There are many surgical procedures which fall under the broad category of hemispherectomy. The main goal of each procedure is to stop the seizures by completely disconnecting one cerebral hemisphere from the other in order to prevent seizures from spreading to other parts of the brain.
What are the various hemispherectomy procedures?
There are several different types of hemispherectomy procedures. They include the anatomical hemispherectomy, subtotal hemispherectomy, the functional hemispherectomies, and the hemispherotomies. There are also other procedures which fall under this category which include hemidecortication and other newer procedures.
Surgeons are not trained in all techniques and some techniques are more complicated than others. Most surgeons perform only the procedures they have been trained to perform and are familiar with. This video explains the history of hemispherectomy surgery and why different techniques were developed:
What are the chances of total seizure control after hemispherectomy?
A recent systemic review of 15 studies which address seizure outcomes across several different hemispherectomy procedures shows that the long-term seizure control rate at five years or more after surgery is 71%.
What factors affect seizure control?
Children whose seizures began after 3 1/2 months of age have a higher chance of long-term seizure control. Also, children who have abnormal MRI findings prior to surgery also have higher rates of control. Sturge-Weber syndrome, Rasmussen’s encephalitis, and pediatric stroke syndrome have the highest seizure control rate of approximately 80%.
Children with hemimegalencephaly have the lowest at seizure control rate at approximately 66%.
What are the surgical risks of hemispherectomy?
Hemispherectomy is an extremely delicate procedure which should only be performed by an experienced pediatric epilepsy surgeon.
Hydrocephalus is the most significant risk after hemispherectomy surgery. Approximately 23% of patients will develop hydrocephalus, with 27% of those children developing hydrocephalus 90 days or more after surgery. The risk of developing hydrocephalus is 20% after functional hemispherectomy and 30% after anatomical hemispherectomy. Children with hemimegalencephaly have a higher chance of developing hydrocephalus – about 40%.
This risk is across the lifespan, with cases reported ten or more years after surgery.
If your child is having or has had hemispherectomy surgery, we strongly encourage you to familiarize yourself with hydrocephalus and its symptoms. Learn more about the risk of hydrocephalus here. We also have a downloadable guide titled Hydrocephalus After Hemispherectomy for you to share with your child’s care team, teachers, and other aligned professionals.
Blood loss requiring transfusion is also risk, especially for babies and infants. In very rare cases, stroke, brain swelling (cerebral edema), or other complications can occur.
Post-operative fevers are common after surgery and may occur for several months later. This is because blood product and protein in the cerebrospinal fluid from the surgery can irritate the brain, causing the body to respond as though there is an infection. Most surgeons use an external ventricular drain to evacuate blood product and other matter from the cerebrospinal fluid, as well as to monitor intracranial pressure. The use of this drain can also reduce the incidence of fevers after surgery.
In some cases, fever can be caused by meningitis after craniotomy caused by introduction of bacterial or virus (usually Staphylococcus) during placement of the extraventricular drain or from medical personnel, family, or visitors touching the drain after placement without appropropriate hand washing or glove wearing. The risk of infection increases with the length of time the drain is in place.
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