Medical Device Daily Contributing Writer
Steven Glazier, MD, assistant professor of neurosurgery at Wake Forest University Baptist Medical Center (Winston-Salem, North Carolina), recently performed a temporal lobectomy during a live Internet broadcast.
The surgery removed a small part of the temporal lobe, the part of the brain that extends from the temples to just past the ears. Parts of it may cause epileptic seizures, and the surgery offers hope to epilepsy patients who have not been responsive to medical therapy. To be considered for the surgery, patients must have failed at least one standard and one new medication to be considered for surgery.
William Bell, MD, associate professor of neurosurgery and neurology served as moderator of the webcast.
About the procedure, Glazier said, “We are working in high-risk territory, so we use imaging tests to carefully pinpoint the origin of the seizures so that we make sure we leave the pathways for speech, movement and memory intact.” He said that with the procedure 80% of patients are cured and 95% “have a dramatic reduction of their seizures. It greatly enhances their quality of life.”
Neurologists and neurosurgeons at the medical center use electroencephalograms, positron emission tomography and MRI in the hospital's state-of-the-art Epilepsy Monitoring Unit to pinpoint the exact origin of the disease. Also sometimes used is magnetoencephalography, which measures the magnetic fields produced by electrical activity in the brain. Once the targeted tissue is mapped, the surgeon can precisely remove the scarred tissue to reduce or eliminate the seizures.
The basic criteria for epilepsy surgery includes: medically refractory partial seizures; single cortical seizure focus; focus respectable with minimal functional impairment; and that surgery will be expected to improve quality of life.
To the e-mailed question “How prevalent is epilepsy?” Bell explained: “In the general population about 10% will have at least one seizure in their lifetime. True epilepsy is seen in 0.5% to 1% of the population. Epilepsy is defined as two or more uncontrolled seizures and is diagnosed by electroencephalogram, CT scan or MRI.”
Glazier explained that he had begun the operation about two hours earlier at the hospital. “This operation takes us approximately 3.5 hours from start to finish.” He first made a keyhole incision through the scalp and skull. Then he opened the meninges (material covering layers of the brain) to see the posterior and anterior half of temporal lobe.
Bell showed a taped similar operation illustrating the beginning steps of the procedure. The entire incision is behind the hairline.
The patient has been anesthetized and positioned with his head in a rigid frame. A surgical microscope is in place, sending images directly to the surgeon's eyes and projecting to overhead monitors. The team is guided by real-time visualization. The anesthesiologist watches to best control the patient's pressure and vital signs.
As Glazier cut through the skin down to temporalis muscle, surgical clips are applied for blood control of small vessels. A surgical resident assists with blood control and retraction.
A question from the web audience: “Will scar tissue from the surgery cause seizures?” Bell said that the likelihood of this happening is “quite small – only 2%. We do keep patients on their medications for at least six months. The majority of patients stay on some sort of medication after surgery.”
Back in the operating room, as the skin and muscle are retracted, the skull is exposed at the temporal bone. The skull is opened with a burr hole using a special drill that cuts bone, but stops at soft tissue. A jigsaw attachment is used to cut a window of bone out that will be replaced at closure.
The first covering of the brain is the dura. This was incised and the surgery moved to the superior temporal gyrus. Resection of a portion of the temporal lobe begins using bipolar cautery to dissect and cauterize small vessels along the way. Glazier disconnected the tip of the outer surface of the brain – the neocortex, or thinking section of the brain. As Glazier coagulated the small vessels from the tissue to be removed, he was careful to spare critical arteries and veins. The microscope was frequently repositioned to keep the temporal lobe dissection in view.
Glazier explained, “It takes us about an hour to get down to the hippocampus and remove it. This is the part of the temporal lobe that is propagating the seizures very quickly throughout the brain. It is really a team effort to accomplish this surgery.”
He reached the temporal fossa, just behind the ear on the left side, and he uses bayonet forceps to gently dissect the soft brain substance. The temporal brain cells are gray, and the white tissue is the processing area of the brain.
The third cranial nerve which controls the eye is very carefully identified and avoided. Blood vessels feeding the tissue to be removed are cauterized and the dissection moved under the hippocampal gyrus and posterior to it. Then the medial side of hippocampus was freed up. As the hippocampus was mobilized Glazier reached way back to sever the tail of the hippocampus from the brain.
“What really matters is that you cure the seizures,” he noted. “Then the patient can drive and learn and have a normal life.”
Another web question: “How long before a patient can return to work?”
“That depends on the type of work,” Bell answered. “About 12 weeks for real heavy duty work. You need time for the skull to heal and be strong. If you have a more paperwork type of job you can probably start back at four to six weeks. Our patients are in hospital for three days postoperatively, though they generally feel good after one day.”
He added: “The patient will be somewhat uncomfortable because of residual air in the head irritating the brain until enough spinal fluid is produced to fill in the hole left by the removed tissue.”
The disconnected hippocampus was rolled forward and removed. The wound was carefully checked to stop bleeding and irrigated to check the surface of the brain. Glazier checked the third cranial nerve and other delicate, critical tissues to assure their safe condition. The wound was closed traditionally by layers.
Glazier concluded the presentation by explaining, “Some of the new antiepileptic drugs started in 1980. Since 1990 we have seen many new medications, and these are revolutionary in the sense they have many fewer side effects. But even with this success with drugs, it left about a third of the patients who are not able to be controlled. Looking at all the potential patients, about 36% will remain with seizures despite the best new medical therapies. Approximately 2,000 temporal lobectomy procedures are performed per year.”