Faculty Bibliography

As endoscopic skull base resections have advanced, appropriate reconstruction has become paramount. The reconstructive options for the skull base include both avascular and vascular grafts. We review these and provide an algorithm for endoscopic skull base reconstruction. One hundred and sixty-six skull base dural defects, reconstructed with an endonasal vascular flap, were examined. As an adjunct, avascular reconstruction techniques are discussed to illustrate all options for endonasal skull base reconstruction. Cerebrospinal fluid (CSF) leak rates are also discussed. Small CSF leaks may be successfully repaired with various avascular grafting techniques. Endoscopic endonasal approaches (EEAs) to the skull base often have larger dural defects with high-flow CSF leaks. Success rates for some EEA procedures utilizing avascular grafts approach 90%, yet in high-flow leak situations, success rates are much lower (50 to 70%). Defect location and complexity guides vascularized flap choice. When nasoseptal flaps are unavailable, anterior/sellar defects are best managed with an endoscopically harvested pericranial flap, whereas clival/posterior defects may be reconstructed with an inferior turbinate or temporoparietal flap. An endonasal skull base reconstruction algorithm was constructed and points to increased use of various vascularized reconstructions for more complex skull base defects.

BACKGROUND: Understanding the course of the most medially located parasellar cranial nerve, the abducens, becomes critical when performing an expanded endonasal approach. OBJECTIVE: We report an anatomoclinical study of the abducens nerve and describe relevant surgical nuances to avoid its injury. METHODS: Ten anatomic specimens were dissected using endoscopes attached to an high-definition camera. A series of anatomic measurements and relationships of the abducens nerve were noted. Illustrative clinical cases are described to translate those findings into practice. RESULTS: Cisternal, interdural, gulfar, and cavernous segments of the abducens were identified intracranially. The mean distance from the vertebrobasilar junction (VBJ) to the pontomedullary sulcus (PMS) was 4 mm; horizontal distance between both abducens nerves at the PMS was 10 mm, and between both abducens at the interdural segment was 18.5 mm. The upper limit of the lacerum segment of the internal carotid artery was at the same level of the dural entry point of the sixth cranial nerve posteriorly. The sellar floor at the sphenoid sinus marks the level of the gulfar segment in the craniocaudal axis. At the superior orbital fissure, the abducens nerve and V2 were at an average vertical distance of 11.5 mm. CONCLUSION: Anatomic landmarks to localize the abducens nerve intraoperatively, such as the VBJ for the transclival approach, the lacerum segment of the carotid, and the sellar floor for the medial petrous apex approach, and V2 for Meckel's cave approach, are reliable and complementary to the use of intraoperative electrophysiological monitoring.

OBJECTIVE: The endoscopic endonasal transclival approach is a valid alternative for treatment of lesions in the clivus. The major limitation of this approach is a significant lateral extension of the tumor. We aim to identify a safe corridor through the occipital condyle to provide more lateral exposure of the foramen magnum. METHODS: Sixteen parameters were measured in 25 adult skulls to analyze the exact extension of a safe corridor through the condyle. Endonasal endoscopic anatomic dissections were carried out in nine colored latex-injected heads. RESULTS: Drilling at the lateral inferior clival area exposed two compartments divided by the hypoglossal canal: the jugular tubercle (superior) and the condylar (inferior). Completion of a unilateral ventromedial condyle resection opens a 3.5 mm (transverse length) * 10 mm (vertical length) lateral surgical corridor, facilitating direct access to the vertebral artery at its dural entry point into the posterior fossa. The supracondylar groove is a reliable landmark for locating the hypoglossal canal in relation to the condyle. The hypoglossal canal is used as the posterior limit of the condyle removal to preserve more than half of the condylar mass. The transjugular tubercle approach is accomplished by drilling above the hypoglossal canal, and increases the vertical length of the lateral surgical corridor by 8 mm, allowing for visualization of the distal cisternal segment of the lower cranial nerves. CONCLUSION: The transcondylar and transjugular tubercle "far medial" expansions of the endoscopic endonasal approach to the inferior third of the clivus provide a unique surgical corridor to the ventrolateral surface of the ponto- and cervicomedullary junctions.

OBJECT: Rathke cleft cysts (RCCs) are benign lesions that can be diagnosed as an incidental finding associated with headaches, pituitary dysfunction, or vision deterioration. Typically, they occur in a sellar or suprasellar location. The aim of this study was to review the clinical presentation and outcomes associated with endoscopic endonasal resection of these lesions. METHODS: The authors retrospectively reviewed a series of 35 patients with a diagnosis of RCC after endoscopic endonasal resection at the University of Pittsburgh between January 1998 and July 2008. RESULTS: All 35 patients underwent a purely endoscopic endonasal approach (EEA). The average patient age was 34 years (range 12-67 years), and the average follow-up was 19 months (range 1-60 months). Clinical follow-up data were available for 32 patients, and radiographic follow-up data were accessible for 33 patients. All of the patients underwent complete removal of the cyst contents, and according to radiography studies 2 patients had a recurrence, neither of which required reoperation. The mean cyst volume was 1052.7 mm(3) (range 114-6044 mm(3)). Headache was a presenting symptom in 26 (81.2%) of 32 patients, with 25 (96.1%) of 26 having postoperative improvement in their headaches. Fifteen (57.7%) of the 26 patients had complete pain resolution, and 10 (38.5%) had a > 50% reduction in their pain scores. Six (18.8%) of 32 patients initially presented with pituitary dysfunction, although 2 (33.3%) had postoperative improvement. Three (9.4%) of 32 patients had temporary pituitary dysfunction postoperatively, although there was no permanent pituitary dysfunction. Neither were there any intraoperative complications, postoperative CSF leaks, or new neurological deficits. The average hospital stay was 1.8 days (range 1-5 days). CONCLUSIONS: The EEA is a safe and effective approach in the treatment of RCCs. None of the patients in this study experienced any worsening of their preoperative symptoms or pituitary function, and 96% of the patients who had presented with headache experienced complete or significant pain relief following treatment.

OBJECT/OBJECTIVE:In rare cases, children with a Chiari malformation Type I (CM-I) suffer from concomitant, irreducible, ventral brainstem compression that may result in cranial neuropathies or brainstem dysfunction. In these circumstances, a 360 degrees decompression supplemented by posterior stabilization and fusion is required. In this report, the authors present the first experience with using an endoscopic transnasal corridor to accomplish ventral decompression in children with CM-I that is complicated by ventral brainstem compression. METHODS:Two children presented with a combination of occipital headaches, swallowing dysfunction, myelopathy, and/or progressive scoliosis. Imaging studies demonstrated CM-I with severely retroflexed odontoid processes and ventral brainstem compression. Both patients underwent an endoscopic transnasal approach for ventral decompression, followed by posterior decompression, expansive duraplasty, and occipital-cervical fusion. RESULTS:In both patients the endoscopic transnasal approach provided excellent ventral access to decompress the brainstem. When compared with the transoral approach, endoscopic transnasal access presents 4 potential advantages: 1) excellent prevertebral exposure in patients with small oral cavities; 2) a surgical corridor located above the hard palate to decompress rostral pathological entities more easily; 3) avoidance of the oral trauma and edema that follows oral retractor placement; and 4) avoidance of splitting the soft or hard palate in patients with oral-palatal dysfunction from ventral brainstem compression. CONCLUSIONS:The endoscopic transnasal approach is atraumatic to the oral cavity, and offers a more superior region of exposure when compared with the standard transoral approach. Depending on their comfort level with endoscopic surgical techniques, pediatric neurosurgeons should consider this approach in children with pathological entities requiring ventral brainstem decompression.

OBJECTIVE:To develop a new staging system for juvenile nasopharyngeal angiofibroma that reflects changes in surgical approaches (endonasal), route of intracranial extension, and the extent of vascular supply from the internal carotid artery. DESIGN/METHODS:Retrospective review of case series. SETTING/METHODS:Academic medical center. PATIENTS/METHODS:Patients undergoing endoscopic endonasal surgery for juvenile nasopharyngeal angiofibroma at the University of Pittsburgh Medical Center (UPMC), Pittsburgh, Pennsylvania, from 1998 through 2008. INTERVENTION/METHODS:Patients were staged according to current systems and compared with a new staging system that also incorporated the route of skull base extension and tumor vascularity. MAIN OUTCOME MEASURES/METHODS:Estimated blood loss, number of operations, and tumor recurrence. RESULTS:Skull base erosion was observed in 74% of cases. Following embolization of external carotid artery tributaries, residual vascularity from the internal carotid artery was seen in 51% of patients. Residual vascularity, classified as UPMC stage IV and V, strongly correlated with blood loss, requirement for multiple procedures, and residual or recurrent tumor. CONCLUSIONS:Tumor size and extent of sinus disease are less important in predicting complete tumor removal with endonasal surgical techniques. The UPMC staging system for juvenile nasopharyngeal angiofibroma accounts for 2 important prognostic factors, route of cranial base extension, and vascularity and is applicable to endoscopic or open approaches. Compared with other staging systems, the UPMC staging system provides a better prediction of immediate morbidity (including blood loss and need for multiple operations) and tumor recurrence.

OBJECTIVE:A practical alternative for endonasal retraction is presented. TECHNIQUE/METHODS:Following 100 endoscopic endonasal procedures at the University of Pittsburgh, a simple alternative for gentle tissue retraction was introduced for endoscopic endonasal procedures: the "Q-tip" cotton swab. Its fine shape allows it to be inserted through one of the nostrils, sharing the space with the other instruments and the endoscope while preserving freedom of movement. Its long dimension allows it to reach deep areas while it is actively held by one of the surgeons, and its stiffness allows more or less force to be applied in any direction. Its soft head permits gentle touch of retraction without causing injury to the noble neurovascular structures of the cranial base. CONCLUSION/CONCLUSIONS:During endoscopic endonasal surgery, the instruments are operated through the nostrils, which are restricted passages. Any retractor utilized has to be thin to share the space with the other instruments, long enough to reach the cranial base, and soft to avoid tissue damage. All of these characteristics were encountered in the "Q-tip" cotton swab.

Neuroendoscopic surgery encompasses minimally invasive approaches to the skull base using endoscopic techniques. There are unique technologic challenges with endoscopic endonasal skull base surgery, such as a limited working space, difficulty in visualization and identification of neurovascular structures and removal of tissue, hemostasis, and dural reconstruction. Technologic advances that have enabled this surgery include specialized operating suites, neurophysiologic monitoring, imaging and visualization technologies, dissection instrumentation, hemostatic materials, and reconstructive materials. Advances in each of these areas and the needs and challenges of the future of neuroendoscopic surgery are discussed.