Laser surgery for focal epilepsy
For patients with focal, medication-resistant epilepsy, temporal lobectomy has been the standard treatment. Although effective in up to 80 percent of patients, the procedure generally involves several days of hospitalization and at least six weeks for recovery.
A minimally invasive laser surgery option is available at all Mayo Clinic campuses. It has been offered for only about two years, so outcome measurements are somewhat preliminary. "But the results are very promising. The vast majority of our patients who have had the surgery are seizure-free," says Jerry J. Shih, M.D., a consultant in the Department of Neurology at Mayo Clinic's campus in Jacksonville, Florida.
The procedure is most appropriate for patients with conditions such as temporal lobe epilepsy or mesial temporal sclerosis, in which seizures originate from focal areas of the hippocampus. These conditions are often resistant to anti-seizure medications, and seizures typically worsen as the patient ages.
"This minimally invasive laser procedure is rapidly becoming an excellent treatment option for patients with focal seizures from a defined seizure focus. The results thus far in selected patients seem to be as good as surgical resection," says Robert E. Wharen Jr., M.D., a consultant in the Department of Neurosurgery at Mayo Clinic's campus in Jacksonville, Florida.
Precise MRI guidance
Unlike temporal lobectomy, which involves craniotomy, laser surgery is done through a burr hole in the back of the skull. A laser-tipped catheter is directed to the hippocampus to ablate the site where seizures originate. The patient, under general anesthesia, is in a stereotactic frame.
Real-time MRI guidance generates a temperature map of the patient's brain. "With this new technique, you not only know the temperature at the tip of the laser, you actually monitor the precise temperature of the brain in the area you're heating," says Richard S. Zimmerman, M.D., a consultant in the Department of Neurosurgery at Mayo Clinic's campus in Phoenix, Arizona. "That allows you to heat the brain tissue just enough and not too much."
Advantages for patients
Because laser ablation is minimally invasive, patients typically are hospitalized only overnight. Many are ready to resume normal activities within two to three weeks. Laser surgery can also lower the risk of damaging the patient's memory and language abilities.
Candidates for laser ablation typically haven't found relief from multiple epilepsy medications and have experienced decreased quality of life. "Most of our patients have been on at least four or five anti-seizure drugs at high doses. Yet they continue to have seizures, they can't drive legally, and they often have difficulty maintaining employment," Dr. Shih says.
Some of these patients have expressed reluctance to undergo surgery. "They are uncomfortable with what an open procedure entails, and therefore have not been able to get the potential benefit of epilepsy surgery," Dr. Shih says. "But they are requesting this minimally invasive option."
In addition to temporal lobe epilepsy, Mayo Clinic has successfully treated hypothalamic hamartomas with laser ablation. The hamartoma's location deep in the brain generally precludes resection; Gamma Knife surgery has been used in some patients, but with incomplete success. "Laser ablation offers a less invasive treatment for some patients with hypothalamic hamartoma," says W. Richard Marsh, M.D., a consultant in the Department of Neurosurgery at Mayo Clinic's campus in Rochester, Minnesota.
Although the results of laser ablation are preliminary, some success stories stand out. The first patient to undergo the procedure at Mayo Clinic's campus in Jacksonville, Florida, was a 29-year-old woman who had seizures since age 6 months. After losing her driver's license, she had to rely on family and friends to drive her to work. The patient is now seizure-free and regained her license.
At Mayo Clinic's campus in Phoenix, Arizona, Dr. Zimmerman cites a patient in her late 50s who had lifelong, medication-resistant seizures. Although developmentally delayed, she had independence within a group home setting. "Any damage to her memory or language from open surgery could result in her moving from semi-independence to total dependence in a nursing home," Dr. Zimmerman says. After laser ablation, the patient is seizure-free; she continues to live in the group home but is now able to work part time in her family's business.
Some Mayo patients continue to experience seizures after laser surgery. Pinpointing all tissue involved in seizure activity, particularly in patients without abnormality on MRI, remains a challenge during minimally invasive surgery.
"We've shown that minimally invasive surgery can work, and we've shown that it's safe," Dr. Marsh says. "What we'd like to learn now is the correct amount of tissue to ablate to optimize seizure control."
Mayo's integrated practice facilitates the smooth running of minimally invasive epilepsy surgery. In addition to neurosurgeons, the procedure requires highly trained epileptologists, neuroradiologists and allied health workers. "This is a good example of something we are increasingly seeing in neurology: the importance of a multidisciplinary team," says Gregory A. Worrell, M.D., Ph.D., a consultant in the Department of Neurology at Mayo Clinic's campus in Rochester, Minnesota. "Mayo has the tools and experience to create the best possible environment for a safe and effective procedure."