ARTICLE IN BRIEF
A team of neurosurgeons reported findings from a small study suggesting that minimally invasive stereotactic laser ablation was a promising approach for removing epileptogenic hypothalamic hamartomas: there were no permanent surgical complications, neurological deficits, or neuroendocrine disturbances, and 61 percent of participants were free from seizures.
Opening the window of the skull and surgically splitting the hemispheres to gain access to the hypothalamus is risky business for surgeons attempting to remove epileptogenic hypothalamic hamartomas. Now, a team of neurosurgeons is testing the feasibility of minimally invasive stereotactic laser ablation as a safer alternative that could avoid many of the serious side effects of traditional open surgery.
Daniel J. Curry, MD, director of pediatric surgical epilepsy and functional neurosurgery at Texas Children's Hospital and assistant professor of neurosurgery at Baylor College of Medicine, and his colleagues have been searching for surgical alternatives to traditional techniques that have moderate effects — a 37- to 50- percent for seizure freedom — and a high percentage (7- to 10-percent) of permanent surgical morbidity.
Hypothalamic hamartomas are generally rare, but three to four cases a year have been seen in large referral centers. The seizures are primarily gelastic and can occur every few minutes, said Dr. Curry. Surgical complications can include profound memory problems (for 45 percent of patients), obesity (40 percent), and diabetes insipidus (15 percent).
Minimally invasive stereotactic thermal ablation has been used successfully for brain metastasis and other tumors. University of Texas child neurologist Angus Wilfong, MD, asked Dr. Curry if he'd be interested in bringing patients into the surgical suite to test the minimally invasive surgery technique. They brought their first patient into the operating room in March 2011 and reported on their first 13 patients at the AAN annual meeting in San Diego.
During the procedure, patients are fitted into a stereotactic frame that is attached to an MR-compatible laser catheter (1.6mm diameter) through a 3.2mm twist drill hole. An FDA-cleared laser surgery system (Visualase) was used to monitor the ablation of epileptogenic foci with real-time MRI thermometry. Temperature limits were set to protect nearby structures like the hypothalamus, basilar artery, fornices, or mammillothalamic tracts, said Dr. Curry. So far, about half of the patients have been followed for about a year. According to Dr. Curry, there were no permanent surgical complications, neurological deficits, or neuroendocrine disturbances. Eight of the 13 cases (61 percent) were free from seizures — 72 percent in the pediatric patients.
There have been no memory deficits, obesity, or diabetes triggered by the laser surgery. “Seizure freedom was achieved without surgical comorbidity,” said Dr. Curry. “Real-time MRI thermometry enabled protection of adjacent critical structures.”
The best results from treatment of the hypothalamic hamartomas will likely result if the treatment occurs before the evolution of the seizure pattern into a widespread secondary generalized epilepsy, Dr. Curry said, adding the laser technology is also being tested in temporal lobe epilepsy and focal cortical dysplasia.
The non-invasive radiofrequency gamma knife has also been tried but its effectiveness is slow in coming, more than a year after the surgery. It is also associated with swelling, which can require steroid treatment.
EXPERTS WEIGH IN
This is the first report of laser-guided surgery for hypothalamic hamartomas, said Jacqueline A. French, MD, a professor of neurology at the New York University Comprehensive Epilepsy Center and a member of the Neurology Today editorial advisory board. “These are the early days but this could be safer and better tolerated than other surgical treatments. This is a very positive result.” [For more commentary from Dr. French, watch the accompanying video.]
Harold Rekate, MD, a neurosurgeon and director of the Chiari Institute at the North Shore-LIJ Health System in New York, said that, while the numbers are small, “it is an exciting new technology.” He said it is too early to know the long-term outcomes for these patients. He agrees that the open surgery is risky, but he said that patients do better when surgeons have had more experience reaching these hamartomas.
Dr. Rekate said that laser ablation would only be useful with small lesions. The patients selected for the laser treatment all had small lesions of around one centimeter. He added that the complication rates generally occur in patients with larger lesions, between two and four centimeters. He added that he'd like to know about outcomes three years down the line when incomplete hamartomas can grow back and require another surgical treatment.
Michael R. Sperling, MD, the Baldwin Keyes professor of neurology at Thomas Jefferson University and director of the Jefferson Comprehensive Epilepsy Center, has used thermal ablation to treat patients with mesial temporal lobe epilepsy and has reviewed the results with hypothalamic hamartomas. “These cases generally involve very small lesions that are nicely ablated with this device. As people use it more frequently, we will begin to understand the benefits and the limitations,” he added. “We have to see how well it works in practice.”
“Regarding the new technique, experience should tell us about optimal lesion size, which will require further study and a comparison of different-sized lesions and implications for endocrine function and seizure control,” Dr. Sperling continued. “I cannot think of any real barriers, other than cost, for hospitals having to acquire the new technology. However, this equipment will become more widespread at hospitals with significant tumor programs, so that should not be a major issue.”
Cornelia Drees, MD, an assistant professor of neurology who works in the Epilepsy Division at the University of Colorado in Aurora, added: “Anything that is more refined is better than open surgery, given the high risk for complications.” She said that the real advantage is the use of real-time MRI to help guide the surgeon to the hamartoma and then heat the tissue in a more restricted way. There is better control in this procedure than with resection. Even gamma radiation is not as discrete, she said, adding that some radiation will compromise normal tissue.
Dr. Drees, who worked with patients with hypothalamic hamartomas at the Barrow Neurological Institute, said that “it remains to be seen how permanent the success will be. Even two years is not a long time.” She said that it is also possible that the smaller lesion size increased the effectiveness of the procedure. She said that it is not known whether heating the lesion will work on bigger tumors or ones that are more complex in structure.
Gregory Bergey, MD, a professor of neurology at Johns Hopkins Hospital and director of the Johns Hopkins Epilepsy Center, agreed that these are the early days. Still, he said, one “could argue that it could ultimately be the first line treatment for these difficult-to-treat lesions.”
TUNE IN: A team of neurosurgeons reported at the AAN annual meeting that minimally invasive stereotactic laser ablation could be a safer alternative than traditional surgery for removing epileptogenic hypothalamic hamartomas. In a video discussion, Jacqueline A. French, MD — professor of neurology at New York University Comprehensive Epilepsy Center, president of the American Epilepsy Society, and a member of the Neurology Today editorial advisory board — discusses why this is a development that clinicians may welcome, but offers caveats for future research that is needed before the surgery should be considered: http://bit.ly/aNQ4KB.
A ‘BEST PAPER’ PICK:Neurology Today editorial advisory board member Jacqueline A. French, MD, professor of neurology at New York University Comprehensive Epilepsy Center and president of the American Epilepsy Society, selected this as one of the noteworthy papers on epilepsy from the AAN annual meeting.
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