What is hemispherectomy?
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.
What is the history of hemispherectomy?
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.
What patients are appropriate for a hemispherectomy?
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 the body with loss of dexterity of the hand with, or without, peripheral visual loss.
- Developmental retardation or arrest of maturation due to intractable seizures.
- Diffuse abnormality of one cerebral hemisphere which is contributing to the intractable epilepsy.
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.
What are the various types of hemispherectomy?
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.