Four-dimensional maps of the human somatosensory system.

A fine-grained description of the spatiotemporal dynamics of human brain activity is a major goal of neuroscientific research. Limitations in spatial and temporal resolution of available noninvasive recording and imaging techniques have hindered so far the acquisition of precise, comprehensive four-dimensional maps of human neural activity. The present study combines anatomical and functional data from intracerebral recordings of nearly 100 patients, to generate highly resolved four-dimensional maps of human cortical processing of nonpainful somatosensory stimuli. These maps indicate that the human somatosensory system devoted to the hand encompasses a widespread network covering more than 10% of the cortical surface of both hemispheres. This network includes phasic components, centered on primary somatosensory cortex and neighboring motor, premotor, and inferior parietal regions, and tonic components, centered on opercular and insular areas, and involving human parietal rostroventral area and ventral medial-superior-temporal area. The technique described opens new avenues for investigating the neural basis of all levels of cortical processing in humans.

Stereo-EEG-guided radiofrequency thermocoagulations.

The rationale and the surgical technique of stereo-electroencephalography (SEEG)-guided radiofrequency thermocoagulation (RF-TC) in the epileptogenic zone (EZ) of patients with difficult-to-treat focal epilepsy are described in this article. The application of the technique in pediatric patients is also detailed. Stereotactic ablative procedures by RF-TC have been employed in the treatment of epilepsy since the middle of the last century. This treatment option has gained new popularity in recent decades, mainly because of the availability of modern imaging techniques, which allow accurate targeting of intracerebral epileptogenic structures. SEEG is a powerful tool for identifying the EZ in the most challenging cases of focal epilepsy by recording electrical activity with tailored stereotactic implantation of multilead intracerebral electrodes. The same recording electrodes may be used to place thermocoagulative lesions in the EZ, following the indications provided by intracerebral monitoring. The technical details of SEEG implantation and of SEEG-guided RF-TC are described herein, with special attention to the employment of the procedure in pediatric cases. SEEG-guided RF-TC offers a potential therapeutic option based on robust electroclinical evidence with acceptable risks and costs. The procedure may be performed in patients who, according to SEEG recording, are not eligible for resective surgery, and it may be an alternative to resective surgery in a small subset of operable patients.

A new tool for touch-free patient registration for robot-assisted intracranial surgery: application accuracy from a phantom study and a retrospective surgical series.

OBJECTIVE The purpose of this study was to compare the accuracy of Neurolocate frameless registration system and frame-based registration for robotic stereoelectroencephalography (SEEG). METHODS The authors performed a 40-trajectory phantom laboratory study and a 127-trajectory retrospective analysis of a surgical series. The laboratory study was aimed at testing the noninferiority of the Neurolocate system. The analysis of the surgical series compared Neurolocate-based SEEG implantations with a frame-based historical control group. RESULTS The mean localization errors (LE) ± standard deviations (SD) for Neurolocate-based and frame-based trajectories were 0.67 ± 0.29 mm and 0.76 ± 0.34 mm, respectively, in the phantom study (p = 0.35). The median entry point LE was 0.59 mm (interquartile range [IQR] 0.25-0.88 mm) for Neurolocate-registration-based trajectories and 0.78 mm (IQR 0.49-1.08 mm) for frame-registration-based trajectories (p = 0.00002) in the clinical study. The median target point LE was 1.49 mm (IQR 1.06-2.4 mm) for Neurolocate-registration-based trajectories and 1.77 mm (IQR 1.25-2.5 mm) for frame-registration-based trajectories in the clinical study. All the surgical procedures were successful and uneventful. CONCLUSIONS The results of the phantom study demonstrate the noninferiority of Neurolocate frameless registration. The results of the retrospective surgical series analysis suggest that Neurolocate-based procedures can be more accurate than the frame-based ones. The safety profile of Neurolocate-based registration should be similar to that of frame-based registration. The Neurolocate system is comfortable, noninvasive, easy to use, and potentially faster than other registration devices.

Surgical treatment of polymicrogyria-related epilepsy.

OBJECTIVE: The role of resective surgery in the treatment of polymicrogyria (PMG)-related focal epilepsy is uncertain. Our aim was to retrospectively evaluate the seizure outcome in a consecutive series of patients with PMG-related epilepsy who received, or did not receive, surgical treatment, and to outline the clinical characteristics of patients who underwent surgery. METHODS: We evaluated 64 patients with epilepsy associated with magnetic resonance imaging (MRI)-documented PMG. After presurgical evaluation, 32 patients were excluded from surgical treatment and 32 were offered surgery, which was declined by 8 patients. Seizure outcome was assessed in the 40 nonsurgical and 24 surgical patients. RESULTS: Of 40 nonsurgical patients, 8 (20%) were seizure-free after a mean follow-up of 91.7 ± (standard deviation) 59.5 months. None of the eight patients who declined surgical treatment was seizure-free (mean follow-up: 74.3 ± 60.6 months). These seizure outcomes differ significantly (p = 0.000005 and p = 0.0003, respectively) from that of the 24 surgical patients, 18 of whom (66.7%) were Engel's class I postoperatively (mean follow-up: 66.5 ± 54.0 months). Of the eight patients excluded from surgery for seizure control at first visit, two had seizure recurrence at last contact. At last contact, antiepileptic drugs (AEDs) had been withdrawn in 6 of 24 surgical and in one of 40 nonsurgical cases (p = 0.0092). SIGNIFICANCE: The present study indicates that, at least in a subset of adequately selected patients with PMG-related epilepsy, surgery may provide excellent seizure outcomes. Furthermore, it suggests that surgery is superior to AEDs for achieving seizure freedom in these cases.

Multimodal responses induced by cortical stimulation of the parietal lobe: a stereo-electroencephalography study.

The functional complexity of the parietal lobe still represents a challenge for neurophysiological and functional neuroimaging studies. While the somatosensory functions of the anterior parietal cortex are well established, the posterior parietal cortex has a relevant role in processing the sensory information, including visuo-spatial perception, visual attention, visuo-motor transformations and other complex and not completely understood functions. We retrospectively analysed all the clinical manifestations induced by intracerebral bipolar electrical stimulation in 172 patients suffering from drug-resistant focal epilepsy (mean age 25.6, standard deviation 11.6; 44% females and 56% males) with at least one electrode stereotactically implanted in the parietal cortex. A total of 1186 electrical stimulations were included in the analysis, of which 88 were subsequently excluded because of eliciting pathological electric activity or inducing ictal symptomatology. In the dominant parietal lobe, clinical responses were observed for 56 (25%) of the low-frequency stimulations and for 76 (50%) of the high-frequency stimulations. In the non-dominant parietal lobe, 111 (27%) low-frequency and 176 (55%) high-frequency stimulations were associated with a clinical response. Body scheme alteration was the only clinical effect showing a lateralization, as they were evoked only in the non-dominant hemisphere. The occurrence of somatosensory sensations, motor symptoms, dysarthria and multimodal responses were significantly associated with stimulation of the postcentral gyrus (odds ratio: 5.83, P < 0.001; odds ratio: 8.77, P < 0.001; odds ratio: 5.44, P = 0.011; odds ratio: 8.33, P = 0.006; respectively). Stimulation of the intraparietal sulcus was associated with the occurrence of sensory illusions or hallucinations (odds ratio: 8.68, P < 0.001) and eyeball/eyelid movements or sensations (odds ratio: 4.35, P = 0.047). To our knowledge, this is the only currently available complete revision of electrical stimulation of the entire parietal cortex with the aim to evaluate the neurophysiology of this relevant brain region. Our analysis offers a general overview of the multiple roles of the parietal cortex and supports its crucial involvement in different networks related to complex integrative functions.media-1vid110.1093/brain/awv187_video_abstractawv187_video_abstract.

Epilepsy surgery in the posterior part of the brain.

Posterior cortex epilepsy surgery is rarely performed and is associated with a high number of surgical failures, partly because accurate localization of the epileptogenic zone in the posterior part of the brain is extremely difficult. We present the characteristics as well as the surgical outcome and its determinants of a cohort of 208 consecutive patients (adults/children: 125/83) operated on for drug-resistant posterior cortex epilepsy at the "Claudio Munari" Epilepsy Surgery Centre, Milan between May 1996 and May 2013 (mean postsurgical follow-up: 9.6years). In addition, we highlight the differences in anatomoelectroclinical features and outcome between (i) patients who necessitated an invasive preoperative evaluation and those who proceeded directly to surgery and (ii) adults and children. Mean age at epilepsy onset was 6.8years (91.4% with onset before 14years of age). A high seizure frequency was reported by 51% of subjects, interictal and ictal EEG features were localizing in 16% and 28% of cases, and 86% of patients had a positive, judged as more or less informative, MRI. Invasive presurgical evaluation by stereoelectroencephalography was performed in 54% of patients; explorations may schematically be grouped in three main implantation patterns. Globally, 70% of subjects achieved seizure freedom, and further, 10% achieved Engel class II, with the patients operated on in childhood achieving significantly better postsurgical results in terms of seizure freedom and drug discontinuation. Duration of epilepsy represented the most consistent predictor of surgical outcome, with early surgery being correlated with higher chances of surgical success. Therefore, we recommend an early surgical referral in cases of pharmacoresistant posterior cortex seizures. Furthermore, we suggest that surgical failure might be predicted very early, namely within the first 6 postoperative months. We conclude that surgical management of posterior cortex epilepsy may attain excellent results.

Risk factors for postoperative depression: A retrospective analysis of 248 subjects operated on for drug-resistant epilepsy.

The aim of this retrospective case series analysis was to identify the predictors of postoperative depression (PostOp-D) in a sample of 248 subjects with focal drug-resistant focal epilepsy. The presence or absence of PostOp-D during a 12-month follow-up period was the outcome variable. Demographic, neurologic, psychiatric characteristics, and antiepileptic therapy were the explanatory variables. After preliminary bivariate analysis, a multivariate logistic regression model was fitted to identify variables associated with PostOp-D. Sixty-seven patients (27%) experienced PostOp-D. At multivariate analysis, lifetime depression, age at surgery, and levetiracetam (LEV) are positive predictors of PostOp-D; carbamazepine (CBZ) and anxiety disorders are protective factors. LEV increases the risk for PostOp-D by about half; the relative risk (RR) is 1.48. Conversely, CBZ decreases the risk for PostOp-D by about half (RR 0.59). Our results suggest that careful psychiatric evaluation and follow-up should be recommended for subjects at risk. It is advisable to treat patients with depression before surgery. Antiepileptic drugs should be selected carefully when patients present with not modifiable risk factors, such as positive personal history for depression.

Epilepsy surgery of focal cortical dysplasia-associated tumors.

The goal of the present study was to evaluate the clinical characteristics and postoperative seizure outcome of epileptogenic tumors associated with focal cortical dysplasias (FCDs) compared to both solitary FCD type I and solitary tumors. Particular attention is given to FCD type IIIb (tumors associated with FCD type I), which have been recently classified as a separate entity. We retrospectively reviewed the clinical charts of 1,109 patients who were operated on for drug-resistant focal epilepsy, including 492 patients with a histologic diagnosis of solitary FCD I and II (83 and 157 cases, respectively), solitary tumors (179 cases), and FCD-associated tumors (73 cases, 58 of which met the criteria of FCD IIIb of the new International League Against Epilepsy [ILAE] classification). The different subgroups were evaluated for clinical characteristics and postoperative surgical outcome. Clinical variables and postoperative seizure outcome of patients with coexisting tumor and FCDs (FCD IIIb and tumor associated FCD II) were similar to those of patients with a solitary tumor and differed significantly from patients with solitary FCDs. Nevertheless, tumors associated with FCDs are characterized by a striking male predominance and a higher seizure frequency as compared to solitary tumors. Patients with drug-resistant focal epilepsy secondary to a solitary tumor or with a tumor-associated FCD have similar basic clinical presentation and postoperative seizure outcome. Nevertheless, the epileptogenic contribution of the associated FCDs can be crucial, and it needs to be adequately assessed. The impact of FCD on tumor-related epilepsy deserves future research in order to optimize the surgical strategies aimed at seizure relief.

The interlaminar contralateral approach to far-lateral lumbar disc herniations: a single-center comparison with traditional techniques.

BACKGROUND: The interlaminar contralateral approach (ICA) is a promising surgical alternative for the treatment of far-lateral lumbar disc herniations (FLLDH). To date no study has compared ICA and FLLDH conventional surgical treatments, namely the intertransverse, the transmuscular and the intermuscular approaches, in terms of safety and outcome. METHODS: Patients who underwent FLLDH surgery at our Institution between January 2015 and September 2018 were reviewed. ICA complications and clinical outcomes were compared with those of conventional approaches at 1-month postoperatively and at the last follow-up available. Improvement was defined as reduction of at least two point in the Visual Analogue Scale (VAS) or increase of at least 1 point in the Medical Research Council (MRC) scale of muscle strength. Patient-reported outcome was assessed with the Oswestry Disability Index (ODI). RESULTS: Among 38 patients, 18 underwent ICA and 20 a conventional approach (intertransverse in 16, transmuscular in two, intermuscular in two). Median follow-up was 21 months (range, 2-47). At 1 month, no differences between the two groups were noticed in terms of clinical outcome and symptoms relief (P> 0.05). The median postoperative ODI score was significantly lower in the Conventional approach group at 1 month (P<0.05), but this difference was no longer significant at the last follow-up evaluation (P>0.05). No differences were found between the two groups in surgical complication and recurrence rates. CONCLUSIONS: Our data suggest that the ICA is a safe and effective alternative to conventional approaches in FLLDH surgery. Larger prospective studies are needed to confirm our results.

What is the role of the uncinate fasciculus? Surgical removal and proper name retrieval.

The functional role of the uncinate fasciculus is still a matter of debate. We examined 44 patients submitted to awake surgery for removal of a left frontal or temporal glioma. In 18 patients, the removal included the uncinate fasciculus. We compared patients with or without removal on a series of neuropsychological tasks, performed at different time intervals: pre-surgery, in the first week after surgery and 3 months after surgery. Functional magnetic resonance and diffusion tensor imaging, fibre-tracking techniques were performed before surgery. At the last examination, patients with uncinate removal were significantly impaired in naming of famous faces and objects as compared with patients without removal. We further divided patients according to the site of the tumour (either frontal or temporal). At the follow-up, patients with a temporal glioma who underwent uncinate removal had the worst loss of performance in famous face naming. In addition, on the same task, the group with a frontal glioma that underwent resection of the frontal part of the uncinate performed significantly worse than the group with a frontal glioma but without uncinate removal. In conclusion, the resection of the uncinate fasciculus, in its frontal or temporal part, has long-lasting consequences for famous face naming. We suggest that this fibre tract is part of a circuitry involved in the retrieval of word form for proper names. Retrieval of conceptual knowledge was intact.

Intraoperative use of diffusion tensor imaging fiber tractography and subcortical mapping for resection of gliomas: technical considerations.

Resection of lesions involving motor or language areas or pathways requires the intraoperative identification of functional cortical and subcortical sites for effectively and safe guidance. Diffusion tensor (DT) imaging and fiber tractography are MR imaging techniques based on the concept of anisotropic water diffusion in myelinated fibers, which enable 3D reconstruction and visualization of white matter tracts and provide information about the relationship of these tracts to the tumor mass. The authors routinely used DT imaging fiber tractography to reconstruct various tracts involved in the motor and/or language system in a large series of patients with lesions involving the motor and/or language areas or pathways. The DT imaging fiber tractography data were loaded into the neuronavigational system and combined intraoperatively with those obtained from direct electrical stimulation applied at the subcortical level. In this paper the authors report the results of their experience, describing the findings for each tract and discussing technical aspects of the combined use as well as the pitfalls.

Intraoperative mapping and monitoring of brain functions for the resection of low-grade gliomas: technical considerations.

Low-grade gliomas ([LGGs] WHO Grade II) are slow-growing intrinsic cerebral lesions that diffusely infiltrate the brain parenchyma along white matter tracts and almost invariably show a progression toward malignancy. The treatment of these tumors forces the neurosurgeon to face uncommon difficulties and is still a subject of debate. At the authors' institution, resection is the first option in the treatment of LGGs. It requires the combined efforts of a multidisciplinary team of neurosurgeons, neuroradiologists, neuropsychologists, and neurophysiologists, who together contribute to the definition of the location, extension, and extent of functional involvement that a specific lesion has caused in a particular patient. In fact, each tumor induces specific modifications of the brain functional network, with high interindividual variability. This requires that each treatment plan is tailored to the characteristics of the tumor and of the patient. Consequently, surgery is performed according to functional and anatomical boundaries to achieve the maximal resection with maximal functional preservation. The identification of eloquent cerebral areas, which are involved in motor, language, memory, and visuospatial functions and have to be preserved during surgery, is performed through the intraoperative use of brain mapping techniques. The use of these techniques extends surgical indications and improves the extent of resection, while minimizing the postoperative morbidity and safeguarding the patient's quality of life. In this paper the authors present their paradigm for the surgical treatment of LGGs, focusing on the intraoperative neurophysiological monitoring protocol as well as on the brain mapping technique. They briefly discuss the results that have been obtained at their institution since 2005 as well as the main critical points they have encountered when using this approach.

A mirror mechanism for smiling in the anterior cingulate cortex.

It was recently proposed that the neural substrate mediating smile production might play a key role also in the recognition of others' smile. This hypothesis, however, has been challenged by difficulties in eliciting ecological smiling in standard laboratory settings. Here we report of a case where these difficulties were overcome by combining electrical stimulation and intracranial electroencephalogram recording in a patient with drug-resistant focal epilepsy. The stimulation of the pregenual anterior cingulate cortex (pACC) elicited a smiling facial expression. The same leads exploring pACC showed an increase of gamma band activity (50-100 Hz) during the observation of video-clips depicting actors laughing, relative to video-clips depicting actors crying or producing a neutral expression. These findings indicate that both smile production and recognition are encoded in pACC and further support the role of this region in social cognition. (PsycINFO Database Record

Implantation of Stereoelectroencephalography Electrodes: A Systematic Review.

BACKGROUND: Stereoelectroencephalography (SEEG) was developed by Talairach and Bancaud in Paris in the late 1950s. Subsequently, the Talairach methodology was adopted at a number of additional centers in Europe and Canada. Technical aspects remained essentially unchanged for the following 30 years. Only in the last two decades, because of advancements in image-guided surgery systems, robotics, and computer-aided planning, use of SEEG has become more widespread, and reports describing these new developments have been published. OBJECTIVES: This systematic review was designed to assess published reports of SEEG surgical techniques and safety profile. DATA SOURCES: An electronic search was performed of Medline, Embase, and Scopus databases. In addition, the content pages of several standard epilepsy surgery textbooks were searched. Full-text English studies describing SEEG surgical technique or pertinent epidemiological data were included. Conference abstracts, reviews, posters, editorials, comments, and letters were excluded. RESULTS: Three hundred fifty-nine of 2,903 potentially eligible studies published by 32 centers were reviewed. Thirty-one of these primarily discussed the surgical technique. Thirty-five major complications (including 4 fatalities) were reported among 4,000 patients (0.8%) implanted with 33,000 electrodes. LIMITATIONS: The number of SEEG patients is likely to be underestimated because only a few groups have exhaustively reported their experience. Moreover, it is possible that a number of teams performing SEEG have not published studies on the topic. CONCLUSIONS: Rigorous SEEG, thanks to its basic principles and updated technologies, is a safe and accurate method to define the epileptogenic zone by means of stereotactically implanted intracerebral electrodes.

Hand-tool-tissue interaction forces in neurosurgery for haptic rendering.

Haptics provides sensory stimuli that represent the interaction with a virtual or tele-manipulated object, and it is considered a valuable navigation and manipulation tool during tele-operated surgical procedures. Haptic feedback can be provided to the user via cutaneous information and kinesthetic feedback. Sensory subtraction removes the kinesthetic component of the haptic feedback, having only the cutaneous component provided to the user. Such a technique guarantees a stable haptic feedback loop, while it keeps the transparency of the tele-operation system high, which means that the system faithfully replicates and render back the user's directives. This work focuses on checking whether the interaction forces during a bench model neurosurgery operation can lie in the solely cutaneous perception of the human finger pads. If this assumption is found true, it would be possible to exploit sensory subtraction techniques for providing surgeons with feedback from neurosurgery. We measured the forces exerted to surgical tools by three neurosurgeons performing typical actions on a brain phantom, using contact force sensors, while the forces exerted by the tools to the phantom tissue were recorded using a load cell placed under the brain phantom box. The measured surgeon-tool contact forces were 0.01-3.49 N for the thumb and 0.01-6.6 N for index and middle finger, whereas the measured tool-tissue interaction forces were from six to 11 times smaller than the contact forces, i.e., 0.01-0.59 N. The measurements for the contact forces fit the range of the cutaneous sensitivity for the human finger pad; thus, we can say that, in a tele-operated robotic neurosurgery scenario, it would possible to render forces at the fingertip level by conveying haptic cues solely through the cutaneous channel of the surgeon's finger pads. This approach would allow high transparency and high stability of the haptic feedback loop in a tele-operation system.

Sleep Related Hypermotor Seizures with a Right Parietal Onset.

Nocturnal frontal lobe epilepsy (NFLE) is a syndrome characterized by the occurrence of sleep related seizures of variable complexity and duration. Hypermotor seizures (HMS) represent a classic manifestation of this syndrome, associated with a perturbation of the ventromesial frontal cortex and anterior cingulate gyrus regions. Nevertheless, in recent years, reports have showed that the seizure onset zone (SOZ) need not be of frontal origin to generate HMS. Here we report an unusual case of a patient presenting with a seven-year history of drug-resistant sleep related HMS arising from the mesial parietal region. The presence of an infrequent feeling of levitation before the HMS was key to suspecting a subtle focal cortical dysplasia in the right precuneus region. A stereo-EEG investigation confirmed the extra-frontal seizure onset of the HMS and highlighted the interrelationship between unstable sleep and seizure precipitation.

Stereoelectroencephalography-guided radiofrequency thermocoagulation in the epileptogenic zone: a retrospective study on 89 cases.

OBJECT: Radiofrequency thermocoagulation (RF-TC) of presumed epileptogenic lesions and/or structures has gained new popularity as a treatment option for drug-resistant focal epilepsy, mainly in patients with mesial temporal lobe epilepsy. The role of this minimally invasive procedure in more complex cases of drug-resistant epilepsy, which may require intracranial electroencephalographic evaluation, has not been fully assessed. This retrospective study reports on a case series of patients with particularly complex focal epilepsy who underwent stereoelectroencephalography (SEEG) evaluation with stereotactically implanted multicontact intracerebral electrodes for the detailed identification of the epileptogenic zone (EZ) and who received RF-TC in their supposed EZ (according to SEEG findings). METHODS: Eighty-nine patients (49 male and 40 female; age range 2-49 years) who underwent SEEG evaluation and subsequent RF-TC of the presumed EZ at the authors' institution between January 2008 and December 2013 were selected. Brain MRI revealed structural abnormalities in 43 cases and no lesions in 46 cases. After SEEG, 67 patients were judged suitable for resective surgery (Group 1), whereas surgery was excluded for 22 patients (Group 2). Thermocoagulation was performed in each of these patients by using the previously implanted multicontact recording electrodes and delivering RF-generated currents to adjacent electrode contacts. RESULTS: The mean number of TC sites per patient was 10.6 ± 7.2 (range 1-33). Sustained seizure freedom occurred after TC in 16 patients (18.0%) (13 in Group 1 and 3 in Group 2). A sustained worthwhile improvement was reported by 9 additional patients (10.1%) (3 in Group 1 and 6 in Group 2). As a whole, 25 patients (28.1%) exhibited a persistent significant improvement in their seizures. More favorable results were observed in patients with nodular heterotopy (p = 0.0001389), those with a lesion found on MRI (not significant), and those with hippocampal sclerosis (not significant). Other variables significantly correlated to seizure freedom were the patient's age (p = 0.02885) and number of intralesional TC sites (p = 0.0271). The patients in Group 1 who did not benefit at all (21 patients) or who experienced only a transient benefit (30 patients) from TC underwent microsurgical resection of their EZ. Thermocoagulation was followed by severe permanent neurological deficits in 2 patients (an unexpected complex neuropsychological syndrome in one patient and an expected and anticipated permanent motor deficit in the other). CONCLUSIONS: This study provides evidence that SEEG-guided TC in the EZ may be a treatment option for particularly complex drug-resistant focal epilepsy that requires invasive evaluation. A small subset of patients who achieve seizure freedom or worthwhile improvement may avoid open surgery or take advantage of an otherwise unexpected treatment if resection is not an option. Patients with epileptogenic nodular heterotopy are probably ideal candidates for this treatment.

Cerebral Angiography for Multimodal Surgical Planning in Epilepsy Surgery: Description of a New Three-Dimensional Technique and Literature Review.

OBJECTIVE: Cerebrovascular imaging is critical for safe and accurate planning of Stereo-ElectroEncephaloGraphy (SEEG) electrode trajectory. We developed a new technique for Cone Beam Computed Tomography (CBCT) Three-Dimensional Digital Subtraction Angiography (3D DSA). METHODS: The workflow core is the acquisition of computed tomography datasets without (bone mask) and with selective injection of contrast medium in the main brain-feeding arteries, followed by dataset registration and subtraction. The images were acquired with the O-armTM 1000 System (Medtronic). Images were postprocessed with FSL software package. We retrospectively analyzed 191 3D DSA procedures and qualitatively analyzed the quality of each 3D DSA dataset. RESULTS: The quality of 3D DSA was good in 150 procedures, sufficient in 37, and poor in 4. 3D rendering of the vascular tree was helpful for both SEEG implantation and resective surgery planning. Angiography complications occurred in only one procedure that was aborted due to a major allergic reaction to contrast medium. No other complications directly related to 3D DSA occurred. Minor intracerebral hemorrhage occurred in 2/191 patients after SEEG implantation, with no permanent sequelae. CONCLUSIONS: CBCT 3D DSA is a safe diagnostic procedure for SEEG electrode trajectory planning and for 3D reconstructions of the vascular tree in multimodal scenes for resections. The high fidelity and geometric accuracy contribute to the safety of electrode implantation.

Drug-resistant focal sleep related epilepsy: results and predictors of surgical outcome.

In this study we report the results of surgery in a large population of patients affected by drug-resistant focal sleep related epilepsy (SRE) and the identified prognostic factors. We conducted a retrospective analysis of a case series of 955 patients operated on for drug-resistant focal epilepsy from 1997 to 2009. Ninety-five patients with focal SRE and a follow-up of at least 2 years were identified. Presurgical, surgical and histopathological variables were analyzed. Risk of seizures recurrence was assessed by univariate and multivariate analysis. Mean age at epilepsy onset was 5.6 ± 4.9 years. MRI revealed a focal abnormality in 78.9% of cases. Sixty-two percent of patients required a Stereo-EEG investigation. The cortical resection involved the frontal lobe in 61.1% of cases, while in 38.9% an extrafrontal resection was performed. Focal cortical dysplasia (FCD) type II was the most frequent histopathological finding. Mean postoperative follow-up was 82.3 months. Seventy-three patients (76.8%) were in Engel's class I. At univariate analysis, variables associated with a favorable outcome were: absence of Stereo-EEG investigation; positive MRI; complete removal of the epileptogenic zone (EZ); presence of FCD type II and FCD type IIb. A diagnosis of FCD type I was associated with postoperative recurrence of seizures. Multivariate analysis identified the complete removal of the EZ and FCD type I as independent predictors of a favorable and unfavorable outcome respectively. SRE can frequently originate outside the frontal lobe and a favorable surgical outcome is achieved in three-fourths of cases independently from the location of the EZ.