Visual and quantitative ictal EEG predictors of outcome after temporal lobectomy

PURPOSE: We investigated whether visual and quantitative ictal EEG analysis could predict surgical outcome after anteromesial temporal lobectomy (AMTL) in which mesial structures, basal, and temporal tip cortex were resected. METHODS: We retrospectively reviewed 282 presurgical scalp-recorded ictal EEGs (21- to 27-channel) from 75 patients who underwent AMTL. We examined the pattern of seizure onset (frequency, distribution, and evolution) and estimated the principal underlying cerebral generators by using a multiple fixed dipole model that decomposes temporal lobe activity into four sublobar sources (Focus 1.1). We correlated findings with a 2-year postoperative outcome. RESULTS: Sixteen patients had seizures with a well-lateralized, regular 5 to 9-Hz rhythm at onset, that most often had a temporal or subtemporal distribution. All patients became seizure free after surgery. In 51 patients, seizure onset was remarkable for lateralized slow rhythms (<5 Hz), which sometimes appeared as periodic discharges, were often irregular and stable only for short periods (<5 s), and had a widespread lateral temporal distribution. Among these a favorable surgical outcome was encountered in patients with seizures having prominent anterior-tip sources ( 16 of 17 seizure free), whereas those with dominant lateral or oblique sources had a less favorable outcome (three of 14 and 13 of 18, respectively). Irregular, nonlateralized slowing characterized seizure onsets in eight patients. Three patients became seizure free after surgery. CONCLUSIONS: Both visual and quantitative sublobar source analysis of scalp ictal EEG can predict surgical outcome in most cases after AMTL and complement non-invasive presurgical evaluation.     

Continuous source imaging of scalp ictal rhythms in temporal lobe epilepsy

PURPOSE: We wished to determine whether continuous EEG source imaging can predict the location of seizure onset with sublobar accuracy in temporal lobe epilepsy (TLE). METHODS: We retrospectively analyzed the earliest scalp ictal rhythms, recorded with 23- to 27-channel EEG, in 40 patients with intractable TLE. A continuous source analysis technique with multiple fixed dipoles (Focus 1.1) decomposed the EEG into source components representing the activity of major cortical sublobar surfaces. For the temporal lobe, these were basal, anterior tip, anterolateral, and posterolateral cortex. Ictal EEG onset was categorized according to its most prominent and leading source component. All patients underwent intracranial EEG studies before epilepsy surgery, and all had a successful surgical outcome (follow-up >1 year). RESULTS: Most patients with ictal rhythms having a predominant basal source component had hippocampal-onset seizures, whereas those with seizures with prominent lateral source activity had predominantly temporal neocortical seizure origins. Seizures with a prominent anterior temporal tip source component mostly had onset in entorhinal cortex. Seizures in some patients had several equally large and nearly synchronous source components. These seizures, which could be modeled equally well by a single oblique dipole, had onset predominantly in either entorhinal or lateral temporal cortex. CONCLUSIONS: Multiple fixed dipole analysis of scalp EEG can provide information about the origin of temporal lobe seizures that is useful in presurgical planning. In particular, it can reliably distinguish seizures of mesial temporal origin from those of lateral temporal origin.     

Routine microbiological testing in sudden and unexpected infant death

We reviewed 187 depth recorded seizures in 33 patients with non-lesional temporal lobe complex partial seizures. All patients had a minimum of 1 year follow-up following temporal lobectomy. We classified seizure onset pattern as rhythmic activity, attenuation, or repetitive spikes or spike wave complexes. The most common pattern of seizure onset was rhythmic activity and the next most common pattern was repetitive spikes. Seventy-five seizures (49%) had only one seizure onset pattern, and 79 seizures (51%) had a combination of seizure onset patterns. The degree of hippocampal gliosis strongly predicted the type of seizure onset pattern (Chi square = 24.07, 2 d.f., P < 0.01). The rhythmic activity pattern was associated with mild gliosis, and the repetitive spike pattern was associated with severe gliosis. We classified seizure onset as focal or regional based on the number of electrode contacts that were involved by the ictal EEG. A focal seizure onset was associated with an excellent outcome following temporal lobectomy.     

Scalp-recorded, ictal focal DC shift in a patient with tonic seizure

PURPOSE: We recorded focal ictal DC shifts from scalp electrodes in a 9-year-old boy with intractable, clinically generalized tonic seizures. The patient had a high intensity signal abnormality of the left temporal cortex with thickening of the gyri on T2-weighted MRI. METHODS: Scalp digital EEGs were recorded using electrodes made of silver/silver chloride. The low frequency filter (LFF) was set at 0.016 Hz. Recorded seizures were subsequently analyzed with LFF settings of 1.0, 0.016 and 0.03 Hz. RESULTS: All recorded seizures initially showed diffuse, low voltage, high frequency activity (electrodecremental pattern) followed 10-20 s later by quasirhythmic activity over the left frontotemporal region. In two seizures, LFF of 0.016-0.03 Hz revealed a slow negative shift over the left frontotemporal area simultaneously with onset of the bilateral electrodecremental pattern. However, in the other seizures, this initial slow negative shift was obscured by artifacts. Subsequent electrocorticography (ECoG) delineated frequent epileptiform discharges in the left temporal as well as frontal cortex. CONCLUSIONS: Scalp-recorded ictal DC shifts may help identify focal epileptogenic brain area in patients with clinically generalized seizures although the technique is vulnerable to artifact.     

Nonlinear dynamics of epileptic seizures on basis of intracranial EEG recordings

PURPOSE: An understanding of the principles governing the behavior of complex neuronal networks, in particular their capability of generating epileptic seizures implies the characterization of the conditions under which a transition from the interictal to the ictal state takes place. Signal analysis methods derived from the theory of nonlinear dynamics provide new tools to characterize the behavior of such networks, and are particularly relevant for the analysis of epileptiform activity. METHODS: We calculated the correlation dimension, tested for irreversibility, and made recurrence plots of EEG signals recorded intracranially both during interictal and ictal states in temporal lobe epilepsy patients who were surgical candidates. RESULTS: Epileptic seizure activity often, but not always, emerges as a low-dimensional oscillation. In general, the seizure behaves as a nonstationary phenomenon during which both phases of low and high complexity may occur. Nevertheless a low dimension may be found mainly in the zone of ictal onset and nearby structures. Both the zone of ictal onset and the pattern of propagation of seizure activity in the brain could be identified using this type of analysis. Furthermore, the results obtained were in close agreement with visual inspection of the EEG records. CONCLUSIONS: Application of these mathematical tools provides novel insights into the spatio-temporal dynamics of "epileptic brain states". In this way it may be of practical use in the localization of an epileptogenic region in the brain, and thus be of assistance in the presurgical evaluation of patients with localization-related epilepsy.     

Effects of altitude and latitude on ambient UVB radiation

PURPOSE: Spitting as an ictal automatism has been rarely reported. We aimed to establish its potential lateralizing and localizing significance. METHODS: Review of patients undergoing surgery for intractable epilepsy at two comprehensive epilepsy centers. RESULTS: Five patients were found who had spitting as a stereotyped automatism of their complex partial seizures. All had evidence of right temporal ictal onset and underwent resective surgery. Two had tumors; one, a cavernous angioma; one, hippocampal gliosis, and one, hippocampal sclerosis. We found no instances of ictal spitting in patients with left hemisphere onset. CONCLUSIONS: Spitting as an automatism in complex partial seizures, although uncommon, may be a localizing sign to the nondominant temporal lobe.     

Ictal cerebral blood flow in seizures originating in the posterolateral cortex

In selecting patients for epilepsy surgery, it is important to distinguish mesial temporal seizures from seizures originating in the posterolateral cortex. We studied ictal cerebral perfusion in five patients with complex partial seizures with clear posterior EEG ictal onsets and clinical seizures semiology suggesting seizure origin in the posterolateral cortex. METHODS: Ictal SPECT was performed during video EEG monitoring using 99mTc-HMPAO as a cerebral perfusion tracer and a rotating gamma camera to acquire images. RESULTS: Three patterns of ictal hyperperfusion were seen: pattern A = temporoparieto-occipital junction extending into the lateral temporal cortex, involving the mesial temporal cortex and basal ganglia to a lesser degree and a small area of hyperperfusion in the contralateral parietal cortex (two patients); pattern B = pattern A but with no hyperperfusion of the mesial temporal cortex (one patient); and pattern C = localized hyperperfusion in the area of the temporoparieto-occipital junction (two patients). CONCLUSION: Our results suggest distinct patterns of ictal perfusion in seizures with posterolateral ictal EEG onsets. Ictal SPECT may be useful in distinguishing such seizures.     

Rhodamine 123 efflux modulation in the presence of low or high serum from CD56+ hematopoietic cells or CD34+ leukemic blasts by B9309-068, a newly designed pyridine derivative

BACKGROUND: Although magnetoencephalography (MEG) provides accurate information on the spatial distribution and temporal patterns of the "interictal" epileptic activities, it is interictal in nature and therefore also prone to all the problems associated with interictal data. METHODS: We investigated the subclinical "ictal" epileptic activity with a 37-channel, large-array biomagnetometer and mapped the data onto a three-dimensional image in a patient with intractable frontal lobe epilepsy. Dipole source localization was calculated based on magnetic fields for both the interictal and subclinical ictal activities. RESULTS: The current dipoles of the interictal MEG spikes (MEG irritative zone) were revealed to be scattered in the left anterior frontal lobe, whereas that of the subclinical ictal onset (MEG subclinical ictal onset zone) was surrounded by the interictal dipole cluster. The dipole source localization of the propagating activities was not calculated with a single dipole model. The MEG subclinical ictal onset zone correlated well with the ictal onset zone subsequently recorded by invasive subdural electrophysiological monitoring. After multiple subpial transection of the deduced epileptogenic area, a dramatic reduction of the seizures occurred. CONCLUSION: These results illustrate the potential of MEG for localizing the epileptogenic foci with high spatial and temporal resolution.     

Clinical and electrographic manifestations of lesional neocortical temporal lobe epilepsy

To determine whether lesional neocortical temporal lobe epilepsy (NTLE) can be differentiated from mesial temporal lobe epilepsy (MTLE) during the noninvasive presurgical evaluation, we compared the historical features, seizure symptomatology, and surface EEG of 8 patients seizure free after neocortical temporal resection with preservation of mesial structures and 20 patients after anterior temporal lobectomy for MTLE. Seizure symptomatology of 107 seizures (28 NTLE, 79 MTLE) was analyzed. One hundred one ictal EEGs (19 NTLE, 82 MTLE) were reviewed for activity at seizure onset; presence, distribution, and frequency of lateralized rhythmic activity (LRA); and distribution of postictal slowing. Seizure symptomatology and EEG data were compared between groups, and sensitivity, specificity, and positive and negative predictive values were determined for variables that differed significantly. Multiple logistic regression was used to determine whether patients could be correctly classified as having MTLE or NTLE. MTLE patients were younger at onset of habitual seizures and more likely to have a prior history of febrile seizures, CNS infection, perinatal complications, or head injury. NTLE seizures lacked features commonly exhibited in MTLE, including automatisms, contralateral dystonia, searching head movements, body shifting, hyperventilation, and postictal cough or sigh. NTLE ictal EEG recordings demonstrated lower mean frequency of LRA that frequently had a hemispheric distribution, whereas LRA in MTLE seizures was maximal over the ipsilateral temporal region. We conclude that it may be possible to differentiate lesional NTLE from MTLE on the basis of historical features, seizure symptomatology, and ictal surface EEG recordings. This may assist in the identification of patients with medically refractory nonlesional NTLE who frequently require intracranial monitoring and more extensive or tailored resections.     

Ictal single photon emission computed tomography in occipital lobe seizures

PURPOSE: Ictal single photon emission computed tomography (SPECT) has been evaluated as an adjunctive localizing technique in temporal lobe epilepsies and, to a lesser degree, in some extratemporal epilepsies. The purpose of this study was to determine whether occipital lobe seizures are associated with distinctive ictal cerebral blood perfusion (rCP) patterns. METHODS: SPECT was used with the tracer 99mTc HMPAO to image ictal rCP in 6 patients in whom clinical, EEG, and imaging data indicated occipital lobe seizures. RESULTS: Two patterns of rCP were seen. Four patients had hyperperfusion that was restricted to the occipital lobe, and two patients had hyperperfusion of the occipital lobe and the ipsilateral mesial temporal lobe, with hypoperfusion of the lateral temporal lobe. The latter 2 patients had clinical and surface EEG evidence of temporal lobe involvement in the seizure discharge. CONCLUSIONS: Ictal rCP patterns in occipital lobe seizures are distinct from those in temporal lobe seizures and may vary according to whether or not ipsilateral temporal lobe structures are involved in the ictal discharge.     

Ictal smile

PURPOSE: Smiling is sometimes manifested during partial seizures. Its value for localizing the epileptogenic focus is not known. We analyzed smiling as an ictal manifestation possibly useful for seizure localization. METHODS: We reviewed patients referred to the video-EEG monitoring unit who presented a smile as part of their critical symptoms. Ictal smile was defined as an accordant expression accompanied by other characteristic epileptic symptoms and ictal EEG activity. RESULTS: Five of 86 patients experienced partial seizures with an ictal smile. We observed smiling during parietal (two patients) and temporal lobe (three patients) seizures. The right hemisphere appeared to be involved with greater frequency. CONCLUSIONS: Ictal smile is an uncommon manifestation of partial seizures involving temporal or parietal lobes, localized mainly on the right hemisphere.     

Repair of traumatic orbital wall defects with nasal septal cartilage: report of five cases

PURPOSE: Arachnoid cysts are sometimes encountered in MRIs performed for a variety of reasons. In patients with epilepsy, particularly those with refractory epilepsy, arachnoid cysts are often assumed to be related to their seizure focus. We conducted a study to investigate this putative relationship. METHODS: A retrospective study on the incidence of arachnoid cysts was performed in patients seen in our Epilepsy Clinic who had CT or MRI scans, interictal EEGs or ictal EEGS. Locations of seizure foci in these patients were defined from clinical and electrophysiologic data. RESULTS: Seventeen of 867 patients had arachnoid cysts. Twelve patients had temporal lobe cysts and only 3 of them had temporal lobe seizures. Four patients had frontal lobe cysts and only 1 had frontal lobe seizures ipsilateral to the cyst. One patient had a cerebello-pontine angle cyst and frontal lobe seizures. Thus, clinical manifestations of seizures and EEG findings (interictal and/or ictal) indicated that the seizure focus was adjacent to the cysts in only 4 patients (23.5%). CONCLUSIONS: Our findings suggest that arachnoid cysts are often an incidental finding in patients with epilepsy and do not necessarily reflect the location of the seizure focus.     

The postictal state. A clinically oriented observation of patients with epilepsy

Epileptic seizures are followed by dynamic alterations in neurologic function in the postictal period which have received little attention by clinicians over a long period of time. We therefore retrospectively studied videotapes of 160 patients with focal epilepsy who underwent presurgical evaluation, for the occurrence of postictal symptoms to determine whether these phenomena have any localizing or lateralizing value in defining the seizure onset zone. Results: (1) We found postictal paresis in 22 of 160 patients (18.8%) in each case contralateral to the hemisphere of seizure onset. (2) 'Perservative' automatisms which start during the ictus and continue in the postictal period occurred in 25.2% of 135 patients with temporal lobe epilepsy but not in patients with frontal lobe epilepsy. (3) Sexual automatisms defined as manipulations of the genitals were found exclusively in patients with temporal lobe epilepsy (in 5.9% of 135 patients). (4) Postictal 'Nose-wiping' was evident in 51.3% of 76 temporal lobe epilepsy patients but only in 12.0% of 25 extratemporal lobe epilepsy patients and was performed with the hand ipsilateral to the hemisphere of seizure onset in 86.5% of all temporal lobe seizures. (5) Postictal language disturbances were observed only in patients with temporal lobe epilepsy (34% of 97 patients) and pointed to a seizure onset in the dominant hemisphere in 80.8%. We conclude that postictal phenomena can provide reliable information for the localization of the seizure onset zone in patients with complex partial seizures. Thus, more attention should be given to the postictal state during presurgical epilepsy monitoring.     

EEG findings in frontal lobe epilepsies

As a group, epilepsies of frontal lobe origin are thought to be poorly localized using surface EEG recordings. This finding may depend on the specific areas of frontal lobe from which the seizures originate or the pathologic substrate. We reviewed the presurgical surface EEGs of patients with frontal lobe epilepsy who underwent epilepsy surgery. The specific area of the frontal lobe where seizures originated was determined by 1) intracranial ictal EEG recordings, or 2) the presence of a structural lesion, identified by imaging studies in patients who achieved complete seizure control following surgery. We differentiated patients whose seizures began in the dorsolateral frontal convexity from those whose seizures began in the medial frontal region, and we correlated EEG findings in the interictal, postictal, and ictal states with seizure semiology, pathologic substrate, and surgical outcome. Four of nine patients had seizures originating in the dorsolateral frontal convexity and five had medial frontal onset seizures. Patients whose seizures originated from the dorsolateral convexity had focal interictal epileptiform abnormalities that localized to the region of seizure onset. Patients whose seizures began in the medial frontal region had either no interictal epileptiform abnormality or had multifocal epileptiform discharges. Patients whose seizures began in the dorsolateral convexity showed focal electrographic seizure activity that was localizing. This rhythmic fast activity did not appear to be substrate-specific. Patients whose seizure onset localized to the medial frontal region did not show focal electrographic seizure at clinical onset. We conclude that the scalp EEG recordings of frontal lobe epilepsies contain features that enable differentiation of seizures originating from two different regions of the frontal lobe.     

Preictal SPECT in temporal lobe epilepsy: regional cerebral blood flow is increased prior to electroencephalography-seizure onset

Peri-ictal SPECT provides unique information on the dynamic changes in regional cerebral blood flow (rCBF) that occur during seizure evolution and, thus, could be useful in clarifying the poorly understood interplay of the interictal and ictal states in human focal epilepsy. The regional hyperperfusion observed on ictal SPECT is generally believed to be a consequence of electrical seizure activity. However, recent studies using invasive long-term cortical CBF monitoring have demonstrated that rCBF changes occur up to 20 min prior to ictal electroencephalography (EEG) onset. Because of apparent technical difficulties, no preictal SPECT studies have been reported so far. Therefore, we present our results on two patients with temporal lobe epilepsy in whom preictal SPECT scans were performed fortuitously under continuous video-EEG monitoring control. METHODS: Technetium-99m-hexamethyl propyleneamine oxime was injected 11 min (Patient 1) and 12 min (Patient 2) before clinical and EEG seizure onset, as documented from simultaneous video-EEG monitoring in two patients with temporal lobe epilepsy. We obtained accurate anatomical reference of CBF changes visible on SPECT by a special coregistration technique of MRI and SPECT. RESULTS: Whereas interictal SPECT showed a hypoperfusion of the temporal lobe ipsilateral to the seizure focus, on preictal SPECT, a significant increase in rCBF in the epileptic temporal lobe could be observed. These rCBF changes were not accompanied by any significant changes of the ongoing EEG. CONCLUSION: Our study provides evidence that rCBF is increased in the epileptic temporal lobe several minutes before EEG seizure onset. Thus, rCBF changes observed on peri-ictal SPECT scan cannot be considered a mere consequence of EEG seizure activity but may rather reflect a change in neuronal activity precipitating the transition from the interictal to the ictal state.     

Single photon emission computed tomography (SPECT) in a patient with bilateral temporal seizures: correlation between ictal EEG and postictal/ictal SPECT

We report a patient with bilateral independent temporal lobe seizures in whom two [99mTc]HMPAO single photon emission computed tomograph (SPECT) scans were performed during two different seizures. In the first periictal SPECT, [99mTc]HMPAO was injected in the interval between two closely spaced seizures (one localized in the left temporal lobe and the other in the right temporal lobe). SPECT images showed hypoperfusion in the left lateral temporal lobe, hyperperfusion of the left mesial temporal region, and pronounced hyperperfusion in the right anterior temporal lobe. These results suggest both a postictal left temporal SPECT pattern and an ictal right temporal pattern. In the second periictal SPECT, [99mTc]HMPAO was injected immediately after a right temporal lobe seizure and showed right lateral temporal lobe hypoperfusion and right mesial hyperperfusion, suggesting a postictal right temporal SPECT pattern. Interpretation of the periictal SPECT should take into account EEG changes at the time or in the minutes immediately after injection of [99mTc]HMPAO.     

Semiological seizure classification

We propose an epileptic seizure classification based exclusively on ictal semiology. In this semiological seizure classification (SSC), seizures are classified as follows: a. Auras are ictal manifestations having sensory, psychosensory, and experiential symptoms. b. Autonomic seizures are seizures in which the main ictal manifestations are objectively documented autonomic alterations. c. "Dialeptic" seizures have as their main ictal manifestations an alteration of consciousness that is independent of ictal EEG manifestations. The new term "dialeptic" seizure has been coined to differentiate this concept from absence seizures (dialeptic seizures with a generalized ictal EEG) and complex partial seizures (dialeptic seizures with a focal ictal EEG). d. Motor seizures are characterized mainly by motor symptoms and are subclassified as simple or complex. Simple motor seizures are characterized by simple, unnatural movements that can be elicited by electrical stimulation of the primary and supplementary motor area (myoclonic, tonic, clonic and tonic-clonic, versive). Complex motor seizures are characterized by complex motor movements that resemble natural movements but that occur in an inappropriate setting ("automatisms"). e. Special seizures include seizures characterized by "negative" features (atonic, astatic, hypomotor, akinetic, and aphasic seizures). The SSC identifies in detail the somatotopic distribution of the ictal semiology as well as the seizure evolution. The advantages of a pure SSC, as opposed to the current classification of the International League Against Epilepsy (ILAE), which is actually a classification of electroclinical syndromes, are discussed.     

Pedicled and microvascular reanastomosed transplants for reconstruction in the head-neck area

In seizures starting gradually, careful examination of the background is required to determine the time and region of onset. We propose a method for displaying EEG variables which characterize seizure onset: changes in amplitude and in average frequency compared to background. These variables are displayed topographically for each EEG channel so that 1 or 2 min of EEG may be viewed on a standard screen, thus representing pre-ictal and ictal periods. We evaluated the ability of this display to indicate seizure onset, by comparing the times and regions of seizure onset indicated by traditional EEG and by the display. The comparison was performed on 30 seizures from scalp recordings and 49 seizures from depth recordings. Seizures were selected for having a gradual onset with no or minimal artefact. Onset times from traditional EEG and the computer method, examined independently, coincided (within 3 sec) in 77% of scalp seizures and 63% of depth seizures. In 14% of seizures the computer display indicated an onset more than 3 sec earlier than visual examination; upon reexamination, however, this onset was thought to be possibly correct. This quantitative display, which in practice should be used with traditional EEG, may thus be useful for computer-assisted seizure interpretation and for a condensed representation of seizures.     

Quantitative analysis of Epstein-Barr virus load by using a real-time PCR assay

BACKGROUND: Previous studies have suggested a variety of factors that may be associated with the presence of hippocampal formation (HF) atrophy in patients with complex partial seizures (CPS), including a history of complex or prolonged febrile seizures (FS), age at seizure onset, and epilepsy duration. OBJECTIVE: To determine whether epilepsy duration is related to HF atrophy. Methods: We performed MRIs on 35 patients with uncontrolled CPS who had temporal lobe ictal onset on video-EEG. None had evidence for an alien tissue lesion or extra-hippocampal seizure onset. All had a history of secondary generalization. Brain structures were drawn on consecutive images and pixel points summed from successive pictures to calculate volumes. RESULTS: Nine patients with a history of complex or prolonged FS had smaller ipsilateral HF volume and ipsilateral/contralateral ratio than did patients without a history of FS. Epilepsy duration had a significant relation to ipsilateral HF volume and ipsilateral/contralateral ratio. In a multivariate analysis, the effect of duration, but not age at onset or scan, was significant. Patients with a history of FS did not have earlier age at epilepsy onset or longer duration. Conclusions: A history of FS predicted the severity of HF atrophy in our patients. Age at onset or study was not a significant factor. Epilepsy duration, however, did have a significant effect, suggesting that, after an initial insult, progressive HF damage may occur in patients with persistent seizures.