J Neurosurg 115:1169–1174, 2011. DOI: 10.3171/2011.7.JNS11536

Seizures are the most common presenting symptom of supratentorial cerebral cavernous malformations (CCMs) and progress to medically refractory epilepsy in 40% of patients. Predictors of seizure freedom in the resection of CCMs are incompletely understood.

Methods. The authors systematically reviewed the published literature on seizure freedom following the resection of supratentorial CCMs in patients presenting with seizures. Seizure outcomes were stratified across 12 potential prognostic variables. A total of 1226 patients with supratentorial CCMs causing seizures were identified across 31 predominantly retrospective studies; 361 patients had medically refractory epilepsy.

Results. Seventy-five percent of the patients were seizure free after microsurgical lesion removal, whereas 25% continued to have seizures. All patients had had preoperative seizures and > 6 months of postoperative follow-up. Modifiable predictors of postoperative seizure freedom included gross-total resection (OR 36.6, 95% CI 8.5–157.5) and surgery within 1 year of symptom onset (OR 1.83, 95% CI 1.30–2.58). Additional prognostic indicators of a favorable outcome were a CCM size < 1.5 cm (OR 15.4, 95% CI 5.2–45.4), the absence of multiple CCMs (OR 2.02, 95% CI 1.13–3.60), medically controlled seizures (OR 2.38, 95% CI 1.29–4.39), and the lack of secondarily generalized seizures (OR 3.33, 95% CI 2.09–5.30). Other factors, including extended resection of the hemosiderin ring, were not significantly predictive.

Conclusions. In the surgical treatment of supratentorial CCMs, gross-total resection and early operative intervention may improve seizure outcome. While surgery should not be considered the first-line treatment for CCM-related epilepsy, it is important to understand the variables associated with seizure freedom in CCM resection given the considerable morbidity and diminished quality of life associated with epilepsy.

Neurosurgery 68:431–436, 2011 DOI: 10.1227/NEU.0b013e318201c293

The development of newer diagnostic technologies has reduced the need for invasive electroencephalographic (EEG) studies in identifying the epileptogenic zone, especially in adult patients with mesial temporal lobe epilepsy and hippocampal sclerosis (MTLE-HS).

OBJECTIVE: To evaluate ictal single photon emission computed tomography (SPECT) in the evaluation and treatment of patients with MTLE-HS.

METHODS: MTLE patients were randomly assigned to those with (SPECT, n = 124) and without ictal SPECT (non-SPECT, n = 116) in an intent-to-treat protocol. Primary end points were the proportion of patients with invasive EEG studies, and those offered surgery. Secondary end points were the length of hospital stay and the proportion of patients with secondarily generalized seizures (SGS) during video-EEG, postsurgical seizure outcome, and hospital cost.

RESULTS: The proportion of patients offered surgery was similar in the SPECT (85%) and non-SPECT groups (81%), as well as the proportion that had invasive EEG studies (27% vs 23%). The mean duration of hospital stay was 1 day longer for the SPECT group (P , 0.001). SGS occurred in 51% of the SPECT and 26% of the non-SPECT group (P , 0.001). The cost of the presurgical evaluation was 35% higher for the SPECT compared with the non-SPECT group (P , 0.001). The proportion of patients seizure-free after surgery was similar in the SPECT (59%) compared with non-SPECT group (54%).

CONCLUSION: Ictal-SPECT did not add localizing value beyond what was provided by EEG-video telemetry and structural MRI that altered the surgical decision and outcome for MTLE-HS patients. Ictal-SPECT increased hospital stay was associated with increased costs and a higher chance of SGS during video-EEG monitoring. These findings support the notion that a protocol including ictal SPECT is equivalent to one without SPECT in the presurgical evaluation of adult patients with MTLE-HS.

J Neurosurg Pediatrics 6:000–000, 2010. (DOI: 10.3171/2010.9.PEDS10267)

Surgery for medically intractable epilepsy secondary to unihemispheric pathology has evolved from more aggressive hemispherectomy to less aggressive variations of hemispherotomy. The authors propose a novel minimally invasive endoscopic hemispherotomy that should give results comparable to conventional open craniotomy and microsurgery.

Methods. Endoscopic transventricular hemispherotomy was performed in 5 silicon-injected cadaveric heads in the authors’ minimally invasive neurosurgery laboratory. The lateral ventricle was accessed endoscopically through a frontal and occipital bur hole. White matter disconnections were performed to unroof the temporal horn and to disconnect the frontobasal region, corpus callosum, and fornix.

Results. Using an endoscopic transventricular approach, all white matter disconnections were successfully performed in all 5 cadavers.

Conclusions. The authors have demonstrated the feasibility of endoscopic transventricular hemispherotomy in a cadaveric model. The technique is simple and could be useful in a subgroup of patients with parenchymal volume loss and ventriculomegaly.

J Neurosurg 113:1135–1143, 2010.(DOI: 10.3171/2010.3.JNS091832)

The aim of this study was to evaluate, using diffusion tensor tractography, the white matter fibers crossing the hippocampus and the amygdala, and to perform a volumetric analysis and an anatomical study of the connections of these 2 structures. As a second step, the authors studied the white matter tracts crossing a virtual volume of resection corresponding to a selective amygdalo-hippocampectomy.

Methods. Twenty healthy right-handed individuals underwent 3-T MR imaging. Volumetric regions of interest were manually created to delineate the amygdala, the hippocampus, and the volume of resection. White matter fiber tracts were parcellated using the fiber assignment for continuous tracking tractography algorithm. All fibers were registered with the anatomical volumes.

Results. In all participants, the authors identified fibers following the hippocampus toward the fornix, the splenium of the corpus callosum, and the dorsal hippocampal commissure. With respect to the fibers crossing the amygdala, the authors identified the stria terminalis and the uncinate fasciculus. The virtual resection disrupted part of the fornix, fibers connecting the 2 hippocampi, and fibers joining the orbitofrontal cortex. The approach created a theoretical frontotemporal disconnection and also interrupted fibers joining the temporal pole and the occipital area.

Conclusions. This diffusion tensor tractography study allowed for good visualization of some of the connections of the amygdala and hippocampus. The authors observed that the virtual selective amygdalohippocampectomy disconnected a large number of fibers connecting frontal, temporal, and occipital areas

Neurosurgery 67:918–924, 2010 DOI: 10.1227/NEU.0b013e3181eb5032

Patients with cerebral cavernomas have an estimated risk of the development of epilepsy of 1.5% to 2.4% per patient-year.

OBJECTIVE: To clarify the predictive value of different risk factors for epilepsy in patients with supratentorial cavernomas.

METHODS: We retrospectively analyzed data of 109 patients with supratentorial cavernomas. The correlation of epilepsy with the variables of single or multiple cavernomas, sex, age, side, cortical involvement, mesiotemporal archicortical vs neocortical involvement, lobar location of neocortical cavernomas, the presence of a hemosiderin rim and of edema, and the maximal diameters of cavernoma, hemosiderin rim, and edema, if present, were calculated using univariate and multivariate penalized likelihood logistic regression models.

RESULTS: Cortical involvement was the most relevant risk factor for epilepsy (P , .0001). No patient with a subcortical cavernoma presented with epilepsy. Epilepsy was more common in patients with mesiotemporal archicortical cavernomas than in patients with neocortical cavernomas (P = .02), whereas the lobar location of neocortical cavernomas was not significantly associated with the risk of the development of epilepsy. In the multivariate analysis, a greater diameter of the cavernoma, the absence of edema, and localization in the left hemisphere were also associated with the occurrence of epilepsy (P , .05).

CONCLUSION: The epileptogenicity of supratentorial cavernomas depends on cortical, especially mesiotemporal archicortical, involvement. Exclusively subcortical cavernomas are highly unlikely to cause epilepsy. This information is helpful in counseling patients with cavernomas regarding their risk of epileptic seizures and in patients with multiple cavernomas and epilepsy to generate a valid hypothesis of which cavernoma may cause epilepsy.

The aim of this study was to review the indications for and results of deep brain stimulation (DBS) of the posterior hypothalamus (pHyp) in the treatment of drug-refractory and severe painful syndromes of the face, disruptive and aggressive behavior associated with epilepsy, and below-average intelligence. The preoperative clinical picture, functional imaging studies, and overall clinical results in the literature are discussed.

Methods. All patients underwent stereotactic implantation of deep-brain electrodes within the pHyp. Data from several authors have been collected and reported for each clinical entity, as have clinical results, adverse events, and neurophysiological characteristics of the pHyp.

Results. The percentage of patients with chronic cluster headache who responded to DBS was 50% in the overall reported series. The response rate was 100% for short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing and for chronic paroxysmal hemicrania, although only 2 patients and 1 patient, respectively, have been described as having these conditions. None of the 4 patients suffering from refractory neuropathic trigeminal pain benefited from the procedure (0% response rate), whereas all 5 patients (100%) affected with refractory trigeminal neuralgia (TN) due to multiple sclerosis (MS) and undergoing pHyp DBS experienced a significant decrease in pain attacks within the first branch of cranial nerve V. Six (75%) of 8 patients presenting with aggressive behavior and mental retardation benefited from pHyp stimulation; 6 patients were part of the authors’ series and 2 were reported in the literature.

Conclusions. In carefully selected patients, DBS of the pHyp can be considered an effective procedure for the treatment of refractory trigeminal autonomic cephalalgias, aggressive behavior, and MS-related TN in the first trigeminal branch. Only larger and prospective studies along with multidisciplinary approaches (including, by necessity, neuroimaging studies) can lead us to better patient selection that would reduce the rate of nonresponders.

Minimally invasive percutaneous single trajectory stereotactic radiofrequency amygdalohippocampectomy was used to treat mesial temporal lobe epilepsy (MTLE). The aim of the study was to evaluate complications and effectiveness of this procedure.

Materials and methods A group of 51 patients with MTLE was treated using stereotactic thermo-lesion of amygdalohippocampal complex under local anaesthesia. The target was reached through the occipital approach with a single trajectory using MRI stereotactic localisation. Thermocoagulation of the amygdalohippocampal complex was planned according to the individual anatomy of each patient. Amygdalohippocampectomy was performed using a string electrode with a 10-mm active tip, and 16–38 lesions (median=25) were performed in all patients along the 30- to 45-mm trajectory (median=35) in the amygdalohippocampal complex.

Results The procedure was well tolerated by all patients with no severe permanent morbidity; meningitis was recorded in two patients (4%), hematoma was detected in four patients, clinically insignificant in three of them, and one patient required temporary ventricular drainage (2%). Thirty-two patients were followed up over at least 2 years, and the clinical outcomes were evaluated by Engel’s classification; 25 of them (78%) were Engel I, five (16%) were Engel II, and two (6%) were Engel IV.

Conclusions Stereotactic amygdalohippocampectomy is a minimally invasive procedure with low morbidity and good results that can be the method of choice in selected patients with MTLE.

Intracranial monitoring for temporal lobe seizure localization to differentiate neocortical from mesial temporal onset seizures requires both neocortical subdural grids and hippocampal depth electrode implantation. There are 2 basic techniques for hippocampal depth electrode implantation. This first technique uses a stereotactically guided 8-contact depth electrode directed along the long axis of the hippocampus to the amygdala via an occipital bur hole. The second technique involves direct placement of 2 or 3 4-contact depth electrodes perpendicular to the temporal lobe through the middle temporal gyrus and overlying subdural grid. The purpose of this study was to determine whether one technique was superior to the other by examining monitoring success and complications.

Methods. Between 1997 and 2005, 41 patients underwent invasive seizure monitoring with both temporal subdural grids and depth electrodes placed in 2 ways. Patients in Group A underwent the first technique, and patients in Group B underwent the second technique.

Results. Group A consisted of 26 patients and Group B 15 patients. There were no statistically significant differences between Groups A and B regarding demographics, monitoring duration, seizure localization, or outcome (Engel classification). There was a statistically significant difference at the point in time at which these techniques were used: Group A represented more patients earlier in the series than Group B (p < 0.05). The complication rate attributable to the grids and depth electrodes was 0% in each group. It was more likely that the depth electrodes were placed through the grid if there was a prior resection and the patient was undergoing a new evaluation (p < 0.05). Furthermore, Group A procedures took significantly longer than Group B procedures.

Conclusions. In this patient series, there was no difference in efficacy of monitoring, complications, or outcome between hippocampal depth electrodes placed laterally through temporal grids or using an occipital bur hole stereotactic approach. Placement of the depth electrodes perpendicularly through the grids and middle temporal gyrus is technically more practical because multiple head positions and redraping are unnecessary, resulting in shorter operative times with comparable results.

Epilepsy that originates outside of the temporal lobe can present some of the most challenging problems for surgical therapy. These epilepsies can be broadly categorized as lesional or non-lesional, with the nonlesional cases being the most difficult to localize. Lesional cases can result from malformations of cortical development, tumors, vascular malformations, or areas of old injury. Some lesions, such as focal cortical dysplasia, can be challenging, in that the boundaries of the pathology can be difficult to define. Presurgical goals include defining the structural lesion, the physiologic abnormality, and normal function in the area. These goals can be achieved using a variety of noninvasive and invasive tests. Surgical techniques vary depending on location and pathology but they always include removal of the epileptic brain tissue while preserving en passage vessels and underlying white matter tracts. Surgical outcomes vary depending on the underlying pathology. Surgeries are usually planned with a goal of no expected postoperative deficits, although temporary deficits may be anticipated in some areas, such as the supplementary motor cortex. Extratemporal epilepsy can be managed well with surgical treatment; but proper patient selection, evaluation, and discussion of expected outcomes and risks are critical in this challenging patient population.