Specific Surgeries

TEMPORAL LOBECTOMY

Anterior temporal lobectomy is the most common surgical procedure for the treatment of intractable epilepsy in

Figure 52-8 Interictal and ictal Tc-99m SPECT in coronal and transverse planes in a patient with right mesial temporal lobe epilepsy. There is a reduction in blood flow in the right temporal lobe interictally and hyperperfusion in the same region during a typical partial seizure. (See CD-ROM for color versionfPhofo courtesy of C. Oliver Wong, MD, PhD, FACP.)

adolescents and adults. The resection typically includes the anterior 3.0 to 3.5 cm of the inferior and middle temporal gyri, uncus, part of the amygdala, and the anterior 2.0 to 3.0 cm of the hippocampus and adjacent parahippocampal gyrus. In patients with mesial temporal sclerosis, selective amygdalo-hippocampectomy may suffice. Lesionectomy with preservation of the mesial temporal structures may be indicated in patients with discrete temporal lobe lesions without evidence of mesial involvement. Language mapping is required when lesions are located near the language cortex. The use of tailored resections based on intraoperative electrocorticography remains controversial. A seizure-free state is achieved in 60 to 70 percent of patients, although auras may persist. y A risk of verbal memory impairment exists in patients with normal preoperative memory scores undergoing dominant hemisphere anterior temporal lobectomy. Transient dysnomia after dominant anterior temporal lobectomy occurs in approximately 30 percent of patients.

EXTRATEMPORAL LESION RESECTION, HEMISPHERECTOMY, CORPUS CALLOSOTOMY

The procedure of choice for patients with extratemporal epilepsy due to a structural brain lesion is complete resection

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of the lesion and surrounding epileptogenic cortex. Lesionectomy is the most common type of epilepsy surgery performed in infants and children. Subtotal removal of a structural lesion is associated with a lower likelihood of seizure remission. Patients with nonlesional extratemporal epilepsy generally require intracranial monitoring to delineate the epileptogenic zone, and cortical mapping if the proposed resection is located in or around eloquent cortex. Surgical outcome in these cases depends on the certainty with which the epileptogenic zone is defined and the completeness of the resection. Only 25 to 35 percent of patients become seizure-free, and another 20 to 30 percent has a significant reduction in seizures. U

Hemispherectomy is indicated in patients with intractable partial and secondarily generalized seizures in whom an entire hemisphere is considered epileptogenic with little or no remaining functional cortex. The procedure is usually performed in patients with Rasmussen's encephalitis, Sturge-Weber syndrome, hemimegancephaly, or large hemispheric infarctions. Functional hemispherectomy consists of the removal of the frontal and temporal lobes and complete disconnection of the remaining cortex and corpus callosum. This procedure is an alternative to total hemispherectomy, which is associated with a high rate of cerebral hemosiderosis and hydrocephalus. Seizures are completely abolished in nearly 80 percent of patients. U

Corpus callosotomy should be considered in patients with frequent secondary generalized tonic-clonic, tonic, and atonic seizures that lead to falls and injuries. The goal of the procedure is to disrupt the major central pathways necessary for the propagation of generalized seizures. Complete callosal section may result in mutism, apraxia, or frontal lobe dysfunction. For this reason, the procedure is often performed in two stages beginning with sectioning of the anterior two thirds followed by section of the remainder of the corpus callosum, if necessary. Nearly two thirds of patients experience a significant reduction in seizures, although few are rendered seizure-free.y

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