Anterior, Total, and Two-Stage Corpus Callosum Section: Differential and Incremental Seizure Responses

Summary: Published reports suggest that control of generalized seizures is improved by callosotomy but do not necessarily indicate that completion of failed anterior callosotomy is beneficial. We studied 42 patients after anterior callosotomy and 22 after total callosotomy, of whom 14 underwent a two-stage procedure. Cure or marked diminution of seizures was most dramatic for atonic and tonic-clonic seizures after anterior callosotomy (100 and 83%), and for tonic-clonic and tonic seizures after total callosotomy (68 and 57%). For the 14 patients who failed to improve after anterior section and then underwent total section, incremental responses were noted for all seizure types, with cure or marked diminution of partial seizures in 2 of 14 patients, of tonic-clonic seizures in 6 of 10, of tonic seizures in 2 of 4, of atonic seizures in 2 of 5, and of myoclonic seizures in 1 of 1. More than two seizure types, verbal IQ <80, and diffuse ictal EEG patterns were significantly more common in the anterior callosotomy failures. Total callosotomy can be of benefit when anterior callosotomy fails, especially for persistent tonic- clonic and tonic seizures, and will most often be necessary in patients with diffuse cerebral abnormalities.     

Value of Intraoperative EEG Changes During Corpus Callosotomy in Predicting Surgical Results

Summary: The intraoperative transformation of generalized epileptiform discharges (GED) to lateralized epileptiform activity during the course of corpus callosum sectioning for intractable epilepsy in 37 patients was correlated with percentage of decrease in atonic-tonic seizures with "drops" at mean follow-up of 26 months (range 12– 86 months). Twenty-seven (73%) patients had intraoperative interictal discharges, and 21 (78%) showed varying degrees of lateralization of GED during corpus callosum sectioning (two thirds to total). All patients experienced >80% reduction in atonic-tonic seizures with drops. The group (n = 7) with largest decrease in GED had the greatest decrease in seizures (95.5%). Six patients without change in GED had 88% decrease in seizures, as did 14 patients (85–86%) with mild or moderate decreases in GED, but there was no statistically significant correlation between decrease in GED and seizure frequency after operation. Thus, although lateralization of GED after corpus callosum sectioning was evident in 78% of patients with GED, the degree of lateralization of GED did not correlate with degree of reduction of tonic-atonic seizures. Therefore, intraoperative surface EEG monitoring does not appear to be helpful at this time as a guide to extent of callosotomy.     

Corpus Callosum Section and Other Disconnection Procedures for Medically Intractable Epilepsy

Summary: Corpus callosum section for carefully selected patients with uncontrolled epilepsy has become more acceptable as operative complications have decreased. From consideration of anatomical pathways utilized in the spread of seizure discharges, section of the corpus callosum is expected to decrease, but-not abolish, bilaterally synchronous EEG abnormalities arising from most cerebral locations, perhaps excluding the temporal lobe. Clinical experience confirms this expectation. Persistence of some bilateral synchrony, presumably through subcortical relays, does not usually diminish the effectiveness of corpus callosum section on clinically generalized seizures that are eliminated or markedly decreased in 85% of patients after total corpus callosum section. Generalized seizure types that respond include tonic, atonic, tonic-clonic, and absence seizures. Patients who continue to have generalized seizures usually have low IQ and perhaps extensive bilateral cerebral involvement increases the extent to which subcortical structures participate in generalization. Complex partial seizures may cease, usually in patients with well-circumscribed, often extratemporal seizure foci. Focal seizures intensify in 25% of patients, a predictable consequence of sectioning interhemispheric inhibitory connections. Permanent disconnection syndromes, which are only rarely symptomatic, include sensory disconnection after posterior section, and split-brain syndrome after total section. A small percentage of patients develop impairments in language, motor, or memory functions. Language and motor deficits are predicted by pre-existing unilateral mild or moderate central nervous system damage. Partial section of the corpus callosum produces control of generalized seizures half as frequently as complete section. Neurologic sequelae of partial section occur nearly as frequently but are less severe.     

Response of Multiple Seizure Types to Corpus Callosum Section

Twenty-four patients (16 men, 8 women) underwent corpus callosum section specifically for improvement of control of atonic or tonic seizures that resulted in falls and injuries. All patients suffered from multiple seizure types, including complex partial (CP) and tonic-clonic (TC) seizures, in addition to the tonic or atonic episodes. Preoperative seizure frequency was quantified for all types for 1 year immediately before surgery and for the most recent year since the procedure; average monthly counts were obtained for each seizure type. The period of follow-up since surgery averaged 43 months (range, 23-79 months). Statistically significant improvements were documented, not only for the atonic/tonic seizures (p less than 0.0001) for all patients, but also for TC seizures (17 patients; p less than 0.001) and CP seizures (20 patients; p less than 0.02). Six patients experienced an exacerbation of CP seizures postoperatively, and three developed new simple partial (SP) seizures. In all of the CP group and all three of the SP group, ictal video and EEG features suggested that the new seizures were an aborted expression of the previously generalized seizures. From these data, we conclude that callosotomy is an effective treatment for tonic, atonic, and TC seizures intractable to anticonvulsant medications. Three patients became seizure free. The procedure may also be useful for certain specific subgroups of CP epilepsy, but further studies are required before expanding callosotomy to intractable CP seizures not amenable to focal resection.     

Effect of Anterior Callosotomy on Bilaterally Synchronous Spike and Wave and Other EEG Discharges

Summary: We analyzed pre- and postoperative interictal and ictal EEG patterns in relation to seizure outcome in 29 patients with intractable epilepsy who had undergone anterior callosotomy. Twenty-two patients had generalized bilaterally synchronous sharp or spike and slow wave discharges (GSW) and 7 did not: Postoperatively, patients with preoperative GSW showed disruption of synchrony, increased amplitude asymmetry, and a decreased amount of GSW. No significant decrease was noted in the amount of total epileptic discharge after operation. There was a significant relation between seizure outcome and decrease in amount of GSW. The degree of disruption of synchrony, total amount of epileptic discharge, and pre- and postoperative EEG patterns were not good indicators of seizure outcome. Postoperative changes in lateralization of epileptic foci consisted either of increased lateralization, less lateralization but increased independent discharges in the previously nonpredominant hemisphere, or appearance of some lateralization. There appears to be a spectrum of GSW: Both sec-ondary bilateral synchrony and secondarily generalized corticoreticular epileptic discharges are distributed along this spectrum.     

胼胝体动静脉畸形

报告19例胼肥体动静脉畸形(AVM),20个病灶(1例多发)。其中,膝部3个,体部2个,压部15个。所有病人都有蛛网膜下腔出血,而以癫痫大发作为首发症状者仅1例。以胼周动脉为主要供血动脉,大脑后动脉分支亦参与供血。除1例行供血动脉结扎术外,其余19个AVM均采用显微外科手术完整切除,无死亡。     

Interhemispheric Osteolipoma with Agenesis of the Corpus Callosum

Osteolipoma is an ossified lipoma with distinct components of fat and bone. We present a case of interhemispheric osteolipoma associated with total agenesis of the corpus callosum. A 20-year-old man complained of severe headache, nausea and vomiting. Brain computed tomography showed a low-density mass in an interhemispheric fissure, with high T1 and T2 magnetic resonance signals compatible with fat. The mass measured 4.9 × 2.9 cm in size and showed peripheral calcifications. There was another small piece of same signal mass within the lateral ventricular choroid plexus. The interhemispheric lesion was removed by an interhemispheric approach. Osteolipoma is rare in interhemispheric region, however, it should be a differential diagnosis of lesions with fat intensity mass and calcifications.     

Corpus callosotomy in refractory idiopathic generalized epilepsy

RATIONALE: A small percentage of patients with idiopathic generalized epilepsy (IGE) do not respond to medical therapy. Generalized tonic-clonic (GTC) seizures are especially debilitating and can be associated with severe injuries. The benefit, safety and effect of corpus callosotomy (CC) in patients with IGE have not been studied. METHODS: We reviewed patients with presumed IGE who underwent CC between 1991 and 2000. Criteria for selection included history, examination, brain imagining, interictal and ictal EEG. All patients had refractory and debilitating tonic-clonic seizures (GTCS) and had failed four or more antiepileptic drugs. Seizure frequency was calculated per month over the last year and pre-operative baseline was compared to last follow-up using paired t-tests. IQ, executive function, language and verbal, non-verbal memory and quality of life (QOL) was compared before and after surgery. Serial EEGs after surgery were reviewed. RESULTS: There were nine patients (seven men), mean age 37.9 (range: 22-49), mean IQ 87.3 (range: 75-107). All had anterior CC. Mean follow-up time was 5.4 years (range: 0.6-10.3 years). One patient died from sudden death in epilepsy 9 months after surgery. There was a significant reduction of GTC seizures from 6.3 to 1.1 (p<0.005). Four patients had more than 80% and eight more than 50% reduction. Of five patients with absence seizures, two became seizure free and one had more than 80% reduction and two worsened slightly, and of three with myoclonic seizures one had more than 90% reduction. One patient had completion of the CC with improvement of myoclonus and absence seizures, but not of GTC seizures and suffered a disconnection syndrome. Another had right frontal focal resection without improvement after new seizures of focal onset. Cognitive testing showed a good outcome (improved or no change) in all cognitive domains. Post-surgical EEG showed new focal slowing and sharp waves. There was no change in QOL. CONCLUSION: CC can be effective in reducing GTC, absence and myoclonic seizures in patients with refractory IGE. These findings suggest that interhemispheric communication of the cerebral cortices plays an important role in the generation of seizures in IGE. Anterior CC appears safe while complete callosotomy has a risk of disconnection syndrome.     

Corpus Callosum Morphometrics in Young Children with Autism Spectrum Disorder

This study assessed midsagittal corpus callosum cross sectional areas in 3–4 year olds with autism spectrum disorder (ASD) compared to typically developing (TD) and developmentally delayed (DD) children. Though not different in absolute size compared to TD, ASD callosums were disproportionately small adjusted for increased ASD cerebral volume. ASD clinical subgroup analysis revealed greater proportional callosum reduction in the more severely affected autistic disorder (AD) than in pervasive developmental disorder-not otherwise specified (PDD-NOS) children. DD children had smaller absolute callosums than ASD and TD. Subregion analysis revealed widely distributed callosum differences between ASD and TD children. Results could reflect decreased inter-hemispheric connectivity or cerebral enlargement due to increase in tissues less represented in the corpus callosum in ASD.     

Corpus Callosotomy for Intractable Epilepsy: Seizure Outcome and Prognostic Factors

We reviewed the outcome of corpus callosal section in 64 adult and pediatric patients to identify factors associated with a good outcome: 48% of patients had a favorable outcome for overall seizure frequency. Improvement was noted in several seizure types and was most likely for drop attacks, particularly in the setting of a unilateral focal cerebral lesion or a true generalized epilepsy of Lennox-Gastaut type. Poor outcomes for drop attacks were more likely if there was associated severe intellectual handicap or bilateral independent spikes on interictal EEG. Complex partial seizures (CPS), most commonly of frontal lobe origin, also responded favorably. The complications of callosal section were usually mild and transient. New focal seizures occurred in only 2 patients and were not as frequent or disabling as preoperative seizure types. A worthwhile improvement in seizure outcome was achieved by completion of the callosotomy in 6 of 10 patients with unsatisfactory results from anterior callosotomy.     

Corpus Callosotomy for Seizures Associated with Band Heterotopia

Summary: Band heterotopia is a severe form of neuronal migration disorder associated with intractable epilepsy and neurologic impairment. Surgical treatment of seizures associated with this malformation has not been reported previously. We report a patient with band heterotopia and poorly controlled atonic seizures causing falls and injury. The patient was treated with anterior corpus callosotomy, with significant postoperative decrease in seizure frequency. Corpus callosotomy is a reasonable alternative to consider in management of patients with cortical heterotopia and intractable seizures.     

Corpus Callosum Volume and Neurocognition in Autism

The corpus callosum has recently been considered as an index of interhemispheric connectivity. This study applied a novel volumetric method to examine the size of the corpus callosum in 32 individuals with autism and 34 age-, gender- and IQ-matched controls and to investigate the relationship between this structure and cognitive measures linked to interhemispheric functioning. Participants with autism displayed reductions in total corpus callosum volume and in several of its subdivisions. Relationships were also observed between volumetric alterations and performance on several cognitive tests including the Tower of Hanoi test. These findings provide further evidence for anatomical alterations in the corpus callosum in autism, but warrant additional studies examining the relationship of this structure and specific measures of interhemispheric connectivity.     

Reversible Corpus Callosum Splenial Lesion Due to Steroid Therapy

Reversible corpus callosum splenial (CCS) lesions are rare findings and usually detected incidentally. We presented a case of 15‐year‐old boy with a diagnoses of nephrotic syndrome. He was referred for neuropsychiatric symptoms following dose reduction on steroid treatment. Brain magnetic resonance imaging (MRI) revealed a focal lesion in the CCS, hyperintense on T2 and FLAIR and hypointense on T1 images with diffusion restriction on apparent diffusion coefficient map. Follow‐up MRI 3 weeks later showed complete resolution of the lesion. It was probably result of focal intramyelinic edema due to excytotoxic mechanisms and/or arginine‐vasopressin release.     

Feline Agenesis of the Corpus Callosum

The unusual pattern of seizure development and developed seizure in a cat kindled at the ventral hippocampus is discussed in the light of agenesis of the corpus callosum (CC). In this animal, not only the CC but also the hippocampal commissure was completely absent and the dorsal portion of the septal area was separated in the midline. There was no other morphological anomaly except for slightly enlarged lateral ventricles. No behavioral or physical peculiarities were noted. The unusual profile of kindling in this animal was characterized by (a) very rapid kindling at the primary site, (b) the lateralized nature of the kindled primary site convulsion preceded by repetitive and violent contralateral axial rotation, and (c) the complete absence of positive transfer effect expected at the contralateral homotopic secondary site. These features are strikingly reminiscent of the pattern of amygdaloid kindling in forebrain-bisected cats. These observations add strength to our hypothesis that the CC (and possibly the hippocampal commissure) is the major anatomic substratum for convulsive generalization and the transhemispheric positive transfer effect in feline limbic kindling.     

Effect of Chronic Electrical Stimulation of the Centromedian Thalamic Nuclei on Various Intractable Seizure Patterns: I. Clinical Seizures and Paroxysmal EEG Activity

Twenty-three patients with various intractable seizure patterns were divided into four groups based on their most frequent seizure type and their clinical and EEG response to chronic electrical stimulation of the centromedian thalamic nuclei (ESCM): group A, generalized tonic-clonic (GTC, n = 9); group B, partial motor (Rasmussen type) (n = 3); group C, complex partial seizures (CPS, n = 5); and group D, generalized tonic seizures (Lennox-Gastaut type) (n = 6). CM were radiologically and electrophysiologically localized by means of stereotaxic landmarks and by thalamically induced scalp recruitinglike responses and desynchronization. ESCM consisted of daily 2-h stimulation sessions for 3 months. Each stimulus consisted of a 1-min train of square pulses with a 4-min interstimulus interval, alternating right and left CM. Each pulse was 1.0 ms in duration at 60/s frequency and 8–15 V (400–1,250 μ-A) amplitude. Voltage (V), current flow (μA) and impedance (kΩ) at the electrode tips were kept constant. A significant decrease in the number of seizures per month and paroxysmal EEG waves per 10-s epochs occurred in group A patients between the baseline period (BL) and the ESCM period. These changes persisted for >3 months after discontinuation of ESCM (poststimulation period, Post). Post was accompanied by a significant decrease in the number of paroxysmal EEG discharges. A substantial decrease in seizures and paroxysmal discharges was also observed in patients of group B. In contrast, patients of groups C and D showed no significant changes from BL to ESCM and Post periods, except for a significant decrease in the number of seizures in group D patients from BL to Post periods.     

Social and Behavioral Problems of Children with Agenesis of the Corpus Callosum

Archival data from a survey of parent observations was used to determine the prevalence of social and behavioral problems in children with agenesis of the corpus callosum (ACC). Parent observations were surveyed using the Child Behavior Checklist (CBCL) for 61 children with ACC who were selected from the archive based on criteria of motor development suggesting a relatively high general level of functioning. Younger children with ACC (ages 2–5) were rated as primarily having problems with sleep. Older children with ACC (ages 6–11) manifested problems in attention, social function, thought, and somatic complaints. The older children with ACC were also compared to CBCL data from 52 children with autism who were selected from a previous study. Children with ACC were generally less impaired than children with autism on nearly all scales, with significantly less severe problems in the areas of attention, anxiety/depression, social function, and unusual thoughts. A further questionnaire related to diagnostic criteria for autism indicated that some children with ACC had traits that are among those that contribute to the diagnosis of autism within the domains of social interaction and social communication, but fewer who manifest repetitive and restricted behaviors.