Influence of the Severity of Osteogenesis Imperfecta on Cranial Measurements

Osteogenesis Imperfecta (OI) is a disease that causes bone fragility and deformities, affecting both the cranial base and the craniocervical junction, and may lead to other neurological disorders. A retrospective cross-sectional study was carried out based on cephalometric analysis of the cranial base in a sample of patients with OI, in lateral skull radiographs and magnetic resonance imaging (MRI), comparing them with a sample of age-matched controls. When the different variables of the craniocervical junction were analyzed, significance was found in comparisons with the different age groups. All measurements of the variables studied stabilized as growth progressed. For most of the variables, the severity of the disease influences the measurements of the skull base, with statistically significant differences. Both age and severity of the disease are factors that directly influence the anatomy of the craniocervical junction in these patients and may serve as indicators in the early detection and prevention of other derived alterations.

Intraoperative Cortico-Cortical Evoked Potentials for Monitoring Language Function during Brain Tumor Resection in Anesthetized Patients

BACKGROUND

Cortico-cortical evoked potentials (CCEPs) have been used to map the frontal (FLA) and parietal (PLA) cortical regions related to language function. However, they have usually been employed as a complementary method during sleep-awake surgery.

METHODS

Five male and two female patients received surgery for tumors located near language areas. Six patients received general anesthesia and the sleep-awake method was used for patients with tumors located near the cortical language areas. We performed motor and somatosensory mapping with CCEPs to identify language areas and we monitored responses during surgery based on the mapping results. Electrocorticography was performed throughout the surgery. Single pulses of 1 ms duration at 5-20 mA were delivered by direct cortical stimulation using one grid at one region (e.g., FLA) and then recording using a second gird at another area (i.e., PLA). Next, reversed stimulation (from PLA to FLA) was performed. The charge density for electrical stimulation was computed. Sensibility, specificity, predictive positive values, and predicted negative values were also computed for warning alterations of CCEPs.

RESULTS

Gross tumor resection was achieved in four cases. The first postsurgical day showed language alterations in three patients, but one year later six patients remained asymptomatic and one patient showed the same symptomatology as previously. Seizures were observed in two patients that were easily jugulated. CCEPs predicted warning events with high sensibility and specificity. Postsurgical language deficits were mostly transitory. Although the latency between frontal and parietal regions showed symmetry, the amplitude and the relationship between amplitude and latency were different for FLA than for PLA. The charge density elicited by CCEPs ranged from 442 to 1768 μC/cm2.

CONCLUSIONS

CCEPs have proven to be a reliable neurophysiological technique for mapping and monitoring the regions associated with language function in a small group of anesthetized patients. The high correlation between warning events and postsurgical outcomes suggested a high sensitivity and specificity and CCEPs can be used systematically in patients under general anesthesia. Nevertheless, the small number of studied patients suggests considering these results cautiously.

Neuroanatomical and psychological considerations in temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy and is associated with a variety of structural and psychological alterations. Recently, there has been renewed interest in using brain tissue resected during epilepsy surgery, in particular 'non-epileptic' brain samples with normal histology that can be found alongside epileptic tissue in the same epileptic patients - with the aim being to study the normal human brain organization using a variety of methods. An important limitation is that different medical characteristics of the patients may modify the brain tissue. Thus, to better determine how 'normal' the resected tissue is, it is fundamental to know certain clinical, anatomical and psychological characteristics of the patients. Unfortunately, this information is frequently not fully available for the patient from which the resected tissue has been obtained - or is not fully appreciated by the neuroscientists analyzing the brain samples, who are not necessarily experts in epilepsy. In order to present the full picture of TLE in a way that would be accessible to multiple communities (e.g., basic researchers in neuroscience, neurologists, neurosurgeons and psychologists), we have reviewed 34 TLE patients, who were selected due to the availability of detailed clinical, anatomical, and psychological information for each of the patients. Our aim was to convey the full complexity of the disorder, its putative anatomical substrates, and the wide range of individual variability, with a view toward: (1) emphasizing the importance of considering critical patient information when using brain samples for basic research and (2) gaining a better understanding of normal and abnormal brain functioning. In agreement with a large number of previous reports, this study (1) reinforces the notion of substantial individual variability among epileptic patients, and (2) highlights the common but overlooked psychopathological alterations that occur even in patients who become "seizure-free" after surgery. The first point is based on pre- and post-surgical comparisons of patients with hippocampal sclerosis and patients with normal-looking hippocampus in neuropsychological evaluations. The second emerges from our extensive battery of personality and projective tests, in a two-way comparison of these two types of patients with regard to pre- and post-surgical performance.

Neurosurgical Treatment of Pain

The aim of this review is to draw attention to neurosurgical approaches for treating chronic and opioid-resistant pain. In a first chapter, an up-to-date overview of the main pathophysiological mechanisms of pain has been carried out, with special emphasis on the details in which the surgical treatment is based. In a second part, the principal indications and results of different surgical approaches are reviewed. Cordotomy, Myelotomy, DREZ lesions, Trigeminal Nucleotomy, Mesencephalotomy, and Cingulotomy are revisited. Ablative procedures have a limited role in the management of chronic non-cancer pain, but they continues to help patients with refractory cancer-related pain. Another ablation lesion has been named and excluded, due to lack of current relevance. Peripheral Nerve, Spine Cord, and the principal possibilities of Deep Brain and Motor Cortex Stimulation are also revisited. Regarding electrical neuromodulation, patient selection remains a challenge.

Surgical treatment of brainstem cavernous malformations: an international Delphi consensus

OBJECTIVE

Indication for surgery in brainstem cavernous malformations (BSCMs) is based on many case series, few comparative studies, and no randomized controlled trials. The objective of this study was to seek consensus about surgical management aspects of BSCM.

METHODS

A total of 29 experts were invited to participate in a multistep Delphi consensus process on the surgical treatment of BSCM.

RESULTS

Twenty-two (76%) of 29 experts participated in the consensus. Qualitative analysis (content analysis) of an initial open-ended question survey resulted in 99 statements regarding surgical treatment of BSCM. By using a multistep survey with 100% participation in each round, consensus was reached on 52 (53%) of 99 statements. These were grouped into 4 categories: 1) definitions and reporting standards (7/14, 50%); 2) general and patient-related aspects (11/16, 69%); 3) anatomical-, timing of surgery-, and BSCM-related aspects (22/37, 59%); and 4) clinical situation-based decision-making (12/32, 38%). Among other things, a consensus was reached for surgical timing, handling of associated developmental venous anomalies, handling of postoperative BSCM remnants, assessment of specific anatomical BSCM localizations, and treatment decisions in typical clinical BSCM scenarios.

CONCLUSIONS

A summary of typical clinical scenarios and a catalog of various BSCM- and patient-related aspects that influence the surgical treatment decision have been defined, rated, and interpreted.

Network Substrates of Centromedian Nucleus Deep Brain Stimulation in Generalized Pharmacoresistant Epilepsy

Deep brain stimulation (DBS), specifically thalamic DBS, has achieved promising results to reduce seizure severity and frequency in pharmacoresistant epilepsies, thereby establishing it for clinical use. The mechanisms of action are, however, still unknown. We evidenced the brain networks directly modulated by centromedian (CM) nucleus-DBS and responsible for clinical outcomes in a cohort of patients uniquely diagnosed with generalized pharmacoresistant epilepsy. Preoperative imaging and long-term (2-11 years) clinical data from ten generalized pharmacoresistant epilepsy patients (mean age at surgery = 30.8 ± 5.9 years, 4 female) were evaluated. Volume of tissue activated (VTA) was included as seeds to reconstruct the targeted network to thalamic DBS from diffusion and functional imaging data. CM-DBS clinical outcome improvement (> 50%) appeared in 80% of patients and was tightly related to VTAs interconnected with a reticular system network encompassing sensorimotor and supplementary motor cortices, together with cerebellum/brainstem. Despite methodological differences, both structural and functional connectomes revealed the same targeted network. Our results demonstrate that CM-DBS outcome in generalized pharmacoresistant epilepsy is highly dependent on the individual connectivity profile, involving the cerebello-thalamo-cortical circuits. The proposed framework could be implemented in future studies to refine stereotactic implantation or the parameters for individualized neuromodulation.

Simulation with 3D Neuronavigation for Learning Cortical Bone Trajectory Screw Placement

BACKGROUND AND OBJECTIVE

 Learning a new technique in neurosurgery is a big challenge especially for trainees. In recent years, simulations and simulators got into the focus as a teaching tool. Our objective is to propose a simulator for placement of cortical bone trajectory (CBT) screws to improve results and reduce complications.

METHODS

 We have created a platform consisting of a sawbone navigated with a 3D fluoroscope to familiarize our trainees and consultants with CBT technique and later implement it in our department. Objective Structured Assessment of Technical Skills (OSATS) and Physician Performance Diagnostic Inventory Scale (PPDI) were obtained before and after the use of the simulator by the five participants in the study. Patients who were operated on after the implementation of the technique were retrospectively reviewed.

RESULTS

 During the simulation, there were 4 cases of pedicle breach out of 24 screws inserted (16.6%). After having completed simulation, participants demonstrated an improvement in OSATS and PPDI (p = 0.039 and 0.042, respectively). Analyzing the answers to the different items of the tests, participants mainly improved in the knowledge (p = 0.038), the performance (p = 0.041), and understanding of the procedure (p = 0.034). In our retrospective series, eight patients with L4-L5 instability were operated on using CBT, improving their Oswestry Disability Index (ODI) score (preoperative ODI 58.5 [SD 16.7] vs. postoperative ODI 31 [SD 13.4]; p = 0.028). One intraoperative complication due to a dural tear was observed. In the follow-up, we found a case of pseudoarthrosis and a facet joint violation, but no other complications related to misplacement, pedicle fracture, or hardware failure.

CONCLUSION

 The simulation we have created is useful for the implementation of CBT. In our study, consultants and trainees have valued very positively the learning obtained using the system. Moreover, simulation facilitated the learning of the technique and the understanding of surgical anatomy. We hope that simulation helps reducing complications in the future.

Language hemispheric dominance analyzed with magnetic resonance DTI: correlation with the Wada test

OBJECTIVE

Language lateralization is a major concern in some patients with pharmacoresistant epilepsy who will face surgery; in these patients, hemispheric dominance testing is essential to avoid further complications. The Wada test is considered the gold standard examination for language localization, but is invasive and requires many human and material resources. Functional MRI and tractography with diffusion tensor imaging (DTI) have demonstrated that they could be useful for locating language in epilepsy surgery, but there is no evidence of the correlation between the Wada test and DTI MRI in language dominance.

METHODS

The authors performed a retrospective review of patients who underwent a Wada test before epilepsy surgery at their institution from 2012 to 2017. The authors retrospectively analyzed fractional anisotropy (FA), number and length of fibers, and volume of the arcuate fasciculus and uncinate fasciculus, comparing dominant and nondominant hemispheres.

RESULTS

Ten patients with temporal lobe epilepsy were reviewed. Statistical analysis showed that the mean FA of the arcuate fasciculus in the dominant hemisphere was higher than in the nondominant hemisphere (0.369 vs 0.329, p = 0.049). Also, the number of fibers in the arcuate fasciculus was greater in the dominant hemisphere (881.5 vs 305.4, p = 0.003). However, no differences were found in the FA of the uncinate fasciculus or number of fibers between hemispheres. The length of fibers of the uncinate fasciculus was longer in the dominant side (74.4 vs 50.1 mm, p = 0.05). Volume in both bundles was more prominent in the dominant hemisphere (12.12 vs 6.48 cm3, p = 0.004, in the arcuate fasciculus, and 8.41 vs 4.16 cm3, p = 0.018, in the uncinate fasciculus). Finally, these parameters were compared in patients in whom the seizure focus was situated in the dominant hemisphere: FA (0.37 vs 0.30, p = 0.05), number of fibers (114.4 vs 315.6, p = 0.014), and volume (12.58 vs 5.88 cm3, p = 0.035) in the arcuate fasciculus were found to be statistically significantly higher in the dominant hemispheres. Linear discriminant analysis of FA, number of fibers, and volume of the arcuate fasciculus showed a correct discrimination in 80% of patients (p = 0.024).

CONCLUSIONS

The analysis of the arcuate fasciculus and other tract bundles by DTI could be a useful tool for language location testing in the preoperative study of patients with refractory epilepsy.

Prediction of Memory Impairment in Epilepsy Surgery by White Matter Diffusion

OBJECTIVE

To analyze the relationship between cognitive performance and white matter integrity in patients with temporal lobe epilepsy (TLE) to establish radiologic criteria to help with patient selection for surgery.

METHODS

The study included 19 adults with temporal lobe epilepsy. A tractography analysis of fractional anisotropy and mean diffusivity (MD) of the following fascicles was performed: arcuate fascicle, cingulum, fornix, inferior fronto-occipital fascicle, inferior longitudinal fascicle, parahippocampal fibers of the cingulum, and uncinate fascicle. The Wechsler Memory Scale-Third Edition neuropsychological test was performed to evaluate short- and long-term verbal (Logical Memory I and II subtests) and nonverbal (Visual Reproduction I and II subtests) memory. Relationships between memory scores and diffusion were calculated.

RESULTS

Lower Logical Memory I subtest scores were correlated with lower MD of the right inferior fronto-occipital fascicle, while lower Logical Memory II subtest scores were related to higher values of fractional anisotropy in bilateral cingulum, right uncinate, and right parahippocampal fibers of the cingulum and lower MD in left cingulum fascicle. Finally, lower values in Visual Reproduction I subtest scores were associated with lower values in MD in right cingulum and inferior fronto-occipital fascicles.

CONCLUSIONS

Structural changes of some white matter tracts were associated with deterioration of both short- and long-term memory. These alterations were more associated with verbal memory than with nonverbal memory. These changes mainly consist of an increase in fractional anisotropy and a decrease in MD, which could be interpreted as reorganization phenomena. Diffusion tensor imaging could be a useful tool for cognitive assessment in surgical candidates with temporal lobe epilepsy who are not suitable for neuropsychological testing or in whom their results do not lead to definitive conclusions.

[Is it possible to extract intracranial pressure information based on the EEG activity?]

INTRODUCTION

The capability of the electroencephalography (EEG) of recording the bioelectrical activity of the brain has made of it a fundamental tool for the evaluation of the patient's neurological condition. In recent years, moreover, it has also begun to be used in obtaining information for other kind of variables, as the ones related with the cerebral hemodynamics.

AIM

To study the potential relationship between the EEG activity and the intracranial pressure (ICP) in patients suffering from traumatic brain injury and subarachnoid hemorrhage, during their stay at the intensive care unit.

PATIENTS AND METHODS

Twenty-one adult patients (10 women) were included in the present observational prospective cohort study. They suffered from either traumatic brain injury or subarachnoid hemorrhage, requiring continuous EEG and ICP monitoring. In every patient, Granger causality between spectral functions of the EEG and the ICP was evaluated. Temporal windows of 10 minute were used to evaluate whether a causal relationship between those variables exist or not. In all of the cases, several days of continuous recording and assessment were performed.

RESULTS

In most patients and during most of the time, Granger causality turns out to be significant in the direction from the EEG to the ICP, meaning that the EEG dynamics actually leads the ICP dynamics.

CONCLUSIONS

The present work provides useful information and shed light in discovering a hidden relationship between the ICP and EEG dynamics. The potential use of this relationship could lead to develop a medical device to measure ICP in a non-invasive fashion.

Potential EEG biomarkers of sedation doses in intensive care patients unveiled by using a machine learning approach

OBJECTIVE

Sedation of neurocritically ill patients is one of the most challenging situation in ICUs. Quantitative knowledge on the sedation effect on brain activity in that complex scenario could help to uncover new markers for sedation assessment. Hence, we aim to evaluate the existence of changes of diverse EEG-derived measures in deeply-sedated (RASS-Richmond agitation-sedation scale  -4 and  -5) neurocritically ill patients, and also whether sedation doses are related with those eventual changes.

APPROACH

We performed an observational prospective cohort study in the intensive care unit of the Hospital de la Princesa. Twenty-six adult patients suffered from traumatic brain injury and subarachnoid hemorrhage were included in the present study. Long-term continuous electroencephalographic (EEG) recordings (2141 h) and hourly annotated information were used to determine the relationship between intravenous sedation infusion doses and network and spectral EEG measures. To do that, two different strategies were followed: assessment of the statistical dependence between both variables using the Spearman correlation rank and by performing an automatic classification method based on a machine learning algorithm.

MAIN RESULTS

More than 60% of patients presented a correlation greater than 0.5 in at least one of the calculated EEG measures with the sedation dose. The automatic classification method presented an accuracy of 84.3% in discriminating between different sedation doses. In both cases the nodes' degree was the most relevant measurement.

SIGNIFICANCE

The results presented here provide evidences of brain activity changes during deep sedation linked to sedation doses. Particularly, the capability of network EEG-derived measures in discriminating between different sedation doses could be the framework for the development of accurate methods for sedation levels assessment.

Morphometrical evaluation of decompression obtained through corpectomy. Heading towards to posterior approaches

INTRODUCTION

We analysed the decompression obtained by dorsal or dorsolumbar corpectomy measured by Cobb angle and the spinal area prior to and after surgery and compared the evolution of the technique over the last five years of the study.

MATERIAL AND METHOD

A retrospective review of patients operated between 2005 and 2015 through anterior or posterior approaches was performed.

RESULTS

24 patients were studied and a significant improvement was observed between the preoperative and postoperative morphometrical measurement (4.18° correction of the kyphosis and an increase of 130.8mm² in the spinal canal, p<.001 in both cases) and in clinical parameters (45.8% of patients improved in ASIA, and Karnofsky showed 13 points of improvement, p<.001 in both cases). However, there was no correlation between clinical and morphological parameters. We also observed that in the last five years of the study posterior approaches were more frequently used with good results.

CONCLUSIONS

Dorsal corpectomy allows significant spinal decompression, with neurological improvement but this does not correlate with the measurement of decompression. Thanks to technical improvements, less invasive techniques (posterior approaches and MISS) allow good clinical results, which are similar to those obtained by anterior techniques.

Identifying causal relationships between EEG activity and intracranial pressure changes in neurocritical care patients

OBJECTIVE

To explore and assess the relationship between electroencephalography (EEG) activity and intracranial pressure (ICP) in patients suffering from traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH) during their stay in an intensive care unit.

APPROACH

We performed an observational prospective cohort study of adult patients suffering from TBI or SAH. Continuous EEG-ECG was performed during ICP monitoring. In every patient, variables derived from the EEG were calculated and the Granger causality (GC) methodology was employed to assess whether, and in which direction, there is any relationship between EEG and ICP.

MAIN RESULTS

One-thousand fifty-five hours of continuous multimodal monitoring were analyzed in 21 patients using the GC test. During 37.88% of the analyzed time, significant GC statistic was found in the direction from the EEG activity to the ICP, with typical lags of 25-50 s between them. When recordings were adjusted by sedation-perfusion and/or bolus-and handling, these percentages hardly changed.

SIGNIFICANCE

Long-lasting, continuous and simultaneous EEG and ICP recordings from TBI and SAH patients provide highly rich and useful information, which has allowed for uncovering a strong relationship between both signals. The use of this relationship could lead to developing a medical device to measure ICP in a non-invasive way.

Image guidance in transdiscal fixation for high-grade spondylolisthesis in adults with correct spinal balance

OBJECTIVE Spondylolisthesis is a prevalent spine disease that recent studies estimate could be detected in 9% of the population. High-grade spondylolisthesis (HGS), however, is much less frequent, which makes it difficult to develop a general recommendation for its treatment. Posterior transdiscal fixation was proposed in 1994 for HGS, and the use of spine navigation could make this technique more accessible and reduce the morbidity associated with the procedure. The purpose of this study was to present a case series involving adult patients with HGS and correct spinal alignment who were treated with transdiscal pedicle screw placement guided with neuronavigation and compare the results to those achieved previously without image guidance. METHODS The authors reviewed all cases in which adult patients with correct spinal alignment were treated for HGS with posterior transdiscal instrumentation placement guided with navigation between 2014 and 2016 at their institution. The authors compared preoperative and postoperative spinopelvic parameters on standing radiographs as well as Oswestry Disability Index (ODI) scores and visual analog scale (VAS) scores for low-back pain. Follow-up CT and MRI studies and postoperative radiographs were evaluated to identify any screw malplacement or instrumentation failure. Any other intraoperative or postoperative complications were also recorded. RESULTS Eight patients underwent posterior transdiscal navigated instrumentation placement during this period, with a mean duration of follow-up of 16 months (range 9-24 months). Six of the patients presented with Meyerding grade III spondylolisthesis and 2 with Meyerding grade IV. In 5 cases, L4-S1 instrumentation was placed, while in the other 3 cases, surgery consisted of transdiscal L5-S1 fixation. There was no significant difference between preoperative and postoperative spinopelvic parameters. However, there was a statistically significant improvement in the mean VAS score for low-back pain (6.5 ± 1.5 vs 4 ± 1.7) and the mean ODI score (49.2 ± 19.4 vs 37.7 ± 22) (p = 0.01 and p = 0.012, respectively). Six patients reduced their use of pain medication. There were no intraoperative or postoperative complications during the hospital stay, and as of the most recent follow-up, no complications related to pseudarthrosis or hardware failure had been observed. CONCLUSIONS Treatment with posterior transdiscal pedicle screws with in situ fusion achieved good clinical and radiological outcomes in patients with HGS and good sagittal spinal balance. The use of navigation and image guidance was associated with improved results in this technique, including a reduction in postoperative and intraoperative complications related to screw malplacement, pseudarthrosis, and instrumentation failure.

[Bilateral two-stage implantation for deep brain stimulation in the treatment of bilateral idiopathic Parkinson's disease: clinical outcomes]

AIMS

Simultaneous bilateral implantation of electrodes in the subthalamic nucleus for idiopathic Parkinson's disease (IPD) is associated with long surgery time, language disorders and post-operative confusion. Moreover, there is evidence of ipsilateral improvement after stimulation of the subthalamic nucleus. In order to optimise perioperative management a prospective study is conducted with deep brain stimulation (DBS) in the subthalamic nucleus in two consecutive unilateral procedures.

PATIENTS AND METHODS

We conducted a prospective study of 41 patients with bilateral IPD, with DBS implantation in two unilateral surgical phases. Its clinical outcomes are analysed according to the Unified Parkinson's Disease Rating Scale (UPDRS), the Hoehn and Yahr, and the Schwab and England scales, together with their complications.

RESULTS

The mean age was 61 ± 7 years old, 23 males. Five patients (12%) did not undergo surgery of the contralateral subthalamic nucleus due to good control. The mean on the motor UPDRS and the Hoehn and Yahr in preoperative pharmacological off was 44 ± 14 and 3, respectively, and 19 ± 8 and 1.8 at six months' follow-up. The mean improvement on the Schwab and England scale in the pre-operative period and at six months was 39%. Two patients suffered post-operative confusion, and one of them had transient dysarthria.

CONCLUSIONS

Bilateral DBS in two unilateral stages was an effective option with few complications in our series of patients with IPD. 10% of the patients did not require contralateral electrodes. It would be necessary to conduct a randomised study in patients who underwent bilateral surgery in one and two stages in order to confirm these results.

[Medullar thoracic compression by tophaceous gout: presentation of a case and review of the literature]

INTRODUCTION

Spine involvement in gout is an extremely uncommon complication. Dorsalgia and quadriplegia are some manifestations that may occur, although these symptoms are seen more frequently in other more prevalent pathologies, such as spinal tumors.

CASE REPORT

We present an unusual case of thoracic spinal cord compression at T10-T11 level caused by the extradural deposit of tophaceous material in a 52-year-old woman with uncontrolled chronic tophaceous gout. In addition to intensive medical treatment, the patient required surgery (hemilaminectomy and spinal decompression) and subsequent rehabilitation. Overall and neurological evolution were satisfactory.

[New thalamic potential associated with somatosensory evoked potentials]

INTRODUCTION

The response of the thalamus during the study with somatosensory evoked potentials (SSEP) is not sufficiently understood.

CASE REPORT

A 17-year-old man undergoing surgery for deep brain stimulation in the centromedian nucleus for drug-resistant epilepsy under complete sedation. During the intervention, the responses to SSEPs of the thalamic nuclei were recorded by means of four microelectrodes. These responses can be decomposed into three types: local field potentials (LFP), low amplitude fast oscillations (LFO), and high amplitude slow oscillations (HSO). LFO are widespread in much of the registered regions. However, HSOs are located at a single point in the registry and are closely associated with LFPs.

CONCLUSIONS

Although the presence of LFO has been considered as an indicator of the presence of the sensory thalamus, its wide extension by different thalamic nuclei suggests that it is an unspecific response to SSEPs. However, the restricted spatial location of HSO and their association with LFP suggest that these newly described potentials are the markers for the presence of the sensory thalamus. Their identification may prove very useful in thalamic deep brain stimulation either in awake patients or especially in those requiring sedation.

Usefulness of Reintervention in Recurrent Glioblastoma: An Indispensable Weapon for Increasing Survival

BACKGROUND

Glioblastoma is the most frequent primary brain tumor and despite of complete treatment survival is still poor. The aim of this study is to define the utility of reoperation for improving survival in patients with recurrent glioblastoma, and determine other prognostic factors associated with longer survival.

METHODS

We performed a retrospective analysis of those patients who underwent surgery and compared those who were operated two or more times and those who received surgery only once. We studied overall survival (OS), progression-free survival (PFS), and clinical variables that could be related with higher survival.

RESULTS

A total of 121 patients were eligible for the study, of whom 31 (25%) underwent reoperation. The reoperation group had a mean and median increase survival of 10.5 and 16.4 months in OS and 3.5 and 2.7 months for PFS compared with the non-reoperation group (P < 0.001 and 0.01, respectively). Although complications were higher in patients that underwent reintervention (19.3%) there was no statistical difference with complication rate in first surgery (12.4%, χ² = 1.86; P = 0.40). Cox multivariable analysis revealed that age (hazard ratio [HR] 1.03; 95% confidence interval [CI], 1.006-1.055; P = 0.013), reoperation (HR, 0.48; 95% CI, 0.285-0.810; P = 0.006), extent of resection >95% (HR, 0.547; 95% CI, 0.401-0.748; P < 0.001), and complete adjuvant therapy (HR, 0.389; 95% CI, 0.208-0.726; P = 0.003) were correlated with a higher OS.

CONCLUSIONS

Reoperation and the extent of resection (EOR) are the only surgical variables that neurosurgeons can modify to improve survival in our patients. Higher EOR and reoperation rates in patients who can be candidates for second surgery, will increase OS and PFS.

[When does post-ictal period start in temporal lobe epilepsy? A quantitative EEG perspective]

INTRODUCTION

In partial seizures, from a clinical point of view or even from electroencephalography characterization of post-ictal period can be difficult. The spectral and complex network analysis could lead to a more accurate definition of its limits, as well as to a great understanding of the seizures.

PATIENTS AND METHODS

Digital EEG recordings from scalp and foramen oval electrodes were used, 32 seizures, from 15 patients with drug-resistant mesial temporal lobe epilepsy (Engel I). We analyzed numerically: the spectral entropy, the different frequency bands and several variables used to characterize the cortical network, density of links, modularity, cluster coefficient and average path length. Variations of for post-ictal versus pre-ictal periods were quantified.

RESULTS

The cortical network density of links increased during the post-ictal period of complex seizures matching with an spectral entropy decrease, mainly due to an increase in Delta band activity. This variables reached extreme values around one minute after seizure end, defined by classical electroencephalography.

CONCLUSIONS

Our results can be explained by the appearance of an 'ending' mechanism that starts in the ictal period, classically defined, and reach their maximum effect during the post-ictal period. These results could be useful to define the post-ictal period start, as the moment with maximum synchrony, which has a highest density of links and a lowest spectral entropy.

[Bromocriptine: could it be the cure for post-surgical akinetic mutism?]

INTRODUCTION

Akinetic mutism is considered as an alteration of the motivational state of the person, which the patient is unable to initiate verbal or motor responses voluntary, even with preserved sensorimotor and surveillance functions.

CASE REPORT

A 43 year-old male involved in a cerebellum arteriovenous fistula complicated with hydrocephalus, who responded dramatically to treatment with bromocriptine.

CONCLUSION

Typically, akinetic mutism is described as a transient surgeries posterior fossa. However, it can also occur after multiple valvular failure in patients with hydrocephalus.

Network Analysis of Foramen Ovale Electrode Recordings in Drug-resistant Temporal Lobe Epilepsy Patients

Approximately 30% of epilepsy patients are refractory to antiepileptic drugs. In these cases, surgery is the only alternative to eliminate/control seizures. However, a significant minority of patients continues to exhibit post-operative seizures, even in those cases in which the suspected source of seizures has been correctly localized and resected. The protocol presented here combines a clinical procedure routinely employed during the pre-operative evaluation of temporal lobe epilepsy (TLE) patients with a novel technique for network analysis. The method allows for the evaluation of the temporal evolution of mesial network parameters. The bilateral insertion of foramen ovale electrodes (FOE) into the ambient cistern simultaneously records electrocortical activity at several mesial areas in the temporal lobe. Furthermore, network methodology applied to the recorded time series tracks the temporal evolution of the mesial networks both interictally and during the seizures. In this way, the presented protocol offers a unique way to visualize and quantify measures that considers the relationships between several mesial areas instead of a single area.

[The role of diffusion tensor imaging in the pre-surgical study of temporal lobe epilepsy]

INTRODUCTION

Diffusion tensor imaging (DTI) is a non-invasive technique that can be used to assess the integrity of the white matter in the brain.

AIMS

To investigate the usefulness of DTI in patients with temporal lobe epilepsy (TLE) and to observe its relationship with lateralisation of the epileptogenic focus in these patients.

PATIENTS AND METHODS

We analysed 11 patients diagnosed with TLE in accordance with the pre-surgical protocol of our epilepsy unit, and who were seizure-free two years after performing a temporal lobectomy plus amygdalohippocampectomy (Spencer technique). As part of their pre-operative study, a 1.5 T magnetic resonance brain scan with diffusion tensor imaging was performed. A voxel-based analysis was then employed to study the differences in connectivity between the hemisphere that underwent surgery and the contralateral hemisphere.

RESULTS

Compared with the contralateral hemisphere, a statistically significant reduction in fractional anisotropy (p < 0.05) was observed in the corpus callosum, the cingulate, the superior longitudinal fasciculus, the anterior thalamic radiations, the internal capsule, the ventral lateral and pulvinar nuclei of the thalamus, the inferior frontooccipital fasciculus, the uncinate fasciculus, the inferior longitudinal fasciculus and the parahippocampal gyrus, all ipsilateral to the epileptogenic focus.

CONCLUSIONS

The characterisation of the abnormalities in the connectivity of the cerebral white matter, by means of DTI in patients with TLE, can be a valuable aid for the lateralisation of the epileptogenic focus in the pre-surgical evaluation of these patients. Further studies with a higher number of patients would be needed to confirm these results.

[Haemorrhagic pineal cysts: two clinical cases successfully treated by means of microsurgery]

INTRODUCTION

Pineal cysts are a relatively frequent incidental finding in imaging tests; yet, pineal apoplexy is considered to be rare and is associated to severe symptoms.

CASE REPORTS

We report the cases of a 25-year-old male and a female aged 15 years who visited the emergency department with signs and symptoms of intracranial hypertension. The existence of a pineal haemorrhage was confirmed by imaging tests. They were successfully treated by means of microsurgery.

CONCLUSION

In our experience, and backed by the literature, we believe that the best treatment for this infrequent pathology is the microsurgical approach. Nevertheless, we do not rule out the possibility that, sometime in the future, endoscopic techniques may play an important role in the treatment of pineal apoplexy.

[Myelopathy secondary to an aneurysmal bone cyst of thoracic spine]

INTRODUCTION

Spinal aneurysmal bone cysts are very infrequent benign osteolytic lesions consisting of blood-filled cavities that are separated by osteo-connective septa and osteoclast-type giant cells. Clinically they manifest with local pain, neurological symptoms secondary to spinal cord compression, and fractures, deformities and vertebral instability. We report a case of an aneurysmal bone cyst in the thoracic spine with neurological signs and symptoms treated by means of a full microsurgical resection, with no associated neurological sequelae.

CASE REPORT

A 47-year-old woman, with no previous history of traumatic injuries, who was examined following several weeks with clinical signs and symptoms of paraesthesia in the lower limbs. Thoracic magnetic resonance imaging revealed the existence of a lytic lesion with clearly defined edges and marginal sclerosis in T4, in addition to involvement of the posterior vertebral elements and compression of the underlying spinal cord. The whole lesion was removed surgically, and the sensitive clinical symptoms disappeared after the procedure. The definite pathological diagnosis was spinal aneurysmal bone cyst.

CONCLUSION

Despite their low incidence, aneurysmal bone cysts of the spine must be taken into account in the differential diagnosis of spinal bone tumours as a possible cause of subacute or chronic compressive myelopathy. Full surgical removal of the tumour is considered the preferred treatment, which is often curative and is associated with a good prognosis of the patient in the long term.

Infratentorial angioleiomyoma: case report and review of the literature

INTRODUCTION

Intracranial angioleiomyomas are extremely rare lesions. Only 22 intracranial angioleiomyomas have been described in the literature and only three were infratentorial.

CASE REPORT

We report a case of an infratentorial angioleiomyoma in a 43 year-old-man, who underwent a brain computer tomography because of hearing loss. The MRI showed a 1.4 cm tumor, initially described as a meningioma, with progressive enhancement after gadolinium injection, an augmented apparent diffusion coefficient and a generalized metabolite decreased in the spectroscopy. The lesion was surgically removed through a suboccipital approach with a good evolution and without postoperative complications. In the immunohistological study, the lesion was mainly composed of multiple vessels and the immunohistochemistry was positive for actin and caldesmon. Two years after surgery, no recurrence has been found in the MRI.

CONCLUSION

Angioleiomyomas diagnostic may be complex, but some radiological features could help in the differential diagnostic. Angioleiomyomas are benign tumors associated with favorable outcomes after total resection, that in our case, did not show a significant bleeding risk.

Classification of structural lesions in magnetic resonance imaging. Surgical implications in drug-resistant epilepsy patients

INTRODUCTION

The presence of a structural lesion in the preoperative magnetic resonance imaging (MRI) of drug-resistant epilepsy patients has been usually associated with a favourable surgical outcome. We present our experience in our Epilepsy Surgery Unit.

PATIENTS AND METHODS

Clinical records from 265 patients, operated on from 1990-2010 in our institution, were reviewed. Patients were classified, according to MRI findings, into three groups: surgical lesion (SL), tumors or vascular malformations requiring surgery 'per se'; orientative lesion (OL), dysplasia, atrophy or mesial temporal sclerosis; and (NL) group, with normal MRI. Seizure outcomes were analysed in relation to this classification.

RESULTS

Period 1990-2000, 151 patients: 87% of SL, 65% of OL and 57% of NL patients were in Engel class I or II at the two-year follow-up. Among temporal lobe epilepsy cases (TLE), 87% of SL, 67% of OL and 56% of NL patients achieved seizure control. Differences were statistically significative. Period 2001-2010, 114 patients: 100% of SL, 90% of OL, and 81% of NL patients were in Engel's class I or II. Both TLE and extratemporal (ETLE) SL patients obtained a 100% seizure control. Among the OL patients, 95% with TLE and 43% of ETLE achieved seizure control. In the NL group, the percentages were 88% in TLE, and 50% in ETLE.

CONCLUSIONS

In our series, SL was a predictor of a favorable outcome. In TLE patients, good results were achieved despite normal MRI. Patients with ETLE and NL did not have a worse outcome than those with OL. A classification in SL, OL and NL seems more helpful for predicting the surgical outcome than the traditional classification lesion versus non-lesion MRI. Radiological findings must be carefully evaluated in the context of a complete epilepsy surgery evaluation.

[Stimulation of the centromedian nucleus in refractory epilepsy associated to ring chromosome 20]

INTRODUCTION

Ring chromosome 20 syndrome is a rare genetic disorder, with a late diagnosis.

CASE REPORT

A 43-year-old woman who had had refractory epilepsy since the age of six years, for which she was treated with deep brain stimulation of the centromedian nucleus, and also a ring chromosome 20.

CONCLUSIONS

From the findings of the study it can be concluded that deep brain stimulation of the centromedian nucleus is ineffective in patients with ring chromosome, but note must be taken of the importance of genetic characterisation for the management of refractory epilepsy.

[Occipital nerve stimulation for refractory chronic migraine]

INTRODUCTION

Occipital nerve stimulation (ONS) is an emerging and promising preventive treatment for refractory chronic migraine.

AIM

To evaluate the mechanisms of actions, clinical studies, implantation techniques and inclusion criteria of the ONS as a preventive treatment for migraine.

DEVELOPMENT

This work includes a non-systematic review of the literature on the above-mentioned aspects of ONS as a treatment for refractory chronic migraine. This disease affects approximately 2% of the population and results in a significant impairment in quality of life, economic burden and interference with labor and social activities. ONS is an emerging and promising therapy for the treatment of chronic migraine with greater than 50% pain reduction in most of open-label studies and published clinical trials. Although the mechanisms of action remain unknown, there seem to be a neuromodulation of the transmitted nociceptive trigeminal information in the trigeminal caudal nucleus, what could be explained by means of the Melzack and Wall pain gate theory. ONS is a safe and well tolerated treatment, and its most frequent side effects are usually local such as electrodes displacement or infections of the surgical incision. These complications do not usually require the electrodes withdrawal.

CONCLUSIONS

ONS is an effective, well tolerated and safe treatment for the prevention of chronic migraine and could emerge as a useful option for those patients with medically refractory chronic migraine.

Intrasellar chordoma associated with a primitive persistent trigeminal artery

Chordomas located primarily in the sellar region are uncommon, and may be misdiagnosed non-functioning pituitary adenoma. Furthermore, the association of a persistent primitive trigeminal artery (PPTA) with an intrasellar chordoma is extremely rare, and no similar cases have been reported in the literature to date. The coexistence of intrasellar chordoma (ISC) and PPTA makes safe and complete tumor resection challenging, and preoperative endovascular occlusion of this artery may be helpful. We report a case of a 32-year-old man who developed right hemifacial paresthesias and a cranial nerve six palsy. MRI study demonstrated the presence of a primary ISC associated with a PPTA. Angiographic balloon test occlusion of the PPTA revealed no neurological changes, so this vessel was endovascularly occluded by coiling. The lesion was subtotally removed through a sublabial transsphenoidal approach, without intraoperative bleeding complications. Histological examination of the lesion was consistent with the diagnosis of chordoma. Detailed preoperative neurovascular evaluation may be useful to detect vascular anomalies associated with intracranial chordomas, such as PPTA. In this report we emphasize the importance of appropriate treatment of vascular anomalies prior intrasellar lesions resection that may facilitate surgery and avoid potential hazardous intraoperative bleeding complications.

[Chronic subdural haematomas. The internal architecture of the haematoma as a predictor of recurrence]

INTRODUCTION

The internal architecture of a chronic subdural haematoma (CSDH) is an important factor that must be taken into account as a predictor of recurrence.

AIM

To analyse the factors that are possibly associated to the recurrence of CSDH, with special emphasis on the above-mentioned architecture.

PATIENTS AND METHODS

We reviewed 147 patients treated between 2010 and 2013. The CSDH were classified into four types, in accordance with Nakaguchi's classification published in 2001. Moreover, we gathered different clinical characteristics and they were submitted to a statistical analysis in order to evaluate the possible association between them and the rate of recurrence of CSDH.

RESULTS

The rate of recurrence was 14.75% and the mortality rate was 4.76%. Treatment with anticoagulants, the type of haematoma and not using subdural drainage were statistically significant risk factors for the recurrence of CSDH. In terms of the internal architecture, the rate of recurrence was 36.36% for the separated type, 15.90% for the laminar type, 8.82% for the homogenous and 0% for the trabecular type. This rate was significantly higher in the separated type with respect to the homogenous and trabecular types.

CONCLUSIONS

We have observed that treatment with anticoagulants and not using subdural drainage are risk factors for the recurrence of CSDH. Furthermore, dividing CSDH up in accordance with Nakaguchi's classification can be useful for predicting the risk of relapse, since the rate of recurrence of the separated type was significantly greater than that of the other types.

[Electroclinical characteristics of a patient with ring chromosome 20 syndrome]

INTRODUCTION

The ring chromosome 20 syndrome (r20) is a rare genetic disorder with a late diagnosis.

CASE REPORT

A 17 year old boy with drug-resistant epilepsy of 14 years of evolution, which has moderate mental retardation, behavioral alterations and seizures consisting of complex non-convulsive status and generalized seizures during wakefulness, along with more subtle epileptic manifestations during sleep. Karyotype in peripheral blood showed the existence of a ring chromosome 20, whose breakpoints were p13q13.3, presenting a mosaicism 46,XY[23]/46,XY,r(20)(p13q13.3)[25].

CONCLUSIONS

The epileptic r20 syndrome seems to have a characteristic electroclinical phenotype and, although not pathognomonic, should be sufficient for all patients who meet a karyotype in peripheral blood, thus avoiding multiple trials with unnecessary drugs and exhaustive studies. In this sense, the study of sleep EEG may be helpful.

[Functional connectivity and complex networks in focal epilepsy. Pathophysiology and therapeutic implications]

INTRODUCTION

The traditional surgical approach to treat drug-resistant focal epileptic patients is in the resection or disconnection of the epileptic focus. However, a significant minority of patients continue to experience seizures after surgery, which shows the incomplete level of knowledge that currently we have of this pathology.

AIM

This paper introduces some concepts of functional connectivity and complex networks methodology with its application to the study of neurophysiological recordings from patients suffering from drug-resistant focal epilepsy.

DEVELOPMENT

In order to fully understand the new developments in the area of complex networks and its applications to the study of epilepsy, we will here review fundamental concepts in complex networks methodology, synchronization and functional connectivity. Some of the most recent published works dealing with focal epilepsy viewed under this new perspective will be revised and commented.

CONCLUSIONS

We think that a wider perspective in the study of epilepsy, such as the one reviewed in this work, will allow epileptologists to consider surgical alternatives in the usual treatment of focal epilepsy at those currently performed in most medical centers around the world. Combining the traditional knowledge with new insights provided by network theory will certainly fill many of the gaps we have today in the fragmented understanding of epilepsy.

Influence of paroxysmal activity on background synchronization in epileptic recordings

BACKGROUND

The presence of spikes and sharp waves in recordings of epileptic patients contaminates background signal synchronization. When estimating functional connectivity between extended cortical areas, the influence of epileptic spikes in specific areas should be considered; however, this step is sometimes overlooked. We present a simple method for quantifying the influence of epileptic activity on background signal synchronization.

METHOD

Standard synchronization measures were calculated for both pure correlated Gaussian signals and correlated Gaussian signals with different levels of epileptic spikes in order to determine the influence of epileptic activity on synchronization estimates.

RESULTS

Synchronization from invasive epileptic recordings (e.g., depth electrodes) displays a much higher bias due to epileptic activity than superficial electrodes. Moreover, statistical methods such as mutual information are more affected by spike presence than phase synchronization methods. The influence of spikes is far greater at low values of background synchronization.

CONCLUSIONS

The information provided by this procedure makes it possible to differentiate true background synchronization from spike synchronization. Thus, our procedure serves as a guide for analyzing synchronization and functional connectivity calculations in epileptic recordings.

Role of intraoperative neurophysiological monitoring during fluorescence-guided resection surgery

BACKGROUND

Fluorescence-guided resection (FGR) using 5-aminolevulinic acid (5-ALA) exhibits a potential risk of permanent neurological deficits that can be minimized using intraoperative neurophysiological monitoring (IONM). We assessed the role of IONM in FGR surgery in patients harboring tumors in or near eloquent areas.

METHODS

IONM and FGR surgeries were performed on 34 patients (49.8 ± 2.4 years) harbored malignant primary gliomas near eloquent cortical areas or semioval center. Different combinations of neurophysiological techniques were used depending on each patient.

RESULTS

Gross total resection (GTR) was achieved in 66.7 % of the patients, mean 90.4 ± 3.7 % without neurological deficits. Resection in four patients was stopped by the occurrence of severe warning criteria despite the presence of fluorescence. Hemispheric transcranial electrical stimulation was safe and confident even in cortical surgery. Notably, a significant percentage of patients exhibited clinical improvement after the surgery. One week after surgery, only one patient worsened, and seven patients improved. At 3 months, 27.8 % of the patients improved, and the other patients maintained a similar status to their pre-surgery condition. Warning common criteria (amplitude reduction and/or latency increase) appeared in 68.2 and 50.0 % of patients during cortical or semioval surgery, respectively, with neither a false-negative nor a false-positive clinical outcome. Although 5-ALA exhibits phototoxicity, VEP did not induce any secondary effects in the visual system, including eyelids.

CONCLUSIONS

IONM can be helpful during surgery to maximize the tumor resection, meanwhile help to avoid neurological deficits and, therefore, to improve the quality of life of these patients.

Long-term results of posteromedial hypothalamic deep brain stimulation for patients with resistant aggressiveness

OBJECT

Erethism describes severe cases of unprovoked aggressive behavior, usually associated with some degree of mental impairment and gross brain damage. The etiology can be epileptic, postencephalitic, or posttraumatic, or the condition can be caused by brain malformations or perinatal insults. Erethism is often refractory to medication, and patients must often be interned in institutions, where they are managed with major restraining measures. The hypothalamus is a crucial group of nuclei that coordinate behavioral and autonomic responses and play a central role in the control of aggressive behavior. Deep brain stimulation (DBS) of the posteromedial hypothalamus (PMH) has been proposed as a treatment for resistant erethism, although experience with this treatment around the world is scarce. The objective of this study was to examine the long-term outcome of PMH DBS in 6 patients with severe erethism treated at the authors' institution.

METHODS

Medical records of 6 patients treated with PMH DBS for intractable aggressiveness were reviewed. The therapeutic effect on behavior was assessed by the Inventory for Client and Agency Planning preoperatively and at the last follow-up visit.

RESULTS

Two patients died during the follow-up period due to causes unrelated to the neurosurgical treatment. Five of 6 patients experienced a significant reduction in aggressiveness (the mean Inventory for Client and Agency Planning general aggressiveness score was -47 at baseline and -25 at the last follow-up; mean follow-up 3.5 years). Similar responses were obtained with low- and high-frequency stimulation. In 4 cases, the patients' sleep patterns became more regular, and in 1 case, binge eating and polydipsia ceased. One of the 3 patients who had epilepsy noticed a 30% reduction in seizure frequency. Another patient experienced a marked sympathetic response with high-frequency stimulation during the first stimulation trial, but this subsided when stimulation was set at low frequency. A worsening of a previous headache was noted by 1 patient. There were no other side effects.

CONCLUSIONS

In this case series, 5 of 6 patients with pathological aggressiveness had a reduction of their outbursts of violence after PMH DBS, without significant adverse effects. Prospective controlled studies with a larger number of patients are needed to confirm these results.

[Neurophysiological assisted transsulcal approach to a high grade glioma without affect neither motor nor somatosensory function]

INTRODUCTION

Intraoperative mapping and neuronavigation permitted a safe approach through the rolandic sulcus, minimizing the impact onto the motor or somatosensory functions. Fluorescence-guide resection defines a limit that allows a total resection without exceed the border of the tumor.

CASE REPORT

A 39-year-old man who was operated by a tumor placed into the rolandic area. With the patient anesthetized (propofol+remyfentanil), we performed cortical mapping, neuronavigation and fluorescence-guide resection with 5-aminolevulinic acid. Post-resection neurophysiologic assessment showed a minor and highly localized effect onto the somato-sensory system.

CONCLUSION

Rolandic area surgery can be safely performed in anesthetized patients when extensive neurophysiological, anatomical and biological assessments are performed.

[Contamination of paroxysmal activity in quantitative EEG methods in epileptic patients]

INTRODUCTION. The presence of an acute spike-wave pattern in the recordings of epileptic patients can contaminate the calculated synchronisation values between pairs of electrodes. MATERIALS AND METHODS. We present a simple procedure, involving a numeric simulation of a bivariate electroencephalogram recording with paroxysmal activity, to determine whether or not a method for quantifying synchronisation must be used on any of the recordings that are typically employed in the preoperative evaluation of patients with epilepsy. RESULTS. The information provided by this procedure makes it possible to distinguish between the authentic synchronisation of baseline activity and that produced by paroxysmal activity, such as acute spike-wave patterns. The procedure developed in this study makes it possible to quantify the degree of 'contamination' produced by the synchronisation of the paroxysmal activity on the synchronisation values of the baseline activity. CONCLUSIONS. The issue addressed in this work is of fundamental importance when automatic methods are utilised in the clinical applications of quantitative electroencephalography and can help to prevent diagnostic errors in which synchronisation is used as a marker of the pathology.

Long-term results of vagal nerve stimulation for adults with medication-resistant epilepsy who have been on unchanged antiepileptic medication

PURPOSE

Several studies suggest that vagal nerve stimulation (VNS) is an effective treatment for medication-resistant epileptic patients, although patients' medication was usually modified during the assessment period. The purpose of this prospective study was to evaluate the long-term effects of VNS, at 18 months of follow-up, on epileptic patients who have been on unchanged antiepileptic medication.

METHODS

Forty-three patients underwent a complete epilepsy preoperative evaluation protocol, and were selected for VNS implantation. After surgery, patients were evaluated on a monthly basis, increasing stimulation 0.25mA at each visit, up to 2.5mA. Medication was unchanged for at least 18 months since the stimulation was started. The outcome was analysed in relation to patients' clinical features, stimulation parameters, epilepsy type, magnetic resonance imaging (MRI) results, and history of prior brain surgery.

RESULTS

Of the 43 operated patients, 63% had a similar or greater than 50% reduction in their seizure frequency. Differences in the responder rate according to stimulation intensity, age at onset of epilepsy, duration of epilepsy before surgery, previous epilepsy surgery and seizure type, did not reach statistical significance. Most side effects were well tolerated.

CONCLUSIONS

62.8% of our series of 43 medication-resistant epileptic patients experienced a significant long-term seizure reduction after VNS, even in a situation of on unchanged medical therapy. Patient characteristics predictive of VNS responsiveness remain subject to investigation. Controlled studies with larger sample sizes, on VNS for patients with medication-resistant epilepsy on unchanged medication, are necessary to confirm VNS efficacy for drug-resistant epilepsy, and to identify predictive factors.

[Continuous monitoring of cortical visual evoked potentials by means of subdural electrodes in surgery on the posterior optic pathway. A case report and review of the literature]

INTRODUCTION

Intraoperative monitoring of functional language and motor areas is a commonly used technique which makes it possible to minimise the post-operative sequelae and to perform an optimal resection of lesions in these areas. Monitoring of the visual cortex, however, is not usually carried out nowadays. The scarce spatial resolution and its sensitivity to anaesthesia are some of the technical difficulties that reduce its clinical usefulness. The study reports a case of resection of an occipital lesion under general anaesthetic, with intraoperative monitoring of the cortical visual evoked potentials (VEP) by means of subdural electrodes.

CASE REPORT

A 50-year-old female who underwent surgery involving the resection of an occipital lesion that was suggestive of radionecrosis. The VEP were monitored by administering flashing light at 4.1 Hz and recording with subdural strip electrodes on the occipital cortex. During the operation, a progressive lowering of the amplitude of the cortical VEP was observed when 50% of the baseline amplitude was exceeded, and thus the resection was finished. The increase in latency was below 10% of the baseline value. The patient recovered well during the post-operative period and her sight did not present any changes with respect to the baseline values.

CONCLUSIONS

In our case, monitoring the cortical VEP by cortical recordings produced stable recordings with a good correlation with the post-operative visual function. Cortical recordings performed either directly or by means of subdural electrodes make it possible to achieve adequate spatial resolution and response intensity. Further studies need to be conducted with a greater number of patients in order to obtain decisive conclusions.

[Significance of complex analysis of electrical activity in temporal lobe epilepsy: electrocorticography]

INTRODUCTION

Locating and excising epileptogenic zones is the traditional treatment in pharmacoresistant temporal lobe epilepsy. Some patients, however, continue to suffer from attacks even after surgery. Therefore, new hypotheses must be formulated in order to account for the apparent shortcomings of correctly performed surgical procedures.

AIMS

An approach that is not traditional in the field, namely complex networks, is used to attempt to show that modifying the properties of the limbic network can lead to the elimination of the attacks, regardless of the location of the epileptogenic zones.

PATIENTS AND METHODS

The intraoperative electrocorticographic recordings of 20 patients with pharmacoresistant temporal lobe epilepsy were utilised in the study. An analysis of complex networks was used to study the local synchronisation activity in the lateral and mesial cortex of the temporal lobe and, essentially, the zones with the highest temporal stability were determined.

RESULTS

Those cortical zones with higher synchronic activity are associated with a greater temporal stability and when these zones are excised during surgery, the patient no longer suffers any disabling attacks. In contrast, when these zones are not excised, the patient continues to have attacks in the post-operative period.

CONCLUSIONS

The findings support the hypothesis of the existence of a limbic network, which the lateral and mesial cortices of the temporal lobe are part of, and whose capacity to establish an overall synchronisation is affected when certain zones are removed.

[Intracerebral neurenteric cysts in newborn infants]

INTRODUCTION

Intracranial neurenteric cysts are very infrequent congenital lesions. Within the nervous system, they are most commonly located in the rachis. Another frequent site is the craniocervical junction. Few cases of supratentorial location have been reported. A differential diagnosis is required to distinguish them from other cysts. They are not often diagnosed in the paediatric age. The clinical features they give rise to are due to the mass effect or episodes of chemical meningitis. Magnetic resonance imaging is the best diagnostic method although on many occasions they cannot be distinguished from arachnoid cysts. Treatment consists in surgery with complete resection of the membranes in order to prevent recurrences.

CASE REPORTS

We report two cases of infants who, in the last weeks of gestation, presented supratentorial intracerebral cystic lesions that resembled arachnoid cysts. A neonatal magnetic resonance scan confirmed the existence of such supratentorial cysts with septae inside them. After presenting an increase in the cranial perimeter, surgical treatment was undertaken with a neuronavigation-guided craniotomy and debridement of the cysts. The cysts contain mucus and have thick membranes. Pathological study results are consistent with a neurenteric cyst. One of the patients presented complete resolution after the intervention with good cerebral expansion. In the second case, there was persistence of an adjoining arachnoid cyst, in which placement of a cyst-peritoneal shunt was necessary with full resolution.

CONCLUSIONS

Most intracranial cysts are arachnoid cysts, but there are other cystic lesions that must be treated by surgical means so that they can be completely excised and sent for pathological analyses.

[Neurosurgical techniques for the neuromodulation of pain]

Neuromodulation for treating pain goes back to the times of the ancient Egyptians, who applied natural electric currents to modulate the painful sensation. Since then, this concept has been developed in parallel with the scientific and technological development, and various forms of neuromodulation with different indications and characteristics have originated. Chronic pain may produce significant disability, which leads to important physical, social and psychological consequences. Peripheral nerve, spinal cord, deep brain and motor cortex stimulation are safe and effective techniques that control pain and improve quality of life in selected patients.