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Epilepsy surgery

 

How is it different from adults

Why is it more preferred in children

Who is the candidate

Who cannot be the candidate

What Types of Epilepsy are Suitable

What are the risks involved

 

How is surgery performed different from that in adults 

First of all, the evaluation of children with complex epilepsy problems should be done by an epileptologist who specializes in pediatric problems. 

Second of all, brain surgery in infants and children is a specialty in itself which requires a pediatric neurosurgeon, pediatric anesthesiologists and a pediatric intensive care unit with experience in dealing with this delicate surgery. 

 

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Why surgery is more preferred in children than adult?

Chronic epilepsy can have severe effects on the developing brain of children. Long-term follow-up of children with epilepsy has shown that they have a higher incidence of psychomotor retardation, psychiatric disease and learning difficulties, as well as lower I.Q.s, than the general population. These are  believed to be caused not only by recurrent seizures but also by widespread changes in a brain with an abnormal, epileptogenic area. Similarly, use anticonvulsant medication may slow psychomotor development. Following successful surgical treatment, these drugs may be stopped. 

Another reason to operate on infants and children is that their brains are more resilient ( also called neuronal plasticity ). In the developing brain, the wiring is less rigid such that if an area (of certain function) is removed, other areas of the brain can take over that function. For example, removal of the area of the brain responsible for language before 6 years of age may slow language development, but should not significantly impair the child's ability to speak in the long run. Removal of the same area in an adult would be devastating. Neuronal plasticity in children allows removal of larger areas with a greater likelihood of curing the patient, without an unacceptable increased risk of post-operative neurological deficits.

 

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Who is a candidate?

Patients, both adults and children, must fulfill the following criteria: 

  1. recurrent epilepsy that continues despite adequate trials of anti-epileptic medication
  2. disabling seizures the disorder must be a significant detriment to the patient's lifestyle
  3. anatomic localizability the origin of the convulsions must reside in a specific area of the brain that can be removed safely. 

Any patient who may fit the previous criteria should be further evaluated by an epileptologist. The decision to proceed should be made by a dedicated group of specialists including epileptologists, neurophysiologists, neuropsychologists, neuroradiologists and epilepsy surgeons. A variety of tests may need to be performed during the evaluation includes neuropsychological testing, MRI, PET or SPECT scanning, video-EEG monitoring (which requires admission to the hospital) and possibly surgical implantation of electrodes.

 

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Who is not a suitable candidate?

Patients with severe medical illnesses may not tolerate surgery. Children with degenerative or metabolic diseases often do not improve from surgery. Mental retardation, or an IQ < 70, may indicate widespread disease and is a poor prognostic indicator (poor surgical outcome). Severe psychiatric illness such as depression is also not allowed in surgery.

 

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Types of Pediatric Epilepsy Suitable for Surgery

 

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Temporal Lobe Epilepsy    Epilepsy associated with lesions    Cortical dysplasia  Hemimegalencephaly    Tuberous sclerosis     Sturge-Weber Syndrome    Rasmussen's encephalitis Lennox-Gastaut   Functional hemispherectomy   Corpus callosotomy

 

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a) Temporal Lobe Epilepsy

The most common epilepsy amenable to surgical resection is temporal lobe epilepsy which is also called complex-partial seizures, psychomotor epilepsy or limbic epilepsy. Many of these patients suffered initially from febrile seizures and these seizures may ultimately evolve into generalized tonic-clonic seizures.

Temporal lobe epilepsy is usually associated with a focal lesion in the brain hippocampus called mesial temporal sclerosis. Removal of this area of the brain, in carefully selected patients, results in cessation of seizures in over 70% of patients, many of whom can be taken off their medication after a few years. Another 10-20% of patients will be improved from the surgery but will continue to have some seizures and the rest may not improve significantly. Some patients may notice some difficulty remembering certain words or recognizing places after the surgery but these deficits are felt by patients to be minor and are often transient. The risk of serious morbidity is less than 2%.

b) Epilepsy associated with lesions

These lesions may be slow growing tumors, vascular malformations, infections or congenital abnormalities which is causing the seizures and can be seen in MRI scans. Curative outcome of such surgery to remove the abnormal process depend on the number and frequency of the seizures and the location of the lesion. If the seizures have been present for many years, a more extensive surgery may be required. In this case, the patient should be evaluated by a comprehensive epilepsy center and the operation should be performed by a dedicated epilepsy surgeon.

These are several diseases unique to children which may respond well to surgical treatment.

c) Cortical dysplasia (changed in size and shape o brain cells) also called migrational disorders are congenital abnormalities (present at birth) in the architecture of the cerebral cortex. These islands of abnormal brain may promote seizures, and their removal may be curative.

d) Hemimegalencephaly is a dysplasia and enlargement of most of one hemisphere.

e) Tuberous sclerosis is a genetic disorder associated with focal, abnormal areas of brain which may also cause epilepsy.

f) Sturge-Weber Syndrome is a genetic disorder of the veins of one half of the brain associated with a facial angiomatous (blood vessel-related) discoloration and mental retardation. The abnormal blood vessels cause calcification of the cortex and seizures which may respond to removal of the malfunctioning areas.

g) Rasmussen's encephalitis - an inflammation of one half of the brain associated with progressive weakness of the arm and leg on one side and seizures. These seizures may become continuous and are then called epilepsia partialis continua. Infantile spasms, also called West syndrome, are defined by this characteristic seizure type associated with developmental delay and a characteristic EEG pattern called hypsarhythmia. Although the seizures are generalized, sometimes it is possible to identify a zone of cortical abnormality which can be safely removed to effect a reduction in seizure frequency.

h) Lennox-Gastaut - a syndrome defined by psychomotor retardation, a characteristic EEG pattern, and multiple seizure types including drop attacks which are sudden and without warning and may result in lacerations, broken bones and other forms of bodily injury. Surgical division of the corpus callosum, a bundle of fibers connecting the two cerebral hemispheres, may reduce the frequency of the drop attacks.

Special pediatric epileptic surgeries

There are two unique epilepsy surgical operations performed in children:

i) Functional hemispherectomy

This involves removal of a significant amount of one hemisphere (half of the brain) and disconnection of the remaining parts. This is indicated only in patients with severely debilitating seizures arising from one hemisphere such that patient is unable to use the other half of the body even to move their fingers or tap their feet, since following the operation their weakness on that side will be more obvious.

The following diseases may improve following hemispherectomy: hemimegalencephaly, extensive cortical dysplasia, Sturge-Weber, Rasmussen's encephalitis, and extensive porencephalic cysts. Post-operatively many patients exhibit a 10 point rise in their I.Q. tests and improvements in behavior. Not all patients are cured, however, since these diseases are often widespread and up to 25% of patients may still have some seizures after surgery, although many of these will still have a significant decrease in seizure frequency.

j) Corpus callosotomy

This involves surgical division of the anterior 4/5 of the corpus callosum, a bundle of fibers connecting the two cerebral hemispheres (the right and left hemispheres). The indications for this procedure include severe refractory seizures (not response to drug therapy) and with no single localizable area responsible for those seizures that can be surgically removed. 

Corpus callosotomy usually does not cure all of the seizures. For about 80% of patients, the generalized seizures (i.e. "drop attacks") are stopped. Epileptic disorders amenable to corpus callosotomy include generalized atonic seizures ("drop attacks") and atypical absence seizures which are all associated with Lennox-Gastaut. These may improve with surgery and finally seizures spread only from an area that can not be safely removed.

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The risks of epilepsy surgery can be divided into three categories:

1. The risk of the anesthesia used and the procedure itself:

All patients undergoing general anesthesia have a very small risk of death from the anesthesia itself. These risks vary depending on the patient's health conditions, age and so on. There might be risks of severe blood loss as well as the development of hydrocephalous which causes pressure to build up in the brain as a result of cerebrospinal fluid obstruction. Surgery also increase likelihood of brain infection which can be life-threatening. The overall death rate for pediatric epilepsy surgery is probably less than 1% at medical centers that have experience with the procedure.

2. The risks of neurological deficits: 

Brain surgery has the potential for creating additional neurological deficits--or abnormal functioning in the brain. Most children who undergo multilobar resection or hemispherectomy already have neurological abnormalities. Such abnormalities can worsen with surgery include problems in movement (particularly hand coordination), sensation, thought, and language. For instance, children undergoing removal of the major motor structures that control hand coordination will never recover the fine movements of the fingers whereas  children under the age of nine years who have their major language centers removed will recover language function. In general, the younger the child is at the time of surgery, the better the recovery. However, for surgery in very young infants (0-5 months), it is considerably more dangerous than at other ages.

3. The risk of surgery failure:

Pediatric epilepsy surgery usually significantly reduces the number of seizures and improves the lives of the patients and their families. However, complete seizure control, or cure, is achieved in only approximately 50% of the children undergoing surgery since epilepsy is usually caused by problems in many parts of the brain. Surgical treatment may remove only the most obvious problem such that seizures of many children which does not initially respond to medication are readily controlled with medication following surgery.

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Useful link/s:

MedicineNet.com Pediatric Epilepsy Surgery

Pediatric Surgery Website

 

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