Combination of corpus callosotomy and vagus nerve stimulation in the treatment of refractory epilepsy

Added value of corpus callosotomy following vagus nerve stimulation in children with Lennox-Gastaut syndrome: A multicenter, multinational study

OBJECTIVE

Lennox-Gastaut syndrome (LGS) is a severe form of epileptic encephalopathy, presenting during the first years of life, and is very resistant to treatment. Once medical therapy has failed, palliative surgeries such as vagus nerve stimulation (VNS) or corpus callosotomy (CC) are considered. Although CC is more effective than VNS as the primary neurosurgical treatment for LGS-associated drop attacks, there are limited data regarding the added value of CC following VNS. This study aimed to assess the effectiveness of CC preceded by VNS.

METHODS

This multinational, multicenter retrospective study focuses on LGS children who underwent CC before the age of 18 years, following prior VNS, which failed to achieve satisfactory seizure control. Collected data included epilepsy characteristics, surgical details, epilepsy outcomes, and complications. The primary outcome of this study was a 50% reduction in drop attacks.

RESULTS

A total of 127 cases were reviewed (80 males). The median age at epilepsy onset was 6 months (interquartile range [IQR] = 3.12-22.75). The median age at VNS surgery was 7 years (IQR = 4-10), and CC was performed at a median age of 11 years (IQR = 8.76-15). The dominant seizure type was drop attacks (tonic or atonic) in 102 patients. Eighty-six patients underwent a single-stage complete CC, and 41 an anterior callosotomy. Ten patients who did not initially have a complete CC underwent a second surgery for completion of CC due to seizure persistence. Overall, there was at least a 50% reduction in drop attacks and other seizures in 83% and 60%, respectively. Permanent morbidity occurred in 1.5%, with no mortality.

SIGNIFICANCE

CC is vital in seizure control in children with LGS in whom VNS has failed. Surgical risks are low. A complete CC has a tendency toward better effectiveness than anterior CC for some seizure types.

Corpus Callosotomy Is a Safe and Effective Procedure for Medically Resistant Epilepsy

Corpus callosotomy (CC) is an effective surgical treatment for medically resistant generalized or multifocal epilepsy (MRE). The premise of CC extrapolates from the observation that the corpus callosum is the predominant commissural pathway that allows spread and synchroneity of epileptogenic activity between the hemispheres. Candidacy for CC is typically reserved for patients seeking palliative epilepsy treatment with the goal of reducing the frequency of drop attacks, although reduction of other seizure semiologies (absence, complex partial seizures, and tonic-clonic) has been observed. A reduction in morbidity affiliated with evolution of surgical techniques to perform CC has improved the safety profile of the procedure without necessarily sacrificing efficacy.

Corpus Callosotomy in the Modern Era: Origins, Efficacy, Technical Variations, Complications, and Indications

Corpus callosotomy is among the oldest surgeries performed for drug-resistant epilepsy (DRE). First performed in 1940, various studies have since assessed its outcomes in various patient populations in addition to describing different extents of sectioning and emerging technologies (i.e. endoscopic, laser interstitial thermal therapy, and radiosurgery). In order to capture the current state and offer a reappraisal, we comprehensively review corpus callosotomy's origins, efficacy for various seizure types, technical variations, complications, and indications and compare the procedure to vagus nerve stimulation therapy which has similar indications. We consider corpus callosotomy to be a safe and efficacious procedure that should be considered by clinicians when appropriate. Furthermore, it can also play an important role in treating patients with DRE in low-to-middle-income countries where resources are limited.

Vagal Nerve Stimulation in the Management of Epilepsy - Recent Concepts

Epilepsy surgery currently offers the best treatment for patients with drug-refractory epilepsy (DRE). Resective surgery, in the presence of a well-localized epileptogenic focus, remains the best modality towards achieving seizure freedom. However, localization of the focus may not be possible in all the cases of DRE, despite comprehensive epilepsy workup. Neuromodulation techniques such as vagal nerve stimulation (VNS), deep brain stimulation (DBS) and responsive neurostimulation (RNS) may be a good alternative in these cases. This article intends to provide an overview of VNS in the management of DRE, including indications, comprehensive preoperative workup, exemplified by case illustrations and outcomes by reviewing the evidence available in the literature.

Health Technology Assessment Report on Vagus Nerve Stimulation in Drug-Resistant Epilepsy

Background: Vagus nerve stimulation (VNS) is a palliative treatment for medical intractable epileptic syndromes not eligible for resective surgery. Health technology assessment (HTA) represents a modern approach to the analysis of technologies used for healthcare. The purpose of this study is to assess the clinical, organizational, financial, and economic impact of VNS therapy in drug-resistant epilepsies and to establish the congruity between costs incurred and health service reimbursement. Methods: The present study used an HTA approach. It is based on an extensive detailed bibliographic search on databases (Medline, Pubmed, Embase and Cochrane, sites of scientific societies and institutional sites). The HTA study includes the following issues: (a) social impact and costs of the disease; (b) VNS eligibility and clinical results; (c) quality of life (QoL) after VNS therapy; (d) economic impact and productivity regained after VNS; and (e) costs of VNS. Results: Literature data indicate VNS as an effective treatment with a potential positive impact on social aspects and on quality of life. The diagnosis-related group (DRG) financing, both on national and regional levels, does not cover the cost of the medical device. There was an evident insufficient coverage of the DRG compared to the full cost of implanting the device. Conclusions: VNS is a palliative treatment for reducing seizure frequency and intensity. Despite its economic cost, VNS should improve patients’ quality of life and reduce care needs.

Challenges of Epilepsy Surgery

Though frequently effective in the management of medically refractory seizures, epilepsy surgery presents numerous challenges. Selection of the appropriate candidate patients who are likely to benefit from surgery is critical to achieving seizure freedom and avoiding neurocognitive morbidity. Identifying the seizure focus and mapping epileptogenic networks involves an interdisciplinary team dedicated to formulating a safe and effective surgical plan. Various strategies can be employed either to eliminate the epileptic focus or to modulate network activity, including resection of the focus with open surgery or laser interstitial thermal therapy; modulation of epileptogenic firing patterns with responsive neurostimulation, deep brain stimulation, or vagus nerve stimulation; or non-invasive disconnection of epileptic circuits with focused ultrasound, which is also discussed in greater detail in the subsequent chapter in our series. We review several challenges of epilepsy surgery that must be thoughtfully addressed in order to ensure its success.

Efficacy and safety of corpus callosotomy after vagal nerve stimulation in patients with drug-resistant epilepsy

OBJECTIVE Vagal nerve stimulation (VNS) and corpus callosotomy (CC) have both been shown to be of benefit in the treatment of medically refractory epilepsy. Recent case series have reviewed the efficacy of VNS in patients who have undergone CC, with encouraging results. There are few data, however, on the use of CC following VNS therapy. METHODS The records of all patients at the authors' center who underwent CC following VNS between 1998 and 2015 were reviewed. Patient baseline characteristics, operative details, and postoperative outcomes were analyzed. RESULTS Ten patients met inclusion criteria. The median follow-up was 72 months, with a minimum follow-up of 12 months (range 12-109 months). The mean time between VNS and CC was 53.7 months. The most common reason for CC was progression of seizures after VNS. Seven patients had anterior CC, and 3 patients returned to the operating room for a completion of the procedure. All patients had a decrease in the rate of falls and drop seizures; 7 patients experienced elimination of drop seizures. Nine patients had an Engel Class III outcome, and 1 patient had a Class IV outcome. There were 3 immediate postoperative complications and 1 delayed complication. One patient developed pneumonia, 1 developed transient mutism, and 1 had persistent weakness in the nondominant foot. One patient presented with a wound infection. CONCLUSIONS The authors demonstrate that CC can help reduce seizures in patients with medically refractory epilepsy following VNS, particularly with respect to drop attacks.

Palliative epilepsy surgery in Dravet syndrome-case series and review of the literature

PURPOSE

Dravet syndrome (DS), also known as severe myoclonic epilepsy of infancy (SMEI), is a rare genetic disorder that results in severe childhood-onset epilepsy. Children with DS initially present with seizures in the first year of life that are often associated with fevers. With age, multiple seizure types develop. There are few reports and no guidelines regarding palliative surgical treatment for DS. Therefore, we reviewed our surgical experience with DS.

METHODS

We conducted a retrospective review of all patients with genetically confirmed DS who underwent either vagal nerve stimulator (VNS) implantation or corpus callosotomy (CC) from May 2001 to April 2014 at our institution. All inpatient and outpatient relevant documentation were reviewed. Demographic information, genetic mutation, operation performed, and preoperative and postoperative seizure frequency were recorded. Inclusion criteria required greater than one-year postoperative follow-up.

RESULTS

Seven children with DS were assessed. Six patients were treated with VNS and one patient was treated with CC. In one child, VNS was followed by CC as a secondary procedure. Therefore, in total, eight surgeries were performed on seven patients during the study period. At least 1 year elapsed from presentation to our hospital and surgery for all patients. Average time after the first seizure to VNS was 4.1 years, and the average time after the first seizure to CC was 7.6 years. The mean age of patients undergoing VNS implantation was 4.3 years, and the mean age for patients undergoing CC was eight. Average follow-up for all seven patients was 6.6 years. Seizures were decreased in five of the six patients with VNS and decreased in the two patients after CC. Four of the six patients who had VNS implanted had a greater than 50 % reduction in seizure frequency, and one of the six patients who had VNS implanted had a less than 50 % reduction in seizure frequency. One patient did not respond effectively to the VNS and had very limited change in seizure frequency. Both patients who had a CC had a greater than 50 % reduction in seizure frequency.

CONCLUSIONS

Both VNS and CC in patients with DS can be effective at reducing seizure frequency. Patients with DS may benefit from earlier and more aggressive surgical intervention. Studies using larger patient cohorts will help clarify the role that surgery may play in the multidisciplinary approach to controlling seizures in DS. Further studies will help determine the appropriate timing of and type of surgical intervention.

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.

Combined surgical intervention with vagus nerve stimulation following corpus callosotomy in patients with Lennox-Gastaut syndrome

BACKGROUND

Lennox-Gastaut syndrome (LGS) is a drug-resistant pediatric epilepsy characterized by multiple seizure types, including drop attacks (DAs). Palliative procedures such as corpus callosotomy (CC) and vagus nerve stimulation (VNS) may be effective for adequate seizure control in LGS patients who are not candidates for resective surgery. We evaluated the efficacy of the combination of these two procedures for LGS-related seizures.

METHOD

Ten patients with LGS (age 3-30 years at VNS implantation) underwent CC and subsequent VNS. We evaluated surgical outcomes, particularly with respect to the efficacy of VNS on seizure reduction rates for different residual seizure types after CC. We compared clinical parameters, including sex, age, seizure duration, history, MRI findings, extent of CC, number of antiepileptic drugs, and neuropsychological states, between VNS responders and non-responders to predict satisfactory seizure outcomes with respect to residual seizures after CC.

FINDINGS

VNS was effective for residual seizures regardless of seizure type (except for DAs) after CC in patients with LGS. Six of ten (60%) patients had a satisfactory seizure outcome (≥50% seizure reduction) for all residual seizure types after VNS. Two of ten (20%) patients were seizure-free at 12 months post-VNS. Even those patients that were non-responders, with respect to all seizures including DAs, after prior CC showed favorable responses to subsequent VNS. Compared to VNS, excellent seizure outcomes for DAs were achieved after CC in seven of nine (77.8%) patients with DAs. Among the clinical parameters, only conversation ability before VNS was significantly different between responders and non-responders (p = 0.033).

CONCLUSION

Combined VNS and prior CC produced satisfactory seizure outcomes in LGS patients with different seizure types, including DAs. Even non-responders to prior CC responded to subsequent VNS for residual seizures, except for DAs. There is a greater likelihood that these procedures may be more feasible in patients who possess conversation ability prior to VNS.