Until last spring, six-year-old Santiago Peña had hundreds of seizures every day — most of which were unnoticeable to his parents.
The result of a genetic condition called tuberous sclerosis, the seizures continued until Santiago underwent two surgeries at the Montreal Children’s Hospital that were planned with the help of a robot.
Santiago’s condition causes hundreds of benign masses (or “tubers”) to grow through his body, affecting vital organs such as his eyes, heart, lungs, kidney and brain.
“In Santiago’s case, he had something called cortical tubers in his brain that were causing him seizures and also caused him to have developmental regression,” said Kenneth Myers, a pediatric neurologist and epileptologist at the Montreal Children’s Hospital.
Santiago was referred to Myers after the family moved to Canada in 2019 to get affordable care for their son, whose condition appeared to be worsening.
“One of the things that got us really worried is he’d start to learn some things, he’d have the seizures and he forgot the things he learned,” said Santiago’s father, Yonny Peña. “That’s why we started to get really frustrated, because when you see your son learning something, and he has a seizure, and he forgets everything he learns — that’s really tough for us.”
Santiago has been on a variety of anti-seizure medications his entire life, but the seizures continued. Myers explored whether Santiago could be a candidate for surgery.
“I was quite concerned because he was having quite frequent seizures and he had previously been speaking and had stopped speaking,” Myers said. “And we know that the earlier you can intervene in children, the better their long-term development is likely to be.”
Once the team discovered it could operate on Santiago, it began trying to pinpoint which tubers out of the dozens in his brain were responsible for his seizures. To do so, it used ROSA, which implants electrodes into the brain to monitor activity. ROSA is the first robot of its kind in a Quebec pediatric hospital.
“Nowadays we use a robot to help with the precision of the electrode placement,” said Dr. Roy Dudley, a pediatric neurosurgeon at Montreal Children’s Hospital.
To program ROSA, the imaging of a patient’s brain is uploaded to the software so the team can map where exactly to insert the electrodes.
“In Santiago’s case, we had 17 electrodes,” Dudley said. “So we designed those electrodes to make sure that they’re going into the areas that we think are causing his seizures.”
After hours of careful trajectory planning by the surgeons — who ensure blood vessels will be avoided — ROSA’s arm drills a small hole measuring about one millimetre in diameter through the patient’s scalp and membrane of the brain.
“Then we screw in an anchoring bolt, we pass a stylet into the brain, and that stylet is a small semi-rigid wire that is measured to the distance decided by the robot,” Dudley said. “And then we take the stylet out and we implant the electrode that is the same distance to the target for that particular electrode.”
The electrodes — which are used to monitor brain activity for one to two weeks — have multiple points of contact, Dudley explained.
“We’re measuring anywhere from 10 to 15 points in the brain with a single electrode, and remember we’re putting in anywhere from 10 to 18 electrodes,” he said. “The way to think about this is EEG in three dimensions.”
The electrodes confirmed the neurosurgery team’s hypothesis that most of Santiago’s seizures were coming from the back left side of his brain, with a few more on the right side that were noticeable to his parents.
Dr. Jean-Pierre Farmer, the chief of neurosurgery at the Montreal Children’s Hospital, explained that without the means to pinpoint where exactly seizures are originating from — especially in patients like Santiago with multiple lesions — in previous years, only the area that seemed the most active would have been removed.
“Which would have been the left side, and we would not probably have gone after the right side as quickly,” Farmer said. “We would have seen if he did better and then waited for him to get more seizures — or not — and then reinvestigated him now that the main trigger has been removed.”
Prior to the implantation method — which has been used for decades in adult patients — sheets of electrodes were put on the surface of the brain to monitor activity.
“We used to do an incision almost the whole half of the head, and remove a piece of bone, almost the whole half of the skull … and then open the membrane around the brain,” Dudley said.
Dudley suspects that may have seemed less invasive to parents than passing electrodes through their child’s brain, but he said that’s not the case — especially with ROSA’s precision.
“That old procedure was fraught with many complications — there would be inflammation of the brain … there was a relatively high infection rate, there was (cerebrospinal fluid) leak because we opened that membrane around the brain and we can’t close it water-tight because these electrodes are coming out,” he said.
Santiago’s condition means he will be monitored regularly for the rest of his life, but both his surgeons and parents have taken comfort in knowing he is seizure-free and moving forward with his development.
“As a family it makes us feel so happy because now we can share more time with him,” Peña said. “We’re not worried about the seizures, we’re very happy because his progress at the school is (good), and he’s with us more as a family.”