RESEARCH—HUMAN—CLINICAL STUDIES TOPIC RESEARCH—HUMAN—CLINICAL STUDIES Endoscopic Endonasal Approach for Nonvestibular Schwannomas Samuel S. Shin, PhD* Paul A. Gardner, MD‡ S. Tonya Stefko, MD§ Ricky Madhok, MD‡ Juan C. FernandezMiranda, MD‡ Carl H. Snyderman, MDk *University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Departments of ‡Neurological Surgery, §Ophthalmology, and kOtolaryngology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania Correspondence: Paul A. Gardner, MD, Department of Neurological Surgery, University of Pittsburgh Medical Center, UPMC Presbyterian, Ste B-400, 200 Lothrop St, Pittsburgh, PA 15213. E-mail: gardpa@upmc.edu Received, September 1, 2010. Accepted, March 25, 2011. Published Online, March 25, 2011. BACKGROUND: Nonvestibular schwannomas of the skull base often represent a challenge owing to their anatomic location. With improved techniques in endoscopic endonasal skull base surgery, resection of various ventral skull base tumors, including schwannomas, has become possible. OBJECTIVE: To assess the outcomes of using endoscopic endonasal approach (EEA) for nonvestibular schwannomas of the skull base. METHODS: Seventeen patients operated on for skull base schwannomas by EEA at the University of Pittsburgh Medical Center from 2003 to 2009 were reviewed. RESULTS: Three patients underwent combined approaches with retromastoid craniectomy (n = 2) and orbitopterional craniotomy (n = 1). Three patients underwent multistage EEA. The rest received a single EEA operation. Data on degree of resection were found for 15 patients. Gross total resection (n = 9) and near-total (.90%) resection (n = 3) were achieved in 12 patients (80%). There were no tumor recurrences or postoperative cerebrospinal fluid leaks. In 3 of 7 patients with preoperative sensory deficits of trigeminal nerve distribution, there were partial improvements. Patients with preoperative reduced vision (n = 1) and cranial nerve VI or III palsies (n = 3) also showed improvement. Five patients had new postoperative trigeminal nerve deficits: 2 had sensory deficits only, 1 had motor deficit only, and 2 had both motor and sensory deficits. Three of these patients had partial improvement, but 3 developed corneal neurotrophic keratopathy. CONCLUSION: An EEA provides adequate access for nonvestibular schwannomas invading the skull base, allowing a high degree of resection with a low rate of complications. KEY WORDS: Cranial, Endonasal, Endoscopic, Schwannoma Copyright ª 2011 by the Congress of Neurological Surgeons Neurosurgery 69:1046–1057, 2011 DOI: 10.1227/NEU.0b013e3182287bb9 S chwannomas are benign tumors that arise from Schwann cells, affecting peripheral, autonomic, and cranial nerves (CNs). They account for 8% to 10% of intracranial tumors1 and occur mostly in patients between 20 and 50 years of age.2 Patients affected by schwannoma may be asymptomatic or present with symptoms related to the nerve of origin or surrounding nerves. Depending on the location, size, and nerve of origin, they can manifest in a variety of motor and sensory symptoms, including muscle weakness, pain, numbness, paresthesia, and sensory deficit. ABBREVIATIONS: CN, cranial nerve; EEA, endoscopic endonasal approach; ICA, internal carotid artery; RMC, retromastoid craniectomy 1046 | VOLUME 69 | NUMBER 5 | NOVEMBER 2011 www.neurosurgery-online.com The most common intracranial schwannomas involve the vestibular nerve, with an annual incidence of 1 in 100 000.3 Treatment strategies for these tumors have been studied extensively and range from observation to radiosurgery to microsurgical resection with middle fossa, translabyrinthine, or retrosigmoid approaches.4,5 Nonvestibular schwannomas are less common, and their resection strategies are not as thoroughly investigated. Previous studies on surgical treatments of nonvestibular schwannoma looked at microsurgical approaches6 or a combination of radiosurgery and microsurgery.7 In the Sarma et al6 report of microsurgical resection of nonvestibular schwannomas, new CN deficits were observed in 24% of the patients, and the most common postoperative morbidity was cerebrospinal fluid (CSF) leak, which occurred www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. ENDONASAL ENDOSCOPIC APPROACH FOR SCHWANNOMAS in 10.9% of patients. In the Safavi-Abbasi et al7 study, new CN deficits were identified in 14.3% of nonvestibular schwannomas treated by microsurgical resection alone. Those treated by radiosurgery alone had new CN deficits in 22.2% of the cases. The rate of CSF leak after microsurgical resection was reported in 12% of the patients (6 of 50 cases). Reports of functional outcomes of patients who underwent microsurgical resection of trigeminal schwannoma, which make up the majority of nonvestibular schwannomas, have been favorable. In a report by Dolenc,8 there were no new neurological deficits after the microsurgical resection of trigeminal schwannoma other than temporary corneal sensory deficits in 2 of 85 cases. There were improvements in preoperative CN deficits in many patients; the largest improvements were seen for CN VI deficit (45% preoperatively to 9% postoperatively) and CN V sensory deficit (100% preoperatively to 85% postoperatively). However, there was no improvement in atrophy of temporalis and masseter muscles after surgery. Unlike these various studies that assessed outcomes after using microsurgical approaches, the effectiveness of the endoscopic endonasal approach (EEA) in the treatment of nonvestibular schwannomas has not been reported. Complete resection is the treatment of choice for schwannomas because subtotal resection of vestibular schwannomas may result in higher recurrence rates compared with near-total or gross total resections.9 This may be difficult when the tumor invades CNs and important vascular structures of the skull base, and subtotal resection is often performed to preserve neural or vascular integrity.10 Although various surgical approaches such as middle fossa, retrosigmoid, infratemporal, and translabyrinthine approaches are good options for resection of skull base schwannomas, EEA can provide a direct approach for tumors in and around the paranasal sinuses and skull base. We report the role of EEA in the resection of nonvestibular schwannomas of the cranial base in 17 patients. placed supine with his/her head fixed by a 3-pin head holder and held in neutral position with slight neck turn to right side. A 0.05% oxymetazoline was applied topically with pledgets to decongest the nose. Throughout all operations, somatosensory evoked potentials and CN electromyography (as indicated) were monitored. The procedure was initiated with a right-sided middle turbinectomy to provide space for suction and endoscope. The left middle turbinate was lateralized for passing of additional instruments. For the purpose of flap reconstruction at the end, nasoseptal flaps were harvested for some patients. This technique has been well described previously.12,13 The flap was raised at the beginning of the surgery and stored in nasal cavity or maxillary sinus until reconstruction. Sphenoid Sinus Exposure For the patients in this series with anterior and middle skull base schwannomas, sphenoid sinus exposure was performed initially. The floor of the sphenoid sinus was drilled bilaterally with a 0° endoscope, handheld irrigation, and a 3-mm hybrid cutting/diamond burr. A wide bilateral sphenoidotomy was necessary to allow easy access of endoscope and instruments in critical situations such as in the event of bleeding of the internal carotid artery (ICA). In certain cases, when ICA control was important for tumor resection around or posterior to the ICA, bone over the paraclival and petrous horizontal parts of the ICA was thinned and removed. The floor of the sphenoid sinus was widened laterally to access areas lateral to the ICA, and access increased anteriorly by removal of posterior ethmoid air cells. Transplanum/Transcribriform Exposure In the case of olfactory schwannoma (patient 17), the tumor was approached by exposure of planum sphenoidale and cribriform plate. After exposure of the sphenoid sinus and removal of ethmoid air cells, superior attachment of nasal septum was resected up to the skull base. Anterior and posterior ethmoid arteries were cauterized bilaterally during the approach. Planum sphenoidale and cribriform plate and the medial and superior aspects of orbit were drilled to access the tumor, which was then internally debulked before performing extra capsular dissection. Meckel Cave Exposure This retrospective case series study was approved by the University of Pittsburgh Medical Center Institutional Review Board. Patient records from February 2003 to August 2009 were reviewed retrospectively. All skull base schwannoma cases that underwent EEA at the University of Pittsburgh Medical Center were reviewed. Vestibular schwannoma cases were not included in this study because they are not deemed appropriate for EEA. Operative notes, radiographic images, and office notes were used for data collection of presentations, clinical outcomes, demographics, and surgical details. Multiple surgical corridors were considered for each case as previously described.11 In some patients, a combination of EEA and open retromastoid craniectomy (RMC) or EEA and open orbitopterional craniotomy was performed to provide optimal access while minimizing brain retraction and risk to neighboring neurovascular structures. For schwannomas of Meckel cave, exposure began by accessing the maxillary sinus as previously described.14 Nasal antrostomy was performed with backbiting rongeurs. The maxillary sinus ostium was opened widely, and sphenopalatine foramen was identified. The posterior wall of the maxillary sinus was removed with a Kerrison rongeur, and the pterygopalatine fossa was thereby exposed. Removal of the posterior wall continued to the area just lateral to the infraorbital foramen. At this point, the vidian nerve and artery were visualized at the confluence of the medial pterygoid plate and floor of sphenoid sinus.15 Image guidance was used to confirm the location of the ICA and vidian canal. The wall of the vidian canal was then drilled cautiously when ICA control was necessary. For access to Meckel cave, the vidian nerve was usually sacrificed, and the artery (when present) was coagulated by bipolar electrocautery and transected. Foramen rotundum was identifiable lateral to the vidian canal, and the bone around V2 was drilled until the insertion of V2 into dura mater at the middle cranial fossa was visible. Preparation for EEA Infratemporal Fossa Exposure All patients underwent EEA by a team composed of an otolaryngologist and a neurosurgeon using a binarial approach. The patient was After initial sphenoid sinus exposure, the posterior aspect of the inferior turbinate was resected and a wide nasal antrostomy was performed. METHODS NEUROSURGERY VOLUME 69 | NUMBER 5 | NOVEMBER 2011 | 1047 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. SHIN ET AL Through this window, the posterior wall of the maxillary sinus was accessed and removed with Kerrison rongeurs. Branches of the internal maxillary artery, greater palatine artery, posterior nasal artery, and sphenopalatine arteries were transected after bipolar cauterization. The pterygoid plates were then drilled to fully expose the infratemporal fossa tumor. Orbital Apex Exposure After removal of posterior and anterior ethmoidal air cells, exposure of the orbital apex was started by removing the posterior lamina papyracea. Then the entire optic canal was exposed posteriorly to the lateral edge of the tuberculum sellae. Further bone removal over the superior orbital fissure and optic canal proceeded to expose the tumor in the orbital apex. Jugular Fossa Exposure The jugular foramen approach is also called the infrapetrous16 or sublacerum (A.L. Rhoton, MD, personal communication, 2010) approach. The jugular foramen, which is formed by the clival bone (medial) and the petrous bone (lateral), sits at the caudal opening of the petroclival fissure. For exposure into the jugular fossa, the initial opening into the sphenoid sinus was followed by removal of the sphenoid sinus floor and subjacent clival bone. Drilling in the clival region was extended laterally toward the jugular tubercle region, as previously described.17 The vidian canal was identified laterally, and the pterygoid body and medial plate inferior to the vidian canal were completely drilled out. The infrapetrous approach to the jugular foramen is a transpterygoid infravidian approach. The thick tissue of the pharyngobasilar fascia was stripped down, and the mucosa and fibrocartilage between the nasopharynx and Eustachian tube were then dissected. The image guidance system and Doppler were used to identify and avoid the ICA in the parapharyngeal space as dissection continued laterally. To access the inferior surface of the petrous bone and jugular foramen, the torus tubarius was transected at the nasopharynx and displaced inferiorly and laterally. This key maneuver allowed the opening of the sublacerum route to the target. The diamond drill was used to further remove the bone around the genu of the lacerum segment of the ICA without exposing the artery. It is critical to note that at the jugular foramen the pars nervosa is anterior to the pars venosa; therefore, the ventral (endonasal) approach to the jugular foramen is suitable only for lesions extending ventrally and displacing the lower CNs out of the endonasal trajectory. Combined Craniotomy Approaches The posterior components of schwannomas invading the cerebellopontine angle were resected by a standard retromastoid approach. Orbitopterional craniotomy was used to access tumor that extended anterior and lateral to the optic nerve and superior orbital fissure. Reconstruction Nasal septal flap was used in the more recent patients (n = 9) who underwent EEA. At the end of the dissection, a Duragen (Integra Life Sciences, Boston, Massachusetts) inlay was placed over the dural defect. Nasal septal flap prepared before approaching the tumor was placed over this layer of inlay and was fixed by dural sealant. Fat autograft or Gelfoam was placed superficially over the flap to support the construct. Occasionally, an inflated Foley catheter balloon was placed over the various layers of reconstruction to prevent the construct from migrating. 1048 | VOLUME 69 | NUMBER 5 | NOVEMBER 2011 RESULTS Between 2003 and 2009, 17 patients had nonvestibular schwannomas operated on by EEA (Table). There were 8 male (47%) and 9 female (53%) patients with a mean age of 36.5 years (range, 14-72 years). The lesions approached via EEA originated in various areas around the skull base. There were 11 trigeminal schwannomas located primarily in the following areas: 4 in the Meckel cave, 2 in the middle fossa, 2 in the orbital apex, and 3 in the infratemporal fossa. There were 1 olfactory schwannoma and 2 jugular schwannomas, and 3 were of unknown nerve of origin: 2 intranasal and 1 intraconal/orbital. Two patients were lost to follow-up, and 1 patient’s surgery was aborted early without tumor removal owing to limited access related to the ICA. Average operative time was 8 hours 39 minutes when multiple staged operations are considered 1 operation. Average operative time for single-stage EEA surgeries was 5 hours 17 minutes, whereas that of multistage combined surgeries was 14 hours 14 minutes (average operative time for individual stages, 6 hours 34 minutes). There were no postoperative CSF leaks. Intraoperative CSF leaks were reconstructed with Duragen (collagen matrix) and either Alloderm (earlier in the series) or nasoseptal flap followed by tissue sealant and packing. Average follow-up time for the patients was 15 months. Among the 17 patients in our case series who underwent resection of schwannoma by EEA, we have recorded data on the degree of resection for 15 patients. One patient had no record of degree of resection, and another surgery was aborted because of concern about control of the ICA. Among the remaining 15 patients, 9 patients had gross total resection (60%), 3 patients had near-total resection (20%), and 3 patients had subtotal resection (20%). For cases with subtotal resections, complete resection was not planned for the operation as a result of the proximity or involvement of critical neurovascular structures such as the carotid artery or optic nerve. The goals of the operations were to maximize symptom relief by debulking the tumor while minimizing morbidity from damaging these critical structures. As mentioned, 1 case was aborted. A 33-year-old male patient (patient 13) had a 2.5 3 1.4 3 1.6-cm schwannoma within the right jugular foramen that was adjacent to the carotid artery and compressing and laterally displacing the internal jugular vein. An EEA was attempted to access this tumor. After the initial procedure and removal of inferior aspect of sphenoid sinus and part of a clivus, dissection continued deep to the Eustachian tube toward the hypoglossal canal. However, there was only a small window between the lateral clival bone (medial jugular tubercle) and the carotid artery, limiting access to the tumor. The surgery was aborted because of concern for ICA injury. The patient was offered a far lateral approach but elected to undergo radiosurgery treatment 2 weeks after EEA to control the tumor. Complications One young female patient (patient 4) who underwent resection of a trigeminal schwannoma by combined EEA and RMC developed www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. ENDONASAL ENDOSCOPIC APPROACH FOR SCHWANNOMAS TABLE. Clinical Data of Schwannoma Patients Treated by Endoscopic Endonasal Approacha Age, Patient y/Sex Category Tumor Location Degree of Resection Procedures Preoperative Symptoms Postoperative Complications V1. V2. V3 numbness HA 1 51/M Trigeminal Infratemporal, Meckel cave Near total EEA 2 46/F Trigeminal Orbital apex, Meckel cave Gross total EEA 3 24/M Trigeminal Meckel cave Subtotal EEA 4 19/F Trigeminal Meckel cave, CP angle Near total 5 23/F Trigeminal Middle fossa, Meckel cave Gross total EEA V1, V2, V3 numbness, CN VI palsy 6 21/F Trigeminal Meckel cave Gross total EEA 7 49M Trigeminal Gross total 8 34/M Unknown Middle fossa, posterior fossa Intraconal, orbital EEA, RMC EEA, OPC V1, V2, V3 pain/numbness, mastication weakness, corneal abrasion, neurotrophic cornea Dry eye, CN X palsy V1, V2 numbness, mild CN X palsy (after RMC) V1 numbness, optic CN III palsy neuropathy 9 34/F Trigeminal Near total 10 11 12 72/M 26/F 20/F Trigeminal Jugular Trigeminal Infratemporal, middle fossa Orbital apex Jugular fossa Meckel cave 3-Stage V1, V2, V3 numbness, EEA CN VI palsy Gross total EEA Reduced vision Subtotal 2-Stage EEA Gross total EEA V1 numbness 13 33/M Jugular Jugular fossa 14 15 16 17 54/F 30/F 51/M 14/M Trigeminal Unknown Unknown Olfactory Infratemporal Nasal cavity Nasal cavity Frontal lobe Surgery Aborted Gross total Gross total Unknown Gross total Subtotal Postoperative Improvements Improved upper teeth sensation, improved HA CN VI, CN III palsy V1 numbness/paresthesia, neurotrophic cornea CN VI palsy EEA, Dysesthesia of RMC, GKS teeth, V1, V2 Improved CN VI, III palsy, improved V1 paresthesia V1, V2 numbness/pain, HA, Resolved CN VI palsy, improved HA, dry eye, neurotrophic improved cornea sensation of roof of mouth V3 numbness/paresthesia mastication muscle weakness/atrophy, dry eye, CN VI palsy (after RMC) Mastication weakness/ muscle atrophy, HA, dry eye HA Resolved CN VI palsy Improved V3 numbness, improved HA No mastication weakness Improving vision, improving CN III palsy Resolved CN VI palsy HA HA, dry eye Fully recovered vision Resolved HA Improved V1 numbness LTF LTF LTF LTF EEA, GKS EEA EEA EEA 2-Stage EEA LTF LTF HA, personality changes a CN, cranial nerve; CP, cerebellopontine; EEA, expanded endonasal approach; GKS, Gamma Knife surgery; HA, headache; LTF, lost to follow-up; OPC, orbitopterional craniotomy; RMC, retromastoid craniectomy. Near total resection indicates $90% resection; subtotal resection, ,90% resection. a transient CN VI palsy after the RMC. A male patient (patient 8) with an intraconal schwannoma developed a CN III palsy after EEA. After further resection of tumor by orbitopterional craniotomy, the CN III palsy began to improve. A preexisting voice hoarseness caused by CN X palsy was exacerbated in 1 patient (patient 7) after RMC (presumably resulting from intubation). This patient (patient 7) is discussed in detail in the Illustrative Cases section. NEUROSURGERY Five of 11 patients (45%) who had trigeminal schwannoma developed postoperative deficits in the trigeminal nerve. Three of these 5 patients (60%) with postoperative trigeminal nerve deficits had partial recovery of function. Of these 5 patients, 2 had sensory deficits only, 1 had motor deficit only, and 2 had both motor and sensory deficits. Three of the patients experienced neurotrophic keratopathy after EEA of tumor in the Meckel cave. In addition, VOLUME 69 | NUMBER 5 | NOVEMBER 2011 | 1049 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. SHIN ET AL 5 patients with trigeminal schwannomas had decreased lacrimation causing subjective dry eye after resection of tumors, presumably a result of vidian nerve sacrifice as part of the approach. Improvements There were significant improvements of preoperative deficits in 8 of 15 patients (53%). Three of 7 trigeminal schwannoma patients (43%) with preoperative trigeminal sensory deficit had partial recovery of function. Recovery from preoperative CN VI palsies occurred in 3 of 4 patients (75%), with one of them also having partial recovery from CN III palsy. Visual outcome was generally positive in patients with schwannoma of the orbit. Visual improvement was reported after EEA resection of a trigeminal schwannoma of orbital apex in a male patient (patient 10). Preoperative vision in the right eye was 20/50, but this had improved to 20/30 at 9 months postoperatively. Another male patient with orbital schwannoma of unknown origin (patient 8) had subtotal resection because the tumor closely involved the optic nerve. Preoperative vision was 20/30, and there was no postoperative change in his vision test after EEA. Four years later, he presented with regrowth of the tumor with resultant severe optic neuropathy and underwent orbitopterional craniotomy. He did not have improvement from preoperative optic neuropathy. A female patient (patient 2) with trigeminal schwannoma of the left orbital apex also had a favorable visual outcome. She had complete CN VI palsy and partial CN III palsy of the left eye. Her preoperative vision in the left eye was 20/20. Postoperatively at 2.5 years, the vision was unchanged at 20/20, and her CN VI and III palsies had nearly resolved. ILLUSTRATIVE CASES Patient 4 A 19-year-old female patient with sudden loss of consciousness presented to the emergency department. On physical examination, the patient was found to be neurologically stable. Magnetic resonance imaging (MRI) scans (Figure 1) showed enhancing mass in the right middle and posterior fossa. Six weeks after the initial presentation to the hospital, the patient developed rightsided numbness of the teeth and V1 and V2 distributions. The patient underwent EEA for resection of Meckel cave component of the tumor at this time and was followed up with RMC for posterior fossa component 4 weeks after EEA. Near-total resection was achieved after both surgical procedures. The patient developed a postoperative CN VI palsy, trigeminal distribution numbness, and mastication weakness 1 month after RMC. By 4 months postoperatively, the CN VI palsy completely resolved, but V2 and V3 complete anesthesia and V1 partial anesthesia resulted. To treat the residual trigeminal schwannoma, which was 6% of original volume, the patient received radiosurgery at 17 months after RMC. Patient examination 5 months after radiosurgery showed improvement in sensation to 80% for V1 distribution and 70% for V2 distribution. Masseter atrophy and slight wasting in the subtemporal fossa were also noted. 1050 | VOLUME 69 | NUMBER 5 | NOVEMBER 2011 Patient 5 A 23-year-old woman with numbness of V1, V2, and V3 distribution and CN VI palsy presented to the neurosurgical office. A very large dumbbell-shaped V3 schwannoma in the middle fossa extending into Meckel cave was found on radiological imaging (Figure 2). Complete resection of the tumor was possible by EEA, and the patient was discharged 4 days later. Temporary jaw and ear pain developed postoperatively but resolved within weeks. The patient also developed a dry eye, which was treated by eye drops. At 10 months postoperatively, there was wasting of left masticator muscles. Numbness in V1 and V2 distributions recovered fully, and V3 numbness partially recovered. Patient 7 A 49-year-old man with a history of near-total resection of a trigeminal schwannoma by an RMC 7 years ago presented to the neurosurgical office with right-sided facial paresthesias. These had developed in V1 and V2 distributions 1 year before the visit. The patient had sensory deficits in right V1 and V2 areas and a neurogenic ulcer of his right nostril upon physical examination. A giant schwannoma measuring 7 3 5 3 4 cm occupying the right middle fossa and part of the cerebellopontine angle coursing along the trigeminal nerve was revealed by MRI (Figure 3). To achieve maximal resection of the tumor, combined operations by EEA and RMC in 2 stages were planned. The patient underwent an EEA in which tumor in Meckel cave, cavernous sinus, and medial wall of the sphenoid sinus with extension into the orbital apex and infratemporal fossa was resected. The patient was discharged 1 day after EEA. Three weeks after the EEA procedure, the patient underwent RMC for resection of residual posterior fossa contents of the schwannoma. Total resection was achieved by these combined approaches, and MRI revealed no residual schwannoma mass. At 3 months postoperatively, sensory deficit remained the same as preoperatively, with 0% sensation in right V1 and V2 but 100% sensation in V3. The patient also had exacerbation in voice hoarseness, likely a result of the intubation procedure. There were no signs of choking, coughing, or swallowing difficulty. The patient also developed dry eye postoperatively, which was treated with eye drops. At the 10-month follow-up, the patient did not have recurrence of the tumor. Patient 9 A 34-year-old female patient presented to the emergency department with diplopia and hypesthesia of V1, V2, and V3 distribution. Five months before surgery, the patient noticed occasional double vision, which was found to be CN VI palsy. A giant schwannoma of the left middle cranial fossa was found on MRI scan, and EEA surgeries in 3 stages were performed in a 4-week period (Figure 4). In stages 1 and 2, the infratemporal fossa portion of the tumor was resected. In stage 3, the Meckel cave component was resected. After the 3 staged EEA surgeries, approximately 7% of the original volume of tumor remained along the medial cavernous www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. ENDONASAL ENDOSCOPIC APPROACH FOR SCHWANNOMAS FIGURE 1. Preoperative axial (A) and coronal (C) T1-weighted MRI scans with contrast for patient 4. Postoperatively after endoscopic endonasal approach and retromastoid craniectomy, axial (B) and coronal (D) images show near-total resection of this trigeminal schwannoma affecting the Meckel cave and cerebellopontine angle. sinus. Nine months after EEA, examinations revealed complete recovery of CN VI palsy. At this time, the patient underwent radiosurgery to treat residual schwannoma. Patient 17 This 14-year-old male patient had a large schwannoma in the anterior lobe. The patient had a 2-year history of headaches, personality changes, and declining cognitive function. Neurological examination showed bilateral papilledema and diminished sense of smell but otherwise normal findings. A large olfactory schwannoma was found on an MRI scan (Figure 5), and the decision was made to proceed with EEA resection of this tumor. After the initial exposure of the tumor by transplanum and transcribriform approach, the tumor was debulked and biopsied. The biopsy at the time showed the presence of NEUROSURGERY a fibrous tumor, but a final diagnosis was not made. Because the tumor capsule was found to be densely adherent to the left A2, tumor resection was stopped until a definitive diagnosis was made. Six days later, the second stage of this surgery proceeded with a confirmed diagnosis of olfactory schwannoma. Complete resection of the tumor was possible at this stage. Two weeks after the surgery, the patient had no signs of CSF leak or other complications. DISCUSSION The most common schwannomas of the skull base are vestibular schwannoma,18 followed by trigeminal schwannoma, which account for about 8% of intracranial schwannomas. Other schwannomas of the skull base and head and neck region are VOLUME 69 | NUMBER 5 | NOVEMBER 2011 | 1051 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. SHIN ET AL FIGURE 2. Preoperative (A) and postoperative (B) coronal T1-weighted MRIs with contrast showing a dumbbell-shaped trigeminal schwannoma in patient 5. T2-weighted axial images show the superior aspect of the tumor preoperatively (C) and postoperatively (D) and the inferior aspect of the tumor preoperatively (E) and postoperatively (F). rarer, arising in the orbit, jugular foramen, nasal cavity, and olfactory nerve sheath. Numerous previous studies have discussed the effectiveness of radiosurgery and microsurgery on vestibular schwannoma.19-22 However, reports on the treatment of nonvestibular schwannoma are less common. With improved techniques in endoscopic skull base surgery and intraoperative image guidance, resection of various tumors of the ventral skull base has become possible. The current technique of EEA has gradually evolved to access various structures of the anterior, middle, and posterior skull base.23,24 In this case series, we report the outcomes of 17 patients who received EEA for the treatment of nonvestibular schwannomas. Considering the trigeminal schwannoma cases, which make up the largest group in this study (11 cases), 7 cases resulted in total resection (64%), 3 cases resulted in near-total resection (27%), and 1 case resulted in subtotal resection (9%). Given that a more complete resection of schwannoma is correlated to a reduced rate of recurrence, a high degree of resection is an important goal for successful long-term treatment of schwannoma.25 Because of the small number of cases in this report, the total resection rates 1052 | VOLUME 69 | NUMBER 5 | NOVEMBER 2011 cannot be directly compared with the rates reported in other larger studies, which range from 70% to 94%.26-29 In addition, the average trigeminal schwannoma resected via EEA in our report was generally large in diameter (3.5 cm), which likely contributed to lower total resection rates than reported in the current literature, because a small tumor has a higher possibility of total resection. Trigeminal schwannoma with a diameter ,2 cm had total resection 100% of the time in previous studies.27,30 In this report, 4 of 11 trigeminal schwannoma patients had tumors that were .4 cm, with 2 requiring multiple staged surgeries. The direct access to trigeminal schwannoma in EEA offers advantages similar to previously described conventional approaches such as infratemporal fossa approach.31 There is no need for temporal lobe exposure or retraction in either technique, and both provide direct access to the tumor. However, infratemporal fossa approach provides the advantage of wide exposure of the tumor for the ease of resection, whereas EEA provides the advantage of avoiding temporalis muscle split and minimizing surgical opening. The optimal choice between using www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. ENDONASAL ENDOSCOPIC APPROACH FOR SCHWANNOMAS FIGURE 3. Preoperative axial (A) and coronal (C) T1-weighted MRIs with contrast for patient 7 showing trigeminal schwannoma. With combined endoscopic endonasal approach and retromastoid craniectomy, gross total resection was possible, as shown in the axial (B) and coronal (D) images. EEA or this conventional approach will depend on the anatomic detail of each case of trigeminal schwannoma, the patient’s preference, and the surgeon’s level of comfort. In our present clinical series, there was no case of recurrence of trigeminal schwannoma. Because most of the EEA procedures on trigeminal schwannoma in this study were performed within the last 2 years with an average follow-up time of 15 months, the recurrence rates of this study also cannot be compared directly with previously reported recurrence rates after other surgical approaches. The time to recurrence after resection of trigeminal schwannomas varies widely, ranging from 1 to 9 years.26,28 Previous reports have also compared recurrence rates of trigeminal schwannoma after conventional surgical approaches such as frontotemporal transsylvian, subtemporal-intradural, subtemporal-transtentorial, and suboccipital approaches or skull NEUROSURGERY base approaches such as frontotemporal extradural-intradural, fronto-orbitozygomatic, subtemporal anterior petrosal, and presigmoid posterior petrosal approaches.32 Conventional approaches resulted in 65% recurrence rate, and skull base approaches resulted in 10% recurrence rate. Whether EEA is more effective than other skull base approaches or conventional approaches requires further follow-up evaluation of patients over several years. In addition, the number of patients in this series is small, making direct comparison with larger open series difficult. The most commonly reported symptoms for trigeminal schwannoma are numbness and paresthesia, presenting in 70% to 95% of patients.25 Other reported symptoms are facial pain, weakness, and wasting of masticator muscles. These symptoms were present preoperatively in 7 patients with trigeminal schwannoma in this report. Three of these 7 patients (43%) had VOLUME 69 | NUMBER 5 | NOVEMBER 2011 | 1053 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. SHIN ET AL FIGURE 4. Preoperative axial (A) and coronal (C) T1-weighted MRIs with contrast for trigeminal schwannoma occupying the middle fossa and infratemporal fossa for patient 9. Postoperative axial (B) and coronal (D) scans show near-total resection. partial recovery from preoperative numbness in trigeminal nerve area after the EEA procedure. Of 11 trigeminal schwannoma patients, 2 patients (18%) developed sensory deficit only, 2 patients (18%) developed motor and sensory deficit, and 1 patient (9%) developed motor deficit only after EEA. Overall, 4 patients (36%) developed new sensory deficits, and 3 patients (27%) developed new motor deficits postoperatively. However, one of these patients had partial recovery of motor deficits with resolving of jaw tightness, and 2 patients had partial recovery of sensory deficits. This compares favorably with other surgical approaches for trigeminal schwannoma that show higher rates of worsened trigeminal sensory and motor outcome. In a previous study,32 70% of the patients had worsened sensory deficits and 56% of the patients had worsened motor deficits after conventional and skull base approaches. Improvement in trigeminal sensory deficit was achieved in 19% of the patients in this 1054 | VOLUME 69 | NUMBER 5 | NOVEMBER 2011 previous study, whereas we show improvements in 3 of 7 patients (43%) after EEA. In general, patients appear to have low rates of trigeminal deficits after EEA compared with conventional or skull base approaches for resection of trigeminal schwannoma. Another commonly reported symptom among the trigeminal schwannoma patients was eye dryness, which resulted in 5 of 11 patients (45%). These symptoms were reported from 2 weeks to several months after undergoing EEA and were successfully treated with eye drops. In addition, headache was a commonly presented preoperative symptom in trigeminal schwannoma patients. In 4 of 11 trigeminal schwannoma patients, reduction of headaches after EEA was reported after resection of schwannoma. A few patients in this study reported improvements in their symptoms of diplopia after undergoing EEA resection. Among the 4 patients presenting with preoperative CN VI palsy, 3 had improvement of CN VI function and resolution of diplopia. www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. ENDONASAL ENDOSCOPIC APPROACH FOR SCHWANNOMAS FIGURE 5. T1-weighted MRI scans with contrast showing olfactory schwannoma occupying the frontal lobe in patient 17. After 2 staged endoscopic endonasal approaches, preoperative images (A and C) and postoperative images (B and D) show gross total resection of the schwannoma. Because schwannomas are generally slow growing and benign, patients with orbital schwannoma are managed by a conservative approach unless there is compression of the optic nerve and neighboring structures, causing loss of vision, proptosis, and pain. Preservation of vision was considered an important goal throughout the EEA cases for schwannoma in orbital areas. Accessing medial orbital schwannoma by craniotomic approaches may risk trauma to the optic nerve, which can lead to visual deterioration after surgery. However, EEA allows resection of schwannoma involving the orbit and decompression of optic nerve from a medial and inferior trajectory without manipulation of the optic nerve. The visual outcomes after EEA for all 3 patients (patients 2, 8, and 10) with orbital schwannoma were generally positive, as previously described. Vision either improved (patient 10) or was preserved (patients 2 and 8) after EEA. NEUROSURGERY The 3 other types of schwannomas in this series (jugular, olfactory, and nasal schwannoma) were less common lesions with fewer previous reports on their optimal surgical approaches. Jugular foramen schwannoma may arise from CN IX or X ganglia and were previously reported to be resected with juxtacondylar approach, 33 microsurgery,34 and petro-occipital transsigmoid approach,35 among many other approaches. These approaches have shown a high rate of total or near-total resection and preservation of CN function postoperatively. Olfactory schwannoma and nasal cavity schwannoma are even less common than jugular schwannoma and were mostly reported in case reports with no sizeable case series analyzing the outcomes, rate of total resection, and rate of recurrence after surgery. Among these nontrigeminal schwannomas in this series, 2 of the 4 cases resulted in gross VOLUME 69 | NUMBER 5 | NOVEMBER 2011 | 1055 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited. SHIN ET AL total resection. One other case underwent subtotal resection, and 1 case was aborted. Both were jugular schwannoma cases, suggesting that this approach may not be ideal. The group performing these surgeries is well versed in conventional approaches, which is key in offering patients an unbiased opinion. With any new approach, there is both an anatomic and a technical learning curve. One of the greatest concerns after EEA is reconstruction of the barrier separating subarachnoid space from sinonasal tract to prevent CSF leak and to avoid meningitis and abscess formation. Fifteen patients underwent cranial base reconstruction after EEA. Among these 15 patients, 9 received nasoseptal flap reconstruction; 5 received reconstruction with a combination of Tisseel, Gelfoam, or Alloderm cover; and 1 received reconstruction with free mucosal graft from the middle turbinate (patient 10). High postoperative CSF leaks have been reported in early EEA cases, but there have been many advances in cranial base reconstruction techniques using neurovascular pedicled flap of nasal septal mucosa. This made it possible to decrease the rate of CSF leak after EEA.12,13,36 Multilayer reconstruction has been designed using subdural collagen matrix and then extracranial acellular dermis onlay graft placement supported by fat autograft. The advancement of reconstruction technique is evidenced by the fact that none of the 9 patients who received nasoseptal flap reconstruction in this report had postoperative CSF leaks. This is in agreement with a previous prospective study using nasoseptal flap, which reported a low risk of CSF leak at 5%.37 The 5 other patients who underwent EEA before 2007 were not subjected to the novel nasoseptal flap reconstructive technique. They received reconstruction with the synthetic materials described but fortunately had no CSF leaks. CONCLUSION For nonvestibular schwannomas in the anterior and posterior skull base such as pterygopalatine fossa, infratemporal fossa, Meckel cave, and medial orbit, EEA is a useful technique to maximize exposure and access. It provides an additional corridor for treating nonvestibular skull base schwannomas that does not require brain retraction and reduces the risk of manipulating important neurovascular structures. As a result, postoperative complication rates are low and operative times are short among the patients in this report. Thus, EEA allows a team consisting of a neurosurgeon and an otolaryngologist to achieve a high rate of total or near-total resection with a low rate of postoperative CN deficits and CSF leak. As an addition to conventional skull base approaches and radiosurgery, EEA provides another option in the arsenal of the skull base surgeons. However, it should be noted that this approach requires an experienced endoscopic skull base team given the anatomic and technical learning curve required. This small series is promising, but a larger series with longer follow-up times is needed to fully understand the role of EEA in the treatment of nonvestibular schwannomas. 1056 | VOLUME 69 | NUMBER 5 | NOVEMBER 2011 Disclosure The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Esposito F, Cappabianca P, Del Basso De Caro M, Cavallo LM, Rinaldi C, De Divitiis E. Endoscopic endonasal transsphenoidal removal of an intrasuprasellar schwannoma mimicking a pituitary adenoma. Minim Invasive Neurosurg. 2004;47(4):230-234. 2. Wilson JA, McLaren K, McIntyre MA, von Haacke NP, Maran AG. Nerve-sheath tumors of the head and neck. Ear Nose Throat J. 1988;67(2):103-107, 110. 3. Rosenberg SI. Natural history of acoustic neuromas. Laryngoscope. 2000;110(4): 497-508. 4. Smouha EE, Yoo M, Mohr K, Davis RP. Conservative management of acoustic neuroma: a meta-analysis and proposed treatment algorithm. 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COMMENTS T he authors have demonstrated surgery of otherwise pure neurosurgical-cranial problems by an transnasal route. Although alternative treatment options should always be explored and encouraged, the NEUROSURGERY approach to types of tumors treated by the authors by the nasal route appears to complicate an otherwise straightforward and safe surgery that has been practiced and refined for over a century. Cranial approach provides a quick, safe, and wide exposure to the tumor. The resection can be done under direct surgical vision of the tumor and the displaced neural and vascular structures. The control of bleeding is also far superior when the exposure is wide. The handling of any surgical disaster can be more controlled. Even if elaborate basal reconstruction methods are possible, communication of the cranial cavity with the nose should be avoided, unless it is absolutely mandatory. The basal meninges tend to be strong, for biological reasons. To open them is to put the meningeal spaces and their contents into a direct communication with a microbial cesspool called the pharynx and nasopharynx. The endoscope sets about creating a working space by tunneling though often tightly placed vital neural and vascular structures at the base of the brain. The dangers are far too many. For intracranial lesions, the nasal approach looks good from a distance but smells foul and can leave a bad taste. Atul Goel Mumbia, India his is a retrospective report reviewing the authors’ experience with using the expanded endonasal approach (EEA) for the treatment of nonvestibular schwannomas. The authors report its use in 17 patients in whom EEA was used alone or in combination with open surgical approaches. The tumors most commonly treated in this series arose from the trigeminal nerve and invaded Meckel cave. This is a well-written report by a group well known for its experience in using the EEA for treating intradural pathology. For such groups, advantages over conventional approaches remain unclear, although equivalency in efficacy seems a reasonable conclusion for the limited number of cases in this report. Whether such endoscopic approaches become a mainstream method for treating intradural pathology remains to be seen, although in experienced hands there is clearly a role for their use with acceptable complication rates. T Nicholas C. Bambakidis Cleveland, Ohio VOLUME 69 | NUMBER 5 | NOVEMBER 2011 | 1057 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited.