VIDIAN NERVE SCHWANNOMA WITH MIDDLE CRANIAL FOSSA EXTENSION RESECTED VIA A MAXILLARY SWING APPROACH. Schwannomas are well-circumscribed, encapsulated

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1 CASE REPORT Russell B. Smith, MD, Section Editor VIDIAN NERVE SCHWANNOMA WITH MIDDLE CRANIAL FOSSA EXTENSION RESECTED VIA A MAXILLARY SWING APPROACH Keigo Honda, MD, 1 Ryo Asato, MD, 2 Shinzo Tanaka, MD, 2 Tsuyoshi Endo, MD, 3 Kazunari Nishimura, MD, 4 Juichi Ito, MD 2 1 Department of Otolaryngology Head and Neck Surgery, Kurashiki Central Hospital, Okayama, Japan. khonda@ent.kuhp.kyoto-u.ac.jp 2 Department of Otolaryngology Head and Neck Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan 3 Department of Otolaryngology Head and Neck Surgery, Toyo-oka Hospital, Hyogo, Japan 4 Department of Otolaryngology Head and Neck Surgery, Otsu Red-Cross Hospital, Shiga, Japan Accepted 24 October 2007 Published online 19 February 2008 in Wiley InterScience ( DOI: /hed Abstract: Background. Vidian nerve schwannoma is an extremely rare type of facial nerve schwannoma. To the best of our knowledge, only 1 case has been reported. Methods. We report an additional case of vidian nerve schwannoma with middle cranial fossa extension in a 49-yearold Japanese woman. The surgical approaches for infratemporal fossa schwannomas are reviewed, and the maxillary swing approach we used is described. Results. We adopted a maxillary swing approach combined with endonasal endoscopic techniques for the resection of the lesion. Gross total resection was achieved without sacrificing the trigeminal nerves or the facial motor nerves. The postoperative course was uneventful. Conclusion. Vidian nerve schwannoma is located in the retromaxillary space. It can grow silently until it involves the median skull base extensively. The maxillary swing approach was useful in this case. VC 2008 Wiley Periodicals, Inc. Head Neck 30: , 2008 Keywords: infratemporal fossa; maxillary swing approach; middle cranial fossa; schwannoma; vidian nerve Correspondence to: K. Honda VC 2008 Wiley Periodicals, Inc. Schwannomas are well-circumscribed, encapsulated benign tumors that arise from Schwann cells. Vidian nerve schwannomas are an extremely rare type of facial nerve schwannomas. To the best of our knowledge, only 1 case has been reported thus far. 1 We report an additional case of a vidian nerve schwannoma that involved the petrous apex and the middle cranial fossa along the course of the greater superficial petrosal nerve. CASE REPORT The patient was a 49-year-old Japanese woman who was seen with left hearing loss. On head and neck examination, she had left otitis media. A flexible nasopharyngoscopy revealed an expanding mass in the nasopharynx that had completely obstructed the left posterior choana. There was no facial dysesthesia or paresis. Other findings were normal and her medical history was unremarkable. Vidian Nerve Schwannoma HEAD & NECK DOI /hed October

2 FIGURE 1. Preoperative T1-weighted gadolinium-enhanced MR images. (A) A homogeneously enhanced tumor occupies the retromaxillary space. There is a cystic component inside the tumor (). (B) The middle cranial fossa is occupied by the tumor. There is no posterior fossa extension. A magnetic resonance (MR) image revealed a well-defined lobulated mass in the infratemporal fossa. The lesion had eroded the root of the pterygoid process and extended into the maxillary sinus, the inferior orbital fissure, the petrous apex, and the middle cranial fossa. The petrous internal carotid artery was displaced by the tumor. There was no involvement of the posterior fossa (Figures 1A and 1B). The presumptive diagnosis of trigeminal schwannoma was made. On CT scan, however, the foramen rotundum and the foramen ovale remained intact, whereas the left pterygoid canal was extensively expanded (Figures 2A and 2B). The final radiologic diagnosis was a vidian nerve schwannoma extending into the petrous apex and the middle fossa along the course of the greater superficial petrosal nerve. The biopsy specimen was taken from the naso- FIGURE 2. Preoperative plain CT images. (A) The petrous apex is occupied by the tumor. No lesion is present inside the tympanic space. (B) The osseous wall of the foramen rotundum remains intact (arrowhead), whereas the pterygoid canal is considerably expanded by the tumor. T, tumor; arrowhead, pterygoid canal, undiseased side Vidian Nerve Schwannoma HEAD & NECK DOI /hed October 2008

3 FIGURE 3. Histology revealing a mixture of the cellular area (Antoni A) and the looser myxoid areas (Antoni B). Tumor cells are spindle in shape (hematoxylin-eosin stain; original magnification, 340). [Color figure can be viewed in the online issue, which is available at pharyngeal mass. Histopathologic examination confirmed the diagnosis of benign schwannoma; the tumor was composed of a mixture of cellular areas (Antoni A) and looser myxoid areas (Antoni B) (Figure 3). The tumor cells were positive for S- 100 immunostaining. The surgery was performed via a maxillary swing approach. After a transfacial Weber-Ferguson skin incision, osteotomies including paramedian palatal splitting were performed. The upper osteotomy was placed below the level of the infraorbital foramen to preserve palpebral sensation. The disassembled maxilla was swung laterally with the anterior cheek flap as an osteomyocutaneous flap. By removing the posterior wall of the maxillary sinus, the surface of the retromaxillary tumor was clearly exposed (Figures 4A and 4B). The tumor capsule was incised longitudinally and the intracapsular resection was performed in a piece-by-piece fashion. After removal of the extracranial portion of the tumor, the tumor in the petrous apex and the middle cranial fossa was resected under the guidance of an endonasal rigid endoscopy. Gross total resection was achieved without sacrificing the trigeminal nerves or the facial motor nerves. No cerebrospinal fluid leak was observed and no attempt was made to reconstruct the skull base defect. After nasal packing, the flap was returned to its original position and the maxilla was fixed with titanium miniplates and screws. The patient s postoperative course was uneventful. No neurological deficit occurred except hypesthesia of the cheek, caused by the infraorbital skin incision. Residual tumor was not evident on a follow-up MRI at 1 month postoperative (Figures 5A and 5B). DISCUSSION At the geniculate ganglion, the facial nerve gives off its parasympathetic fibers as the greater superficial petrosal nerve, which runs superficially over the middle cranial fossa along the course of FIGURE 4. Intraoperative pictures. (A) Weber-Ferguson transfacial skin incision. (B) The operative field after the maxillary swing. The posterior wall of the maxillary sinus was removed. The retromaxillary part of the tumor is clearly exposed. F, buccal fat pat; M, maxilla; T, tumor. [Color figure can be viewed in the online issue, which is available at Vidian Nerve Schwannoma HEAD & NECK DOI /hed October

4 FIGURE 5. Postoperative T1-weighted gadolinium-enhanced MR images at 1 month postoperative. (A) and (B) correspond to the preoperative images of Figures 1A and 1B, respectively. No evidence of remnant lesion is apparent. the petrous carotid canal. By joining with the sympathetic deep petrosal nerve, it forms the vidian nerve and enters the pterygoid canal to innervate the lacrimal gland and the mucosa of the upper aerodigestive tract. Although schwannomas can arise in any portion of the facial nerve and its branches, the vidian nerve is an extremely rare site of origin. In our patient, the tumor had grown silently until it formed a huge mass. No obvious abnormality of lacrimation or nasal mucus secretion was present. Hearing loss was due to otitis media caused by obstruction of the auditory tube. No direct involvement of the geniculate ganglion and the tympanic cavity was present, which is in contrast to greater superficial petrosal nerve schwannomas. 2 5 Biopsy was essential to rule out other pathologies such as nasopharyngeal squamous cell carcinoma, giant cell tumor, and chondroblastoma. Evaluation of the foramen ovale, rotundum, and pterygoid canal was easy with the reconstructed coronal images of the CT scan, which helped greatly in localization of the nerve of origin. The most reliable treatment of schwannoma is surgical resection. Various surgical approaches for infratemporal fossa schwannomas have been studied in trigeminal schwannomas. These approaches can be categorized based on means of access: transmandibular approaches; transcranial approaches, and anterior approaches. Transmandibular approaches include a mandibular swing approach and a transmandibular transpterygoid approach. 6 Because exposure of the retromaxillary and the skull base regions is inappropriate, these approaches are used solely for the lesion limited in the parapharyngeal space. Extracranial mandibular nerve schwannoma should be a good indication for these approaches. Transcranial approaches include a subtemporal infratemporal approach and an orbitozygomatic approach. 7 These approaches expose the upper part of the infratemporal fossa excellently. Although these approaches are applicable in cases involving the middle cranial fossa, complete resection is difficult when the petrous apex is involved. 8 Furthermore, these surgical approaches are accompanied by a significant risk of injury to important structures. A part of the temporal muscle and the pterygoid muscles are frequently sacrificed for better vision. The mandibular condyle is sometimes resected or dislocated in patients with a posterior extension. Branches of the facial nerve crossing over the zygomatic arch and the mandible are also subjected to injury. We believe these approaches are suitable for small skull base schwannomas of the maxillary or mandibular nerve origin without involvement of the petrous apex. For larger lesions, a transmandibular approach can be added to expose the lower part of the infratemporal fossa. 9 Anterior approaches are not the mainstay of surgical routes for infratemporal fossa schwannoma. The classical Caldwell Vidian Nerve Schwannoma HEAD & NECK DOI /hed October 2008

5 Luc approach through the maxillary sinus with or without a Weber-Ferguson transfacial incision was reported to be inappropriate for cases with orbital or middle cranial fossa involvement because of the long distance involved in accessing these regions. 6,7 However, several modified transmaxillary approaches have been anatomically studied and reported for their usefulness in the management of the medial skull base regions. 10,11 The maxillary swing approach was first reported by Wei et al 12 in 1991 as a novel anterior approach for recurrent nasopharyngeal cancer. With this approach, the central skull base and the infratemporal fossa medial to the pterygoid muscles are widely exposed. By removing the posterior wall of the maxillary sinus and the pterygoid process, the foramen ovale and the petrous apex are exposed. Although the relatively long distance to the skull base has been regarded as a drawback, this can be overcome by combining the endonasal endoscopic technique with this approach. The usefulness of endoscopy has been reported in endonasal surgery for skull base and intracranial lesions and currently, the technique is being included in the armamentarium of neurosurgeons and otolaryngologists We could manipulate precisely the petrous apex, the orbital apex, and the middle cranial fossa under the guidance of endoscopy. CONCLUSIONS We report an exceptionally rare case of vidian nerve schwannoma. The diagnosis was greatly helped by the CT scan. The intracranial lesion was resected successfully via a maxillary swing approach without craniotomy. Although the maxillary swing is not widely accepted as a surgical approach for infratemporal fossa schwannomas, our experience showed its usefulness in selected cases in which wide exposure of the medial skull base is required. With the continuing advancement of tools and techniques, indications for this approach will be expanded. REFERENCES 1. Cheong JH, Kim JM, Bak KH, Kim CH, Oh YH, Park DM. Bilateral vidian nerve schwannoma associated with facial palsy. Case report and review of the literature. J Neurosurg 2006;104: Schmidinger A, Deinsberger W. Greater petrosal nerve schwannoma. Acta Neurochir (Wien) 2005;147: Wittekindt C, Liu WC, Hampl JA, Guntinas-Lichius O. Radiology quiz case 1: intracranial schwannoma originating from the greater petrosal nerve. Arch Otolaryngol Head Neck Surg 2006;132: Kumon Y, Sasaki S, Ohta S, Ohue S, Nakagawa K, Tanaka K. Greater superficial petrosal nerve neurinoma. Case report. J Neurosurg 1999;91: Michel O, Wagner M, Guntinas-Lichius O. Schwannoma of the greater superficial petrosal nerve. Otolaryngol Head Neck Surg 2000;122: Roh JL. Removal of infratemporal fossa schwannoma via a transmandibular transpterygoid approach. Eur Arch Otorhynolaryngol 2005;262: Krishnamurthy S, Holmes B, Powers SK. Schwannomas limited to the infratemporal fossa: report of two cases. J Neurooncol 1998;36: Al-Mefty O, Ayoubi S, Gaber E. Trigeminal schwannomas: removal of dumbbell-shaped tumors through the expanded Meckel cave and outcomes of cranial nerve function. J Neurosug 2002;96: Prades JM, Timoshenko A, Merzougui N, Martin C. A cadaveric study of a combined trans-mandibular and trans-zygomatic approach to the infratemporal fossa. Surg Radiol Anat 2003;25: Gonul E, Erdogan E, Duz B, Timurkaynak E. Transmaxillary approach to the orbit: an anatomic study. Neurosurgery 2003;53: Sabit I, Schaefer SD, Couldwell WT. Modified infratemporal fossa approach via lateral transantral maxillotomy: a microsurgical model. Surg Neurol 2002;58: Wei WI, Lam KH, Sham JST. New approach to the nasopharynx: the maxillary swing approach. Head Neck 1991;13: Kassam AB, Gardner P, Shyderman C, Mints A, Carrau R. Expanded endonasal approach: fully endoscopic, completely transnasal approach to the middle third of the clivus, petrous bone, middle cranial fossa, and infratemporal fossa. Neurosurg Focus 2005;19:E Alfieri A, Jho HD. Endoscopic endonasal cavernous sinus surgery: an anatomic study. Neurosurgery 2001;48: Alfieri A, Jho HD, Schettino R, Tschabitscher M. Endoscopic endonasal approach to the pterygopalatine fossa: anatomic study. Neurosurgery 2003;52: Vidian Nerve Schwannoma HEAD & NECK DOI /hed October