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Objective The management of lesions involving the cavernous sinus remains a formidable challenge. To optimize care for patients with tumors extending into this skull base region a detailed understanding of the surrounding osteology as well as neural and vascular relationships is requisite. This thesis examines the gross anatomy of the region and highlights important surgical implications drawn from these as well as previously published studies. Methods A review of the historical scientific, anatomic, clinical, and surgical literature extending to the present (1992) relating to the cavernous sinus has been performed and discussed. Additionally, the author has performed and described cadaveric dissections revealing novel details about the macroscopic (dural and neurovascular anatomic relationships) and microscopic structure of the cavernous sinus. A series of cases of cavernous sinus pathologies that were addressed in an interdisciplinary surgical approach at the author's institution is also reported. Results Included in this report is a comprehensive review of the embryology of the cavernous sinus and its associated neurovascular structures. Cadaveric dissections have also revealed novel details about dural/meningeal compartments of the cavernous sinus as well as well as associated arterial, venous, and neural relationships. Microscopic observations also reveal novel fundamental insights into the components and structure of the cavernous sinus. Clinical examples from 20 patients illustrate the critical importance for clinical application of cavernous sinus anatomic knowledge to the surgical treatment of pathologies in this region. Conclusion The cavernous sinus is a tripartite venous osteomeningeal compartment intimately neighboring vital structures including the optic tracts, pituitary gland, cranial nerves III, IV, V, V, VI, and the internal carotid artery. Surgical management of cavernous sinus lesions has and continues to evolve with increasing anatomic and clinical study as well as advancements in diagnostic and surgical methodologies. Level of Evidence NA. This manuscript examines the gross anatomy of the region and highlights important surgical implications drawn from these as well as previously published studies. Herein, I perform a review of the historical scientific, anatomic, clinical, and surgical literature and additionally perform and describe cadaveric dissections revealing novel details about the macroscopic (dural and neurovascular anatomic relationships) and microscopic structure of the cavernous sinus. A series of cases of cavernous sinus pathologies are also reported which demonstrate clinical application of the anatomic insights that have been gained relative to the cavernous sinus.

Abstract Background: Facial nerve preservation surgery for large vestibular schwannomas is a novel strategy for maintaining normal nerve function by allowing residual tumor adherent to this nerve or root-entry zone. Objective: To report, in a retrospective study, outcomes for large Koos grade 3 and 4 vestibular schwannomas. Methods: After surgical treatment for vestibular schwannomas in 52 patients (2004–2013), outcomes included extent of resection, postoperative hearing, and facial nerve function. Extent of resection defined as gross total, near total, or subtotal were 7 (39%), 3 (17%), and 8 (44%) in 18 patients after retrosigmoid approaches, respectively, and 10 (29.5%), 9 (26.5%), and 15 (44%) for 34 patients after translabyrinthine approaches, respectively. Results: Hearing was preserved in 1 (20%) of 5 gross total, 0 of 2 near-total, and 1 (33%) of 3 subtotal resections. Good long-term facial nerve function (House-Brackmann grades of I and II) was achieved in 16 of 17 gross total (94%), 11 of 12 near-total (92%), and 21 of 23 subtotal (91%) resections. Long-term tumor control was 100% for gross total, 92% for near-total, and 83% for subtotal resections. Postoperative radiation therapy was delivered to 9 subtotal resection patients and 1 near-total resection patient. Follow-up averaged 33 months. Conclusion: Our findings support facial nerve preservation surgery in becoming the new standard for acoustic neuroma treatment. Maximizing resection and close postoperative radiographic follow-up enable early identification of tumors that will progress to radiosurgical treatment. This sequential approach can lead to combined optimal facial nerve function and effective tumor control rates.

Abstract INTRODUCTION: Petroclival tumors and ventrolateral lesions of the pons present a unique surgical challenge. We aimed to provide qualitative and quantitative anatomic analyses of anterior petrous apicectomy through the transcranial middle fossa (TMF) and the extended endoscopic transphenoidal-transclival (EETT) approaches. METHODS: Ten cadaveric silicon-injected cadaver heads were used for this study. The petrous apex and the clivus were drilled extradurally through both middle fossa and endonasal approaches. Using in situ and frameless stereotactic navigation points, we described and compared consistent data points collected from both approaches to calculate and compare their respective working areas, volumes of bone removed, approach angles and surgical freedom. RESULTS: Mean exposed TMF area was 21.03 ± 3.46 cm2, providing a 44.71 ± 4.13° working angle to the brainstem between cranial nerves (CNs) V and VI. Kawase rhomboid area measured 1.76 ± 0.34 cm2. Mean volume of bone removed at the petrous apex was 1.20 ± 0.12 cm3. GSPN-V3 and petroclival angles were 73.8° ± 8.55° and 70.07 ± 4.7°, respectively. Surgical freedom on the lateral brainstem was higher at a point halfway between CNs V and VI at the center of the rhomboid compared with the midline at the basilar sulcus (P < .01). Following clivectomy and petrous apicectomy through the EETT approach, area exposed was 5.29 ± 0.66 cm2. Its boundaries were: CN V anterosuperiorly, anterior wall of the internal acoustic canal posteroinferiorly, carotid genu at the foramen lacerum anterolaterally, and clivus medially. Two subareas were defined and measured. One corresponded to the petrous apex, the other to the clivus. They measured 1.05 ± 0.44 cm2 and 4.25 ± 0.44 cm2, respectively. There was no statistically significant difference in surgical freedom at the foramen lacerum and the midpoint basilar sulcus when approaching from either nostril (P > .05). At the petrous apex, volume of bone removed and area exposed were significantly larger for TMF approach (P < .001). CONCLUSION: Expanded transclival anterior petrosectomy through the TMF approach provides an adequate corridor to lesions in the upper ventrolateral pons. EETT approach better fits midline lesions not extending laterally beyond CN VI and the C3 carotid when evaluating normal anatomical parameters.

In this case report, delayed facial palsy developed in a patient without any direct manipulation of the main part of the facial nerve during an anterior petrosal approach. We discuss putative etiologies and management techniques that may help avoid this problem. A 21-year-old woman underwent anterior petrosectomy for gross total resection of a low-grade chondrosarcoma. Six days later, the patient presented with left-sided facial weakness in the emergency department. Examination revealed evidence of House-Brackmann grade V/VI left-sided facial palsy, and repeat magnetic resonance imaging revealed diffuse enhancement of the contents of the internal auditory canal that was not present immediately after surgery. After a 10-day course of acyclovir and a tapering dose of methylprednisolone, the facial palsy slowly diminished and resolved 2 months after the onset. This unique development of delayed facial palsy after an isolated anterior petrosal approach is evidence that this complication should be considered when dissecting along the floor of the middle fossa. Exposure of the intracranial or intracanalicular segment of the facial nerve is not necessary for delayed facial palsy to develop. Proposed mechanisms (ie, viral reactivation, vasospasm, neural edema) of this condition remain unproven. Prognosis for recovery has been reported to be excellent, with or without treatment.

Objectives: Although there exist undisputed methods to permanently silence the aberrant end organ, controversy surrounds the durable efficacy of non-ablative interventions. This study provides a contemporary review of our institution's clinical experience in performing endolymphatic mastoid shunt surgery (EMSS) in patients with medically refractory endolymphatic hydrops, or Meniere's disease. Methods: Between 1984 and 2002, 1,612 patients were referred to our institution with a diagnosis of Meniere's disease. Of these referrals, 1,172 patients met the criteria for Meniere's disease. Although 553 patients responded to medical management, 486 patients underwent EMSS and 133 patients had refractory disease that required chemical or surgical obliterative interventions. The retrospective study utilizes data collected on 226 patients who were followed for a minimum of 5 years. Results: Overall, 78% patients responded favorably to EMSS, according to the functional level scale and class categories delineated by the American Academy of Otolaryngology-Head and Neck Surgery 1995 guidelines for control of vertigo. According to the Arenberg anatomic classification for endolymphatic sac location, EMSS achieved adequate control of vertigo in 86% of type I cases, 90% of type II cases, and 82% of type III cases. Conclusions: Endolymphatic mastoid shunt surgery is a relatively safe, effective procedure for the long-term control of vertigo in patients with medically refractory Meniere's disease.

Abstract OBJECTIVE Use of hydroxyapatite cement has been advocated for closure of transpetrosal defects to decrease the incidence of cerebrospinal fluid leaks. We previously identified delayed extrusion of this cement as a significant complication associated with this closure technique and now update our long-term experience. METHODS In our retrospective review, we identified 1231 patients who underwent transpetrosal procedures by our multidisciplinary cranial base team between 1984 and 2005. Of the subgroup of 177 patients who had hydroxyapatite cement used during the closure of the procedure, 13 patients (7.3%) experienced delayed extrusion of hydroxyapatite cement. RESULTS Extrusion occurred in 3 patients within 12 months and in 10 patients within 68 to 140 months. Twelve patients presented with draining fistulae and concomitant Staphylococcus aureus infection; 1 patient presented asymptomatically with a large temporal lobe abscess identified on surveillance magnetic resonance imaging. All 13 patients underwent reoperation, including 1 who underwent a second procedure. CONCLUSION Delayed extrusion of hydroxyapatite cement resulted in significant morbidity to our patients and often presented in an indolent manner. We recommend serial examination and imaging studies in patients who have had transpetrosal closures with hydroxyapatite cement. Because of the complication rates associated with hydroxyapatite cement, we have discontinued its use.

The roof of the parapharyngeal space (PPS) is poorly defined. Although it is generally described as having prestyloid and poststyloid compartments, we believe that these terms are imprecise. Therefore, we define its boundaries, partition, and compartments. We completed macroanatomical and microanatomical dissections in 10 specimens from 5 human cadaver heads; bone measurements in 50 dry skulls; and axial and coronal cross-sectional studies in 2 cadaveric specimens. The PPS roof is bordered laterally by the medial pterygoid fascia and medially by the pharyngobasilar fascia. The tensor veli palatini fascia (TVPF) partitions this roof into an anterolateral compartment containing fat and part of the deep lobe of the parotid gland, and a posteromedial compartment containing the cartilaginous part of the eustachian tube, internal carotid artery, internal jugular vein, and cranial nerves IX through XII. The anteroposterior length measures 32 mm (range, 26.1 to 36.9 mm), and the mediolateral width measures 16.3 mm (range, 12.1 to 21.3 mm). The PPS roof has 3 important bony landmarks (ie, scaphoid fossa, styloid process, sphenoid spine); 3 important fasciae (ie, medial pterygoid fascia, TVPF, pharyngobasilar fascia); and 2 compartments, which are anterolateral and posteromedial to the TVPF. We believe that this is the first report to specifically focus on the roof of the PPS.

The irregular and complex osteology of the bony skull base houses the intrapetrous internal carotid artery (ICA), which represents a potential obstacle to the complete extirpation of benign skull base lesions. This 2-part study 1) investigated the cadaveric basis for the mobilization of the intrapetrous ICA and 2) correlated the cadaveric anatomic findings with the authors' clinical experience. We conclude that the ICA can be mobilized relatively safely. The degree of mobility achieved directly relates to the surgical approach and exposure. Limited mobility is achieved when an anterior petrosal approach is used with various neurosurgical procedures. Conversely, transcochlear and infratemporal approaches allow for optimal ICA translation. The safety of ICA mobilization is documented by the low complication rate in our series.

Exposure of the most distal portion of the cervical segment of the internal carotid artery (ICA) is technically challenging. Previous descriptions of cranial base approaches to expose this segment noted facial nerve manipulation, resection of the glenoid fossa, and significant retraction or resection of the condyle. We propose a new approach using the frontotemporal orbitozygomatic approach to expose the distal portion of the cervical segment of the ICA via the trans-spinosum corridor. Six formalin-fixed injected heads were used for cadaveric dissection. Two blocs containing the carotid canal and surrounding region were used for histological examination. The ICA lies immediately medial to the vaginal process. The carotid sheath attaches laterally to the vaginal process. With use of the trans-spinosum corridor, the surgeon's line of sight courses in front of the temporomandibular joint, through the foramen spinosum, spine of the sphenoid, and vaginal process. Removal of the vaginal process exposes the vertical portion of the petrous segment of the ICA. The loose connective tissue space between the adventitia and the carotid sheath is easily entered from above. Incision of the carotid sheath exposes the ICA without disruption of the temporomandibular joint. Control of the cervical segment of the ICA can be critical when dealing with cranial base tumors that invade or surround the petrous segment of the ICA. This novel technique through the trans-spinosum corridor can effectively expose the distal portion of the cervical segment of the ICA without causing manipulation of the facial nerve and while maintaining the integrity of the temporomandibular joint.