Going to the Source: Advances in Epilepsy Surgery
Ki Lee, MD , is director of the epilepsy surgery program and the epilepsy monitoring unit at Cincinnati Children’s and associate professor in the Department of Neurology.
For years, epilepsy surgery required a high degree of educated guesswork. But thanks to technological advances in the last 10 or so years, surgeons can now draw on an array of sophisticated diagnostic tools to pinpoint the seizure zone and its proximity to primary language, motor and sensory areas of brain.
“Our program is the only one in the country to offer a full complement of diagnostic tests for evaluating pediatric epilepsy patients,” says Ki Lee, MD, director of the epilepsy surgery program and the epilepsy monitoring unit at Cincinnati Children’s. “This helps the surgical team plan each surgery, execute the plan in the operating room and evaluate our success. As a result, our overall surgical outcomes are on par with other leading pediatric epilepsy surgery centers, despite the fact that our surgery program has been in place for only about two years.”
The diagnostic tools the surgeons rely on include magnetoencephalography (MEG), video electroencephalography (EEG), subtraction ictal SPECT co-registered to MRI (SISCOM), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), among others. They are used to perform detailed evaluations, including mapping the brain’s anatomy, evaluating the electrical and magnetic wave forms it generates and measuring the electrographic spread of seizures within hundredths of a second.
A Three-Phase Process
Children who come to the Comprehensive Epilepsy Center to be evaluated for surgery undergo three phases of care. The first involves monitoring and evaluation, in which patients receive extensive non-invasive testing. The surgical team uses these test results to determine whether a child is a candidate for surgery and to begin localizing the seizure site in preparation for the second phase, intracranial electrode monitoring.
An Inside View of the Brain at Work
Neuroimaging technologies such as functional MRI (fMRI)play an important role in pediatric epilepsy research, according to Scott Holland, PhD, director of the Pediatric Neuroimaging Research Consortium (PNRC). Functional MRI involves exposing patients to different stimuli during an MRI study to pinpoint where the brain processes specific information, such as language.
The medical center recently invested $5 million for two 3 Tesla MRI scanners that
will be used for basic and clinical research in neuroimaging. Holland explains, “We expect fMRI to reveal insights about neural
plasticity and re-organization associated with epileptic activity in the brain, and are particularly interested in the influence of
pediatric epilepsies on language function. This and other neuroimaging technology
will provide major breakthroughs in our understanding of pediatric epilepsy within the next 10 years.”
Complementing the work taking place at the PNRC is a multidisciplinary team formed
through the Comprehensive Epilepsy Center at Cincinnati Children’s. “Our goal is to
bring together clinicians and researchers to test some of our hypotheses about epilepsy
and try to advanceunderstanding of the disease,” says Ki Lee, MD. “There is so much to learn about epilepsy, and we’re eager to contribute to that body of knowledge in a significant way.”
Probing Within
In this phase, the surgeon opens a portion of the skull and places electrodes directly on the brain. Wires from the electrodes are connected to an EEG machine, allowing clinicians to continuously monitor for seizure activity as they conduct further evaluations. This second phase of evaluation lasts, on average, one week. Its purpose is to pinpoint as precisely as possible the area of the brain involved in the seizures. Once the area is identified, it’s time for the third phase of treatment, surgery, to resect or disconnect the area of the brain involved in the seizures.
Zeroing In
In the brain suite where the surgery is performed, computer software integrates anatomic and functional data from many sources with threedimensional images of the patient’s brain, matching information from diagnostic tests with the patient’s position on the operating table.
“We work together with neuroradiology to fuse different imaging modalities taken prior to surgery, and compare them with the patient’s brain anatomy during the operation,” says Francesco Mangano, DO, lead neurosurgeon in the Comprehensive Epilepsy Center. “In surgery, we use a sterile probe to compare electrode placement with the fused stereotactic images on the monitor to see exactly where the seizure onset zone is in proximity to primary functional and eloquent areas of the brain. All of this information is used to finesse our surgical plan and navigate safely to the seizure site.”
The goal of surgery is to enable children to live seizure free, or at least to dramatically reduce the occurrence of seizures. In the last two years, 67 patients ranging in age from 2 months to 26 years had epilepsy surgery at Cincinnati Children’s; 71.9 percent of the patients remained seizure free with post-operative follow-up ranging from 6 months to two years. Patients are usually kept on medication for one to two years regardless of seizure freedom.
“Many of our surgical patients have been experiencing seizures for years,” says Mangano. “Some may still need medication to prevent or further reduce seizures after surgery, but even in those cases, surgery is considered successful if it gives the child an opportunity to reach further developmental milestones while improving the overall quality of life.”
