(From the November 2013 Issue of PediatricsOnline)
The field of pediatric neurosurgery has advanced greatly in the past 50 years. Innovations in diagnostic imaging technology and surgical instrumentation have improved patient care beyond measure, saving and improving the lives of thousands of children around the world.
One of the areas most affected by these developments has been minimally invasive neurosurgery, in which endoscopes are used to visualize the delicate structures of the brain, skull base and spinal cord. Highly precise surgical instruments inserted through or around the endoscopes allow neurosurgeons to remove pathologic tissue, correct deformities and repair structural damage caused by disease or trauma. Unlike traditional open neurosurgery, which often requires large incisions and long hospitalizations, minimally invasive procedures need only a few tiny incisions, don’t take as long to perform and often result in a patient discharge within 48 hours or less. The small size of the endoscope means that neurosurgeons can access the surgical site without dissecting large areas of brain tissue or damaging vital anatomical structures.
At Nationwide Children’s Hospital, the neurosurgery team utilizes minimally invasive endoscopy to treat a variety of conditions, ranging from tumors to bone deformities to cerebrospinal fluid blockage. When considering whether to use a minimally invasive technique or a more traditional open approach, neurosurgeons consider many factors. Is the surgical target in a location easily accessible with an endoscope? What other structures is it near? Where are the nerves and blood vessels that must be avoided? Not every patient should have minimally invasive neurosurgery; some conditions are better treated with more traditional approaches. Neurosurgery is all about finding a safe corridor to the target. Whether that is through an open or endoscopic surgery all depends on the fine details.
Some of the more common neurosurgical procedures performed endoscopically at Nationwide Children’s are used to treat hydrocephalus, arachnoid or colloid cysts, tumors of the skull base or pituitary and craniosynostosis. A discussion of some of these conditions follows.
The body continuously produces cerebrospinal fluid (CSF), which surrounds the brain and spinal cord. Normally, CSF flows through the ventricles in the brain, exits the brain at the base of the skull, circulates around the brain and spinal cord, and then is reabsorbed into the venous system at the arachnoid granulations.
In hydrocephalus, that flow is blocked and CSF builds up, putting pressure on the brain. Patients can either be born with the condition or develop it. Classically, hydrocephalus is treated by implanting a shunt system, a plastic tube that drains CSF from the brain to another location in the body where it can be absorbed, usually the peritoneal cavity, the right atrium or the pleural cavity. Because shunts can clog or malfunction over time, neurosurgeons attempt to treat hydrocephalus without a shunt when possible.
Depending on the location of the CSF blockage, some patients may be candidates for an endoscopic third ventriculostomy (ETV). During ETV, neurosurgeons create an opening in the third ventricular floor to allow CSF to pass from the inside to the outside of the brain. If successful, this surgery is a permanent correction for hydrocephalus that does not require a shunt. Historically, ETV has been largely unsuccessful in infants less than 1 year old, possibly due to immature CSF absorption pathways. However, the development of a new procedure that combines ETV with a technique called choroid plexus cauterization (CPC) to reduce cerebrospinal fluid production has shown positive results in these young patients.
During the ETV-CPC procedure, the neurosurgeon endoscopically cauterizes much of the choroid plexus, the tissue that produces CSF. Nationwide Children’s is among a handful of children’s hospitals in the U.S. and the only one in Ohio that offers ETV-CPC, which was pioneered by Benjamin Warf, MD, at Boston Children’s Hospital. Candidates for the procedure are under 1 year of age and have hydrocephalus caused by a blockage in the cerebral aqueduct, the fourth ventricle or the fourth ventricular outflow, as determined by a high-resolution MRI. This includes a portion of patients with hydrocephalus from intraventricular hemorrhage, congenital aqueductal stenosis, and myelomeningocele. In the operation, a neurosurgeon reduces CSF production and bypasses the blockage(s).
Studies of the combined ETV-CPC procedure suggest that it is more effective in treating hydrocephalus in infants less than 1 year old than ETV alone. That said, neurosurgeons must always caution their patients’ parents that even if there is 100 percent technical success in the operating room, there is still a 30 to 50 percent chance that the hydrocephalus could return. If that happens, patients will require another surgery to insert a shunt. If the ETV-CPC procedure treats the hydrocephalus for six months, it is likely to treat it in the long term.
A Hydrocephalus Case Study: Eli Fullerton
Eli Fullerton and twin brother Bryce were born prematurely Nov. 14, 2011 at 30 weeks gestation. Two weeks later, Eli developed a fever and had blood in his cerebrospinal fluid (CSF). An ultrasound revealed a grade 3 intraventricular hemorrhage, a condition that arises in some preemies whose fragile blood vessels rupture, allowing blood to enter the ventricles of the brain. In more severe cases, blood clots can form and block the flow of CSF, leading to hydrocephalus.
Eli was transferred to Nationwide Children’s Hospital on Dec. 4. Pediatric neurosurgeon Lance Governale, MD, inserted a temporary shunt to help drain the CSF, a step designed to allow the child to grow before more permanent hydrocephalus treatment can be done. In a minority of cases, the hydrocephalus can resolve on its own and never require permanent treatment. After a period of inpatient observation, Eli went home on Dec. 27 when he met the usual newborn discharge criteria.
After a few months of close monitoring, it became clear that Eli’s hydrocephalus would require additional surgery. On March 13, 2012, Eli underwent a procedure called ETV-CPC (see main article), which not only bypassed the blockage, but also reduced CSF production—without the need for a shunt. The surgery was successful and Eli went home two days later.
Even if this type of surgery goes as planned, there is still a chance that the hydrocephalus could recur. Eli was evaluated by Dr. Governale frequently following the operation. At each follow up, the ETV-CPC appeared to be treating Eli’s hydrocephalus without a shunt and no post-surgical complications were reported. A little more than a year after his procedure, Eli is a healthy, active, mischievous toddler.
Tumors, Pituitary Lesions, Colloid Cysts and Arachnoid Cysts
Some brain tumors, pituitary lesions, colloid cysts and arachnoid cysts, depending on their exact location and relationship to surrounding structures, can be resected using minimally invasive techniques. Using an endoscope, the neurosurgeon can access the mass through a small opening in the skull via the ventricular system. Other times, the mass can be accessed through the nose via the air sinuses. With these techniques, brain tissue disruption, incision size, postoperative pain and patient recovery time may all be decreased.
Another condition that may be treatable with minimally invasive techniques is an arachnoid cyst. These CSF-filled sacs form in the subarachnoid or intraventricular spaces. Patients with these cysts sometimes can develop hydrocephalus when the cyst blocks the flow of cerebrospinal fluid through the ventricles. Other times, the cyst can be symptomatic from mass effect on the adjacent brain or skull. Most times, however, these cysts are asymptomatic, incidental findings that require no treatment, referral or follow-up.
For the minority of arachnoid cysts that do require treatment, neurosurgeons attempt to fenestrate the wall of the cyst so the fluid within can drain via normal CSF pathways. If this does not work or is not possible, a shunt may be necessary. Intraventricular arachnoid cysts are usually fenestrated via minimally invasive endoscopic techniques. Ones in the subarachnoid spaces can be fenestrated similarly. However, sometimes an open approach will allow more extensive fenestrations, thus lessening the chance a shunt will be needed, which is the ultimate goal.
In so many of these cases, choosing an open or minimally invasive approach depends almost entirely on where the target is located and what critical structures it is near. This is all part of the art of neurosurgery. It requires seeing the space and how best to access it. Some patients are best served with open approaches. But if a minimally invasive option would be superior, we at Nationwide Children’s Hospital aim to offer it.
The sutures of the skull allow brain growth to drive skull growth. In craniosynostosis, one or more of the sutures closes early. The skull then attempts to grow parallel to the fused suture, rather than perpendicular to it. This causes stereotypical head shape abnormalities, usually best viewed from the top of the child’s head.
Sagittal craniosynostosis, the most common nonsyndromic form, causes a long and narrow head. Bilateral coronal craniosynostosis, the most common syndromic form, causes a short and wide head. Unilateral coronal craniosynostosis causes a rotated appearance to the face with flattening of the forehead on the affected side, elevation of the orbital roof on the affected side and rotation of the nose. Sometimes the anterior fontanel is somewhat displaced to the contralateral side. Metopic craniosynostosis causes a triangular shape to the forehead when viewed from above. Metopic ridging without the triangular shape is a normal variant. Sometimes there is palpable ridging over the fused suture, sometimes not. Sometimes the anterior fontanel is open, sometimes not.
Lambdoid craniosynostosis is a very rare entity and the only one that would cause flattening in the back of the head. The vast majority of posterior flattening is positional plagiocephaly which is purely a cosmetic condition that does not affect brain growth or development. In positional plagiocephaly, the ear and possibly forehead on the side of the posterior flattening is displaced anteriorly, giving the head a parallelogram shape. In the rare case of lambdoid craniosynostosis, the ear and possibly forehead on the side of the posterior flattening is displaced posteriorly giving the head a trapezoidal shape.
If indeed there is a fused suture, ultimately it may cause head growth restriction on the growth curves leading to worrisome increased intracranial pressure (ICP). As such, treatment when craniosynostosis is diagnosed is recommended. The two treatment options are the traditional open approach and the newer minimally invasive endoscopic approach.
The open surgery involves removal of at least half of the bones of the skull, reshaping them and reattaching them in conjunction with a craniofacial plastic surgeon. It is done via a bicoronal incision across the top of the scalp from ear to ear. The surgery lasts approximately four hours; often a blood transfusion is required. Postoperatively, the child is observed in the intensive care unit overnight then spends approximately three days on the regular neurosurgical floor. Periorbital edema usually causes the eyes to swell shut then reopen before discharge. To decrease the surgical risk for this larger surgery, we wait until the child is at least 6 months old. They are very unlikely to experience any ICP sequelae of craniosynostosis before then.
The minimally invasive endoscopic surgery involves excision of the fused suture only. It is done via one or two 2-cm incisions. The surgery lasts approximately one hour; a blood transfusion is only rarely required. Postoperatively, the child typically is observed overnight on the regular neurosurgical floor then is ready for discharge. Usually there is no periorbital edema. Unlike the open procedure, postoperative helmeting is necessary for the minimally invasive surgery to work. The helmet is a hard outer shell with moldable foam on the inside worn 23 hours per day until the child’s first birthday. It does not press the skull into shape, but rather directs the growth of the skull into a more normal shape. Because the helmet relies on the high rate of skull growth in the first year of life, the endoscopic surgery must be done earlier than the open surgery. It can only be done between 2.5 and 3.5 months of age, so early diagnosis and referral is key for it to be an option. It is not an option for syndromic cases.
A Craniosynostosis Case Study: James Vida
When James Vida was born on May 23, 2012, there was a noticeable raised ridge along the top of his head. Initially the shape, which bulged slightly in the front and back, was thought to be the result of a very long labor and difficult passage through the birth canal. But a month later, when James’ head was still misshaped, his pediatrician recommended he have a skull x-ray.
The suture between two of the bones in James’ skull had fused prematurely, a condition called craniosynostosis (see main article). Sutures usually remain open in childhood to allow for the skull and brain to grow normally. In James’ case, the sagittal suture that runs along the top of the head fused too early, forcing the skull to grow in a long and narrow shape.
Craniosynostosis is most often repaired with an open surgery that involves an incision from ear to ear and the removal, reshaping and reattachment of affected bones. Otherwise in good health and just over 6 weeks old, James was a candidate for a minimally invasive endoscopic procedure that would correct the problem through just two tiny incisions. Performed by pediatric neurosurgeon Lance Governale, MD, at Nationwide Children’s Hospital on Aug. 10, 2012, the procedure was successful and James went home the following day.
A crucial element to this minimally invasive procedure is the use of a molding helmet, which the child must wear 23 hours a day until his first birthday. The helmet helps direct the skull into the proper shape as the infant’s head grows. James’ parents, Jennifer and Andrew, are devoted fans of The Ohio State University, so his mother painted James’ headpiece to resemble an OSU football helmet. Frequent evaluations following surgery revealed good progress in head growth. On his first birthday, James received the all-clear from Dr. Governale to remove his helmet for good. James’ parents and Dr. Governale are very happy with James’ head shape, which is now normal.
The Future of Minimally Invasive Pediatric Neurosurgery
Efforts to train current and future neurosurgeons in minimally invasive techniques will no doubt lead to advances in the field itself. The more we do, the more we learn and the more skilled we all become. The development of procedures such as ETV-CPC demonstrate the possibilities for improving patient care that come from looking at what we do from a different viewpoint. Endoscopic third ventriculostomy was once rarely successful in infants. Today, children treated successfully with the combined procedure are living healthy, shunt-free lives.
The first step in any surgical process is determining what is in the best interest of the patient, which begins with the surgical consultation. Accurate and early diagnosis is imperative to successful treatment for all neurological disorders, including hydrocephalus and craniosynostosis. It is only through the support of a comprehensive medical team that includes the surgeons, pediatricians and, most importantly, the parents and patients that we will achieve our ultimate goal of a healthy, happy child.
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Kim AH, Governale LS, Kim DH, Black PM. The management of skull base tumors. Handbook of Clinical Neurology. 2012, 105:657-64. PMID: 22230525.
Wong JM, Governale LS, Friedlander RM. Use of a simple internal fiducial as an adjunct to enhance intraoperative ultrasound-assisted guidance: technical note. Neurosurgery. 2011 Sep, 69(1 Suppl Operative):ons34-9; discussion ons39. PMID: 21346649.
About the author:
Lance S. Governale, MD, is a pediatric neurosurgeon at Nationwide Children’s Hospital and an assistant professor of neurosurgery at The Ohio State University College of Medicine. He holds a bachelor’s degree in physiology and neurobiology from the University of Maryland and a medical degree from Harvard Medical School. He remained at Harvard to complete a neurosurgical residency at Brigham and Women’s Hospital and a pediatric neurosurgical fellowship at Children’s Hospital Boston, where he trained with Benjamin Warf, MD, who pioneered the ETV-CPC procedure.