SAN DIEGO – Magnetic resonance-guided stereotactic laser ablation is a safe and effective option in the treatment of hypothalamic hamartoma, results from a multicenter pilot study showed.
At the annual meeting of the American Academy of Neurology, Dr. Daniel J. Curry reported results from 20 patients who have undergone treatment with a Food and Drug Administration–cleared neurosurgical tissue coagulation system called Visualase. Hypothalamic hamartoma (HH) is a rare disorder of pediatric epilepsy with an estimated prevalence of 1:50,000-100,000, said Dr. Curry, director of pediatric surgical epilepsy and functional neurosurgery at Texas Children’s Hospital, Houston.
"The main presentation is the mirthless laughter of gelastic seizures, but patients can have other seizure types," he said. "The diagnosis is frequently delayed, and high seizure burden in the brain can lead to epileptic encephalopathy. Seizures are notoriously resistant to medical managements necessitating surgical intervention ... open, endoscopic, or ablative."
To date, surgical intervention has been limited due to modest outcomes, with 37%-50% achieving seizure freedom. The location of HH tumors makes surgical intervention difficult, and as a result 7%-10% of patients have permanent surgical morbidity.
For the technique using the Visualase, Dr. Curry and his associates at four other medical centers in the United States performed the surgical technique through a single 4-mm incision, a 3.2-mm burr hole, and a 1.65-mm cannula trajectory with Visualase under real-time MR thermography, first with a confirmation test at about 3 W, followed by higher doses of 6-10 W for 50-120 seconds. Temperature limits were set to protect the hypothalamus and basilar artery and optic tract. The surgery had an immediate effect, and patients stayed in the hospital for a mean of 2 days.
The primary measure was seizure frequency at 1 year while the secondary measure was the complication profile of stereotactic laser ablation in epilepsy.
Of the 20 patients, 5 were adults, and the entire study population ranged in age from 22 months to 34 years. A total of 21 ablations were performed in the 20 patients. Dr. Curry reported that all but four patients were seizure free after the procedure. However, the rate of seizures diminished among the four who were not seizure free.
Seizures recurred in one of the pediatric patients. "We re-ablated him and he is now seizure free," Dr. Curry said.
Complications to date have included two missed targets, one case of IV phenytoin toxicity, one case of transient diabetes insipidus, two cases of transient hemiparesis, and one subarachnoid hemorrhage. Perioperative, temporary weight gain was detected in most patients. "With lack of hormonal disturbance, this is thought to be due to the perioperative, high-dose steroid use," Dr. Curry explained.
Postoperative interviews with parents of study participants "have revealed significant improvements in intellectual development, concentration, and interactiveness," he said. "Most families report improvement of mood, decreased behavioral disorders, and rage attacks."
To date, only two patients have completed formal postoperative neuropsychological testing. "There were no significant declines in memory in either patient," Dr. Curry said. One had improved math skills and reading comprehension while the other complained of memory dysfunction but was not below normal on testing.
"We have learned that laser ablation of hypothalamic hamartoma can be accomplished safely," Dr. Curry concluded. "More studies are needed to explain the antiepileptic effect in settings of incomplete radiologic destruction of the target and to advance thermal planning."
Dr. Curry said that he had no relevant financial conflicts to disclose.