The symptoms and signs associated with all stages of a temporal lobe seizure may be helpful in determining both the localization and lateralization of seizure onset. Auras, when present, may be very suggestive of temporal lobe onset and may further localize to a mesiobasal or lateral temporal lobe site of onset. During the ictus, automatisms and motor phenomena may be highly indicative of temporal lobe seizure activity and may even help lateralize the discharge. In the post-ictal period, motor paresis and aphasia are helpful in lateralization. Video E.E.G. data has provided extensive information on the utility of ictal symptomatology in seizure localization. Thus, the seizure semiology provides important adjunctive information in evaluating patients for epilepsy surgery and should be concordant with information obtained from ictal EEG, neuroimaging and neuropsychology.

To fulfill its task of informed clinical decision making and resource allocation, epidemiological studies in epilepsy must adhere to a series of methodological standards. These are reviewed. Because seizure and epilepsy classification systems may be viewed as extensions of the diagnosis, they have direct implications in the acquisition and interpretation of epidemiologic data. The International League Against Epilepsy (ILAE) classification systems are analyzed in this light. Finally, the lack of Canadian epidemiological studies is addressed, and the relevance and potential of Canadian epidemiological data in epilepsy is discussed.

Medical intractability is one of the absolute indications for considering temporal lobe epilepsy surgery. This is a relative concept that has to be highly individualized. It is quite easy to determine when a patient's seizures are fully controlled. On the other hand, “continuing seizures are not necessarily a measure of intractability or disability”. A positive decision to operate would be based on some of the following factors: assurance of a firm diagnosis, seizures that are frequent and disabling, and seizures occurring in patients who are drug refractory to optimal anti-epileptic medications and dosages.

Temporal lobectomy is an under-valued and effective therapy for selected children with temporal lobe seizures. This article details three components of the identification and evaluation of such children. The ictal symptoms and signs remains an essential component. This includes an aura suggesting limbic system involvement, and the nature of automatisms and other motor phenomena which may have lateralising value. Electroencephalography continues to accurately identify a principally epileptogenic focus in children and adults. The value of high quality magnetic resonance imaging is emphasized. Invasive studies are required in only a minority of cases. Several studies have revealed that 73-100% of carefully selected children receive benefit from this procedure whereas significant neurosurgical complications rarely occur.

Electroencephalography (EEG) with standard scalp and additional noninvasive electrodes plays a major role in the selection of patients for temporal lobe epilepsy surgery. Recent studies have provided data supporting the value of interictal and postictal EEG in assessing the site of ictal onset. Scalp ictal rhythms are morphologically complex but at least one pattern (a five cycles/second rhythm maximum at the sphenoidal or anterior temporal electrode) occurs in >50% of patients and has a high predictive value and interobserver reliability for temporal lobe originating seizures. Thorough interictal and ictal scalp EEG evaluation, in conjunction with modern neuroimaging, is sufficient for proceeding to surgery without invasive recordings in some patients. Further studies are required to define the scalp ictal characteristics of mesial vs. lateral temporal lobe epilepsy.

The management of uncontrolled partial epilepsy is a process dependent on a multidisciplinary and analytic approach. It is necessary to understand which lesions are epileptogenic, and if they are indeed responsible for the generation of seizures. In addition to localizing seizure onset, the functional and eloquent areas of the brain need to be identified. As in many other centres, we perform resective surgeries on the basis of combined information derived from seizure semiology, EEG abnormalities, neuroimaging and other tests of cerebral function. If surface EEG recording yields inconclusive or ambiguous results, then invasive intracranial techniques using intracerebral depth or subdural electrodes can be used to improve diagnostic or prognostic accuracy. The indications, principles, results and complications of these recording techniques based on extensive experience at two epilepsy surgery centres are reviewed.

Magnetic resonance imaging (MRI) techniques allow for significantly better imaging of the temporal lobe compared to computed tomography (CT) or other non-invasive modalities. For detection of foreign tissue lesions, MRI surpasses CT. For the highest non-invasive yield for detection of mesial temporal sclerosis, optimal sequences that should be employed are a heavily T1-weighted volumetric acquisition (to enable both volumetric calculation of hippocampal volume, and, if needed, intracranial volume), T2-weighted coronal sequences, with or without T2-mapping, fluid-attenuated inversion recovery (FLAIR) and, to exclude subtle susceptibility effects from hematoma or cavernoma, gradient echo scans. Magnetic resonance spectroscopy (MRS) may show a decrease in N-acetyl aspartate (NAA) concentration, or NAA: Choline + creatine ratio. Functional MRI is a new and exciting tool that offers the promise of accurately localizing hemispheric functions; its role in the preoperative evaluation of temporal lobe seizures remains uncertain at present.

Neuropsychological assessment consists of a comprehensive evaluation of cognitive functioning and most often some evaluation of motor skills and sensory status also. Cognitive functions sampled typically include “intelligence” (IQ tests), attention, language skills, visuospatial abilities, “executive skills” and other abilities associated with frontal-lobe function, and learning and memory. Thus, the assessment samples vary widely among a variety of functions, providing a comprehensive picture of an individual's strengths and weaknesses. The resulting pattern points to the probable site of epileptic focus. Neuropsychological findings also serve to predict the risk for postsurgical cognitive decline and, when performance before and after operation is compared, they provide data on the impact of surgery upon cognitive functioning. Comprehensive evaluation of learning and memory is particularly important in this context, because of the frequency of temporal lobe epilepsy and the prominence of memory dysfunction associated with it. In addition, patients slated for elective surgery may also undergo an intracarotid amobarbital procedure (IAP), which is performed to determine the side of cerebral dominance for language and to test the memory capabilities of each hemisphere alone. All of these specialized neuropsychological tools are discussed in this paper.

Patients with medically intractable epilepsy often present with comorbid psychiatric diseases. When referred to a program for the surgical treatment of the epilepsies, these patients benefit from a pre-admission psychiatric assessment with a view to lessen the chances of a psychiatric crisis during the pre- and postoperative investigations. This article proposes a practical approach to the psychiatric assessment and monitoring of adult candidates to the surgery of epilepsy. It emphasizes, in agreement with a world literature review, that definitive psychiatric contraindications to this elective surgery are few, and that adverse long-term psychiatric outcomes are less frequent when good seizure outcome is achieved.

This paper reviews the importance of adequate communication between the treatment team and the patient and family in epilepsy surgery. Ensuring that patient and family adequately understand the diagnosis, natural history, management alternatives and the risks and outcomes of surgery is a challenge for each epilepsy team. Guidelines as to process and content from the authors'experience and the participants in the workshop are presented.

In 1886, Victor Horsley excised an epileptogenic posttraumatic cortical scar in a 23-year-old man under general anaesthesia and discussed his choice of anaesthesia: “I have not employed ether in operations on man, fearing that it would tend to cause cerebral excitement; chloroform, of course, producing on the contrary, well-marked depression.” His concerns regarding anaesthesia are reiterated 100 years later as evidenced by the ongoing controversy over the choice of anaesthetic in surgical procedures for epilepsy. The current controversies regarding the necessity for local anaesthesia in temporal lobe epilepsy operations concern the utility of electrocorticography in surgical decision making, its relationship to seizure outcome and the value of intraoperative language mapping in dominant temporal lobe resections. The increasing sophistication of pre-operative investigation and localization of both areas of epileptogenesis and normal brain function and the introduction of minimally invasive surgical techniques and smaller focal resections are changing the indications for local anaesthesia in temporal lobe epilepsy. Thus, indications which were previously absolute are now perhaps relative. This article reviews the current indications for craniotomy under local anaesthesia in the surgical treatment of temporal lobe epilepsy.

Anesthetic considerations for temporal lobectomy for refractory epilepsy include ensuring a safe and comfortable perioperative experience for the patient, providing suitable operating conditions for the surgeon, avoiding interference with intraoperative electrocorticographic (ECoG) recordings and facilitating intraoperative functional cortical mapping, if performed. Providing the conditions that simultaneously meet these requirements, using general anesthesia or local anesthesia with sedation, remains a significant challenge for the neuroanesthetist. We review issues pertinent to the choice of anesthetic technique for these procedures.

Numerous studies of the electrophysiology and neuropathology of temporal lobe epilepsy have demonstrated the mesial temporal structures to be the site of seizure origin in the majority of cases. This is the rationale for a transcortical selective approach, first introduced by Niemeyer, for removal of the hippocampus and amygdala. Series from a number of centers have demonstrated the efficacy of selective amygdalohippocampectomy compared to a more traditional resection. The technique described here and used at the Montreal Neurological Institute (MNI) utilizes a strictly endopial resection of the hippocampal formation and amygdala in addition to computer image guidance to perform the procedure. Ninety-five percent of patients at the MNI who underwent selective amygdalohippocampectomy realized a cessation of seizures, or greater than 90% reduction, with minimal risk of complications.

The methodology of this paper is based entirely on the experiential backgrounds of the authors. It outlines those factors which have become recognized as potentially important issues to patients who are considering recommendations of surgical treatment for their intractable epilepsy. Thus, on the one hand, it includes the important generic aspects of Informed Consent, while on the other hand there must be a very comprehensive and, when the operation is to be carried out under local anesthesia, a very detailed explanation of the preparation and the sequential steps in the surgical procedure. This should also entail a brief description of the roles of the various “team” members during the operative procedure. There are well-recognized complications associated with the various surgical procedures for the treatment of epilepsy. Further, there are predictable deficits following some of these procedures, some of which might be permanent and some of which may be transient. These pitfalls are briefly discussed.

In light of the recent resurgence of interest in stereotactic functional procedures, the authors have reviewed the role of stereotactic ablative surgery in the treatment of temporal lobe epilepsy. Literature pertaining to stereotactic amygdalotomy, hippocampotomy and fornicotomy is reviewed and summarized. However, the results presented in those early studies are difficult to interpret given the surgical techniques and outcome assessment used. Modern stereotactic ablative surgery using current image-guided technology offers the opportunity to revisit some of these techniques. In recent studies of stereotactic amygdalohippocampotomy, outcomes are not as favorable as those obtained with standard temporal resections. However, these relatively discrete ablative techniques may shed light on the anatomical substrate underlying temporal lobe epilepsy.

Although in clinical use for many years, the validity of intraoperative electrocorticography (ECoG) in guiding resective temporal lobe epilepsy (TLE) surgery is uncertain. Advances in neuroimaging and extraoperative intracranial recordings have contributed greatly to the identification of epileptogenic lesions and cortex, clarifying the limitations of a brief intraoperative interictal recording. Studies of undifferentiated ECoG findings (which classify all interictal cortical spike discharges as equal) tend to not support this method. This article reviews ECoG and presents data from 86 TLE surgeries at the University of British Columbia suggesting that differentiation of ECoG features may enhance the contribution of this time honored method. Specifically, independent foci may be more important for epileptogenesis than synchronous foci, and postexcision activation appears to be a benign phenomenon, while residual spikes unaltered by the resection correlate with a greater proportion of seizure recurrence.

Seizure control, in addition to quality of life, is an important outcome after epilepsy surgery. However, seizure measurement is not straightforward. We explore some important difficulties in obtaining unbiased, reliable estimates of seizure frequency, and discuss aspects of data analysis as it pertains to validity and clinical meaningfulness. As seizure severity is an integral component of seizure outcome assessment, we discuss aspects of measurement of this outcome. Suggestions for improving validity are offered, based on the literature and on methodological common sense. Finally, we look at the Canadian perspective and the potential for adopting methodology that allows for data pooling and for more powerful analyses.