Lateralization of mesial temporal lobe epilepsy with chronic ambulatory electrocorticography

A Comparison of Machine Learning Classifiers for Energy-Efficient Implementation of Seizure Detection

The closed-loop application of electrical stimulation via chronically implanted electrodes is a novel approach to stop seizures in patients with focal-onset epilepsy. To this end, an energy efficient seizure detector that can be implemented in an implantable device is of crucial importance. In this study, we first evaluated the performance of two machine learning algorithms (Random Forest classifier and support vector machine (SVM)) by using selected time and frequency domain features with a limited need of computational resources. Performance of the algorithms was further compared to a detection strategy implemented in an existing closed loop neurostimulation device for the treatment of epilepsy. The results show a superior performance of the Random Forest classifier compared to the SVM classifier and the reference approach. Next, we implemented the feature extraction and classification process of the Random Forest classifier on a microcontroller to evaluate the energy efficiency of this seizure detector. In conclusion, the feature set in combination with Random Forest classifier is an energy efficient hardware implementation that shows an improvement of detection sensitivity and specificity compared to the presently available closed-loop intervention in epilepsy while preserving a low detection delay.

Responsive brain stimulation in epilepsy

Stimulation devices are considered in patients with drug-resistant epilepsy and who are not surgical candidates. Responsive neurostimulation (RNS) is a cortically based stimulator activated by electrocorticography (ECoG) patterns. Stimulation is applied directly to the seizure focus. The vagal nerve stimulator AspireSR 106 is also a responsive device which, in addition to basal stimulation, is activated by tachycardia. Deep brain stimulation of the anterior nucleus of the thalamus is used in Europe for intractable epilepsy and yields similar response rates to RNS using duty cycle stimulation. Chronic subthreshold cortical stimulation is an experimental form of constant, low-level stimulation applied to a seizure focus. These modalities are discussed and compared in this review.

The phenotype of bilateral hippocampal sclerosis and its management in "real life" clinical settings

OBJECTIVE

There is little detailed phenotypic characterization of bilateral hippocampal sclerosis (HS). We therefore conducted a multicenter review of people with pharmacoresistant epilepsy and bilateral HS to better determine their clinical characteristics.

METHODS

Databases from 11 EPIGEN centers were searched. For identified cases, clinicians reviewed the medical notes, imaging, and electroencephalographic (EEG), video-EEG, and neuropsychometric data. Data were irretrievably anonymized, and a single database was populated to capture all phenotypic information. These data were compared with phenotyped cases of unilateral HS from the same centers.

RESULTS

In total, 96 patients with pharmacoresistant epilepsy and bilateral HS were identified (43 female, 53 male; age range = 8-80 years). Twenty-five percent had experienced febrile convulsions, and 27% of patients had experienced status epilepticus. The mean number of previously tried antiepileptic drugs was 5.32, and the average number of currently prescribed medications was 2.99; 44.8% of patients had cognitive difficulties, and 47.9% had psychiatric comorbidity; 35.4% (34/96) of patients continued with long-term medical therapy alone, another 4 being seizure-free on medication. Sixteen patients proceeded to, or were awaiting, neurostimulation, and 11 underwent surgical resection. One patient was rendered seizure-free postresection, with an improvement in seizures for 3 other cases. By comparison, of 201 patients with unilateral HS, a significantly higher number (44.3%) had febrile convulsions and only 11.4% had experienced status epilepticus. Importantly, 41.8% (84/201) of patients with unilateral HS had focal aware seizures, whereas such seizures were less frequently observed in people with bilateral HS, and were never observed exclusively (P = .002; Fisher's exact test).

SIGNIFICANCE

The current work describes the phenotypic spectrum of people with pharmacoresistant epilepsy and bilateral HS, highlights salient clinical differences from patients with unilateral HS, and provides a large platform from which to develop further studies, both epidemiological and genomic, to better understand etiopathogenesis and optimal treatment regimes in this condition.

The surgical outcome of patients with bilateral temporal lobe epilepsy

OBJECTIVES

The purpose of this study is to explore the surgical outcome of unilateral anterior temporal lobectomy (ATL) for patients with bilateral temporal lobe epilepsy (BTLE).

METHODS

We retrospectively reviewed the data of patients who were diagnosed with BTLE by scalp electroencephalogram (EEG) and underwent ATL from 2001 to 2015. In addition, 80 patients were randomly selected as a control group.

RESULTS

One hundred seventeen patients were included in this study and were divided into four groups by intracranial recordings as follows: 78 patients with unilateral seizure onset (Group 1), 13 patients with lateralizable dominant seizure onset (Group 2), 14 patients with lateralizable neuroimaging abnormalities (Group 3), and 12 patients without lateralizable dominant seizure onset or neuroimaging abnormalities (Group 4). The 12 patients in Group 4 declined surgical resection, whereas the remaining 105 patients received ATL, and 93 of them were followed up for more than 1 year after surgery. At the 1-, 2-, and 3-year follow-ups the percentage of patients who were seizure free was 52.9%, 56.5%, and 58.9%, respectively. For the mean postoperative efficacy, there was a statistical difference in patients who were seizure free either between Group 1 + Group 2 + Group 3 and the control group (44.1% vs. 67.5%, p = 0.002), or between Group 1 and the control group (48.5% vs. 67.5%, p = 0.019), or between Group 2 + Group 3 and the control group (32.0% vs. 67.5%, p = 0.002). However, the difference was significant only at the first year follow-up, and there was no significant difference afterward.

SIGNIFICANCE

Although the surgical outcome of patients with BTLE is not as good as that of patients with unilateral TLE in short-term follow-up, quite a portion of these patients could benefit from unilateral temporal lobe resection in the long term.

Seizure localization by chronic ambulatory electrocorticography

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Two epilepsy patients did not have seizures during three weeks of intracranial EEG.

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They were implanted with a device that enables chronic electrocorticography.

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Seizures were localized by ictal recordings at long intervals after implantation.

Aims

To present two patients with medically-refractory focal epilepsy who, following non-diagnostic intracranial monitoring studies, had seizures localized by chronic ambulatory electrocorticography with an implanted neurostimulation device.

Methods

Case reports with clinical details and electrocorticograms showing seizures.

Results

Using electrodes placed at the suspected seizure onset zones, the neurostimulator recorded seizures in both patients at long intervals following implantation (49 days and 7.5 months).

Conclusions

Chronic ambulatory electrocorticography can provide valuable diagnostic information when there is a narrow hypothesis about seizure localization, though there are important caveats related to limited spatial sampling.

Surgical treatment for refractory epilepsy

The goal of any epilepsy surgery is to improve patient's quality of life by achieving seizure freedom or by reducing the frequency of severely debilitating seizures. To achieve this goal, non-invasive and invasive diagnostic methods must precisely delineate the epileptogenic zone (EZ), which is defined as the area that needs to be resected to obtain seizure freedom. At the same time, the correct identification of eloquent brain areas is inevitable to avoid new neurological deficits from surgery. In recent years, the technical advances in diagnostics have enabled us to achieve these goals in an increasing number of cases. As a consequence, and with new surgical treatment options available, the number of patients who might benefit from epilepsy surgery is constantly increasing. Especially in pediatric epilepsy, early surgical intervention is becoming frequently advocated as it has been shown to improve cognitive and behavioral outcome. Specialized epilepsy centers and multidisciplinary teams are required to provide adequate care and treatment. The goal of this review is to describe important diseases that are accessible to epilepsy surgery and to give an overview of current diagnostic methods. The focus lies on established as well as novel techniques in epilepsy surgery. The presurgical work-up and patient selection is outlined.

The impact of stereotactic laser ablation at a typical epilepsy center

PURPOSE

Stereotactic laser ablation (SLA) is a novel form of epilepsy surgery for patients with drug-resistant focal epilepsy. We evaluated one hundred consecutive surgeries performed for patients with epilepsy to address the impact of SLA on our therapeutic approach, as well as patient outcomes.

METHODS

A retrospective, single center analysis of the last one hundred neurosurgeries for epilepsy was performed from 2013 to 2015. Demographics, surgical procedures, and postoperative measures were assessed up to 5years to compare the effect of SLA on outcome. Confidence intervals (CI) and comparative tests of proportions compared outcomes for SLA and resective surgery. Procedural categorical comparison used Chi-square and Kaplan-Meier curves. Student t-test was utilized for single variables such as age at procedure and seizure onset.

RESULTS

One hundred surgeries for epilepsy yielded thirty-three SLAs and twenty-one resections with a mean of 21.7-month and 21.3-month follow-up, respectively. The temporal lobe was the most common target for SLA (92.6%) and resection (75%). A discrete lesion was present on brain magnetic resonance imaging (MRI) in 27/32 (84.4%) of SLA patients compared with 7/20 (35%) of resection patients with a normal MRI. Overall, 55-60% of patients became seizure-free (SF). Four of five patients with initial failure to SLA became SF with subsequent resection surgery. Complications were more frequent with resection although SF outcomes did not differ (Chi square; p=0.79). Stereotactic laser ablation patients were older than those with resections (47.0years vs. 35.4years, p=0.001). The mean length of hospitalization prior to discharge was shorter for SLA (1.18days) compared with open resection (3.43days; SD: 3.16 days) (p=0.0002).

CONCLUSION

We now use SLA as a first line therapy at our center in patients with lesional temporal lobe epilepsy (TLE) before resection. Seizure-free outcome with SLA and resection was similar but with a shorter length of stay. Long-term follow-up is recommended to determine sustained SF status from SLA.

Changes in the electrocorticogram after implantation of intracranial electrodes in humans: The implant effect

OBJECTIVE

Subacute and long-term electrocorticographic (ECoG) changes in ambulatory patients with depth and cortical strip electrodes were evaluated in order to determine the length of the implant effect.

METHODS

ECoG records were assessed in patients with medically intractable epilepsy who had depth and/or strip leads implanted in order to be treated with brain-responsive stimulation. Changes in total spectral power, band-limited spectral power, and spike rate were assessed.

RESULTS

121 patients participating in trials of the RNS® System had a total of 93994 ECoG records analyzed. Significant changes in total spectral power occurred from the first to second months after implantation, involving 55% of all ECoG channels (68% of strip and 47% of depth lead channels). Significant, but less pronounced, changes continued over the 2nd to 5th post-implant months, after which total power became more stable. Similar patterns of changes were observed within frequency bands and spike rate.

CONCLUSIONS

ECoG spectral power and spike rates are not stable in the first 5 months after implantation, presumably due to neurophysiological and electrode-tissue interface changes.

SIGNIFICANCE

ECoG data collected in the first 5 months after implantation of intracranial electrodes may not be fully representative of chronic cortical electrophysiology.

Recent developments in the surgical management of paediatric epilepsy

Among the 1% of children affected by epilepsy, failure of pharmacological therapy and early age of seizure onset can lead to worse long-term cognitive outcomes, mental health disorders and impaired functional status. Surgical management often improves functional and cognitive outcomes in children with medically refractory epilepsy, especially when seizure remission is achieved. However, surgery remains underused in children with drug-resistant epilepsy, creating a large treatment gap. Several recent innovations have led to considerable improvement in surgical technique, including the recent development of minimally invasive diagnostic and therapeutic techniques such as stereotactic EEG, transcranial magnetic stimulation, MRI-guided laser ablation, as well as novel paradigms of neurostimulation. This article discusses the current landscape of surgical innovation in the management of paediatric epilepsy, leading to a paradigm shift towards minimally invasive therapy and closing the treatment gap in children suffering from drug-resistant seizures.

Failed epilepsy surgery: is this the end?

Resective epilepsy surgery can lead to sustained seizure control in 70-80% of patients evaluated for epilepsy surgery, indicating that up to 30% of patients still have recurrent seizures after surgery. Definitions of failed epilepsy surgery vary amongst studies. This review focuses on seizure outcome predictors after reoperation, possible mechanisms of failure and best management for this difficult patient population.

Chronic ambulatory electrocorticography from human speech cortex

Direct intracranial recording of human brain activity is an important approach for deciphering neural mechanisms of cognition. Such recordings, usually made in patients with epilepsy undergoing inpatient monitoring for seizure localization, are limited in duration and depend on patients' tolerance for the challenges associated with recovering from brain surgery. Thus, typical intracranial recordings, similar to most non-invasive approaches in humans, provide snapshots of brain activity in acute, highly constrained settings, limiting opportunities to understand long timescale and natural, real-world phenomena. A new device for treating some forms of drug-resistant epilepsy, the NeuroPace RNS® System, includes a cranially-implanted neurostimulator and intracranial electrodes that continuously monitor brain activity and respond to incipient seizures with electrical counterstimulation. The RNS System can record epileptic brain activity over years, but whether it can record meaningful, behavior-related physiological responses has not been demonstrated. Here, in a human subject with electrodes implanted over high-level speech-auditory cortex (Wernicke's area; posterior superior temporal gyrus), we report that cortical evoked responses to spoken sentences are robust, selective to phonetic features, and stable over nearly 1.5 years. In a second subject with RNS System electrodes implanted over frontal cortex (Broca's area, posterior inferior frontal gyrus), we found that word production during a naming task reliably evokes cortical responses preceding speech onset. The spatiotemporal resolution, high signal-to-noise, and wireless nature of this system's intracranial recordings make it a powerful new approach to investigate the neural correlates of human cognition over long timescales in natural ambulatory settings.

Management of Adult Onset Seizures

Epilepsy is a common yet heterogeneous disease. As a result, management often requires complex decision making. The ultimate goal of seizure management is for the patient to have no seizures and no considerable adverse effects from the treatment. Antiepileptic drugs are the mainstay of therapy, with more than 20 medications currently approved in the United States. Antiepileptic drug selection requires an understanding of the patient's epilepsy, along with consideration of comorbidities and potential for adverse events. After a patient has failed at least 2 appropriate antiepileptic drugs, they are determined to be medically refractory. At this time, additional therapy, including dietary, device, or surgical treatments, need to be considered, typically at a certified epilepsy center. All these treatments require consideration of the potential for seizure freedom, balanced against potential adverse effects, and can have a positive effect on seizure control and quality of life. This review article discussed the treatment options available for adults with epilepsy, including medical, surgical, dietary, and device therapies.

Recurring Functional Interactions Predict Network Architecture of Interictal and Ictal States in Neocortical Epilepsy

Human epilepsy patients suffer from spontaneous seizures, which originate in brain regions that also subserve normal function. Prior studies demonstrate focal, neocortical epilepsy is associated with dysfunction, several hours before seizures. How does the epileptic network perpetuate dysfunction during baseline periods? To address this question, we developed an unsupervised machine learning technique to disentangle patterns of functional interactions between brain regions, or subgraphs, from dynamic functional networks constructed from approximately 100 h of intracranial recordings in each of 22 neocortical epilepsy patients. Using this approach, we found: (1) subgraphs from ictal (seizure) and interictal (baseline) epochs are topologically similar, (2) interictal subgraph topology and dynamics can predict brain regions that generate seizures, and (3) subgraphs undergo slower and more coordinated fluctuations during ictal epochs compared to interictal epochs. Our observations suggest that seizures mark a critical shift away from interictal states that is driven by changes in the dynamical expression of strongly interacting components of the epileptic network.

Temporal behavior of seizures and interictal bursts in prolonged intracranial recordings from epileptic canines

OBJECTIVE

Epilepsy is a chronic disorder, but seizure recordings are usually obtained in the acute setting. The chronic behavior of seizures and the interictal bursts that sometimes initiate them is unknown. We investigate the variability of these electrographic patterns over an extended period of time using chronic intracranial recordings in canine epilepsy.

METHODS

Continuous, yearlong intracranial electroencephalography (iEEG) recordings from four dogs with naturally occurring epilepsy were analyzed for seizures and interictal bursts. Following automated detection and clinician verification of interictal bursts and seizures, temporal trends of seizures, burst count, and burst-burst similarities were determined. One dog developed status epilepticus, the recordings of which were also investigated.

RESULTS

Multiple seizure types, determined by onset channels, were observed in each dog, with significant temporal variation between types. The first 14 days of invasive recording, analogous to the average duration of clinical invasive recordings in humans, did not capture the entirety of seizure types. Seizures typically occurred in clusters, and isolated seizures were rare. The count and dynamics of interictal bursts form distinct groups and do not stabilize until several weeks after implantation.

SIGNIFICANCE

There is significant temporal variability in seizures and interictal bursts after electrode implantation that requires several weeks to reach steady state. These findings, comparable to those reported in humans implanted with the NeuroPace Responsive Neurostimulator System (RNS) device, suggest that transient network changes following electrode implantation may need to be taken into account when interpreting or analyzing iEEG during evaluation for epilepsy surgery. Chronic, ambulatory iEEG may be better suited to accurately map epileptic networks in appropriate individuals.

Responsive Direct Brain Stimulation for Epilepsy

Closed-loop, responsive focal brain stimulation provides a new treatment option for patients with refractory partial onset seizures who are not good candidates for potentially curative epilepsy surgery. The first responsive brain neurostimulator (RNS® System, NeuroPace), provides stimulation directly to the seizure focus when abnormal electrocorticographic is detected. Seizure reductions of 44% at one year increase to 60 to 66% at years 3 to 6 of treatment. There is no negative impact on cognition and mood. Risks are similar to other implanted medical devices and therapeutic stimulation is not perceived.

High frequency oscillations for lateralizing suspected bitemporal epilepsy

OBJECTIVE

In some cases of single focus epilepsy, conventional video electroencephalography (EEG) cannot reveal the epileptogenic focus even when intracranial electrodes are used. Here, we tested whether analyzing high frequency oscillations (HFOs) can be used to determine the ictal onset zone in suspected bitemporal epilepsy and improve seizure outcome.

METHODS

We prospectively studied 13 patients with refractory temporal seizures who were treated over a 4-year period and underwent bilateral placement of intracranial electrodes. Subdural strips were used in all cases, and depth electrodes were implanted into mesial temporal lobes in 10 patients. The mean patient age was 30.92 years, and 30.7% of patients were male. Patients were monitored by conventional and wide-band frequency amplifiers.

RESULTS

Conventional invasive EEG monitoring of interictal periods showed bilateral epileptiform abnormalities in 12 patients (92.3%) and unilateral epileptiform abnormalities in one (7.7%), and monitoring of ictal periods revealed unilateral seizure origins in nine patients (69.2%) and bilateral origins in four (30.8%). In contrast, high frequency invasive EEG monitoring of interictal periods showed bilateral HFOs in seven patients (53.8%) and unilateral HFOs in six (46.2%), and monitoring of ictal periods revealed unilateral HFOs in all 10 patients who were tested. Three patients were not monitored during ictal periods because of time limitations. All 13 patients subsequently underwent a standard unilateral temporal lobectomy and have been followed-up for a minimum of 12 months. Eleven (84%) had a Class I outcome, one (8%) a Class II outcome, and one a Class III outcome.

SIGNIFICANCE

Bilateral placement of subdural strip and depth electrodes for seizure monitoring in patients with suspected bitemporal epilepsy is both safe and effective. Monitoring high frequency oscillations can help determine the laterality of the onset zone when localization using conventional EEG or brain MRI fails.

Bioresorbable silicon electronics for transient spatiotemporal mapping of electrical activity from the cerebral cortex

Bioresorbable silicon electronics technology offers unprecedented opportunities to deploy advanced implantable monitoring systems that eliminate risks, cost and discomfort associated with surgical extraction. Applications include postoperative monitoring and transient physiologic recording after percutaneous or minimally invasive placement of vascular, cardiac, orthopaedic, neural or other devices. We present an embodiment of these materials in both passive and actively addressed arrays of bioresorbable silicon electrodes with multiplexing capabilities, which record in vivo electrophysiological signals from the cortical surface and the subgaleal space. The devices detect normal physiologic and epileptiform activity, both in acute and chronic recordings. Comparative studies show sensor performance comparable to standard clinical systems and reduced tissue reactivity relative to conventional clinical electrocorticography (ECoG) electrodes. This technology offers general applicability in neural interfaces, with additional potential utility in treatment of disorders where transient monitoring and modulation of physiologic function, implant integrity and tissue recovery or regeneration are required.

Seizure outcomes in nonresective epilepsy surgery: an update

In approximately 30 % of patients with epilepsy, seizures are refractory to medical therapy, leading to significant morbidity and increased mortality. Substantial evidence has demonstrated the benefit of surgical resection in patients with drug-resistant focal epilepsy, and in the present journal, we recently reviewed seizure outcomes in resective epilepsy surgery. However, not all patients are candidates for or amenable to open surgical resection for epilepsy. Fortunately, several nonresective surgical options are now available at various epilepsy centers, including novel therapies which have been pioneered in recent years. Ablative procedures such as stereotactic laser ablation and stereotactic radiosurgery offer minimally invasive alternatives to open surgery with relatively favorable seizure outcomes, particularly in patients with mesial temporal lobe epilepsy. For certain individuals who are not candidates for ablation or resection, palliative neuromodulation procedures such as vagus nerve stimulation, deep brain stimulation, or responsive neurostimulation may result in a significant decrease in seizure frequency and improved quality of life. Finally, disconnection procedures such as multiple subpial transections and corpus callosotomy continue to play a role in select patients with an eloquent epileptogenic zone or intractable atonic seizures, respectively. Overall, open surgical resection remains the gold standard treatment for drug-resistant epilepsy, although it is significantly underutilized. While nonresective epilepsy procedures have not replaced the need for resection, there is hope that these additional surgical options will increase the number of patients who receive treatment for this devastating disorder-particularly individuals who are not candidates for or who have failed resection.

Interaction with slow waves during sleep improves discrimination of physiologic and pathologic high-frequency oscillations (80-500 Hz)

OBJECTIVE

To characterize the interaction between physiologic and pathologic high-frequency oscillations (HFOs) and slow waves during sleep, and to evaluate the practical significance of these interactions by automatically classifying channels as recording from normal or epileptic brain regions.

METHODS

We automatically detected HFOs in intracerebral electroencephalography (EEG) recordings of 45 patients. We characterized the interaction between the HFOs and the amplitude and phase of automatically detected slow waves during sleep. We computed features associated with HFOs, and compared classic features such as rate, amplitude, duration, and frequency to novel features related to the interaction between HFOs and slow waves. To quantify the practical significance of the difference in these features we classified the channels as recording from normal/epileptic regions using logistic regression. We assessed the results in different brain regions to study differences in the HFO characteristics at the lobar level.

RESULTS

We found a clear difference in the coupling between the phase of slow waves during sleep and the occurrence of HFOs. In channels recording physiologic activity, the HFOs tend to occur after the peak of the deactivated state of the slow wave, and in channels with epileptic activity, the HFOs occur more often before this peak. This holds for HFOs in the ripple (80-250 Hz) and fast ripple (250-500 Hz) bands, and different regions of the brain. When using this interaction to automatically classify channels as recording from normal/epileptic brain regions, the performance is better than when using other HFO characteristics. We confirmed differences in the HFO characteristics in mesiotemporal structures and in the occipital lobe.

SIGNIFICANCE

We found the association between slow waves and HFOs to be different in normal and epileptic brain regions, emphasizing their different origin. This is also of practical significance, since it improves the separation between channels recording from normal and epileptic brain regions.

Emerging surgical therapies in the treatment of pediatric epilepsy

In the approximately 1% of children affected by epilepsy, pharmacoresistance and early age of seizure onset are strongly correlated with poor cognitive outcomes, depression, anxiety, developmental delay, and impaired activities of daily living. These children often require multiple surgical procedures, including invasive diagnostic procedures with intracranial electrodes to identify the seizure-onset zone. The recent development of minimally invasive surgical techniques, including stereotactic electroencephalography (SEEG) and MRI-guided laser interstitial thermal therapy (MRgLITT), and new applications of neurostimulation, such as responsive neurostimulation (RNS), are quickly changing the landscape of the surgical management of pediatric epilepsy. In this review, the authors discuss these various technologies, their current applications, and limitations in the treatment of pediatric drug-resistant epilepsy, as well as areas for future research. The development of minimally invasive diagnostic and ablative surgical techniques together with new paradigms in neurostimulation hold vast potential to improve the efficacy and reduce the morbidity of the surgical management of children with drug-resistant epilepsy.

Current Challenges Facing the Translation of Brain Computer Interfaces from Preclinical Trials to Use in Human Patients

Current research in brain computer interface (BCI) technology is advancing beyond preclinical studies, with trials beginning in human patients. To date, these trials have been carried out with several different types of recording interfaces. The success of these devices has varied widely, but different factors such as the level of invasiveness, timescale of recorded information, and ability to maintain stable functionality of the device over a long period of time all must be considered in addition to accuracy in decoding intent when assessing the most practical type of device moving forward. Here, we discuss various approaches to BCIs, distinguishing between devices focusing on control of operations extrinsic to the subject (e.g., prosthetic limbs, computer cursors) and those focusing on control of operations intrinsic to the brain (e.g., using stimulation or external feedback), including closed-loop or adaptive devices. In this discussion, we consider the current challenges facing the translation of various types of BCI technology to eventual human application.

Managing drug-resistant epilepsy: challenges and solutions

Despite the development of new antiepileptic drugs (AEDs), ~20%-30% of people with epilepsy remain refractory to treatment and are said to have drug-resistant epilepsy (DRE). This multifaceted condition comprises intractable seizures, neurobiochemical changes, cognitive decline, and psychosocial dysfunction. An ongoing challenge to both researchers and clinicians alike, DRE management is complicated by the heterogeneity among this patient group. The underlying mechanism of DRE is not completely understood. Many hypotheses exist, and relate to both the intrinsic characteristics of the particular epilepsy (associated syndrome/lesion, initial response to AED, and the number and type of seizures prior to diagnosis) and other pharmacological mechanisms of resistance. The four current hypotheses behind pharmacological resistance are the "transporter", "target", "network", and "intrinsic severity" hypotheses, and these are reviewed in this paper. Of equal challenge is managing patients with DRE, and this requires a multidisciplinary approach, involving physicians, surgeons, psychiatrists, neuropsychologists, pharmacists, dietitians, and specialist nurses. Attention to comorbid psychiatric and other diseases is paramount, given the higher prevalence in this cohort and associated poorer health outcomes. Treatment options need to consider the economic burden to the patient and the likelihood of AED compliance and tolerability. Most importantly, higher mortality rates, due to comorbidities, suicide, and sudden death, emphasize the importance of seizure control in reducing this risk. Overall, resective surgery offers the best rates of seizure control. It is not an option for all patients, and there is often a significant delay in referring to epilepsy surgery centers. Optimization of AEDs, identification and treatment of comorbidities, patient education to promote adherence to treatment, and avoidance of triggers should be periodically performed until further insights regarding causative pathology can guide better therapies.