Dr. Jonathan A. ForbesUSA
University of Cincinnati School of Medicine, USA
| 2018 to present | Staff Neurosurgeon, University of Cincinnati Dept. of Neurosurgery |
| 2017 - 2018 | Skull Base Fellow, Weil Cornell Medical Center |
| 2013 - 2017 | Staff Neurosurgeon United States Air Force |
Dr. Forbes is a fellowship-trained, board-certified neurosurgeon with expertise and interest in open and minimally invasive approaches for the treatment of pathology of the cranial base. During his neurosurgical residency at Vanderbilt University, he received numerous national accolades including the American Association of Neurological Surgeons (AANS) Synthes Craniofacial Award for Research in Neurotrauma as well as the AANS Top Gun Award. After completing his chief year of neurosurgical residency at Vanderbilt in 2013, Dr. Forbes went on to fulfill a 4-year commitment with the U.S. Air Force. After an honorable discharge from the military, he completed a minimally invasive skull base fellowship at Weill Cornell Medical Center in New York City prior to joining the UC Gardner Neuroscience Institute’s Department of Neurosurgery. Since joining UC in 2018, Dr. Forbes has been recognized as a “UC Top 1% of Patient Experience” award winner and a finalist for the Congress of Neurological Surgeons “Innovator of the Year” Award. During his time at UC, Dr. Forbes has been involved in the creation of 6 patents and has received 5 research grants from highly competitive entities such as North American Skull Base Society, AO Spine, and UC Pilot. In 2023, he received Cincinnati Business Courier’s Health Care Hero Award: Innovation Category. To date, Dr. Forbes has contributed to over 90 peer-reviewed publications.
Endonasal approach to the craniovertebral junction: case-based discussion of relevant neuroanatomy and surgical considerations
1108 16:45-16:55
Skull Base/304A
INTRODUCTION:
The endonasal corridor provides direct access to the ventral, midline craniocervical junction without the need to transgress the cranial nerve envelope. There is a paucity of data in the literature describing quantitative exposure of the ventral craniocervical junction through the endonasal corridor in a safe manner mindful of locoregional anatomy.
OBJECTIVE:
To quantify ventromedial exposure of O-C1 and C1-2 articular structures after turning an inverted U-shaped nasopharyngeal flap (IUNF) and to review cases illustrating the clinical utility of such an exposure in treatment of irreducible ventral brainstem compression.
METHODS:
We performed dissection in 8 cadaveric specimens. An IUNF was fashioned using a superior incision below the level of the pharyngeal tubercule of the clivus and lateral incisions in the approximate region of Rosenmuller fossae bilaterally. Measurements with calipers and/or neuronavigation software included flap dimensions, exposure of O-C1 and C1-2 articular structures, inferior reach of IUNF, and proximity of the internal carotid artery (ICA) and hypoglossal nerve to IUNF margins. The clinical utility of such an exposure was then assessed in 4 patients requiring endonasal odontoidectomy.
RESULTS:
The IUNF facilitated exposure of an average of 9 mm of the medial surfaces of the right/left O-C1 joints without transgression of the carotid arteries or hypoglossal nerves. The C1-2 articulation could not be routinely accessed. The margins of the IUNF were not in close (<5 mm) proximity to the ICA in any of the 8 specimens. In 6 of 8 specimens, the dimensions of the IUNF were in close (<5 mm) horizontal or vertical proximity to the hypoglossal foramina. In each of the 4 endonasal odontoidectomies performed, the exposure provided sufficient access for removal of the odontoid process and complete decompression of the ventral brainstem.
CONCLUSION:
The IUNF provided safe and panoramic access to the odontoid process and medial O-C1 articulation. Given the close proximity of the exocranial hypoglossal foramen, neuronavigation assistance and neuromonitoring with attention to the superolateral IUNF margin are recommended. Pre-operative CT angiography for characterization of the internal carotid arteries is also recommended when utilizing this exposure.
Use of Neuronavigation for Selective Access of Trigeminal Rootlets in Radiofrequency Lesioning
1110 09:00-09:10
Functional Neurosurgery & Epilepsy/304A
Background and objective: Radiofrequency lesioning (RFL) is a safe and effective treatment for medically refractory trigeminal neuralgia. Despite gaining mainstream neurosurgical acceptance in the 1970s, the technique has remained relatively unchanged, with the majority of series using anatomic landmarks and lateral fluoroscopy to guide cannula placement. To date, there is a paucity of information in the literature describing neuronavigation-specific parameters to help neurosurgeons selectively target individual trigeminal rootlets.
Methods: 10 embalmed cadaveric specimens were registered to cranial neuronavigation. Frontotemporal craniotomies were performed to facilitate direct visualization of the Gasserian ganglion. A 19-gauge cannula was retrofit to a navigation probe, permitting real-time tracking. Using preplanned trajectories, the cannula was advanced through foramen ovale (FO) to the navigated posterior clival line (nPCL). A curved electrode was inserted to the nPCL and oriented inferolaterally for V3 and superomedially for V2. For V1, the cannula was advanced 5 mm distal to the nPCL and the curved electrode was reoriented inferomedially. A surgical microscope was used to determine successful contact. Morphometric data from the neuronavigation unit were recorded.
The protocol for neuronavigation-directed RFL generated in the cadaveric study was then assessed in 3 consecutive patients who underwent radiofrequency lesioning for trigeminal neuralgia.
Results: Twenty RFL procedures were performed in the cadaveric specimens (10R, 10L). Successful contact with V3, V2, and V1 was made in 95%, 90%, and 85% of attempts, respectively. Mean distances from the entry point to FO and from FO to the clival line were 7.61 cm and 1.26 cm, respectively.
In 3 patient treated with neuronavigation assisted RFL, the posterior clival line could be rapidly accessed at a mean distance of 8.9 cm from skin entry. The protocol advocated in the cadaveric study facilitated successful lesioning without the need for cannula reposition in all 3 patients.
Conclusion: In this proof-of-concept study, we found that reliable access to V1-3 could be obtained with the neuronavigation-specific algorithm described above. While the study is limited by small sample size, neuronavigation for RFL warrants further investigation as a potential tool to improve anatomic selectivity, operative efficiency, and ultimately patient outcomes.