1 Pediatric Epilepsy Surgery: Introduction
An estimated 10.5 million children worldwide have epilepsy. The annual incidence is reported to be 61 to 124 per 100,000 children in developing countries and 41 to 50 per 100,000 children in developed countries.1 Epilepsy, especially pediatric epilepsy, not only causes seizures but also is frequently associated with other disabilities. Almost half of all children with epilepsy have high rates of co-morbid learning disabilities, mental retardation, developmental delay, psychiatric and behavioral difficulties, and psychosocial problems. Therefore, preventing cognitive and developmental stagnation or decline in children with epilepsy is as important as achieving seizure freedom and constitutes one of the main challenges in the management of these patients. However, despite major advances and improvements in diagnostic techniques and medical management options in pediatric epilepsy, approximately 20% of children with this disease continue to suffer from medically intractable epilepsy. Surgical management is often the single remaining treatment option for some of these children, not only to control seizures but also to prevent and improve the co-morbid conditions mentioned previously.2–7
It is a well-known fact that the comprehensive care of children with epilepsy is challenging. Specialized knowledge of and expertise in the medical and surgical management of such patients are required. Thus, a well-coordinated, collaborative relationship between medical and surgical teams in a multidisciplinary environment is critical for successfully managing pediatric epilepsy patients. Today, many pediatric epilepsy centers are designed and organized with this collaboration in mind, although it was not the case for many years.
Historical Evolution of Pediatric Epilepsy Surgery
Although surgical intervention in epilepsy patients has a relatively long history, many decades elapsed before epilepsy surgery became an established and accepted treatment option for adult epilepsy patients. Pediatric epilepsy surgery has followed an even more hesitant course. For years it was performed in only a handful of centers, remaining an option of last resort in the management of children with epilepsy. Even children with intractable epilepsy were rarely referred to specialized epilepsy surgery centers. The outcomes data derived from an early pediatric epilepsy surgery series were also discouraging.
The historical reluctance to perform pediatric epilepsy surgery stemmed from several legitimate concerns at the time, such as the unavailability of epilepsy surgery centers in many locations, poor results, and a general lack of knowledge or misinformation about pediatric epilepsy surgery. Limited data regarding the long-term effects of epilepsy surgery on children as well as epidemiologic data showing that many childhood seizures were benign and had favorable outcomes also contributed to this reluctance to perform pediatric epilepsy surgery.8
As a result, it took almost two decades after publication of the results of initial surgical series with pediatric epilepsy patients to see any increase in the number of centers offering surgery as a management option for children with epilepsy.9–12 As interest in pediatric epilepsy and its surgical management gradually increased, many pediatric neurology programs established separate pediatric epilepsy sections. Gradually, pediatric neurosurgeons, along with epilepsy surgeons, started to operate on increasing numbers of pediatric epilepsy patients. Although the initial surgical series included mostly older children, the patient age gradually decreased to the point that reports of infantile epilepsy surgical cases started appearing in medical journals.5–7,13,14 As a result, there has been a gradual, then an exponential, increase over the past 10 years in the number of centers providing surgical management as an option for pediatric epilepsy patients.
The accumulated data and reported results from the most recent surgical series are encouraging. It is now clear that surgical intervention in children with intractable epilepsy dramatically improves outcomes, providing not only seizure reduction and freedom but also resulting in improved behavior, quality of life, language, and cognitive function.15 Thus, in a relatively short period of time, pediatric epilepsy surgery procedures have been transformed from rarely performed interventions into an established management option for children with intractable epilepsy. These developments have led many children’s hospitals to establish pediatric epilepsy surgery programs. As a result, pediatric epilepsy surgery hasbecome a very active subspecialty interest for many pediatric neurosurgeons in these programs.
Epilepsy Surgery in Children as a Special Expertise
Initially, the main principles behind the surgical management of epilepsy patients, starting with the preoperative assessment and extending to the actual surgical procedures, were primarily developed for adult epilepsy patients. These principles were later extrapolated and applied to pediatric epilepsy patients.16 However, because pediatric epilepsy patients are significantly different from their adult counterparts, pediatric epilepsy surgery should not be viewed simply as an extension of adult epilepsy surgery.
Although there are many common features in the surgical management of pediatric and adult epilepsy patients, there are also many differences. Understanding these differences is of critical importance in patient management.4,17 For example, pediatric epilepsy patients have very diverse epileptic disorders that exhibit different electrophysiological characteristics and clinical semiology from adult epileptic disorders. In addition, pediatric epilepsy patients may have developmental and psychosocial problems that must be taken into account when considering surgery. Therefore, using appropriate pediatric neurosurgery techniques and having expertise in the surgical management of children, especially infants, are as important as having expertise in epilepsy surgery.
Among pediatric epilepsy patients, infants and young children constitute an extremely challenging subset. Awareness of age-related characteristics as well as of the special paradigms and issues related to treating this patient group is an important prerequisite for ensuring good surgical outcomes. For example, the surgical management of medically intractable seizures in children is characterized by several uniquely challenging problems and requires a special approach to presurgical assessment, surgical indications, and surgical strategy. In addition, there is significant controversy regarding issues such as patient selection criteria, presurgical assessment methods, appropriate surgical indications, and the timing of surgery, as well as the appropriate surgical techniques to be used for children of different ages.
To meet these challenges, the Subcommission for Pediatric Epilepsy Surgery was formed by the International League Against Epilepsy (ILAE) in 1998 to formulate appropriate standards for epilepsy surgery in childhood. In 2003, the subcommission organized a meeting to address the following questions4:
Are the unique characteristics of children with epilepsy and their syndromes sufficiently different to justify dedicated pediatric epilepsy centers?
Is adequate information available to propose guidelines regarding patient selection and surgical treatment for pediatric epilepsy surgery patients?
At the end of the meeting, the subcommission agreed that the “neurobiological aspects of epilepsy are unique to children, especially the young, and as such require specific pediatric epilepsy expertise. Collectively these features justify the unique approach necessary for dedicated pediatric epilepsy surgery centers.”4
Characteristics and Special Considerations of Pediatric Epilepsy Surgery
Although many aspects of epilepsy and its surgical management in children are similar to those in adults, there are significant differences and challenges unique to children, especially infants and young children. These differences become critical during many stages of the surgical management of pediatric epilepsy, starting from the preoperative assessment and extending to the surgical intervention itself. We will briefly review these areas to provide a general perspective on the subject.
Preoperative Assessment
Pediatric Epilepsy Syndromes
The causes of epileptic seizures amenable to surgery are much more common and diverse in children1,3: perinatal injuries; infantile spasms; hemispheric syndromes, such as Rasmussen encephalitis; and neurocutaneous disorders, such as Sturge-Weber syndrome. Some causes are seen exclusively in children and rarely or never occur in adults. Each of these disorders has its own unique diagnostic and surgical challenges as an epilepsy syndrome.
The neuropathological substrate of epilepsy and its observed frequency in children are also significantly different from those in adults. Although cortical malformations are the most common neuropathological substrate in children (23–78%), they are much less common in adults. Although mesial temporal sclerosis (MTS) in children is seen much less frequently (17–38%) than in adults, dual pathologies associated with MTS occur much more frequently in children.1,3,4,7
The clinical and electrophysiological spectrum and presentation of intractable, localization-related epilepsy are often heterogeneous and wide ranging in childhood. In childhood, intractable seizures can be quite atypical and poorly defined compared with the relatively well-defined clinical and electro-physiological characteristics of epilepsy syndromes in adults. Unilateral localized or hemispheric etiologies in children may present with generalized seizures and electroencephalography (EEG) patterns, progressive neurological disorders, and bilateral congenital brain syndromes.4,17
Some of the pediatric epilepsy syndromes seen in infants and young children are much more than seizure disorders and can be catastrophic because of the associated cognitive and developmental delay or regression. These cases are problematic, and their management requires a great deal of expertise. The seizures in these patients are also frequently extratemporal and cover large cortical areas, including the eloquent cortex. Invasive monitoring, cortical mapping, and stimulation studies may be needed more frequently in these children than in adults.
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