Radiosurgical posterior corpus callosotomy in a child with Lennox–Gastaut syndrome

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.

Radiosurgical Corpus Callosotomy: A Review of Literature

BACKGROUND

Microsurgical callosotomy is a procedure still under debate and to best a palliative treatment for drug-resistant epilepsy. Unlike microsurgery, radiosurgical callosotomy is an underpracticed treatment option, with no definite account of its safety and outcome profile.

OBJECTIVE

To evaluate the safety, efficacy, and complication profile of radiosurgical callosotomy in the literature.

METHODS

PubMed, SCOPUS, Web of Science, and ResearchGate were reviewed for radiosurgery and callosotomy in the English language following PRISMA guidelines. The patient profile, radiosurgical parameters (dose and isodose), target volume, extent of radiosurgery (anterior third, half, or posterior third callosotomy), and seizure outcome were evaluated. We evaluated the role of radiosurgery as a primary or secondary treatment modality after microsurgery. A literature review was performed to identify the evidence of radiosurgery.

RESULTS

We identified 7 studies detailing 12 patients of mean age 22.8 years (range, 4-58 years) and a mean of 18.9 years of illness (range, 5-37 years). Five series performed Gamma Knife radiosurgery and 2 performed LINAC radiosurgery. The spectrum of seizures ranged from atonic seizures/drop attack (83%), generalized tonic-clonic seizures (75%), complex partial seizures (67%), absence seizures (50%), myoclonic seizures (33%), to focal seizures (16%). Four patients suffered from Lennox-Gastaut syndrome. The average seizure frequency in 11 patients was 297/month (range, 20/day to 15/month). Three patients became free of drop attacks and 2 free of generalized tonic-clonic seizures, and 1 became completely seizure free. The remaining patients continued to have seizures, albeit at a lower frequency. Complex partial seizures and myoclonic seizures were the least responsive seizure types to radiosurgical corpus callosotomy. All patients tolerated the procedure well. After radiosurgery, 3 patients developed symptomatic edema. The symptoms (headache, nausea, hemiparesis, and transient neurologic deficits) were controlled with a short course of steroids. Two patients needed redo radiosurgery (at the same target in 1 patient and complementary middle third callosotomy to previous anterior third callosotomy in another patient). There were no long-term complications.

CONCLUSIONS

Radiosurgery is a viable alternative to microsurgical callosotomy both as a primary and as a secondary treatment modality. It has a specific advantage of better neuropsychological outcomes with comparable seizure control. The neurosurgical community should adopt a more liberal approach with this indication.

Completion Corpus Callosotomy with Stereotactic Radiosurgery for Drug-Resistant, Intractable Epilepsy

BACKGROUND

Stereotactic radiosurgery (SRS) offers a noninvasive technique for division of the corpus callosum, which can confer improved seizure control to patients suffering from frequent atonic seizures due to rapid interhemispheric generalization. This noninvasive approach is well-suited for use in a palliative intervention for improved seizure control in this patient population. To our knowledge, this is the first report of radiosurgical completion corpus callosotomy in an adult in the United States.

CASE DESCRIPTION

A 20-year-old ambidextrous nonverbal man with a history of refractory generalized epilepsy status post open anterior corpus callosotomy at age 10 years, Lennox-Gastaut syndrome, and autism presented after 2 years of incremental, progressive deterioration in seizure control and behavior including 1 year. The family decided to pursue SRS corpus callosotomy. Under general anesthesia, a volume of interest encompassing a full midsagittal plane of the corpus callosum was defined to deliver 60 Gy to the 50% isodose line fully encompassing the target. Gamma Knife was used with 2 isocenters at 90° and 1 at 110° and isodose lines of 60, 20, and 12 Gy. Treatment was carried out without difficulty or complications while the patient remained under close monitoring. The patient was discharged the next day with a 2-week taper of dexamethasone.

CONCLUSIONS

Eight months postradiosurgical corpus callosotomy, the patient is free of atonic seizures and is ambulatory. In carefully selected cases and with protective radiosurgical planning, SRS for completion corpus callosotomy represents an effective option for refractory seizure control.

Stereotactic laser ablation of the splenium for intractable epilepsy

Partial or complete corpus callosotomies have been applied, traditionally via open surgical or radiosurgical approaches, for the treatment of epilepsy in patients with multifocal tonic, atonic, or myoclonic seizures. Minimally invasive methods, such as MRI-guided laser interstitial thermal ablation (MTLA), are being employed to functionally remove or ablate seizure foci in the treatment of epilepsy. This therapy can achieve effectiveness similar to that of traditional resection, but with reduced morbidity compared with open surgery. Here, we present a patient with a history of prior partial corpus callosotomy who continued to suffer from medically refractory epilepsy with bisynchronous onset. We report on the utilization of laser ablation of the splenium in this patient to achieve full corpus callosotomy. Adequate ablation of the splenial remnant was confirmed by postoperative MRI imaging, and at four-month follow-up, the patient's seizure frequency had dropped more than 50%. This is the first reported instance of laser ablation of the splenium to achieve full corpus callosotomy following a previous unsuccessful anterior callosotomy in a patient with intractable generalized epilepsy.

Corpus callosotomy in children with intractable epilepsy using frameless stereotactic neuronavigation: 12-year experience at the Hospital for Sick Children in Toronto

OBJECT

Although corpus callosotomy has been used effectively since the late 1930s to treat severe, medically intractable seizure disorders, particularly atonic or drop-attack seizures, controversy remains as to when, how, and how much surgery should be performed. Intraoperative determination of the extent of callosotomy, the need to stage the procedure, and the side of the interhemispheric approach represent technical issues that remain debatable. The authors report the 12-year experience of the senior author as well as surgical outcomes with corpus callosotomy using a frameless stereotactic neuronavigation system (ISG View Wand and BrainLab).

METHODS

Thirteen consecutive children at The Hospital for Sick Children underwent single-stage corpus callosotomy for medically intractable seizures. The mean age was 10.3 years. Five children underwent partial callosotomy, and 8 underwent complete callosotomy. The side of operative approach to avoid large parasagittal bridging veins was determined by preoperative study of 3D MR imaging/MR venography reconstructed by the neuronavigation system. The extent of callosotomy was determined using intraoperative feedback from the neuronavigation system and postoperative MR imaging.

RESULTS

The extent of callosotomy determined by intraoperative neuronavigation and postoperative MR imaging correlated closely in all cases. There were no operative deaths. There was no significant postoperative morbidity related to venous infarction. Four of 5 patients in the partial callosotomy cohort and 7 of 8 patients in the complete callosotomy cohort showed significant improvement in seizure control.

CONCLUSIONS

The use of frameless stereotactic neuronavigation is a safe, effective, and important surgical adjunct in the planning and execution of successful corpus callosotomy in children with intractable epilepsy.