Connectome biomarkers of drug‐resistant epilepsy

Drug‐resistant epilepsy (DRE) considerably affects patient health, cognition, and well‐being, and disproportionally contributes to the overall burden of epilepsy. The most common DRE syndromes are temporal lobe epilepsy related to mesiotemporal sclerosis and extratemporal epilepsy related to cortical malformations. Both syndromes have been traditionally considered as "focal," and most patients benefit from brain surgery for long‐term seizure control. However, increasing evidence indicates that many DRE patients also present with widespread structural and functional network disruptions. These anomalies have been suggested to relate to cognitive impairment and prognosis, highlighting their importance for patient management. The advent of multimodal neuroimaging and formal methods to quantify complex systems has offered unprecedented ability to profile structural and functional brain networks in DRE patients. Here, we performed a systematic review on existing DRE network biomarker candidates and their contribution to three key application areas: (1) modeling of cognitive impairments, (2) localization of the surgical target, and (3) prediction of clinical and cognitive outcomes after surgery. Although network biomarkers hold promise for a range of clinical applications, translation of neuroimaging biomarkers to the patient's bedside has been challenged by a lack of clinical and prospective studies. We therefore close by highlighting conceptual and methodological strategies to improve the evaluation and accessibility of network biomarkers, and ultimately guide clinically actionable decisions.     

Surgery for drug‐resistant tuberous sclerosis complex‐associated epilepsy: who,when, and what

Objective: Tuberous sclerosis complex (TSC) is a multisystem genetic disorder associated with refractory early‐onset epilepsy. Current evidence supports surgery as the intervention most likely to achieve long‐term seizure freedom, but no specific guidelines are available on TSC pre‐surgical workup. This critical review assesses which TSC patients are suitable for surgical treatment, when pre‐surgical evaluation should start, and what degree of surgical resection is optimal for postsurgical outcome. Methods: We searched for publications from 2000 to 2020 in Pubmed and Embase using the terms “tuberous sclerosis,” “epilepsy,” and “epilepsy surgery”. To evaluate postsurgical seizure outcome, we selected only studies with at least one year of follow‐up. Results: Overall, we collected data on 1,026 patients from 34 studies. Age at surgery ranged from one month to 54 years. Mean age at surgery was 8.41 years. Of the diagnostic non‐invasive pre‐surgical tools, MRI and video‐EEG were considered most appropriate. Promising data for epileptogenic tuber detection is provided from invasive SEEG studies. Data on surgery and related outcome were available for 769 patients. Seizure freedom was seen in 64.4% of patients who underwent tuberectomy, 68.9% treated with lobectomy and 65.1% with multilobar resection. The most effective surgical approach was lobectomy, even though more recently tuberectomy associated with the resection of the perituberal area seems to be the best approach to reach seizure freedom. Published postsurgical seizure freedom rates in patients with TSC were between 65% and 75%, but reduced to 48%‐57% over longer follow‐up periods. Early surgery might positively affect neurodevelopmental trajectory in some patients, even though data on cognitive outcome are still to be confirmed with longitudinal studies. Significance: Considering the strong correlation between epilepsy duration and neurocognitive outcome, all patients with TSC ought to be referred early to a dedicated epilepsy centre for individually tailored pre‐surgical evaluation by a multi‐disciplinary epilepsy surgery team.     

Outcome of vagus nerve stimulation for drug‐resistant epilepsy: the first three years of a prospective Japanese registry

Aims. Vagus nerve stimulation (VNS) is an established option of adjunctive treatment for patients with drug‐resistant epilepsy, however, evidence for long‐term efficacy is still limited. Studies on clinical outcomes of VNS in Asia are also limited. We report the overall outcome of a national, prospective registry that included all patients implanted in Japan. Methods. The registry included patients of all ages with all seizure types who underwent VNS implantation for drug‐resistant epilepsy in the first three years after approval of VNS in 2010. The registry excluded patients who were expected to benefit from resective surgery. Efficacy analysis was assessed based on the change in frequency of all seizure types and the rate of responders. Changes in cognitive, behavioural and social status, quality of life (QOL), antiepileptic drug (AED) use, and overall AED burden were analysed as other efficacy indices. Results. A total of 385 patients were initially registered. Efficacy analyses included data from 362 patients. Age range at the time of VNS implantation was 12 months to 72 years; 21.5% of patients were under 12 years of age and 49.7% had prior epilepsy surgery. Follow‐up rate was >90%, even at 36 months. Seizure control improved over time with median seizure reduction of 25.0%, 40.9%, 53.3%, 60.0%, and 66.2%, and responder rates of 38.9%, 46.8%, 55.8%, 57.7%, and 58.8% at three, six, 12, 24, and 36 months of VNS therapy, respectively. There were no substantial changes in other indices throughout the three years of the study, except for self/family‐accessed QOL which improved over time. No new safety issues were identified. Conclusions. Although this was not a controlled comparative study, this prospective national registry of Japanese patients with drug‐resistant epilepsy, with >90% follow‐up rate, indicates long‐term efficacy of VNS therapy which increased over time, over a period of up to three years. The limits of such trials, in terms of AED modifications and during follow‐up and difficulties in seizure counting are also discussed.     

Long‐term health‐related quality of life in drug‐resistant temporal lobe epilepsy after anterior temporal lobectomy

Epilepsy surgery is beneficial to patients suffering from drug‐resistant temporal lobe epilepsy in the short term, but fewer reports of long‐term outcomes have been published. To clarify the long‐term outcomes of seizure control and health‐related quality of life after epilepsy surgery, we enrolled 48 patients suffering from drug‐resistant temporal lobe epilepsy. All of the patients received comprehensive presurgical evaluations, including the Quality of Life in Epilepsy Inventory‐89 (QOLIE‐89) questionnaire to measure their health‐related quality of life. Among the patients, 28 patients received surgery (surgical group) and 20 patients remained under medication (medical group). Eight years later, the seizure frequency and QOLIE‐89 were evaluated. The seizure‐free rate was much higher in the surgical group (53.6%) than in the medical group (5%), eight years after the initial evaluation. The follow‐up QOLIE‐89 score was significantly higher in the surgical group than in the medical group. Moreover, the seizure frequency inversely correlated to the QOLIE‐89 score, regardless of the treatment group. Our results provide evidence that epilepsy surgery confers benefits with respect to seizure control and health‐related quality of life for drug‐resistant temporal lobe epilepsy patients based on long‐term follow‐up.     

Drug‐resistant epilepsy after treatment for childhood acute lymphocytic leukaemia: from focal epilepsy to Lennox‐Gastaut syndrome

Drug‐resistant epilepsy, not associated with acute brain complications or central nervous system leukaemic involvement, can develop in patients treated for acute lymphocytic leukaemia during childhood. It has been postulated that this rare complication may be due to CNS oncological treatment neurotoxicity, related to intrathecal drugs, such as methotrexate, and brain radiotherapy. We report four patients who developed drug‐resistant epilepsy sometime after receiving treatment for acute lymphocytic leukaemia. All patients were female and received intrathecal methotrexate. One received additional intrathecal cytarabine, and two concomitant brain radiotherapy. Two developed Lennox‐Gastaut type syndrome, one multifocal epilepsy, and one focal epilepsy related to a radiotherapy‐induced cavernous angioma. The development of drug‐resistant epilepsy after treatment for acute lymphocytic leukaemia is a rare complication that may vary, from focal epilepsy to an epileptic encephalopathy. This may appear even years after the treatment has finished and is most likely associated with treatment‐related neurotoxicity.