Medical Device Daily Contributing Writer
Pediatric neurosurgeons at the Rainbow Babies & Children's Hospital (Cleveland) presented a live webcast of a panel discussion and surgical video earlier this year on the subject of posterior fossa tumors in children.
Alan Cohen, MD, chief of pediatric neurosurgery, demonstrated the microsurgical resection of a fourth ventricular brain tumor. Posterior fossa tumors are the most common brain tumors of childhood, and the extent of surgical resection correlates strongly with long-term survival.
John Letterio, MD — chief of pediatric hematology/oncology at Rainbow Babies & Children's Hospital and professor of pediatrics at the Case Western Reserve School of Medicine (also Cleveland) — joined Cohen for the panel event and discussed new strategies for treating pediatric brain tumors at the Brain Tumor Center at Rainbow.
Cohen said, brain cancer is now the No. 1 cause of cancer death in children. "About 2,000 pediatric brain tumors are newly diagnosed each year," he said, "most found at the base of the skull."
Symptoms of a brain tumor in this location can mimic many benign conditions. For instance, children can get migraines. A red flag is headaches occurring in the morning. And when frequency and severity increase and vomiting occurs, parents or other caregivers should be concerned.
During the webcast, the physicians reviewed the case of one of their recent patients, a 6-year-old girl.
"This patient came to our attention after she had headaches, vomiting and developed an unsteady gait," Cohen said. "We found swelling of the optic disk due to increased cranial pressure. And she demonstrated truncal ataxia — an unsteady gait."
"Examination with computed tomography and MRI showed a large 4th ventricular tumor with hydrocephalus," Cohen said. Pointing to films images, he said they revealed a large mass filling the 4th ventricle. "That mass is blocking the drainage of cerebral fluid and takes up space in the skull, increasing pressure to the brain and brain stem."
Letterio then elaborated on the treatment plan. "First we will place the patient on intravenous steroids and perform an emergent external ventriculostomy. Then we will perform a craniotomy to debulk the tumor and determine its type." He added: "Once we have a firm diagnosis, we began to plan long-term treatment."
One possible tumor type, Letterio said, is astrocytoma, "usually benign. The other two possible tumors are malignant in nature, meduloblastoma and ependyoma."
He then took webcast participants to a video to explain a step-by-step treatment approach.
"Before opening the posterior fossa, we need to treat the hydrocephalus to prevent herniation of the brain. Here you can see we are placing a ventricular catheter in the skull to let out CSF (cerebrospinal fluid). This reduces the pressure on the brain. The patient has now been placed on endotracheal general anesthetic and is in the prone position. We are standing at the top of the OR bed looking down at the base of her skull."
He added: "We are doing this posterior craniotomy in order to reach the 4th ventricle of the brain, which sits just behind brain stem. Here we are making an incision at base of skull and removing a small portion of bone."
Someone in the Internet audience asked how long such procedures take.
Cohen said, "We focus on economy of movement, but it still takes a while. As Yogi Berra said, 'This work is 90% mental and the other half is physical.' This particular operation took six hours. We go especially slowly when near the brain stem."
Letterio said, "As we begin, the anesthesiologist is administering antibiotics to prevent infection. We now infiltrate the scalp with epinephrine to reduce bleeding and use a bipolar radio frequency forceps to control larger bleeders.
"Here you see we are exposing the occipital bone at the base of the skull. We next dissect the muscle at the level of C1-C2, cervical vertebrae. Next we use a high-speed drill to make our incision into the skull. The drill has a clutch which stops the drill's spinning when it has cut through the bone and reached soft tissue. A bone flap is lifted and saved. We can see the brain is relaxed, not under extreme pressure. We can begin to see the tumor just under the dura. The protective dura mater is now being dissected."
Cohen added: "We've now Incised the dura with a No. 15 blade, slowly and repetitively. We are careful to avoid the midline of our incision because of proximate large venous sinuses. Now we open the arachnoid and let some fluid out so that the brain relaxes further. Here you can see the brain stem. The tumor is up underneath the brain, so we will attempt to enucleate the tumor without damage to the cerebellum." He noted, "We are working from the inside out."
"What causes these tumors?" — an e-mailed question.
"These are spontaneous," Cohen said, "with no known genetic cause. Most pediatric tumors are spontaneous, and we don't know why they develop."
Returning to the video, he said, "Now back to the OR, where we can see the tumor exposed. We are removing the tumor in a piecemeal fashion. As you can see, the pieces we've removed at this point are firm but vascular. We go very slowly. As we say, brain surgery is measured by the calendar, not the clock."
Cohen said, "Now we've sent a specimen to pathology, where they've determined that the tumor is a juvenile astrocytoma — benign. This surgery will be curative."
Letterio elaborated: "At this point we have completely debulked the tumor. We bring in the surgical microscope to look down into the wound to be sure we've removed all possible parts of the tumor down to the brainstem."
"Cohen said incision closure is extremely important. "It must be completely airtight so there is no leak of CSF. We close the linings of the brain starting with the dura mater. For this we use a dural graft made of bovine pericardium. A leak of CSF through the holes made by the sutures can cause infection, so we take a fair amount of time to do this right. Next we replace the bone flap and use micro-titanium plates and screws to secure the bone flap to the skull. This restores the normal anatomy, protects the wound and reduces pain."
A question from the audience: "Will this tumor grow back?" "Our approach is to get maximal surgical resection," Litterio said, "but they can grow back as a local recurrence. An astrocytoma rarely metastasizes but can regrow in nearby areas. A gross total resection is always the best way."
Cohen added that these procedures "are literally walking through a minefield, looking for problems every step of the way. We are very dependent on concerted coordinated efforts of many specialists — neurosurgeons, radiation therapists, neuroradiologists, anesthesia and nursing."