Epilepsy surgery in children – no longer a last resort

Abstract

Epilepsy surgery is not new; it has been in use for over 100 years. Sir Victor Horsley was the first to carry out a resective procedure for epilepsy in the late 19th century at the National Hospital for Neurology and Neurosurgery, Queen Square, London. However, it is only relatively recently that it has gained momentum as a realistic choice in the management of children with epilepsy. It was Murray Falconer, neurosurgeon at the Maudesley Hospital in London in the 1960s, who suggested that many of the adults who underswent temporal lobe surgery had a history of epilepsy since childhood; he went on to report successful temporal lobe surgery in children.1 Studies of epilepsy surgery in children have since demonstrated rates of seizure freedom similar to adults, with particular success in children with catastrophic early onset focal epilepsy, with limited resultant additional morbidity.2 However, despite this, as well as major advances in technology and surgical techniques, many professionals remain reluctant to refer. One recent study demonstrated that despite a mean age at onset of epilepsy of 14.6 years in individuals with partial epilepsy (the majority of whom had temporal lobe epilepsy), the average age at presentation for evaluation for surgery was 36.7 years.3 Further prospective investigation suggests the decision is more likely to be delayed in focal than catastrophic epilepsy.4 Children with early onset epilepsy are more likely to have a poor neurodevelopmental outcome; the premise is that early surgery will lead to improved long-term seizure control with resultant improved cognition, and certainly studies to date have shown that a shorter duration of epilepsy is more likely to be associated with this, although longitudinal follow-up studies are lacking. Epilepsy surgery in childhood encompasses a much wider spectrum than in adults. Resective surgery is considered where seizures are demonstrated to come from one area of the brain that is functionally silent, but also in those who have longstanding hemiplegia with a structurally abnormal contralateral hemisphere and lateralized seizures, who may be candidates for a hemidisconnection procedure. A recent epidemiological study suggested surgery may be an option in management in as many as 5% of the childhood epilepsy population.5 In 2004, The International League Against Epilepsy’s Paediatric Epilepsy Surgery Subcommission survey of 543 procedures performed in 20 centres found that the majority were multilobar resection or hemispherectomy, and that only 25% were temporal lobe resection. A further 42% had cortical dysplasia as the underlying aetiology; children under 4 years were far more likely to undergo large resections (multilobar resection or hemispherectomy), have a cortical malformation as the aetiology, and have daily seizures than the older age group (8–18y) who were more likely to undergo lobar or focal resections for tumours, cortical dysplasia, and hippocampal sclerosis. This study also supported the suspicion that children were not being considered early enough. Despite 60% having seizure onset at under 2 years of age, only 35% of children had surgery within 2 years.6 So why the reluctance to refer? There remain many myths and misconceptions with regard to epilepsy surgery, not least the belief that a high level of associated morbidity is inevitable, and that surgery should only be considered as a ‘last resort’. All children presenting with a possible focal onset to the epilepsy resistant to drugs, should in theory be possible candidates until proven otherwise. A consensus document published in 2006 as the result of a meeting of 32 individuals from 12 countries concluded that a recommendation should be made that all children with drug-resistant epilepsy should be assessed within a comprehensive epilepsy centre rather than defining criteria for an epilepsy surgery centre.7 They also agreed that significant gains can be made in seizure control, and that there are specific seizure syndromes that require specialized surgical strategies. The consensus group suggested that certain subgroups, namely infants and toddlers, as well as those being evaluated for hemipsherectomy and multilobar resections, should have access to advanced technologies. Advances in neuroimaging have greatly increased the numbers of possible candidates and enabled a less invasive approach. However, a small proportion remain who do require invasive electroencephalographic monitoring, either to delineate the exact area to be removed or where such area lies close to eloquent cortex, and again, this requires specific multidisciplinary expertise. No longer should surgery be considered a last resort in the management of children with focal epilepsy resistant to medication. Drug resistance should be apparent early in the natural history of the epilepsy and, therefore, children should be referred early. Much can be gained from early referral and assessment, even if surgery is not an option. Much can be lost by waiting.