Introduction
In 1928, the first series of anatomical hemispherectomies was carried out by Dandy for the treatment of gliomas. In 1938, the first anatomical hemispherectomy was performed for the treatment of epilepsy. In the 1990s, hemispherectomy techniques were introduced by Delalande et al., Schramm et al., and Villemure and Daniel. Each team came up with their own ideas to attain complete functional disconnection of the hemisphere.
Hemispherectomy is a surgical procedure used for the management of patients with epilepsy secondary to severe unilateral hemisphere damage. Hemispherectomy is generally recommended for specific indications as it has shown great functional and epilepsy outcomes. Extensive disconnection can further result in optimum seizure control; however, these procedures increase the risk of neurological defects along with motor and mental problems.
Therefore, the surgical procedure for epilepsy has to be decided according to the pathology, patient’s age, and developmental status. This surgery is performed on children and adults with seizures who are not responding to medications. Post-surgery, a hospital stay of five to seven days is mandatory. Further, rehabilitation may also be required.
What Are the Indications of Hemispherectomy?
The purpose of hemispherectomy is to isolate or eradicate the functional epileptogenic zone in the brain. In hemispherectomies, the entire hemisphere is disconnected from the other parts of the nervous system.
In 2001, a study conducted by Wiebe et al. showed that this surgery greatly improved the seizure outcomes in patients with epilepsy surgery compared to medical therapy.
Therefore, early surgical referral is recommended for patients resistant to medical therapy. The principle of functional hemispherectomy involves functional disconnection from the contralateral healthy brain and leaving the live, vascularized brain intact. There are two types of hemispherectomies are as follows:
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Functional Hemispherectomies (Disconnective): This technique involves disconnecting the side from the rest of the brain by removing a small area of the brain. This technique has less risk for complications.
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Anatomic Hemispherectomies: This technique is usually carried out on children who have persistent seizures despite the functional or disconnective hemispherectomy. In this type of hemispherectomy, the frontal, temporal parietal, and occipital lobes of the brain are removed. This procedure has a higher risk for complications like extra blood loss and fluid buildup.
Both these types of hemispherectomies have shown success. However, if seizure freedom is not achieved through functional hemispherectomy, an anatomic hemispherectomy might be required.
How Is the Patient Evaluated Before the Surgery?
The following presurgical evaluation is required to ensure desired outcomes:
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Proper personal and family history.
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Complete seizure history, including the onset of epilepsy, its classification according to the international league against epilepsy (ILAE), and frequency of seizures.
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Semiology (clinical characteristics of the seizure).
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The neurologic examination is based on motor and sensory-motor neurologic deficits like hemiparesis (partial weakness or muscle paralysis on one side of the body), unilateral hypotonic syndrome, and hemianopsia (loss of one-half of the visual field).
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Neuropsychological examination.
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24-hour video electroencephalography (EEG).
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Neuroimaging, like brain magnetic resonance imaging (MRI), positron emission tomography, and computed tomography.
What Is the Outcome of the Surgery?
Studies show that after the surgery, a seizure-free rate of 60 % to 90 % is achieved, and significant improvement is seen in around 10 % to 15 % of patients. The outcome of hemispherectomy is usually good in patients with acquired lesions and in patients with congenital malformations of cortical development. However, seizure outcomes vary according to the surgical techniques and etiology of the seizures.
Some studies reveal that anatomical hemispherectomy is the most efficient because early recurrence of seizures is seen in functional hemispherectomy (an evolution of anatomic hemispherectomy in which less brain is removed, but the diseased brain hemisphere is completely disconnected from the normal brain hemisphere) due to incomplete disconnection.
However, most surgeons believe that the complication rate is greater with anatomic hemispherectomy compared to the recently developed functional hemispherectomy.
In most cases, improvement in post-surgery cognitive function is observed. Even if the seizures remain after surgery, the reduction in frequency leads to improvements in daily activities, behavior, and employment capabilities. The outcome of the surgery or the improvement depends on the following factors:
Etiology:
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Duration of Epilepsy Before Surgery: A longer duration of epilepsy prior to surgery is related to poor prognosis for the global outcome, particularly for verbal communication abilities.
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Post-Surgical Seizure Freedom: Post-surgical seizure-free outcomes have shown a positive correlation with verbal language outcomes in children with a developmental etiology when compared to the acquired pathology group. If postoperative cognitive improvement is not seen, it might be related to abnormal metabolism along with MRI (magnetic resonance imaging) abnormalities of the healthy hemisphere.
What Are the Complications Associated With Hemispherectomy?
Patients undergoing hemispherectomy mostly suffer from a transient aggravation of hemiparesis. However, severe aggravation of hemiparesis or hemiplegia (complete paralysis on one side of the body) has never continued to exist for a long period. More severe impairment in residual motor control for hand functions than for walking. Other complications associated with hemispherectomy include:
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Coagulopathy (impaired blood clot formation).
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Aseptic meningitis (inflammation of the brain and spinal cord membranes caused by an infection).
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Cerebral infarction (occurs due to the disruption of blood flow to the brain caused by problems with the blood vessels that supply it).
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Hydrocephalus (excessive fluid build-up in the brain cavities).
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Superficial cerebral hemosiderosis (a chronic condition characterized by linear residues of blood present in the superficial layers of the cerebral cortex).
The most common complication is hydrocephalus which constitutes 10 % to 50 % of complications. Hemianopia (loss of one-half of the vertical visual field) is reported in almost all surgical patients. In around 10 % of the cases, a second-look surgery is needed for complete resolution from seizure if the seizures persist or there is MRI evidence of incomplete disconnection. Careful surgical consideration for younger patients has been required for the analysis of several age-related issues as compared to adults.
Early surgery allows better neurocognitive and psychosocial development. The higher mortality rate in infants is due to the small blood volume and severe cortical malformations that sometimes require greater resection.
Conclusion
Hemispherectomy or cerebral hemispheric disconnection surgery is a well-explored treatment option for intractable epilepsy occurring as a result of a diffuse unilateral hemispheric disease that cannot be managed with medical therapy.
Hemispherectomy might show great results or outcomes in seizure management, further improving the quality of life. It is essential for the neurosurgeon to carefully evaluate the condition of each candidate for hemispheric disconnection and to use the most appropriate technique for that patient.
