Hemispherectomy

Description

Hemispherectomy is a surgical procedure which involves total or partial removal of an affected cerebral hemisphere or disconnecting the affected cerebral hemisphere from the unaffected side.

History

Dr. Walter Dandy first performed anatomical hemispherectomy in 1928 for the treatment of a malignant brain tumor. In the 1950s, Dr. H.G. McKenzie did the first anatomic hemispherectomy as a treatment option for patients with intractable epilepsy. Over the years anatomic hemispherectomy was modified through various techniques to achieve complete disconnection with less tissue removal and to decrease the incidence of postoperative complications. The modified technique includes modified anatomic hemispherectomy, functional hemispherectomy, and hemispherectomies, such as the peri-insular hemispherotomy. All of these techniques include some modifications of the original anatomic technique and have been shown to have similar seizure-free rates.

Eligibility Criteria

Patients with the following clinical and neuroimaging features may be appropriate for a hemispherectomy procedure.

• Medically intractable epilepsy with seizures arising from the pathological side.
• Weakness of one side of body with loss of dexterity of hand with or without peripheral visual loss which is opposite to the
• Developmental retardation or arrest of maturation due to intractable seizures.
• Diffuse abnormality of one cerebral hemisphere which is contributing to the intractable epilepsy.

Common Pathologies or Etiologies:

Diseases presenting with these symptoms include malformations of cortical development, perinatal infarction (stroke), hemimegalencephaly, Sturge-Weber-Dimitri disease, and Rasmussen's encephalitis. Most of these patients start having seizures and weakness early in life. Once the diagnosis of epilepsy is suspected, the patient should be referred to a center specialized in the evaluation and management of pediatric epilepsy.

Hemispherectomy Types:

Two types of hemispherectomies commonly performed include anatomic and functional (disconnective) as shown in Figures 1 and 2. Anatomic hemispherectomy involves the removal of the frontal, parietal, temporal, and occipital lobes. The deeper structures, such as the basal ganglia, thalamus, and brain stem are left in place. The anatomic hemispherectomy has a slightly higher risk of blood loss and delayed hydrocephalus. It is typically performed for patients with hemimegalencephaly. The functional technique involves removing a smaller area of the affected hemisphere and disconnecting the remaining brain tissue. This disconnection includes a corpus callosotomy and allows for electrical isolation of the hemisphere that is left in place. This technique involves less risk of blood loss and hydrocephalus but is not appropriate for all patients. Outcomes after both types of epilepsy surgery are reported to be equal and approach 70% seizure freedom.

Figure 1: Right Anatomic Hemispherectomy

A. Coronal MRI at level of anterior frontal lobe.

B. Coronal MRI at level of brainstem

C. Sagittal MRI demonstrating removal of right hemisphere.

Figure 2: Left Functional Hemispherectomy

A. Coronal MRI demonstrating central resection and temporal lobectomy.

B. Sagittal MRI demonstrating corpus callosotomy and fronto-basal disconnection.

Hospital Stay

After epilepsy surgery, children will spend 2-3 days in the pediatric intensive care unit (PICU) for close monitoring of their neurological status. Antiepileptic medications are continued at previous doses. Antiepileptic drug levels in the blood for some anti-epileptics like carbamazepine and oxcarbazepine are monitored during this period because of the drug interaction with anesthesia. An MRI is performed on the first postoperative morning assess the brain after resection. Once the surgical drains are removed, the patient will be transferred to a regular pediatric nursing floor. PT, OT and speech therapy will be consulted based on the child’s needs. An average hospital stay slightly varies between patients to patients and usually ranges from 5 to 7 days. Length of stay decisions are made by the surgical team and are based on the child’s condition and recovery.

After Discharge

Upon discharge, rehabilitation services are often required to enhance recovery from a hemispherectomy. If medically indicated, the child may be transferred to a rehab facility for intensive physical, occupational, and speech therapy. This is usually followed by home or outpatient services. If inpatient rehabilitation is not required, home or outpatient therapy visits are often indicated. Outpatient therapy can be provided through hospitals and free-standing facilities along with schools. Parents should check with individual school systems to see if this is a service provided.

Complications

• Most children have excellent long-term results following hemispherectomy with no unexpected adverse outcomes. Occasionally, however, some complications may occur.
• Early complications, which occur either during the intraoperative or immediate post operative period include intraoperative blood loss, electrolyte changes, hypothermia and aseptic meningitis.
• Late onset complications can occur months to years after the hemispherectomy. These hydrocephalus and recurrence of seizures. Though rare, some of these complications can be life threatening and need to be treated urgently.

Cleveland Clinic Experience

The hemispherectomy experience at the Cleveland Clinic Pediatric Epilepsy Surgery Center was recently reviewed. From November 1996 through June 2009, 222 pediatric hemispherectomy procedures were performed for nearly 200 patients. Seventy were anatomical and 152 were functional hemispherectomies. Evaluation included inpatient video-EEG monitoring and magnetic resonance imaging (MRI). Some patients also underwent positron emission tomography (PET) scanning or magnetic resonance spectroscopy (MRS), both of which study metabolism of certain chemicals in the brain. All candidates for hemispherectomy have failed antiepileptic medication trials. Patients demonstrated seizure onset in the affected hemisphere and weakness on the opposite side. Most patients had some degree of visual impairment before surgery. Over this eight-year period, pediatric hemispherectomies were performed for the diagnoses listed in Table 1. Overall, 70% of patients are seizure-free with an average follow-up period of 34 months. Functional hemispherectomy was successful for the treatment of seizures caused by perinatal infarction and Sturge-Weber disease, while anatomic hemispherectomy showed to be effective for patients with hemispheric malformations of cortical development, including hemimegalencephaly. Complications were rare, but did include postoperative infection and hydrocephalus, with eight patients (8%) requiring a ventriculoperitoneal shunting procedure (or VP shunt) as treatment. There were no deaths in this series of patients. Recovery of neurological function included ambulation in all patients and good use of the unaffected arm. The function of the hand on the weak side, opposite to the hemispherectomy, is limited to that of a “helper hand.” In most of the children, this was no worse after the surgery when compared to the preoperative motor function in the hand. Recovery of language is age-related, with transfer of function occurring in younger children, although some degree of language transfer may be possible up to 14 years of age. The factors with the most influence on recovery of neurological function include underlying disease, age at which the epilepsy and surgery occur, preoperative neurological function, and which hemisphere is affected.

Results from the Cleveland Clinic series show hemispherectomy is a successful and safe technique to control or cure medically intractable epilepsy in a select group of patients. The appropriate surgical procedure for the treatment of epilepsy is based on the underlying pathology. Specifically, hemispheric malformation of cortical development, like hemimegalencephaly, showed significant seizure freedom with anatomic hemispherectomy, while children with stroke, other MCD, Rasmussen’s encephalitis and Sturge-Weber achieved good seizure control after functional hemispherectomy. Because of the many nuances related to the management of these often-difficult patients, care provided at a tertiary care center with experience specializing in the medical and surgical management of epilepsy can optimize patient outcomes.