Phase–Amplitude Coupling and Epileptogenic Zone Localization of Frontal Epilepsy Based on Intracranial EEG

Objective: This study aimed to explore the characteristics of phase-amplitude coupling in patients with frontal epilepsy based on their electrocorticography data, in order to identify the localization of epileptic regions and further guide clinical resection surgery.Methods: We adopted the modulation index based on the Kullback-Leibler distance, phase-amplitude coupling co-modulogram, and time-varying phase-amplitude modulogram to explore the temporal-spatial patterns and characterization of PAC strength during the period from inter- seizure to post-seizure. Taking the resected area as the gold standard, the epileptogenic zone was located based on MI values of 7 different seizure periods, and the accuracy of localization was measured by the area under the receiver operating curve.Results: (1) The PAC in the inter- and pre-seizure periods was weak and paroxysmal, but strong PAC channels were confined more to the seizure-onset zone and resection region. PAC during the seizure period was intense and persistent, but gradually deviated from the seizure-onset zone. (2) The characteristics of coupling strength of the inter- and pre-seizure EEG can be used to accurately locate the epileptogenic zone, which is better than that in periods after the beginning of a seizure. (3) In an epileptic seizure, the preferred phases of coupling were usually in the rising branches at the pre- and early-seizure stages, while those in the middle- and terminal-seizure were usually in the falling branch. We thus speculate that the coupling occurred in the rising branch can promote the recruitment of abnormal discharge, while the coupling occurred in the falling branch can inhibit the abnormal discharge.Conclusion: The findings suggest that the phase-amplitude coupling during inter- and pre-seizure is a promising marker of epileptic focus location. The preferred phase of coupling changed regularly with the time of epileptic seizure, suggesting that the surge and suppression of abnormal discharges are related to different phases.

Status epilepticus of focal impaired-awareness seizures. Russkiy zhurnal detskoy nevrologii

Background. The status epilepticus of focal impaired-awareness seizures (SE FIAS) is a series of focal seizures with loss or change of consciousness, between which there is no complete recovery of consciousness. This status epilepticus occurs in patients with temporal (especially with hippocampal sclerosis) and frontal epilepsy. It is important to differentiate SE FIAS with the absence status epilepticus, with psychiatric disorder, with postictal confusion. As a rule, this status epilepticus is self-terminate, without special treatment.Objective: to study the features of epidemiology, etiology, diagnosis, therapy and prognosis in patients with SE FIAS.Materials and methods. The study included 1350 consecutive patients diagnosed with epilepsy.Results and discussion. A history of SE FIAS was found in 20 patients (14 women and 6 men), it occurred in the age range from 5 to 66 years. 13 patients (65 %) had mesial temporal lobe epilepsy, 5 patients (25 %) had frontal lobe epilepsy, and 2 patients (10 %) had lateral temporal lobe epilepsy. Only in 80 % of patients treatment was adequate before the development of SE FIAS, in 20 % of patients it was inadequate and subsequently caused the development of status epilepticus. In 40 % of patients the occurrence of SE FIAS is associated with their own non-compliance; in 30 % of patients the development of status epilepticus had iatrogenic causes. Measures to prevent the development of status epilepticus were ineffective only in patients with pharmacoresistant symptomatic epilepsy and in non-compliant patients.Conclusions. SE FIAS occurs in 1 % of patients with epilepsy. Among patients, women with temporal or frontal epilepsy dominate; status epilepticus occurs at any age and is often triggered by changes in therapy due to doctors’ recommendations or patient non-compliance. Usually the status is self-terminating. To prevent its recurrence, adequate antiepileptic therapy is necessary. The prognosis in patients with SE FIAS is favorable; however, the general prognosis remains serious due to the severity of the course of epilepsy.

Functional Dissociation between Cognitive Estimation and Object Naming in Focal Temporal and Frontal Lobe Epilepsies

Purpose This study addresses specific impairments of cognitive estimation and object naming in patients with focal temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE). It was investigated whether selective impairments can be explained by differences in lesion localization and functional hemispheric specialization. Materials and Methods Seventy-eight patients (39 females, 39 males) with FLE and TLE were investigated using the German “Test zum Kognitiven Schätzen” and the “Boston Naming Test” to assess cognitive estimation abilities and visual object naming. Questions According to theoretical models that support a distinct hemispheric dominance for estimation and naming, it was expected that epilepsy localization in the right hemisphere would result in impairments of cognitive estimation, whereas patients with left epileptogenic foci would show deficits in object naming. Results In comparison to a healthy control group, a significant impairment in estimation performance was present in patients with right temporal mesial and right frontal epilepsy. A significant impairment of naming performance was found in patients with left temporal mesial, right temporal mesial, left temporal neocortical, and left frontal epilepsy. Overall, localization-dependent deficits were detected in patients with hippocampal sclerosis (cognitive estimation and object naming), right frontal epilepsy (cognitive estimation), and left temporal neocortical/left frontal epilepsy (object naming). In patients with right temporal neocortical epilepsy, no functional deficits were found. Conclusion It is hypothesized that there is a functional dissociation between cognitive estimation processes and object naming due to different functional specialization of the left and right hemispheres, respectively.

Focal epilepsy

This chapter examines the neurophysiology of focal epilepsy. It discusses the principles of EEG source localization. This is followed by a presentation of nonspecific and epileptiform interictal EEG findings and ictal EEG patterns seen in focal epilepsy, along with normal EEG variants that may be mistaken for epileptiform features. Seizure semiologies and ictal and interictal EEG findings in mesial and neocortical temporal lobe epilepsy, orbitofrontal, dorsolateral, and mesial frontal epilepsy, insular epilepsy, and parietal and occipital epilepsy are presented with illustrative case discussions derived from patients investigated for resective epilepsy surgery. A brief discussion of prognosis and treatment strategies for focal epilepsy follows.

Presurgical evaluation for epilepsy surgery

This chapter describes the preoperative electroclinical assessment of the various epilepsy syndromes and pathologies that are open to surgical treatment. Particular emphasis is placed on medial temporal epilepsy and frontal epilepsy. The assessment of cases considered for hemispherotomy, multiple subpial transection for Landau–Kleffner syndrome, anterior two-thirds callosotomy in symptomatic generalized epilepsy, neural stimulation, and cases with nodular hetertopia are summarized. Throughout the chapter, particular emphasis is placed on the need for multidisciplinary assessment, and the interpretation of the electroencephalogram (EEG) in the context of the clinical features, imaging, and neuropsychology. Evaluation pathways are suggested and the indications for intracranial EEG, the types of electrodes used and the operative complications are discussed in detail. Summaries of the key points in the electroclinical evaluation of temporal and frontal lobe epilepsy are given.

Tailored Unilobar and Multilobar Resections for Orbitofrontal-Plus Epilepsy

BACKGROUND: Surgery for frontal lobe epilepsy often has poor results, likely because of incomplete resection of the epileptogenic zone. OBJECTIVE: To present our experience with a series of patients manifesting 2 different anatomo-electro-clinical patterns of refractory orbitofrontal epilepsy, necessitating different surgical approaches for resection in each group. METHODS: Eleven patients with refractory epilepsy involving the orbitofrontal region were consecutively identified over 3 years in whom stereoelectroencephalography identified the epileptogenic zone. All patients underwent preoperative evaluation, stereoelectroencephalography, and postoperative magnetic resonance imaging. Demographic features, seizure semiology, imaging characteristics, location of the epileptogenic zone, surgical resection site, and pathological diagnosis were analyzed. Surgical outcome was correlated with type of resection. RESULTS: Five patients exhibited orbitofrontal plus frontal epilepsy with the epileptogenic zone consistently residing in the frontal lobe; after surgery, 4 patients were free of disabling seizures (Engel I) and 1 patient improved (Engel II). The remaining 6 patients had multilobar epilepsy with the epileptogenic zone located in the orbitofrontal cortex associated with the temporal polar region (orbitofrontal plus temporal polar epilepsy). After surgery, all 6 patients were free of disabling seizures (Engel I). Pathology confirmed focal cortical dysplasia in all patients. We report no complications or mortalities in this series. CONCLUSION: Our findings highlight the importance of differentiating between orbitofrontal plus frontal and orbitofrontal plus temporal polar epilepsy in patients afflicted with seizures involving the orbitofrontal cortex. For identified cases of orbitofrontal plus temporal polar epilepsy, a multilobar resection including the temporal pole may lead to improved postoperative outcomes with minimal morbidity or mortality.