Recent Advances in Skull Base Surgery

The UPMC Departments of Otolaryngology and Neurological Surgery have been pioneering developers and proponents of the endoscopic endonasal approach (EEA) to skull base surgery for more than 30 years. In that time, the faculty and the skull base surgery program have become internationally sought for their surgical skills, research, and educational programs designed to teach aspects of EEA to new generations of surgeons around the world.

Carl Snyderman, MD, MBA, professor in the Department of Otolaryngology, with a secondary appointment as professor in the Department of Neurological Surgery, has been with UPMC and the University of Pittsburgh since completing his residency in Otolaryngology in 1987. Dr Snyderman and Paul Gardner, MD (associate professor in the Department of Neurological Surgery), are co-directors of the UPMC Center for Skull Base Surgery, the first of its kind in North America. Dr. Snyderman was the first fellow to complete the cranial base surgery fellowship in 1989. Since then, Dr. Snyderman has been at the forefront of cranial base surgery, exploring new applications of the endoscopic endonasal approach, and driving advances in research and education. Dr. Snyderman is a past president (2015) of the North American Skull Base Society (NASBS) and is a current member of its board of advisors.

The last several years have seen the advent of new technological advances, new surgical procedures, and new training programs from Dr. Snyderman and his colleagues, continuing the mission and expanding the legacy of Pittsburgh as a pioneer and leader in skull base surgery across the world.

Technological Achievements

Presented in abstract form during the scientific and poster sessions of the 2018 NASBS meeting, the UPMC Skull Base Team described the use of the fluorescent dye, Indocyanine Green (ICG), during endoscopic skull base surgery.¹ ICG is injected at the time of surgery. As the dye permeates the tissues and blood vessels, the fluorescent properties of the dye, visualized through a special type of endoscope, allow the surgeons to see the blood vessels in question. “The dye gives us a better ability to assess the vascularity of tumors and other tissues during surgery,” says Dr. Snyderman.

Dr. Snyderman explains that the technique is still somewhat investigative, but he and his collaborators are actively researching its applications and use in various skull base surgical approaches. “ICG is FDA-approved for some use, but applications of this modality for EEA with use of a special fluorescent endoscope to visualize the tissues is quite new. We’re excited about the potential prospects for this new technique in differentiating tumors from normal tissues,” says Dr. Snyderman. “We have already demonstrated its value in assessing the viability of vascularized reconstructive flaps.”

New Surgical Technique: The Contralateral Transmaxillary Approach

Published in the Journal of Neurosurgery in October 2017, Dr. Snyderman and colleagues outline a new surgical technique they have developed called the contralateral transmaxillary approach (CTM).²

The CTM approach allows surgeons to access the difficult-to-reach region of the petrous apex with an improved angle of approach of approximately 25 degrees, versus what would normally be required through an endoscopic endonasal approach.

“This region of the skull base is a very challenging area to access; removing large tumors from it with other techniques is difficult and dangerous. CTM allows us to access this region by coming at it from the opposite side via the sinuses. This approach allows us to work behind the carotid artery, greatly diminishing the risk inherent with that area,” says Dr. Snyderman.

Their study and characterization of the technique, performed on a cadaveric model, compared the CTM approach against the standard EEA for accessing this region.

Clinical experience suggests that there may be a reduction in risk and morbidity with the approach because of the improved lateral trajectory of access to the petrous apex and avoidance of the paraclival segment of the internal carotid artery.

The first group of researchers to describe this procedure and publish on it in a medical journal, Dr. Snyderman and colleagues also presented on the topic during the most recent NASBS meeting with poster,³ and oral presentations.^4,5

New Research: Lumbar Drains — To Use or Not Use

One of the current unresolved issues in skull base surgery is whether surgeons ought to use lumbar drains to draw off cerebral spinal fluid (CSF) in order to reduce CSF pressure. “These devices are often placed after surgery to aid in the healing process. When to use them lacks consensus among surgeons. No one had ever done a randomized trial to prove when or under what circumstances they should be used,” explains Dr. Snyderman.

That is until recently, when the UPMC skull base team designed and conducted the first randomized trial of lumbar drains in endoscopic skull base surgery. Results of this study, which clarify when it is appropriate to use lumbar drains, are in the midst of publication.

“Upon completion of our randomized trial, we initiated a follow-up study⁶ to assess the cost-effectiveness of the use of lumbar drains,” says Dr. Snyderman. These results also were presented in February at the NASBS and confirm the value of CSF drainage in selected patient groups. The full abstract of the study is available for viewing at the NASBS meeting website.

Staging System for Angiofibromas

In 2010, Dr. Snyderman and colleagues published their work on the development of a new staging system for juvenile nasopharyngeal angiofibroma,⁷ benign tumors that largely occur in adolescent males. Angiofibromas are slow growing but carry a high risk of intraoperative bleeding and need for additional surgeries. This retrospective study examined surgical cases from 1998 to 2008, and compared a new staging system against the current systems at the time. The UPMC staging system developed by Dr. Snyderman accounts for two important prognostic factors: the route of cranial base extension and tumor vascularity. The UPMC staging system was shown, in comparison, to provide a more accurate prediction of morbidity and tumor recurrence.

Since that initial publication in 2010, Dr. Snyderman has continued to study the UPMC staging system and advocate for its wider adoption. “What is unique about the UPMC system is its consideration of the blood supply to the tumor, not just how large the tumor is or where it is located,” says Dr. Snyderman.

Most recently, Dr. Snyderman and colleagues have published a second retrospective study on surgical cases of angiofibroma at UPMC from 2008 to 2015.8 The findings from this study looked at outcomes related to intraoperative blood loss and transfusions, number of staged operations, postoperative residual disease, and recurrent disease. Results from this study again showed that the UPMC staging system was a better predictive model in determining patients who required staged procedures, received intraoperative transfusions, and had residual postoperative disease.

Dr. Snyderman is collaborating with international sites to further validate the UPMC staging system and presented recent findings at the 2018 NASBS meeting.

Approaches to Learning Skull Base Surgery

Training surgeons to perform endoscopic skull base surgery is a hallmark of the Center for Skull Base Surgery, with Dr. Snyderman and colleagues performing and pioneering many training initiatives, symposia, and conferences for surgeons in the United States and globally. This work continues to expand, and so too does the research into training and educational techniques. “In 2010, we published an article that described how surgeons should approach the learning of endoscopic skull base surgery, and we established a five-level training program,” says Dr. Snyderman. The training is a scaled program, moving from simple to more complex surgeries and a progression in training on the learning curve. Recently, at the 2018 NASBS, Dr. Snyderman and colleagues presented research from two years of cases and categorized them according to the training levels of the program. This research was able to validate the training levels and how they correlated with patient outcomes and risks.

Safety of Live Surgeries

Another recent research project, likely the first of its kind, was a study examining the safety of live surgical procedures for educational courses. “Systematically, there is very little research on the subject. However, there are concerns about whether it is ethical to televise a live surgery for an educational course. We recently analyzed our experience with the televised, live surgical courses we have been doing since 2005 and showed that there really are no serious events, and the outcomes were on par with and sometimes better than non-televised procedures. We presented some of these findings at NASBS 2018 and are now reviewing our experience with live international surgeries,” says Dr. Snyderman. “We have shown that live demonstration surgeries can be performed safely as long as surgeons adhere to certain principles and are aware of the risks.”

Decision Making Tools for Complex Medical Problems

In collaboration with a local Pittsburgh software company, Dr. Snyderman is working to develop a decision-making tool for patients with complex medical problems. “The first one that we are addressing is the choice of therapy for acoustic neuromas,” says Dr. Snyderman. Acoustic neuromas are benign tumors that affect hearing. The decision-making tool, an online application, will help patients choose between observation, surgery, or radiation therapy. “Longer term, I think this tool will be applicable to a wide range of medical problems, and it affords a way of incorporating the values of the patient into the decision-making process. It is really a shared decision-making model that more effectively incorporates the patient’s goals and values into the equation.”

An Ever-Expanding Desire to Improve

Dr. Snyderman’s work with skull base surgery — its procedural complexities, training, research, and development of novel tools and platforms for both surgeons and patients — will continue. New to his portfolio of projects, and new in general, is a project working with a popular “brain-training” company to determine whether, through an analysis of testing results through the platform, predictions can be made as to which surgeons are likely to be better at surgery. These studies are just entering trial phase and will be ongoing for approximately the next 12 months. “If the results are positive, we can then look for ways to improve surgical performance through brain-training exercises.”

References and Further Reading

1 Poster Presentation at the 2018 North American Skull Base Society Annual Meeting. T001: Use of Intraoperative Indocyanine Green Endoscopy in Assessment of Vascularity of Intranasal Flaps. Authors: Ana Carolina Igami Nakassa, MD1, Mathew N Geltzeiler, MD2, Benita Valappil, MPH1, Yue-Fang Chang, PhD3, Georgios A Zenonos, MD3, Eric W Wang, MD2, Juan C Fernandez-Miranda, MD3, Carl H Snyderman, MD, MBA2, Paul A Gardner, MD3. 1UPMC Center for Cranial Base Surgery; 2Department of Otolaryngology, University of Pittsburgh School of Medicine; 3Department of Neurological Surgery, University of Pittsburgh School of Medicine. 2 Patel CR, Wang EW, Fernandez-Miranda JC, Gardner PA, Snyderman CH. Contralateral Transmaxillary Corridor: An Augmented Endoscopic Approach to the Petrous Apex. J Neurosurg. 2017; 20: 1-9. Epub ahead of print. 3 Poster Presentation at the 2018 North American Skull Base Society Annual Meeting: P012: Contralateral Transmaxillary Approach Vs. Purely Transnasal Approach to the Petroclival Region: An Anatomical and Radiological Study. Joao Mangussi-Gomes, MD1, Gustavo F Nogueira, MD2, Eric W Wang, MD3, Juan C Fernandez-Miranda, MD4, Carl H Snyderman, MD, MBA3, Paul A Gardner, MD4. 1Surgical Neuroanatomy Lab, UPMC Center for Cranial Base Surgery; 2Neurological Institute of Curitiba; 3Department of Otolaryngology, University of Pittsburgh School of Medicine; 4Department of Neurological Surgery, University of Pittsburgh School of Medicine. 4 Poster Presentation at the 2018 North American Skull Base Society Annual Meeting: P111: Utilization of the Contralateral Transmaxillary Approach for Chordoma and Chondrosarcoma of the Petrous Apex. Daniel L Faden, MD, Philippe F Lavigne, MD, Juan C Fernandez- Miranda, MD, Paul A Gardner, MD, Eric W Wang, MD, Carl H Snyderman, MD, MBA. UPMC. 5 Scientific Session of the 2018 North American Skull Base Society Annual Meeting. 068: Contralateral Transmaxillary Corridor: Surgical Planning and Pathway Analytics. Rajeev Sen, MD1, Rajeev C. Saxena, MD, MBA1, Nava Aghdasi, PhD1, Yangming Li, PhD1, Randall Bly, MD1, Paul Gardner, MD2, Carl Snyderman, MD2, Kris S Moe, MD1; 1University of Washington; 2University of Pittsburgh. 6 Scientific Session of the 2018 North American Skull Base Society Annual Meeting. 202: Lumbar Drainage May Represent a Cost Saving Method for Skull Base Surgeries. Vishaal Patel, BA1, Gurpreet Gadhoke, MD2, Paul A. Gardner, MD3, Carl H. Snyderman, MD, MBA3; 1University of Pittsburgh School of Medicine; 2Department of Neurological Surgery, University of Pittsburgh School of Medicine; 3UPMC Center for Cranial Base Surgery. 7 Snyderman CH, Pant H, Carrau RL, Gardner PA. A New Endoscopic Staging System for Angiofibromas. Arch Otolaryngol Head Neck Surg. 2010; 136(6): 588-594. 8 Rowan NR, Zwagerman NT, Heft-Neal ME, Gardner PA, Snyderman CH. Juvenile Nasal Angiofibromas: A Comparison of Modern Staging Systems in an Endoscopic Era. J Neurol Surg B Skull Base. 2017; 78(1): 63-67.