Surgical outcome of corpus callosotomy in patients with drop attacks

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.

Falls, faints, fits and funny turns

In this practically oriented review, we will outline the clinical approach of patients with falls due to an impairment or loss of consciousness. Following a set of definitions, we describe the salient clinical features of disorders leading to such falls. Among falls caused by true loss of consciousness, we separate the clinical characteristics of syncopal falls (due to reflex syncope, hypovolemia, orthostatic hypotension or cardiac syncope) from falls due to other causes of transient unconsciousness, such as seizures. With respect to falls caused by an apparent loss of consciousness, we discuss the presentation of cataplexy, drop attacks, and psychogenic falls. Particular emphasis will be laid upon crucial features obtained by history taking for distinguishing between the various conditions that cause or mimic a transient loss of consciousness.

Approach to pediatric epilepsy surgery: State of the art, Part II: Approach to specific epilepsy syndromes and etiologies

The second of this 2-part review depicts the specific approach to the common causes of pediatric refractory epilepsy amenable to surgery. These include tumors, malformations due to abnormal cortical development, vascular abnormalities and certain epileptic syndromes. Seizure freedom rates are high (usually 60-80%) following tailored focal resection, lesionectomy, and hemispherectomy. However, in patients in whom the epileptogenic zone overlaps with unresectable eloquent cortex, and in certain epileptic syndromes, seizure freedom may not be achievable. In such cases, palliative procedures such as callosotomy, multiple subpial transections and vagus nerve stimulation can achieve reduction in seizure severity but rarely seizure freedom. Integration of the new imaging techniques and the concepts of neuronal plasticity, the epileptogenic lesion, the ictal onset, symptomatogenic, irritative, and epileptogenic zones is an expanding and dynamic process that will allow us, in the future, to better decide on the surgical approach of choice and its timing.

Long-term seizure outcome after corpus callosotomy: a retrospective analysis of 95 patients

Object

The authors report long-term follow-up seizure outcome in patients who underwent corpus callosotomy during the period 1981–2001 at the Montreal Neurological Institute.

Methods

The records of 95 patients with a minimum follow-up of 5 years (mean 17.2 years) were retrospectively evaluated with respect to seizure, medication outcomes, and prognostic factors on seizure outcome.

Results

All patients had more than one type of seizure, most frequently drop attacks and generalized tonicclonic seizures. The most disabling seizure type was drop attacks, followed by generalized tonic-clonic seizures. Improvement was noted in several seizure types and was most likely for generalized tonic-clonic seizures (77.3%) and drop attacks (77.2%). Simple partial, generalized tonic, and myoclonic seizures also benefited from anterior callosotomy. The extent of the callosal section was correlated with favorable seizure outcome. The complications were mild and transient and no death was seen.

Conclusions

This study confirms that anterior callosotomy is an effective treatment in intractable generalized seizures that are not amenable to focal resection. When considering this procedure, the treating physician must thoroughly assess the expected benefits, limitations, likelihood of residual seizures, and the risks, and explain them to the patient, his or her family, and other caregivers.

Corpus callosotomy

Corpus callosotomy is a palliative surgical procedure that is suitable for some patients with intractable seizures who are not candidates for focal resective surgery. The rationale for this procedure is based on the hypothesis that the corpus callosum is a critical pathway for interhemispheric spread of epileptic activity. Efficacy and relatively low permanent morbidity in corpus callosotomy for medically intractable epilepsy have been demonstrated by more than six decades of experience. Callosotomy best ameliorates drop attacks (tonic and atonic seizures), though tonic-clonic, absence, and frontal lobe complex partial seizures often respond as well. In addition to seizure reduction, behavior and quality of life may improve. Hence, callosotomy is justified as a therapy for appropriate patients with intractable epilepsy.

Outcomes of epilepsy surgery in adults and children

Surgery is widely accepted as an effective therapy for selected individuals with medically refractory epilepsy. Numerous studies in the past 20 years have reported seizure freedom for at least 1 year in 53-84% of patients after anteromesial temporal lobe resections for mesial temporal lobe sclerosis, in 66-100% of patients with dual pathology, in 36-76% of patients with localised neocortical epilepsy, and in 43-79% of patients after hemispherectomies. Reported rates for non-resective surgery have been less impressive in terms of seizure freedom; however, the benefit is more apparent when reported in terms of significant seizure reductions. In this Review, we consider the outcomes of surgery in adults and children with epilepsy and review studies of neurological and cognitive sequelae, psychiatric and behavioural outcomes, and overall health-related quality of life.

Changing the paradigm of 1-stage total callosotomy for the treatment of pediatric generalized epilepsy

OBJECT

The authors propose that anterior callosotomy -- thought to have some advantages over total callosotomy -- is not superior to total callosotomy for prevention of seizure propagation or other complications.

METHODS

The study comprised 34 patients in whom generalized epilepsy syndrome or frontal lobe seizures with a secondary generalization were diagnosed. Preoperatively, all patients suffered from disabling drop attacks or intense head-drop seizures, and some patients also experienced other types of seizures. The male/female ratio was 22:12, and patients ranged in age between 1 to 19 years (mean 8.7 years). The follow-up period ranged from 1.08 to 5.0 years (mean 2.58 years). Seizure outcome, parental assessment of daily function, and parental satisfaction with the outcome was assessed postoperatively.

RESULTS

After undergoing 1-stage total callosotomy, drop attacks disappeared completely in 25 patients during the follow-up period, and in 6 patients the frequency of drop attacks decreased to < 10% of baseline. With regard to other types of seizures, seizures resolved completely in 12 patients, and in another 18 seizure frequency decreased. Two patients experienced a transient disconnection syndrome for 2 and 4 weeks. One patient experienced ataxic hemiparesis for 3 weeks before it completely abated. The overall daily function of the patients improved, and all parents were satisfied with the surgical outcome.

CONCLUSIONS

For pediatric generalized epilepsy syndrome, 1-stage total callosotomy will be the first choice in treatment for controlling generalized seizures.

Corpus callosotomy in children and the disconnection syndromes: a review

OBJECTS

Disconnection syndromes following corpus callosotomy represent complex and variably expressed groupings of signs and symptoms affecting motor control, spatial orientation, vision, hearing, and language. Little is known, however, about the functional topography of callosal fiber pathways. In addition, most published case reports and case series of corpus callosotomy seldom report neurological deficits. We sought to categorize these deficits based on surgical anatomy.

METHODS

We comprehensively reviewed the literature and described, compiled, and tabulated the most common disconnection syndromes complicating corpus callosotomy. We depict the topography of the cerebral cortex and associated commissural fibers of the corpus callosum through illustrations and diffusion tensor imaging tractography.

CONCLUSIONS

Anatomical classification of disconnection syndromes will provide great value to neurosurgeons embarking on callosotomy, whether partial or complete. Such information will apply to procedures performed for epilepsy and to procedures where the corpus callosum is sectioned for access to lesions within the ventricular system.

Comparison of corpus callosotomy and vagus nerve stimulation in children with Lennox-Gastaut syndrome

PURPOSE

To compare the efficacy of corpus callosotomy and vagus nerve stimulation (VNS) for long-term adjunctive therapy in children with Lennox-Gastaut syndrome (LGS).

METHOD

Fourteen patients underwent a total corpus callosotomy and 10 patients received VNS implantation. The patients were monitored for more than 12 months after treatment, and seizure rates and complications were retrospectively evaluated.

RESULTS

Seizure types among the 24 patients included atonic or tonic seizures with head-drops in 17 patients, generalized tonic seizures in two patients, atypical absence seizures in one patient, generalized tonic-clonic seizures in one patient, and myoclonic seizures in three patients. Of the 14 patients who underwent a corpus callosotomy, nine (64.3%) had a greater than 50% reduction in seizure frequency and five (35.7%) had a greater than 75% reduction. Of the 10 patients who underwent VNS implantation, seven (70.0%) had a greater than 50% reduction in seizure frequency and two (20.0%) had a greater than 75% reduction. There was no significant difference between the two procedures in terms of final efficacy. Complications of corpus callosotomy included aphasia in one patient, ataxia in another, and paresis in a third. Among patients receiving VNS, one patient experienced dyspnea while sleeping and one patient suffered from drooling. These complications were transient and tolerable, and were controlled by simple adjustments of VNS treatment parameters.

CONCLUSION

The efficacy and safety of corpus callosotomy and VNS were comparable in children with LGS.

Outcome after corpus callosotomy in children with injurious drop attacks and severe mental retardation

Wide variability in patient selection, extent of callosal section and definition of successful outcome between studies make impact of corpus callosotomy on patients with medically refractory epilepsies difficult to interpret. Severe mental retardation is considered to be predictive of unfavorable seizure outcome after callosotomy. Very little attention has been paid on the influence of callosotomy on the psychosocial burden on the patients' families. We evaluated the seizure outcome, and parental perception about change in cognition and behavior of 17 children (median age 9.5 years, range 3.5-18 years) with severe mental retardation (IQ<30 in all, except one) and injurious drop attacks, who have completed >or=1-year postoperative follow-up after callosotomy. Nearly two-thirds of our patients had >or=90% reduction in drop attacks and generalized tonic-clonic seizures. In the one-stage total callosotomy group, 9 of 11 (82%) patients had favorable outcome, compared to 2 of the 6 (33%) in the partial callosotomy group. Absence of generalized epileptiform discharges on the 1-year postoperative EEG was significantly associated with a favorable seizure outcome. The mean duration of epilepsy prior to callosotomy tended to be shorter among patients with favorable seizure outcome. Postoperative complications were trivial and transient. Nearly three-fourths of the parents appreciated improvements in behavior and attentiveness of their children and were satisfied with the outcome. We conclude that, in children with severe mental retardation and injurious drop attacks, total callosotomy can be undertaken as a one-stage procedure with insignificant morbidity and results in highly favorable seizure outcome.

Corpus callosotomy for treatment of pediatric epilepsy in the modern era

OBJECTIVE

The purpose of this study was to evaluate seizure outcome in children with intractable secondary generalized epilepsy without a resectable focus who underwent complete corpus callosotomy and compare these results to those of anterior two-third callosotomy.

METHOD

Data were obtained for all patients who underwent a corpus callosotomy from 2000 to 2005. The study involved 37 patients. Eleven patients had anterior two-third corpus callosotomy compared with 28 patients who underwent complete corpus callosotomy. Two of these patients had completion of their callosotomy following initial partial callosotomy. Seizure type, seizure frequency, and family satisfaction were evaluated for all patients pre- and postoperatively.

RESULTS

A reduction of >or=75% in seizures occurred in 75% of the total-callosotomy patients compared to 55% of the partial-callosotomy patients. Family satisfaction for complete and partial callosotomy was 89 and 73%, respectively. No prolonged neurologic deficits were observed in either group.

CONCLUSION

Complete corpus callosotomy is the most effective treatment for secondary generalized intractable seizures not amenable to focal resection in children.

Corpus callosotomy in children

INTRODUCTION

For children of medical resistant epilepsy without resectable epileptogenic zone, corpus callosotomy and vagus nerve stimulation (VNS) therapy are the two commonly used palliative epilepsy surgeries that can be considered. Although their routes and mechanisms to control epilepsy are different, both surgeries have shown their efficacy in selected candidates. The most common candidates for palliative surgery are in infants and children with organic encephalopathic types of epilepsy including infantile spasms/West syndrome, Lennox-Gastaut syndrome (LGS), severe epilepsy with multiple independent spike foci (SE-MISF) and selected symptomatic partial epilepsy to relief seizures and to stabilize co morbidities (Hirsch and Arzimanoglou, Revue Neurologique [Hirsch E and Arzimanoglou A, Rev Neurol (Paris). 160 Spec No 1:5S210-S219, (2004); Ohtahara S and Yamatogi Y, J Clin Neurophysiol 20(6):398-407, (2003); Wheless JW and Epilepsia 45(Suppl 5):17-22, (2004); Trevathan E, J Child Neurol 17 Suppl 2:2S9-2S22, (2002)].

DISCUSSION

Callosotomy is a major and destructive but affordable surgical procedure as compare to the relative simple but costly extracranial procedure of VNS therapy. However, callosotomy is a safe and effective palliative operation in neurosurgeons familiar with the surgical procedure. Equipments for callosotomy can be as simple as headlight and binocular loupes, self-retention brain retractor, bipolar cauterization, and simple microinstruments.

Refractory generalized seizures: response to corpus callosotomy and vagal nerve stimulation

PURPOSE

The vagal nerve stimulator (VNS) and corpus callosotomy can reduce seizure frequency when seizures are refractory to medications. However, the efficacy and safety of these two procedures have not been compared. This study evaluates the two procedures for generalized seizures.

METHODS

All patients with refractory generalized seizures (generalized tonic-clonic, tonic, or atonic) who underwent a corpus callosotomy (anterior or complete) (n = 53) without other forms of epilepsy surgery and those who underwent VNS placement (n = 25) were evaluated for this study. Seizure response and procedure complications were evaluated.

RESULTS

For those with a corpus callosotomy and generalized tonic-clonic seizures (n = 50), 79.5% had >or=50% decrease in the frequency of generalized tonic-clonic seizures, and 60% had >or=80% seizure reduction. For those with a VNS and generalized tonic-clonic seizures (n = 21), 50% had >or=50% seizure reduction, and 33% had >or=80% seizure reduction. Tonic and atonic seizures decreased after either VNS or a corpus callosotomy. The complication rate for corpus callosotomy was higher (21% all complications, 3.8% permanent) than that for VNS (8%; none permanent), but complications for both corpus callosotomy and VNS were rarely permanent.

CONCLUSIONS

Both corpus callosotomy and VNS are effective in reducing generalized seizures. Corpus callosotomy is associated with greater efficacy but higher risk for complications, although these were generally transient.

Extended, One-stage Callosal Section for Treatment of Refractory Secondarily Generalized Epilepsy in Patients with Lennox-Gastaut and Lennox-like Syndromes

PURPOSE

We report on the efficacy and safety of extended one-stage callosal section performed in a large and homogeneous series of patients.

METHODS

Seventy-six patients with Lennox-Gastaut (n = 28) and Lennox-like (n = 48) syndrome were studied (42 male patients; mean age, 11.2 years). All patients had multiple seizure types per day, including atonic, tonic-clonic, atypical absence, myoclonic, and tonic seizures. All of them were developmentally impaired. The EEG showed intense secondary bilateral synchrony in all of them. All patients were submitted to an extended, one-stage, callosal section, leaving only the splenium intact. Mean follow-up time was 4.7 years.

RESULTS

Worthwhile improvement (>50%) was noted in 69 of 76 patients; 52 patients had a > or =90% reduction in seizure frequency. Seven patients were seizure free after surgery. The seizure patterns most responsive to surgery were atonic (92%), atypical absence (82%), and tonic-clonic (57%) seizures. All patients had some degree of a transient acute postoperative disconnection syndrome. A consistent increase in attention level was observed postoperatively.

CONCLUSIONS

We report one of the larger homogeneous series of patients submitted to callosotomy and are the first to report on the effectiveness and safety of performing extended callosal section in a single stage in this patient group. Extended callosal section should be considered a good palliative surgical option for suitable candidates. The increase in attention level was as useful as seizure control in improving quality of life of these patients.

Our Experience with Pediatric Epilepsy Surgery Focusing on Corpus Callosotomy and Hemispherotomy

PURPOSE

In pediatric patients with intractable epilepsy, surgical intervention should be considered in terms of seizure control and prevention of neuronal deterioration. We present our experience with pediatric epilepsy surgery, focusing on corpus callosotomy and hemispherotomy.

METHODS

A total of 257 pediatric patients underwent epilepsy surgeries during the last decade in our clinic. The two most common surgical procedures were corpus callosotomy and hemispherotomy. The surgical outcomes of the patients undergoing these operations were analyzed with regard to seizure outcomes and surgical complications.

RESULTS

Corpus callosotomy proved to be extremely effective in controlling drop attacks, especially when the callosum was totally sectioned. Postoperative improvement of psychomotor function also was noticeable in >70% of the cases. In patients who underwent hemispherotomy, the etiology of unilateral hemispheric lesions was closely related to surgical results, with cases of hemimegalencephaly having the worst seizure outcome and most frequent surgical complications. Incomplete section of the callosum, one of the most important causes of residual seizures, was found in three cases.

CONCLUSIONS

In pediatric epilepsy surgery, corpus callosotomy is very effective in abolishing drop attacks and improving postoperative psychomotor function. For hemispherotomy, cases of hemimegalencephaly had the worst seizure control and surgical complications. Incomplete section of the corpus callosum should be carefully evaluated as a cause of surgical failure.

Surgical removal of corpus callosum infiltrated by low-grade glioma: functional outcome and oncological considerations

Object. Although still controversial, many authors currently advocate extensive resection in the treatment of low-grade gliomas (LGGs). Because these tumors usually migrate along white matter pathways, the corpus callosum is often invaded. Nevertheless, there is evidently no specific study featuring resection of the corpus callosum infiltrated by glioma, despite abundant literature concerning callosotomy in epilepsy surgery or transcallosal ventricular approaches. The aim of this paper was to analyze functional outcome following removal of corpus callosum invaded by LGG and to analyze the impact of this callosectomy on the quality of resection.

Methods. Between 1996 and 2002, a total of 32 patients harboring an LGG involving part of the corpus callosum and having no or only a mild preoperative deficit underwent surgery aided by intraoperative electrical mapping to preserve eloquent structures identified on stimulation and to perform the most extensive resection possible.

Preoperatively, no clinical response was elicited on stimulation of the corpus callosum; thus, the part of this structure that was invaded by LGG was removed. Despite immediate postoperative neurological worsening, all patients but one recovered within 3 months and returned to a normal socioprofessional life. The additional callosectomy allowed for nine total resections, 18 subtotal resections, and five partial resections. Furthermore, only two cases of contralateral hemispherical migration occurred during a median follow up of 3 years.

Conclusions. Resection of the corpus callosum infiltrated by glioma improves the quality of tumor removal without increasing the risk of sequelae.

Callosal lesions and behavior: history and modern concepts

Callosotomy has played a unique role in the treatment of epilepsy and in the understanding of human brain function. The pioneering work of Dejerine and Liepmann presenting the first findings of callosal lesion pathology at the turn of the 20th century was accepted but then quickly forgotten. Two schools resurrected the phoenix of callosal syndromes: Roger Sperry and Michael Gazzaniga leading in experimental neuroscience, and Norman Geschwind leading in clinical neurology. Callosotomy remains an effective technique to treat atonic, tonic, and tonic-clonic seizures, especially in patients with symptomatic generalized epilepsies such as Lennox-Gastaut syndrome. Neurologic, cognitive, and behavioral complications limit its use given that precise characterization of these complications as well as their frequency is difficult. The high frequencies of developmental delays, severe seizures, head injuries, antiepileptic drug burden, and other factors limit the ability to attribute a specific change to surgical intervention, since surgery can change multiple factors. For example, subtle behavioral changes in executive function and personality are difficult to delineate in a population with preexisting neurologic and psychiatric disorders. Despite this, a clearer picture of the effects of callosotomy, as defined by clinical neurology and neuropsychology as well as cognitive neuroscience, is emerging.

Treatment considerations: role of surgery

Patients with developmental disabilities, including retardation and global developmental delay, are not ideal candidates for epilepsy surgery. Because they have an increased likelihood of diffuse brain dysfunction and multifocal or generalized epileptogenic zones, there is an increased chance that a focal cortical resection will not confer a major improvement in their seizure frequency and severity. There is also increased concern that cortical resection will lead to increase in the patient's disability. However, by applying the basic principles of epilepsy surgery selection (i.e., convergence of multiple lines of localizing evidence) to this population, patients with a reasonable likelihood of good seizure control can be identified. Various means of localizing seizure onset are reviewed, including history and examination, electroencephalography, magnetic resonance imaging, position emission tomography, single-photon-emission tomography, and magnetoencephalography.