentioned. This relatively new cardiac clinical entity is called Takotsubo syndrome (TS) (Kawai et al., 2000), also known as neurogenic stunned myocardium or broken heart syndrome. The syndrome has a clinical presentation resembling that of acute coronary syndrome. It causes a characteristic regional ventricular wall motion abnormality affecting all the walls of the left ventricle circumferentially causing a peculiar balloon-like appearance of the ventricle during systole. The ventricular wall motion abnormality is transient and resolves completely within days to weeks. Coronary angiography usually reveals no identifiable lesions explaining the observed ventricular wall motion abnormality. The disease is usually preceded by an emotional or a physical stressor (Sharkey et al., 2010). A variety of critical neurologic illnesses and events, status epilepticus, and recurrent seizure activities may precipitate TS (Lemke et al., 2008). Recurrent episodes of TS triggered by convulsive status epilepticus have been reported (Legriel et al., 2008). During the last few years, many case reports of TS induced by epilepsy have been published. Among the most important electrocardiographic (ECG) findings in TS is evolving QTc prolongation besides ST-segment elevation and T-wave inversion (Kurisu et al., 2004). Certain ECG changes may last for weeks or months. Torsades de pointes and other malignant ventricular arrhythmia and sudden death have been reported as complications of TS. Denney et al. reported a case of TS with QT-interval prolongation in a young man who developed torsades de pointes and experienced aborted sudden cardiac death (Denney et al., 2005). Torsade de pointes associated with bradycardia and TS have been reported (Kurisu et al., 2008). The authors in the review article (Surges et al., 2010) have pointed out that sympathetic stimulation is among the potential mechanisms of periictal QTc prolongation. Cardiac sympathetic overactivation with excessive catecholamine production and intracardiac norepinephrine spill over is also among the discussed pathomechanisms of TS. A 12-lead ECG should be recommended in all patients after an epileptic seizure. If the above-mentioned ECG changes are detected, further investigation with myocardial biomarker control and performance of echocardiography will be necessary. Although specific treatments for TS have not yet been established, accurate diagnosis of the disease is indispensable in order to avoid unnecessary treatments as fibrinolysis. Furthermore, patients with TS may develop other serious complications besides life-threatening arrhythmias during the acute stage of illness as heart failure, pulmonary edema, cardiogenic shock, cardiovascular thromboembolism, and ventricular rupture with cardiac tamponade. The author has no conflict of interest to disclose. I confirm that I have read the Journal’s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.

Ictal and Peri-Ictal Psychopathology

Patients with epilepsy may experience psychiatric symptoms preceding the seizure (pre-ictal), following the seizure (post-ictal), independently of seizure occurrence (interictal), or as an expression of the seizure (ictal). Compared to interictal, peri-ictal psychiatric symptoms are less investigated and recognized. However, they contribute substantially to disability and distress among people with epilepsy.The relationship between interictal and periictal symptoms is still largely unknown but it seems that they are intimately related in epilepsy. Greater appreciation and understanding of the periictal period is clinically important, providing a model for understanding basic mechanisms underlying mood and thought disorders and the substrates of cognition, volition, emotion, and consciousness.The present paper is aimed at reviewing major psychiatric symptoms that may occur around the ictus with special attention to clinical descriptions and relationships with interictal psychopathology.

Ictal and peri-ictal psychopathology.

Patients with epilepsy may experience psychiatric symptoms preceding the seizure (pre-ictal), following the seizure (post-ictal), independently of seizure occurrence (interictal), or as an expression of the seizure (ictal). Compared to interictal, peri-ictal psychiatric symptoms are less investigated and recognized. However, they contribute substantially to disability and distress among people with epilepsy.The relationship between interictal and periictal symptoms is still largely unknown but it seems that they are intimately related in epilepsy. Greater appreciation and understanding of the periictal period is clinically important, providing a model for understanding basic mechanisms underlying mood and thought disorders and the substrates of cognition, volition, emotion, and consciousness.The present paper is aimed at reviewing major psychiatric symptoms that may occur around the ictus with special attention to clinical descriptions and relationships with interictal psychopathology.

Electrophysiological effects of guanosine and MK-801 in a quinolinic acid-induced seizure model

Quinolinic acid (QA) is an N-methyl- d-aspartate receptor agonist that also promotes glutamate release and inhibits glutamate uptake by astrocytes. QA is used in experimental models of seizures studying the effects of overstimulation of the glutamatergic system. The guanine-based purines (GBPs), including the nucleoside guanosine, have been shown to modulate the glutamatergic system when administered extracellularly. GBPs were shown to inhibit the binding of glutamate and analogs, to be neuroprotective under excitotoxic conditions, as well as anticonvulsant against seizures induced by glutamatergic agents, including QA-induced seizure. In this work, we studied the electrophysiological effects of guanosine against QA-induced epileptiform activity in rats at the macroscopic cortical level, as inferred by electroencephalogram (EEG) signals recorded at the epidural surface. We found that QA disrupts a prominent basal theta (4–10 Hz) activity during peri-ictal periods and also promotes a relative increase in gamma (20–50 Hz) oscillations. Guanosine, when successfully preventing seizures, counteracted both these spectral changes. MK-801, an NMDA-antagonist used as positive control, was also able counteract the decrease in theta power; however, we observed an increase in the power of gamma oscillations in rats concurrently treated with MK-801 and QA. Given the distinct spectral signatures, these results suggest that guanosine and MK-801 prevent QA-induced seizures by different network mechanisms.

Peri-ictal Normalization of Visual Cortex Excitability in Migraine: an MEG Study

To delineate if the change in cortical excitability persists across migraine attacks, visual evoked magnetic fields (VEF) were measured in patients with migraine without aura during the interictal (n = 26) or peri-ictal (n = 21) periods, and were compared with 30 healthy controls. The visual stimuli were checkerboard reversals with four different check sizes (15', 30', 60' and 120'). For each check size, five sequential blocks of 50 VEF responses were recorded to calculate the percentage change of the P100m amplitude in the second to the fifth blocks in comparison with the first block. At check size 120', interictal patients showed a larger amplitude increment than controls [28.1 +/- 38.3% (s.d.) vs. 8.7 +/- 21.3%] in the second block and a larger increment than peri-ictal patients in the second (28.1 +/- 38.3% vs. -3.2 +/- 19.2%), fourth (22.7 +/- 31.2% vs. -5.7 +/- 22.3%) and fifth (20.5 +/- 30.4% vs. -10.8 +/- 30.1%) blocks (P < 0.05). There was no significant difference at other check sizes or between peri-ictal patients and controls. In conclusion, there may be peri-ictal normalization of visual cortical excitability changes in migraine that is dependent on the spatial frequency of the stimuli and reflects a dynamic modulation of cortical activities.

The peri-ictal state: cortical excitability changes within 24 h of a seizure

In this study, transcranial magnetic stimulation was used to investigate motor cortical excitability changes in the peri-ictal period, in drug-naive new-onset epilepsy patients. Eighty-seven studies were performed on 58 patients (23 with idiopathic generalized epilepsy and 35 with focal epilepsy) within 72 h before or after a seizure. Fifty studies in 35 patients were within 24 h of a seizure. In all 58 patients, an interictal baseline study was performed, at least 14 days from a seizure. Motor threshold and paired pulse recovery curve results obtained at short (2-15 ms) and long (50-400 ms) interstimulus intervals in each hemisphere (at <24 h pre- or post-seizure and 24-72 h pre- and post-seizure) were compared against the interictal results and normal control values obtained from 32 subjects. The nature of the seizure (generalized, focal or focal with secondary generalization) was also recorded. Increased motor cortex excitability, measured by decreased motor threshold, increased intracortical facilitation and decreased intracortical inhibition at short and long interstimulus intervals was seen in the 24 h before a seizure. Conversely, decreased excitability occurred in the 24 h after a seizure. These effects were bilateral in tonic-clonic seizures in idiopathic generalized epilepsy and also in secondarily generalized seizures in patients with focal epilepsy. Similar changes were seen in the hemisphere ipsilateral to the seizure focus in focal seizures that did not secondarily generalize, accompanied by complex excitability changes in the contralateral hemisphere. These effects were not apparent in the 24-72 h window. These results show that there are major and prolonged changes in motor cortex excitability in the pre and the postictal 24 h. Increased excitation precedes the seizure by hours and there is a similar period of decreased excitability following a seizure.

The autopsy in sudden unexpected adult death: Epilepsy

Summary There are up to 500 epilepsy-related deaths annually in the UK, many of which are unwitnessed. Likely mechanisms for sudden and unexpected death in epilepsy (SUDEP) are cerebrogenic cardiac arrhythmias, or central respiratory depression occurring during the peri-ictal period. Pathologists should be informed of the circumstances of the death, severity of seizures, seizure control and the certainty of the clinical diagnosis of epilepsy; this allows accurate clinicopathological correlation. SUDEP autopsies include neuropathological assessment, histological examination of other organs and toxicology, and require the elimination of other causes of sudden death. Macroscopic (non-fatal) abnormalities described in SUDEP include evidence of previous cerebral injury, hippocampal sclerosis and cerebellar atrophy. Histological examination may reveal neuronal loss and gliosis consistent with seizure-related brain injury. Hippocampal sclerosis shows subfield-specific patterns of neuronal loss, granule cell dispersion and mossy fibre sprouting. Rarely, acute neuronal injury is seen as evidence of a more recent cerebral event. This article discusses the pathological findings and possible mechanisms in SUDEP, and future directions for pathology-based research.

Normalization of periictal bihemispheric cerebral perfusion in temporal lobe epilepsy

Under normal circumstances, cerebral blood flow (CBF), between the two hemispheres is coupled in a direct (i.e. positive slope), linear fashion. However, in temporal lobe epilepsy, the relationship between the two temporal cortices, during the interictal and postictal periods, is the inverse of normal (i.e. correlation is with negative slope and linear). Long-term combined temporal lobe thermal diffusion flowmetry (TDF) subdural regional cerebral blood flow and electroencephalographic (EEG) recording was performed to test the hypothesis that, during the 10 min periictal period (i.e. 5 min before and 5 min following clinical seizure onset), the cerebral perfusion relationship between epileptic and nonepileptic cortex returns to normal (i.e. becomes direct, with positive slope, and linear). A consecutive series of 13 patients with complex partial epilepsy was studied. During continuous monitoring of clinical phenomenology in time sequence with subdural CBF/EEG, the 10 min periictal period was characterized by a direct, linear correlation between epileptic and nonepileptic temporal cortical blood flow ( r=0.302, d.f.=85, t=2.921, P<0.01). The fact that this pertubation in the CBF relationship between the bilateral temporal cortices begins prior to and continues for 5 min following clinical and subdural EEG seizure onset raises the interesting possibility that normalization of periictal bilateral cerebral perfusion may be associated with temporal lobe epileptogenesis.

Treatment strategies in Landau–Kleffner syndrome and paraictal psychiatric and cognitive disturbances

Psychiatric and cognitive disturbances of the peri-ictal period (i.e., the seizure prodrome and the postictal period) can be considered paraictal disturbances, as they are directly related to the ictal event. There are also certain interictal psychiatric and cognitive disturbances that become apparent concomitantly with the onset of a seizure disorder and remit and/or significantly improve upon its remission. Such disorders also fall under the classification paraictal disorders, and are exemplified by Landau–Kleffner syndrome (LKS), a disorder in which language and psychiatric disturbances begin with the onset of epileptic activity and improve upon its disappearance. In this article, we review the treatment of paraictal cognitive and psychiatric disorders presenting as preictal and postictal psychiatric disturbances and LKS.

Noninvasive Continuous Monitoring of Cerebral Oxygenation Periictally Using Near‐Infrared Spectroscopy: A Preliminary Report

To report on the use of near-infrared spectroscopy (NIRS) to examine the changes in cerebral oxygenation in the periictal period in patients with seizures. Cerebral hemoglobin oxygen availability was monitored continuously and noninvasively with NIRS in three patients (one in the pediatric intensive care unit (ICU) and two in epilepsy-monitoring units) in conjunction with continuous EEG monitoring. Ictal events were recorded and compared with the pre-, intra-, and postictal periods for cerebral oxygen availability, as defined by oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (Hb), and the redox state of cytochrome oxidase (cytox). Several important preliminary observations were made by using this technology. First, a preictal increase in cerebral oxygenation began between 1 and 2 h and >10 h before the ictal event. Second, despite adequate perfusion, based on an observed increased HbO2, reduction in cytox indicates a perfusion-metabolism mismatch during seizure activity. Third, continued seizure activity and even isolated ictal events were associated with decreased cerebral oxygen availability. Fourth, differences in cerebral oxygen availability were noted between different types of seizures (e.g., electrographic seizures were accompanied by rapid reductions in HbO2 and cerebral blood volume without reduction of cytox, whereas electroclinical seizures were characterized by marked increases in HbO2 with or without reduction of cytox). In this preliminary report on the use of NIRS for patients with seizures, we believe that NIRS allows continuous and noninvasive monitoring of changes in cerebral oxygenation periictally, thereby permitting investigations into the pathophysiology of seizures and the exploration of the potential of cerebral oximetry as a tool for seizure localization.