Epilepsy surgery continues to expand in clinical use as an effective treatment for correctly selected patients with medically intractable and disabling focal epilepsy. In a broad overview, the authors discuss the history of epilepsy surgery, its scientific basis, indications, presurgical evaluation, and surgical approaches for both mesial temporal lobe epilepsy and neocortical focal epilepsies. Though resective epilepsy surgery has become an important conventional treatment option, it continues to be underutilized. This review details expected postoperative seizure control and quality-of-life outcomes, showing quantitatively how epilepsy surgery benefits patients. Updates include new data on postoperative outcomes for resective epilepsy surgery, emphasizing results from the ongoing prospective Multicenter Study of Epilepsy Surgery. New information about seizure control after operative treatment of epileptogenic cavernous malformations is also discussed. Other updates concern the novel presurgical diagnostic modality of simultaneous electroencephalography and functional magnetic resonance imaging, currently developing in its clinical utility.
Historical note and terminology
Early epilepsy surgery. Epilepsy surgery for focal seizures began more than a century ago and progressed with the technical innovations of EEG and neuroimaging. In the 1860s and 1870s, the pioneering clinical work of the epileptologist John Hughlings Jackson laid the groundwork for understanding the cortical localization of focal epilepsies, while the animal experiments of the neurophysiologists Gustav Theodor Fritsch, Eduard Hitzig, and David Ferrier gave parallel confirmation of Hughlings Jackson's conclusions (Rosenow and Luders 2001). The “beginning of modern epileptology” has been dated to the 1870 publication of Hughlings Jackson's article "A study of convulsions," in which he stated that focal motor seizures originate in the contralateral cerebral cortex or underlying striatum and not in the medulla, the previously accepted site of origin (Eadie 2007). The experimental work of the surgeon and physiologist Victor Horsley in turn was predicated on and also contributed to Hughlings Jackson's explication of certain seizure propagation mechanisms (Eadie 2005).
In the 1870s and 1880s, the first documented resections for epilepsy were performed, making use of newly formulated cortical localization principles (Rosenow and Luders 2001). In 1879 the surgeon William Macewen correctly localized and resected a frontal mass in an epileptic patient in Glasgow; the patient survived removal of the meningioma and his seizure disorder was cured (Macewen 1879; Rosenow and Luders 2001). In 1884 the neurologists Jackson and Alexander Hughes Bennett localized a putative mass in another epileptic patient; the surgeon Rickman Godlee successfully resected the underlying tumor found at their hypothesized site (Bennett and Godlee 1884; Rosenow and Luders 2001).
In 1886 Victor Horsley publicly presented his guidelines for antiseptic and hemostatic brain surgery in humans at the British Medical Association annual meeting, focusing on 3 cases of young men subject to “fits” (Taylor 1986). His lecture consisted of a detailed description of 3 epilepsy surgery cases. Jackson, on whose patient Horsley had operated, was in the audience and advised the conference attendees that surgery should be performed for seizures even in the absence of a mass lesion. Hughlings Jackson's comments were paraphrased in the 1886 publication of Horsley's lecture: “Believing that the starting point of the fit was a sign to us of the seat of the ‘discharging lesion,' he [Hughlings Jackson] would advise cutting out that lesion, whether it was produced by tumour or not” (Horsley 1886). Hughlings Jackson was in fact recommending the resection of what was later to be called “the epileptogenic zone,” regardless of the presence of structural abnormality.
Electrical stimulation brain mapping. Electrical stimulation to reproduce seizure semiology and to map functional cortex has been crucial to the development of epilepsy surgery. In 1870 Fritsch and Hitzig were the first physiologists to stimulate the cerebral cortex of animals. In 1874 Bartholow extrapolated this technique to the human brain when he treated a 30-year old woman whose brain abscess had eroded through her skull (Bartholow 1874; Bernier 1987). Horsley used electrical stimulation mapping of the motor cortex first in nonhuman primates and then in human patients to guide his neurosurgical operations. In the 1920s Wilder Penfield learned this technique from Otfrid Foerster in operations on patients with posttraumatic epilepsy due to World War I gunshot wounds to the head (Foerster and Penfield 1930; Crandall 1987). After Penfield founded the Montreal Neurological Institute in 1934 for the study of the science and surgery of epilepsy, he and his colleagues extended the use of electrical stimulation in the human to map cognitive functions such as language and memory (Penfield and Erickson 1941; Penfield and Jasper 1954).
Advances in localization. In the era before modern imaging, the innovation of preoperative and intraoperative EEG allowed the epilepsy surgeon both to localize an underlying intracranial lesion and to target a nonlesional epileptogenic zone with greater accuracy than clinical semiology had permitted. Human EEG was first reported in 1929 by Hans Berger, following Richard Caton's extensive electrophysiologic recordings from animals (Rosenow and Luders 2001). The neurologist Herbert Jasper introduced the use of EEG at the Montreal Neurological Institute in 1937 and established an EEG laboratory there in 1939, where techniques of intraoperative electrocorticography were developed (Feindel 1993). During the 1930s through the 1950s, Penfield and Jasper studied different techniques to optimize operations for epilepsy and systematically demonstrated that resection of epileptogenic tissue benefited patients (Penfield and Jasper 1954; Wieser and Yasargil 1982).
In the 1950s and 1960s, Bancaud and Talaraich improved localization of the epileptogenic zone by recording from stereotactically implanted depth electrodes, and Crandall and Walker further advanced this work (Bancaud and Talairach 1973; Bernier 1987). In the 1980s, Spencer, Spencer, and colleagues described the stereotactic placement of multicontact depth electrodes, which are currently used both for the presurgical identification of ictal onset regions and for basic neuroscience investigation with microelectrodes and microdialysis probes (Spencer et al 1987; During and Spencer 1993; Fried et al 1999; Kral et al 2002; Wilson 2004; Engel et al 2005). With the advent of modern neuroimaging, in particular with routine clinical use of MRI beginning in the 1980s, radiographic visualization of previously occult structural lesions has improved patient selection and presurgical planning for epilepsy surgery. The development of clinically useful nuclear imaging studies such as interictal 18F-FDG-PET and ictal SPECT contributed further to localization (Engel et al 1982a; Engel et al 1982b). At present, techniques such as MEG and fMRI are being optimized for clinical application to operative planning for epilepsy surgery to continue to improve localization (Rosenow and Luders 2001; Eliashiv et al 2002; Akanuma et al 2003; Sabsevitz et al 2003).
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