Comorbidities of Surgical Treatment




INTRODUCTION



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Epilepsy surgery is an extremely effective therapeutic option for many children with drug-resistant epilepsy. In medically resistant children, the likelihood that further antiepileptic drugs (AEDs) will significantly reduce seizure frequency is less than 10%, whereas surgery leads to seizure freedom in 40–90% of appropriately selected cases, depending on the degree of resection, underlying pathology, and operative procedure. In addition, other positive postoperative outcomes are arguably considered more important and include enhanced development and behavior and improved quality of life.



Epilepsy surgery is not without risk and there is a rare risk of mortality, which must be weighed against the risk of mortality of continual seizures and potential benefits of successful surgery. There are also several surgical complications, some of which may be anticipated, such as a visual field defect following hemispherectomy, whereas others are unexpected. Rarely, there may be postoperative deterioration in other comorbid domains, namely behavior, cognition, and quality of life, all of which have significant implications for the child and family. This chapter will address the mortality and comorbidities associated with epilepsy surgery in children.




MORTALITY



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Historically, there has been a significant risk of mortality associated with neurosurgery in children, including epilepsy surgery. However, with improved surgical technique, anesthesia and postoperative care, the development of dedicated epilepsy surgery centers, and availability of new techniques of evaluation, this risk is now very low and generally estimated at 0–2%.1 Children are at higher risk of mortality in epilepsy surgery than adults. Most reports of mortality in pediatric epilepsy surgery describe isolated cases in large surgical series.2,3,4,5



Causes of early postoperative death include infections, hydrocephalus, dehydration, hemorrhage, and allergic reactions. Most mortalities related to epilepsy surgery occur in children younger than 3 years.4 Infants have a greater risk due to their relatively small blood volume and the development of coagulopathy following hemorrhage in surgery.6,7 Young hemispherectomy candidates have the highest mortality. Anatomical hemispherectomy is associated with even greater mortality due to intraoperative blood loss and of the potential for late hemosiderosis (resulting from numerous acute and chronic hemorrhages from the fragile capillaries in the subdural membrane), obstructed hydrocephalus, bleeding into the hemispherectomy cavity, and progressive brain stem shift.8 Newer functional hemispherectomy techniques involving initial tissue removal followed by disconnection of remaining structures require a shorter operating time and are associated with reduced blood loss and are therefore associated with lower mortality and morbidity than anatomical hemispherectomy procedure. However, risk of mortality in hemispherectomy remains higher than for other epilepsy surgery procedures. Hemispherectomy for hemimegalencephaly is associated with the highest risk of mortality compared with other pathologies (Rasmussen’s, infarct/ischemia) due to the more complex surgery (related to the enlarged megalencephalic hemisphere and distorted anatomical landmarks), longer operative time, and greater blood loss.3



The overall low risk of mortality from epilepsy surgery must be balanced against its benefits (seizure freedom, improved development/cognitive potential, and enhanced quality of life) and risk for death due to chronic epilepsy. Children with epilepsy have a high standardized mortality rate reported at 7–13.2.9 Children with epilepsy die for a variety of reasons but most commonly as a result of comorbid neurological deficits rather than as a direct result of their epilepsy.10,11 There are no studies comparing long-term mortality rates in surgically versus medically treated pediatric patients; thus, it is unclear whether successful surgery actually reduces mortality for children with epilepsy. Several adult studies have addressed this issue, but the data is conflicting. However, overall it is widely believed that mortality rates are lower and approach normal mortality rates in patients who are seizure free postoperatively12 than in patients with continuing seizures.



All families should therefore be counseled about the risk of mortality prior to surgery, albeit small overall and appropriate emphasis given to families of children who are at higher risk, that is, children younger than 3 years who are undergoing hemispherectomy, particularly for hemimegalencephaly.




SURGICAL MORBIDITY



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All epilepsy surgery procedures are associated with blood loss, which varies by procedure. Blood loss during focal or lobar resection is approximately 200 to 500 mL, whereas losses in anatomic hemispherectomy often exceed 1500 mL.7 Infants are at particular risk of significant blood loss for several reasons. First, the volume of cardiac output to the brain is proportionally larger in infants than in older children due to the larger ratio of brain weight compared with body weight. Second, the circulating blood volume in infants is much smaller than in older children and adults. Third, infants more commonly undergo extensive hemispheric surgery, which is associated with larger relative blood loss. When an infant has had significant blood loss, there is a higher probability of postoperative coagulopathy and further hemorrhage. Blood loss is managed with volume replacement, blood transfusion, and, in the case of large hemorrhage, with concomitant use of other blood products.



Epilepsy surgery has an overall infection rate of 2–3%. Infections include wound infections, meningitis, and osteomyelitis of the bone flap. Most wound infections are managed with antibiotics, but it may occasionally be necessary to debride or re-explore the wound. Should osteomyelitis develop, it may be necessary to remove the bone flap and perform a cranioplasty. Chronic invasive monitoring is associated with higher rates of infection ranging from 2% to 16%.13



Invasive monitoring is associated with cerebrospinal fluid (CSF) leaks in 19–33% of patients, 2–14% experience cerebral edema, 0–16% develop subdural hematoma, and 9% have an intracerebral hemorrhage. Figure 58–1 shows an intracranial hematoma overlying a subdural grid. Isolated cases of permanent neurological morbidity and death have been reported.14 However, the complications of invasive monitoring need to be balanced against the benefits of epilepsy surgery for this selective group, and though rates of complications are higher than for children having resective surgery without invasive monitoring, significant improvements in seizure outcome are reported in up to 80% of cases.15




Figure 58–1.


Intracranial hematoma overlying a grid.





Neurological complications of epilepsy surgery can be broadly classified into anticipated neurological sequelae or unexpected neurological morbidity. Neurological deficits resulting from resections involving sensorimotor and visual cortex are generally anticipated and discussed with the family prior to surgery. Many unanticipated neurological deficits such as those related to edema are transient and may fully recover with time.



Typical anticipated neurological sequelae following hemispherectomy include homonymous hemianopia (if not present preoperatively), quadrantanopic field defects following temporal lobectomy, hemiparesis (if not already present) in hemispherectomy, and deterioration in hand function (if well preserved prior to hemispherectomy).



After focal resection, 0–10% of patients have permanent sequelae including hemiplegia, homonymous hemianopia, quadrantanopia, and dysphasia.1 Some children experience a worsening of their hemiparesis after hemispherectomy while others may be unchanged or improved.16,17 Children undergoing corpus callosotomy before puberty do not develop the typical disconnection deficits experienced by one-third of adults.18 However, teenagers may experience this syndrome, particularly after total callosotomy, but this often improves over time.



Greater plasticity of the central nervous system allows young children to better compensate for surgically induced deficits. However, although surgery to language dominant cortex should be avoided, it may be necessary in patients with tumors and/or hemispherectomy of the dominant hemisphere in Rasmussen’s encephalitis. Reorganization of language, due to brain plasticity, to the nondominant hemisphere occurs robustly after surgery in early childhood, diminishes with advancing age, but may still be possible in adolescents.19



Single cases of hydrocephalus have been observed rarely after focal resections.20,21 Figure 58–2 shows hydrocephalus occurring after a left frontal resection. Hemispherectomy is associated with higher rates of hydrocephalus and 8–33% of children will require shunt placement.1 Hydrocephalus was much more common after anatomical hemispherectomy (Fig. 58–3) and the advent of hemispherectomy or functional hemispherectomy has greatly reduced this problem.




Figure 58–2.


Hydrocephalus occurring after a left frontal resection.






Figure 58–3.


Hydrocephalus following anatomical hemispherectomy.






POSTOPERATIVE SEIZURES



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Acute postoperative seizures (APOSs) occurring in the first 7–14 days after surgery are thought to be due to local phenomena as a result of surgery, that is, hemorrhage and edema. The occurrence of postoperative seizures is often disappointing for the families and children but is not necessarily associated with a poor postoperative outcome. While children with APOS experience lower rates of postoperative seizure freedom, there is still a reasonable chance of a favorable surgical outcome. A report of 148 children undergoing epilepsy surgery found APOS in 25% of cases; 51% of these children had good long-term seizure control compared with 81% of children who had not experienced APOS.22



Further management options must be considered if seizures continue after the period of postoperative recovery (Fig. 58–4). Reevaluation for epilepsy surgery is appropriate for some children. Figure 58–5 demonstrates an incomplete frontal dissection in a child who underwent a functional hemispherectomy but continued to experience seizures. Completion of the dissection led to the child becoming seizure free. Other management options include change in AED regimen, institution of the ketogenic diet, or vagal nerve stimulator. Families and children require significant support in this situation.




Figure 58–4.


Algorithm for management of continuing epileptic seizures following surgery.

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Jan 2, 2019 | Posted by in NEUROLOGY | Comments Off on Comorbidities of Surgical Treatment
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