June 25, 2019
Mayo Clinic uses the term "onco-epilepsy" to describe the occurrence of seizures in association with brain tumors. Many people with brain tumors experience seizures, and as many as 30% of them continue to have seizures after tumor resection. Mayo Clinic takes a multidisciplinary and proactive approach, striving for optimal management of both tumors and seizures in a single surgical intervention.
"As neurosurgeons, we have been trained to remove tumors and leave the rest of the brain untouched, including areas that are epileptogenic. Patients often leave the operating room and immediately go on anti-seizure medication," says Alfredo Quinones-Hinojosa, M.D., chair of Neurosurgery at Mayo Clinic in Jacksonville, Florida. "Our approach facilitates the safe removal of noneloquent tissue that is potentially epileptogenic, to manage tumor and epilepsy at the same time."
This approach, described in the September 2018 issue of Mayo Clinic Proceedings, was born of the close collaboration between Mayo's neurologists and neurosurgeons. "That relationship is so critical for identifying the optimal treatment for a patient with more than a single condition," says William Tatum, D.O., a neurologist at Mayo's campus in Florida. "Working together, the neurologist and neurosurgeon can avoid any disconnect and maximize tumor removal while also identifying epileptogenic networks, to improve outcomes."
Focus on quality of life
As a tertiary center, Mayo Clinic has the technology and expertise to meet patients' complex needs. Neuroradiologists use advanced technology to map the patient's brain before tumor resection. The neurology and neurosurgery team uses these images to guide the surgical approach and to obtain a sense of which areas of the brain can be dangerous to touch or remove. During surgery, intraoperative stimulation and electrocorticography are used to identify eloquent and potentially epileptogenic tissue.
"Millimeters make a difference between a patient having movement or no movement, or between talking or not talking, after surgery. Extraordinary precision is needed," Dr. Quinones-Hinojosa says.
After surgery, patients are monitored for seizure control and for neurological and cognitive deficits. "We are in the very early stages of this approach, but our data seem to indicate that these patients are doing better in terms of seizure control," Dr. Quinones-Hinojosa says.
"The goal is to avoid the need for anti-seizure medications, so patients can continue to drive and work and have a better quality of life," he adds. "Mayo Clinic is a unique institution in the sense that neurosurgeons, neurologists, neuropsychologists and neuroradiologists work as a team to answer questions about how we can better provide for our patients who have two very disabling conditions."
Unique neurological nosology
Cysteine-glutamate exchange that underlies onco-epilepsy
A diffuse glioma is associated with a breakdown in the cysteine-glutamate exchange, resulting in excitotoxicity and neuronal cell death, leading to epileptiform abnormalities and high-frequency oscillations with seizures. Illustration reprinted with permission from Mayo Clinic Proceedings.
Dr. Tatum notes that brain tumors and seizures share metabolic pathways and molecular markers. For example, a Mayo Clinic study published in the March 2018 issue of Neurology demonstrated that high-frequency oscillations — which can be safely and reliably recorded during awake craniotomy in patients with brain tumor-related epilepsy — are prevalent in that disease. The researchers also found that the rate of high-frequency oscillations was higher in patients with IDH1-mutant than in IDH1-wild-type tumor genotypes.
"Normally, we think of brain tumor and epilepsy as separate entities. However, there's a great deal of overlap," Dr. Tatum says. "We might think more usefully about a unique neurological nosology."
In addition, treatment for brain tumors and seizures is bidirectional. Anti-seizure medications can increase the life span of a person with glioma, and chemotherapy or radiation treatment for glioma can decrease seizures. "This is very exciting because it means that, rather than thinking of two separate conditions, focusing on the management of onco-epilepsy might be more effective," Dr. Tatum says.
Other neurological conditions, such as traumatic brain injury, can also cause medically refractory seizures. "Eventually, there might be a way to tie together the different approaches that neurologists and neurosurgeons use to treat the huge numbers of patients with seizures who are failing medical therapy," Dr. Tatum says.
"There's a lot we still need to learn about individuals with onco-epilepsy and the outcomes of treatment," he adds. "We need a team approach, with our patients and with other collaborating centers. That's the only way to change the language we use to talk to one another and to patients, and to make greater strides in treatment."
For more information
Tatum WO, et al. Onco-epilepsy: More than tumor and seizures. Mayo Clinic Proceedings. 2018;93:1181.
Feyissa AM, et al. High-frequency oscillations in awake patients undergoing brain tumor-related epilepsy surgery. Neurology. 2018;90:e1119.