Role of the frontal lobes in the propagation of mesial temporal lobe seizures.

The depth ictal electroencephalographic (EEG) propagation sequence accompanying 78 complex partial seizures of mesial temporal origin was reviewed in 24 patients (15 from the University of Pittsburgh Epilepsy Center and 9 from UCLA). All patients were monitored with bilateral mesial frontal and mesial temporal depth electrodes and later received anterior temporal lobectomy. Ictal EEG records were categorized according to sequence of spread from the temporal focus to the other regions. Although propagation patterns varied both within and between patients, certain features were notable: (a) It was very common for seizure activity to spread initially to the ipsilateral frontal lobe (observed in 22 of 24 patients). (b) The most common mode of spread (15 of 24 patients) was initiating temporal lobe----ipsilateral frontal lobe----contralateral frontal lobe----contralateral temporal lobe. (c) Occasionally, seizure discharges invaded the frontal lobes but failed to invade the contralateral temporal lobe (2 of 24 patients). (d) Seizure activity occasionally invaded the contralateral temporal lobe prior to invading the frontal lobes (2 of 24 patients). Other notable features included (i) a clear tendency for mesial temporal seizure discharges initially to invade orbitofrontal (as opposed to anterior cingulate) cortex and (ii) the emergence of a period of clear asymmetry in the frontal lobes during which high-amplitude, rapid discharges were present on the side ipsilateral to the initiating temporal lobe. These results suggest that the prefrontal region, especially the orbitofrontal cortex, is strongly influenced by mesial temporal ictal activity. This region appears to be frequently involved in the propagation of seizures initiated in the mesial temporal lobe and may play a role in the interhemispheric propagation of mesial temporal seizures.     

Ictal automatisms with preserved responsiveness in a patient with left mesial temporal lobe epilepsy

PURPOSE: To describe the possible mechanism of ictal automatisms with preserved responsiveness (APRs) in a patient with left mesial temporal lobe epilepsy, which had not been reported previously. METHODS: Ictal EEGs recorded from bilateral foramen ovale electrodes with scalp-sphenoidal electrodes were analyzed in respect to the ictal semiology. RESULTS: The patient had a right hemispheric language dominance in the dextral. Electroclinical analysis revealed that the onset of oroalimentary automatisms coincided with the involvement of the left mesial and lateral temporal structures by spreading ictal discharges. The ictal discharge spreading was limited to the ipsilateral hemisphere throughout the seizure, which explained the intact consciousness and preserved responsiveness of the patient. CONCLUSIONS: This case suggests that APRs take place in seizures originating from the nondominant temporal lobe, during which ipsilateral mesial and lateral temporal structures are diffusely involved without spreading to the contralateral side.     

颞叶癫痫放电在颅内外传播模式的研究

目的探索颞叶癫痫放电在颅内外的传播方式。方法对无法通过无创手段定侧、定位而高度怀疑为难治性颞叶癫痫的病人行双颞钻孔颅内电极植入术,同步记录10-20头皮脑电和双侧蝶骨电极。对最终确诊的颞叶癫痫病人,分析其同步记录脑电图,测量颅内癫痫起源传播到颅内外各个电极点的时间间隔。研究发作期放电的颅内外传播方式。结果颞下、海马、颞极和颞叶外侧各部位起源的癫痫在颅内外传播有各自的方式：①颞下→对侧海马或颞下→同侧蝶骨→对侧蝶骨→同侧前或中颞头皮→对侧前或中颞头皮;②海马→同侧蝶骨→对侧海马或颞下→对侧蝶骨→同侧前或中颞头皮→对侧前或中颞头皮;③颞极→对侧海马或颞下→同侧蝶骨→同侧前或中颞头皮→对侧蝶骨→对侧前或中颞头皮;④颞叶外侧→同侧中颞头皮→同侧蝶骨→对侧前颞或颞下→对侧蝶骨→对侧前或中颞头皮。结论了解各部位颞叶癫痫放电的颅内外传播顺序有助于癫痫灶的定侧、定位。     

Interictal EEG and ictal scalp EEG propagation are highly predictive of surgical outcome in mesial temporal lobe epilepsy

PURPOSE: Surgical outcome in patients with mesial temporal lobe sclerosis (MTS) is worse than that in patients with temporal lobe activity (TLE) with tumors. Previous studies of the ictal EEG focused on ictal EEG onset in scalp EEG or ictal EEG propagation in invasive recordings. Ictal EEG propagation with scalp electrodes has not been reported. METHODS: Ictal scalp EEG propagation patterns were studied in 347 seizures of 58 patients with MTS or nonlesional TLE. Interictal epileptiform discharges (IEDs) and the presence of unilateral mesial temporal lobe atrophy in magnetic resonance imaging (MRI) also were studied in these 58 patients. Forty-nine patients were operated on (minimal follow-up of 1 year). RESULTS: Postoperatively, seizure-free outcome was seen in (a) 82.8% of patients with regionalized EEG seizure without contralateral propagation, but in only 45.5% of patients with contralateral propagation (p = 0.007); (b) 84.6% of patients with 100% IED lateralized to one temporal lobe, but in only 52.2% with <100% unitemporal IED (p = 0.015); (c) 88.9% with 100% unitemporal IED and regionalized ictal EEG combined, 73.7% with one of both variables, and only 33.3% with <100% ipsitemporal IED combined with contralateral ictal EEG propagation (p = 0.007). CONCLUSIONS: Switch of lateralization or bitemporal asynchrony in the ictal scalp EEG and bitemporal IED are most probably an index of bitemporal epileptogenicity in MTS and are associated with a worse outcome.     

Propagation of human complex-partial seizures: a correlation analysis.

Inter- and intrahemispheric propagation of ictal discharges was analysed in 7 epileptic patients having chronic intracranial electrodes. Five had temporal foci and two had frontal mesial foci. Correlation analysis of seizure discharge was used to detect the emergence of linear relationships between different structures both intra- and interhemispherically. This analysis included mesial and lateral temporal sites, cingulate gyri, anterior ventral and dorsomedial thalamic nuclei during the discharges of 13 ictal episodes. Correlation between temporal mesial structures was found to be low throughout seizure onset. Propagation of paroxysmal activity through the anterior ventral thalamic nuclei and cingulate gyri was observed in all cases with temporal or frontal mesial focus. Propagation of the discharge from the temporal lateral cortex to the contralateral homologue area was observed with a short delay during 4 complex-partial seizures originating in the temporal lobe. These results show that, even though the commissural pathways may have a role in propagation, it is a relatively unimportant one and they suggest that ictal activity during mesial temporal seizures may spread preferentially through the thalamic nuclei and cortical structures.     

Bilateral mesial temporal lobe epilepsy: comparison of scalp EEG and hippocampal MRI-T2 relaxometry

OBJECTIVE: Bilateral hippocampal abnormality is frequent in mesial temporal lobe sclerosis and might affect outcome in epilepsy surgery. The objective of this study was to compare the lateralization of interictal and ictal scalp EEG with MRI T2 relaxometry. MATERIAL AND METHODS: Forty-nine consecutive patients with intractable mesial temporal lobe epilepsy (MTLE) were studied with scalp EEG/video monitoring and MRI T2 relaxometry. RESULTS: Bilateral prolongation of hippocampal T2 time was significantly associated with following bitemporal scalp EEG changes: (i) in ictal EEG left and right temporal EEG seizure onsets in different seizures, or, after regionalized EEG onset, evolution of an independent ictal EEG over the contralateral temporal lobe (left and right temporal asynchronous frequencies or lateralization switch; P = 0.002); (ii) in interictal EEG both left and right temporal interictal slowing (P = 0.007). Bitemporal T2 changes were not, however, associated with bitemporal interictal epileptiform discharges (IED). Lateralization of bilateral asymmetric or unilateral abnormal T2 findings were associated with initial regionalization of the ictal EEG in all but one patient (P < 0.005), with lateralization of IED in all patients (P < 0.005), and with scalp EEG slowing in 28 (82,4%) of 34 patients (P = 0.007). CONCLUSION: Our data suggest that EEG seizure propagation is more closely related to hippocampal T2 abnormalities than IED. Interictal and ictal scalp EEG, including the recognition of ictal propagation patterns, and MRI T2 relaxometry can help to identify patients with bitemporal damage in MTLE. Further studies are needed to estimate the impact of bilateral EEG and MRI abnormal findings on the surgical outcome.     

Inter-hemispheric propagation of human mesial temporal lobe seizures: a coherence/phase analysis

Intra- and inter-hemispheric propagation of ictal discharges was analyzed with computer techniques in 10 patients with complex partial seizures of mesial temporal lobe origin in whom depth electrodes had been stereotaxically implanted. Coherence and phase analysis of seizure discharges was used to detect the emergence of linear relationships between all possible pairs of surface and depth recording derivations both between and within hemispheres. This analysis included mesial temporal, lateral temporal, and frontal lobe sites during both the onset and inter-hemispheric propagation of 28 ictal episodes. Although strong intra-hemispheric coherences and linear phase spectra reliably emerged in both the epileptogenic and non-epileptogenic hemispheres during seizure onset and contralateral spread, these relationships were usually not observed for inter-hemispheric comparisons. Only 3 of 10 patients demonstrated some degree of consistency in the emergence of significant wideband coherences and linear phase spectra between left and right mesial temporal sites during the inter-hemispherics propagation of ictal discharges. Mesial temporal lobe sites which demonstrated such a relationship included the amygdala, pes hippocampi, and parahippocampal gyrus. In 7 of 10 patients, lateral temporal derivations were sampled during ictal events; the emergence of linear relationships between left and right lateral temporal derivations during inter-hemispheric propagation was observed for only two. Various frontal lobe sites were monitored in 3 of the 10 patients; the emergence of linear relationships was observed only between left and right orbitofrontal derivations in the one patient for whom this region was sampled. These results suggest that the hippocampal commissure, parts of the corpus callosum, and parts of the anterior commissure may be relatively unimportant for the inter-hemispheric propagation of mesial temporal seizures in man. Future studies in non-human primates may reveal that ictal discharges which originate in the mesial temporal region propagate preferentially via brain-stem pathways to contralateral homologous regions.     

Intracranial EEG Substrates of Scalp Ictal Patterns from Temporal Lobe Foci

Summary: Purpose: To determine the intracranial EEG features responsible for producing the various ictal scalp rhythms, which we previously identified in a new EEG classification for temporal lobe seizures. Methods: In 24 patients, we analyzed simultaneous intracranial and surface ictal EEG recordings (64 total channels) obtained from a combination of intracerebral depth, subd-ural strip, and scalp electrodes. Results: Four of four patients with Type 1 scalp seizure patterns had mesial temporal seizure onsets. However, discharges confined to the hippocampus produced no scalp EEG rhythms. The regular 5- to 9-Hz subtemporal and temporal EEG pattern of Type 1a seizures required the synchronous recruitment of adjacent inferolateral temporal neocortex. Seizure discharges confined to the mesiobasal temporal cortex produced a vertex dominant rhythm (Type 1c) due to the net vertical orientation of dipolar sources located there. Ten of 13 patients with Type 2 seizures had inferolateral or lateral, temporal neocortical seizure onsets. Initial cerebral ictal activity was typically a focal or regional, low voltage, fast rhythm (20–40 Hz) that was often associated with widespread background flattening. Only an attenuation of normal rhythms was reflected in scalp electrodes. Irregular 2- to 4-Hz cortical ictal rhythms that commonly followed resulted in a comparably slow and irregular scalp EEG pattern (Type 2a). Type 2C seizures showed regional, periodic, 1– to 4-Hz sharp waves following intracranial seizure onset. Seven patients had Type 3 scalp seizures, which were characterized by diffuse slowing or attenuation of background scalp EEG activity. This resulted when seizure activity was confined to the hippocampus, when there was rapid seizure propagation to the contralateral temporal lobe, or when cortical ictal activity failed to achieve widespread synchrony. Conclusions: Type 1, 2, and 3 scalp EEG patterns of temporal lobe seizures are not a reflection of cortical activity at seizure onset. Differences in the subsequent development, propagation, and synchrony of cortical ictal discharges produce the characteristic scalp EEG rhythms.     

False lateralization by surface EEG of seizure onset in patients with temporal lobe epilepsy and gross focal cerebral lesions

Medically intractable temporal lobe seizures developed in 3 patients with radiological and clinical evidence of a gross focal cerebral lesion acquired early in life. All had bilateral independent epileptogenic discharges from the lateral and inferomesial regions of both hemispheres. Scalp and sphenoidal electroencephalographic (EEG) recordings suggested that the seizures originated from the side contralateral to the known cerebral lesion. Because the lateralizing evidence presented by the ictal EEG conflicted with the clinical data, depth electrodes were implanted stereotaxically to determine the side of onset of the seizures. These studies showed that the seizures originated from the limbic structures of the damaged hemisphere in all 3 patients. At operation the mesial temporal lobe structures showed gliotic changes in all. The patients have remained seizure-free for 3 to 13 years postoperatively. These findings suggest that depth electrode recordings may be required to clarify the lateralization of seizure onset in such cases. Extracranial EEG findings must be interpreted with caution in epileptic patients who have gross focal lesions.     

Temporal Lobe Epilepsy Subtypes: Differential Patterns of Cerebral Perfusion on Ictal SPECT

Summary: Purpose : We studied cerebral perfusion patterns in the various subtypes of TLE, as determined by pathology and good outcome after temporal lobectomy (as confirmation of temporal origin).
Methods : We studied clinical features and ictal technetium ^99m hexamethyl-propyleneamineoxime (99mTc-HM-PAO) single-photon emission-computed tomography (SPECT) in four subgroups of patients with intractable temporal lobe epilepsy (TLE) treated with surgery: hippocampal sclerosis (group 1, n = 10), foreign-tissue lesion in mesial temporal lobe (group 2, n = 8), foreign-tissue lesion in lateral temporal lobe (group 3, n = 7), and normal temporal lobe tissue with good surgical outcome (group 4, n = 5).
Results : No major clinical differences in auras, complex partial seizures or postictal states were identified among the groups. Ictal SPECT showed distinct patterns of cerebral perfusion in these subtypes of TLE. In groups 1 and 2, hyperperfusion was seen in the ipsilateral mesial and lateral temporal regions. In group 3, hyperperfusion was seen bilaterally in the temporal lobes with predominant changes in the region of the lesion. Hyperperfusion was restricted to the ipsilateral anteromesial temporal region in group 4. Ipsilateral temporal hyperperfusion in mesial onset seizures can be explained by known anatomic projections between mesial structures and ipsilateral temporal neocortex. Bilateral temporal hyperperfusion in lateral onset seizures can be explained by the presence of anterior commissural connections between lateral temporal neocortex and the contralateral amygdala.
Conclusions : We conclude that the perfusion patterns seen on ictal SPECT are helpful for subclassification of temporal lobe seizures, whereas clinical features are relatively unhelpful. These perfusion patterns provide an insight into preferential pathways of seizure propagation in the subtypes of TLE.     

Mesial temporal versus neocortical temporal lobe seizures: Demonstration of different electroencephalographic spreading patterns by combined use of subdural and intracerebral electrodes

We investigated differences between spatiotemporal intracranial EEG characteristics of temporal lobe seizures with mesiolimbic versus neocortical onset, using both subdural and intracerebral electrodes. In 37 patients we analyzed 128 seizures, assessing time intervals from initial onset of a seizure in either mesial or neocortical temporal (NT) lobe structures to sequential ictal involvement of the contralateral mesiolimbic structures and the ipsi- and contralateral temporal and frontal neocortical areas. We noted significantly more rapid seizure spread from mesiolimbic temporal (MT) structures ipsilateral to contralateral in patients with NT versus MT seizure onset. Time values for total seizure duration and time of spread from ipsilateral limbic to contralateral limbic reliably discriminate between individual seizures of either type. Three different spreading patterns were noted in the MT group and two more were noted in the NT group. Theoretical considerations concerning routes of spread are presented. In neither the MT nor the NT group could a correlation be established between pattern of seizure spread and outcome of surgery.     

An angiographically occult arteriovenous malformation in the medial parietal lobe presenting as seizures of medial temporal lobe origin

We present an unusual case of a patient who was diagnosed with temporal lobe epilepsy and whose seizures were reduced markedly after excision of an angiographically occult arteriovenous malformation (AVM) located in the left medial parietal lobe. A 38-year-old man had complex partial seizures characterized by motionless staring with oroalimentary and behavioral automatisms since the age of 15 years. Magnetic resonance imaging (MRI) demonstrated a small lesion extending from the left posterior cingulate gyrus to the precuneus. There was no MRI evidence of mesial temporal sclerosis. Intracranial EEG recordings showed ictal onset from the left medial parietal lobe propagating to the medial temporal lobes. Clinical signs appeared when these discharges reached the temporal lobes. After excision of the lesion (which was histologically confirmed as an AVM), together with the marginal cortex, seizures were reduced significantly. Careful diagnostic evaluation of lesions such as the this one may reveal an epileptogenic lesion (zone) far from the region where scalp ictal discharges seem to arise. In our case, we hypothesize that false localization was due to propagation of ictal discharges from the parietal focus through the limbic system.     

Electroclinical analysis of postictal noserubbing

BACKGROUND: Postictal noserubbing (PIN) has been identified as a good, albeit imperfect, lateralizing and localizing sign in human partial epilepsy, possibly related to ictal autonomic activation. METHODS: PIN was studied prospectively in a group of consecutive patients admitted for video-EEG monitoring, with the laterality of noserubbing correlated with electrographic sites of seizure onset, intra- and interhemispheric spread, and sites of seizure termination. RESULTS: PIN was significantly more frequent in temporal than extratemporal epilepsy (p<0.001; 23/41 (56%) patients and 41/197 (21%) seizures in temporal lobe epilepsy compared with 4/34 (12%) patients and 12/167 (7%) seizures in extratemporal epilepsy). The hand used to rub the nose was ipsilateral to the side of seizure onset in 83% of both temporal and extratemporal seizures. Seizures with contralateral PIN correlated with spread to the contralateral temporal lobe on scalp EEG (p<0.04). All extratemporal seizures with PIN showed spread to temporal lobe structures. One patient investigated with intracranial electrodes showed PIN only when ictal activity spread to involve the amygdala: seizures confined to the hippocampus were not associated with PIN. PIN was not observed in 63 nonepileptic events in 17 patients. Unexpectedly, one patient with primary generalized epilepsy showed typical PIN after 1/3 recorded absence seizures. CONCLUSIONS: This study confirms PIN as a good indicator of ipsilateral temporal lobe seizure onset. Instances of false lateralization and localization appear to reflect seizure spread to contralateral or ipsilateral temporal lobe structures, respectively. Involvement of the amygdala appears to be of prime importance for induction of PIN.     

EEG of partial seizures.

EEG remains the primary technique in the diagnosis, characterization, and localization of partial seizures. This review examines the significance and character of interictal epileptiform abnormalities, periodic lateralized epileptiform discharges, and ictal patterns in patients with partial epilepsy. Interictal epileptiform discharges are common and assist in the diagnosis and localization of partial seizures. Fortunately, true "false positive" EEGs with focal epileptiform abnormalities are distinctly rare. Periodic lateralized discharges have characteristics of both interictal and ictal activity and are an area of controversy as to their clinical significance. Ictal patterns in partial seizures are variable, with the most distinctive features seen in seizures from a mesial temporal lobe origin. The unifying EEG feature of a partial seizure is in its evolution. A partial seizure begins with a clear delineation of the onset of activity that is distinct from the preceding background, followed by an evolution of this activity in both frequency and amplitude and terminating with an identifiable cessation of the rhythmic pattern that merges again into the background activity.     

Continuous Source Imaging of Scalp Ictal Rhythms in Temporal Lobe Epilepsy

Summary: 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.     

The localizing value of ictal EEG in focal epilepsy.

OBJECTIVE: To investigate the lateralization and localization of ictal EEG in focal epilepsy. METHODS: A total of 486 ictal EEG of 72 patients with focal epilepsy arising from the mesial temporal, neocortical temporal, mesial frontal, dorsolateral frontal, parietal, and occipital regions were analyzed. RESULTS: Surface ictal EEG was adequately localized in 72% of cases, more often in temporal than extratemporal epilepsy. Localized ictal onsets were seen in 57% of seizures and were most common in mesial temporal lobe epilepsy (MTLE), lateral frontal lobe epilepsy (LFLE), and parietal lobe epilepsy, whereas lateralized onsets predominated in neocortical temporal lobe epilepsy and generalized onsets in mesial frontal lobe epilepsy (MFLE) and occipital lobe epilepsy. Approximately two-thirds of seizures were localized, 22% generalized, 4% lateralized, and 6% mislocalized/lateralized. False localization/lateralization occurred in 28% of occipital and 16% of parietal seizures. Rhythmic temporal theta at ictal onset was seen exclusively in temporal lobe seizures, whereas localized repetitive epileptiform activity was highly predictive of LFLE. Seizures arising from the lateral convexity and mesial regions were differentiated by a high incidence of repetitive epileptiform activity at ictal onset in the former and rhythmic theta activity in the latter. CONCLUSIONS: With the exception of mesial frontal lobe epilepsy, ictal recordings are very useful in the localization/lateralization of focal seizures. Some patterns are highly accurate in localizing the epileptogenic lobe. One limitation of ictal EEG is the potential for false localization/lateralization in occipital and parietal lobe epilepsies.     

Clinical and EEG Features of Complex Partial Seizures of Temporal Lobe Origin

Summary: The electrographic and clinical behavioural manifestations of 96 temporal lobe seizures are reviewed from recordings in 19 patients who were submitted to stereotaxic depth electrode implantation in temporal and frontal lobes. Focal onset in hippocampus was recorded in 40% of the seizures. Sixty percent of temporal lobe seizures exhibited a regional seizure onset but in two-thirds of these ictal changes were restricted to amygdaloid and hippocampal structures. Thus, in approximately 80% of seizures, the onset of ictal EEG changes resided in the mesial temporal structures. The main behavioral manifestations observed during seizure discharge restricted to one temporal lobe included warning (67%), motionless stare (24%), automatism (22%), and head-body turning (24%). The predominant ictal behavioural manifestations observed during seizure spread to contralateral temporal and extratemporal structures included warning (3%), motionless stare (36%), automatism (77%), and head-body turning (81%). The direction of head turning did not provide reliable lateralization as to the side of seizure onset.     

Ictal Single Photon Emission Computed Tomography in Occipital Lobe Seizures

Summary: 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.     

Speech preservation during language-dominant, left temporal lobe seizures: report of a rare, potentially misleading finding

PURPOSE: To evaluate the prevalence and mechanism of ictal speech in patients with language-dominant, left temporal lobe seizures. METHODS: We retrospectively reviewed the video-EEG telemetry records for the presence of ictal speech in 96 patients with surgically proven left temporal lobe epilepsy and studied the seizure-propagation patterns in three patients who required intracranial EEG recordings for seizure localization. RESULTS: Ictal speech preservation was observed in five patients. One patient's seizures demonstrated rapid propagation of the ictal discharges to the contralateral temporal area where the seizure evolved, resembling a nondominant temporal lobe seizure. The other two patients had ictal discharges that remained confined to the inferomesial temporal areas, sparing language cortex. CONCLUSIONS: Preservation of speech in complex partial seizures of language-dominant, left temporal lobe origin is rare. Based on intracranial EEG recordings, the likely mechanism underlying this potentially misleading clinical finding is the preservation of language areas due to limited seizure-propagation patterns.     

Mesial temporal versus lateral temporal interictal epileptiform activity: comparison of chronic and acute intracranial recordings

Intracranial interictal epileptiform activity (EA) was recorded by chronic stereotactic depth electroencephalography (SDEEG) and acute electrocorticography (ECOG) in 22 patients with complex partial seizures of temporal lobe origin. Chronic SDEEG recordings defined two groups of patients with respect to the presence of absence of lateral temporal EA; 13 patients showed independent lateral temporal EA during chronic recordings and 9 patients did not. All patients had EA recorded from mesial temporal structures during SDEEG. The presence of lateral temporal EA was correlated with a higher pre-operative seizures frequency but not with ictal onset zones, structural pathology, age at onset of epilepsy, or duration of epilepsy. Results of acute ECOG recordings performed on the same patients 1–24 months after SDEEG accurately reproduced the mesial versus lateral distribution of EA within patients (P < 0.0003). Though ECOG was less sensitive than SDEEG in demonstrating EA confined to mesial structures, positive findings at ECOG were 100% specific with respect to SDEEG. These results suggest that, at least with respect to mesial temporal versus lateral temporal structures, there is a constancy within patients in the distribution of interictal EA recorded with chronic intracranial electrodes. In addition, acute ECOG provides an accurate representation of individual patients' interictal EA.