Endoscopic endonasal surgery for petrous apex lesions

Endoscopic Endonasal Surgery for Cranial Base Chondrosarcomas

BACKGROUND

Microsurgical resection via open approaches is considered the main treatment modality for cranial base chondrosarcomas (CBCs). The use of endoscopic endonasal approaches (EEAs) has been rarely reported.

OBJECTIVE

To present the endoscopic endonasal experience with CBCs at our institution.

METHODS

Retrospective review of the medical records of 35 consecutive patients who underwent EEA for CBC resection between January 2004 and April 2013. Surgical outcomes and variables that might affect extent of resection, complications, and recurrence were analyzed.

RESULTS

Forty-eight operations were performed (42 EEAs and 6 open approaches). Gross-total resection was achieved in 22 patients (62.9%), near total (≥90% tumor resection) in 11 (31.4%). Larger tumors were associated with incomplete resection in univariate and multivariate analysis ( P = .004, .015, respectively). In univariate analysis, tumors involving the lower clivus and cerebellopontine angle were associated with increased number of complications, especially postoperative cerebrospinal fluid leak ( P = .015) and new cranial neuropathy ( P = .037), respectively. Other major complications included 2 cases of meningitis and deep venous thrombosis, and 1 case of hydrocephalus and carotid injury. Involvement of the lower clivus, parapharyngeal space, and cervical spine required a combination of approaches to maximize tumor resection ( P = .017, .044, .017, respectively). No predictors were significantly associated with increased risk of recurrence. The average follow-up time was 44.6 ± 31 months.

CONCLUSIONS

EEAs may be considered a good option for managing CBCs without significant posterolateral extension beyond the basal foramina and can be used in conjunction with open approaches for maximal resection with acceptable morbidity.

Endoscopic Endonasal Transpterygoid Approach to Sphenoid Sinus Lateral Recess Defects

Background  Lesions affecting sphenoid sinus lateral recess (SSLR) are difficult to visualize and manipulate through the transnasal routes, especially when the sinus is highly pneumatized. External approaches to this area involve extensive surgery and are associated with significant morbidity. The aims of this study are to present our experience with the endoscopic transpterygoid approach as a method for approaching lesions of the SSLR and to evaluate the outcomes of this procedure. Methods  Clinical charts of patients who had lesions in the SSLR and who were treated at our institution from September 1998 to June 2018 were retrospectively reviewed. All these patients were managed by the endoscopic endonasal transpterygoid approach. Results  Thirty-nine patients were identified. No cerebrospinal fluid leak recurrences were observed during follow-up (range: 1-19.7 years; median: 2.3 years). Hypoesthesia (temporary, 1; persistent, 4) in the region innervated by the maxillary branch of the trigeminal nerve was detected in five (12.8%) patients, while symptoms due to the Vidian nerve damage (dry eye, 3; dry nasal mucosa, 1) were present in four (10%) patients. Conclusions  Although the endoscopic endonasal transpterygoid approach is an excellent corridor for dealing with lesions of the SSLR, limited rate of neurologic and lacrimal complications was observed. Potential morbidity of the intervention should be discussed during preoperative counselling.

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

The pterygoclival ligament: a novel landmark for localization of the internal carotid artery during the endoscopic endonasal approach

OBJECTIVE

The transpterygoid extension of the endoscopic endonasal approach provides exposure of the petrous apex, Meckel's cave, paraclival area, and the infratemporal fossa. Safe and efficient localization of the lacerum segment of the internal carotid artery (ICA) is a crucial part of such exposure. The aim of this study is to introduce a novel landmark for localization of the lacerum ICA.

METHODS

Ten cadaveric heads were prepared for transnasal endoscopic dissection. The floor of the sphenoid sinus was drilled to expose an extension of the pharyngobasilar fascia between the sphenoid floor and the pterygoid process (the pterygoclival ligament). Several features of the pterygoclival ligament were assessed. In addition, 31 dry skulls were studied to assess features of the bony groove harboring the pterygoclival ligament.

RESULTS

The pterygoclival ligament was identified bilaterally during drilling of the sphenoid floor in all specimens. The ligament started a few millimeters posterior to the posterior end of the vomer alae and invariably extended posterolaterally and superiorly to blend into the fibrous tissue around the lacerum ICA. The mean length of the ligament was 10.5 ± 1.7 mm. The mean distance between the anterior end of the ligament and midline was 5.2 ± 1.2 mm. The mean distance between the posterior end of the ligament and midline was 12.3 ± 1.4 mm. The bony pterygoclival groove was identified at the confluence of the vomer, pterygoid process of the sphenoid, and basilar part of the occipital bone, running from posterolateral to anteromedial. The mean length of the groove was 7.7 ± 1.8 mm. Its posterolateral end faced the anteromedial aspect of the foramen lacerum medial to the posterior end of the vidian canal. A clinical case illustration is also provided.

CONCLUSIONS

The pterygoclival ligament is a consistent landmark for localization of the lacerum ICA. It may be used as an adjunct or alternative to the vidian nerve to localize the ICA during endoscopic endonasal surgery.

Indications and endonasal treatment of petrous apex cholesterol granulomas

PURPOSE OF REVIEW

Lesions of the petrous apex of the temporal bone can be challenging to access and approaches laterally through the mastoid as well as medially through an endonasal approach are utilized to access this region while preserving function of adjacent structures. Cholesterol granulomas of the petrous apex requiring surgery are marsupialized to prevent expansion of the inflamed cyst and relieve associated clinical symptoms. The endonasal approach to the petrous apex has in the past been limited to lesions medial to the internal carotid artery.

RECENT FINDINGS

Endoscopic approaches have been developed to expand the range of petrous apex lesions that are accessible endonasally. These endonasal corridors include a nasopharyngeal/transclival corridor, lateralization of the internal carotid artery to create an expanded medial window, a pterygopalatine infrapetrosal approach, and a contralateral maxillary approach, which allow improved access to the inferior and lateral petrous apex. Nasoseptal flaps may reduce the risk of postoperative stenosis of the drainage tract.

SUMMARY

Endoscopic endonasal approaches can be used safely to address both medial and lateral/inferior petrous apex lesions. Morbidity of these procedures is low and use of a nasoseptal flap may limit restenosis of the drainage pathway.

Lessons learned in the evolution of endoscopic skull base surgery

OBJECTIVEEndoscopic skull base surgery (ESBS) is a relatively recent addition to the neurosurgical armamentarium. As with many new approaches, there has been significant controversy regarding its value compared with more traditional approaches to ventral skull base pathology. Although early enthusiasm for new approaches that appear less invasive is usually high, these new techniques require rigorous study to ensure that widespread implementation is in the best interest of patients.METHODSThe authors compared surgical results for ESBS with transcranial surgery (TCS) for several different pathologies over two different time periods (prior to 2012 and 2012-2017) to see how results have evolved over time. Pathologies examined were craniopharyngioma, anterior skull base meningioma, esthesioneuroblastoma, chordoma, and chondrosarcoma.RESULTSESBS offers clear advantages over TCS for most craniopharyngiomas and chordomas. For well-selected cases of planum sphenoidale and tuberculum sellae meningiomas, ESBS has similar rates of resection with higher rates of visual improvement, and more recent results with lower CSF leaks make the complication rates similar between the two approaches. TCS offers a higher rate of resection with fewer complications for olfactory groove meningiomas. ESBS is preferred for lower-grade esthesioneuroblastomas, but higher-grade tumors often still require a craniofacial approach. There are few data on chondrosarcomas, but early results show that ESBS appears to offer clear advantages for minimizing morbidity with similar rates of resection, as long as surgeons are familiar with more complex inferolateral approaches.CONCLUSIONSESBS is maturing into a well-established approach that is clearly in the patients' best interest when applied by experienced surgeons for appropriate pathology. Ongoing critical reevaluation of outcomes is essential for ensuring optimal results.

Analysis of anterior and posterior maneuvers to enhance intraconal exposure

BACKGROUND

The medial and inferior recti encompass the ideal surgical corridor to approach the intraconal space endonasally. Here, we describe 3 different maneuvers to achieve greater access to orbital contents through an expanded endonasal approach (EEA).

METHODS

Four human cadaver heads were dissected bilaterally (n = 8). EEA to the medial intraconal orbit was executed. The following 3 maneuvers were performed: (1) anterior: extraocular muscles control (EOM); (2) posterior: annulus of Zinn (AZ) release; and (3) anterior/posterior combined. Measurements of the inferior and medial rectus corridor at the level of anterior ethmoidal artery (AEA) and posterior ethmoidal artery (PEA) and extent of optic nerve and medial rectus visualization was performed before and after each maneuver.

RESULTS

Medial rectus length (MRL) and optic nerve length (ONL) achieved were 1.72 ± 0.28 cm and 0.85 ± 0.2 cm, respectively. Mean caudal-rostral distances between the rectus muscles at the level of the AEA and PEA were 3.45 ± 0.7 mm and 1.30 ± 0.3 mm, respectively. After EOM control, mean caudal-rostral distances at the same level were as follows: AEA 4.90 ± 1.15 mm (p = 0.009) and PEA 1.70 ± 0.20 mm (p = 0.016). With AZ release, MRL was 2.20 ± 0.7 cm (p = 0.002) and ONL was 1.30 ± 0.2 cm (p = 0.003), with mean rostral-caudal distance at the level of AEA at 4.03 ± 0.8 mm (p = 0.16) and PEA at 1.71 ± 0.36 mm (p = 0.039). Mean caudal-rostral distances achieved with AZ release and EOM control were as follows: AEA 5.6 ± 1.2 mm (p = 0.001) and PEA 2.15 ± 0.4 mm (p = 0.001).

CONCLUSION

Progressive access to the orbital contents is afforded with the 3 delineated maneuvers. The magnitude of access is optimized with the combined maneuver. The actual anterior/posterior location of the target will determine which maneuvers are required.

Modified endoscopic endonasal approach with a minimally invasive transoral approach-an adjunct to infrapetrous approaches

OBJECTIVES/HYPOTHESIS

To evaluate the potential of a minimally invasive transoral-transpalatal approach (MITA) to the retrocarotid petrous apex, as an adjunct to endoscopic endonasal approaches (EEAs).

STUDY DESIGN

Cadaver study.

METHODS

Five cadaveric specimens were dissected raising an inverted U-shaped palatal mucoperiosteal flap, and drilling a rectangular palatotomy (between the greater palatine foramens, and just anterior to the palatine aponeurosis). This allowed a transpterygoid EEA with cross-court access (contralateral line of sight), followed by an extradural clivectomy that exposed the petroclival junction bilaterally. Surgical targets were marked on the posterior and medial surface of the petrous internal carotid artery (ICA), at its anterior genu, midhorizontal portion, and posterior genu. For each target and approach, the surgical freedom and angles of approach (in the horizontal and vertical planes) were calculated and statistically compared.

RESULTS

Compared to EEA, the MITA resulted in greater surgical freedom for all targets, with the highest values at the anterior genu (1,661.37 mm² vs. 312.76 mm² , P <.001), and maintaining superiority in this regard all the way to the posterior genu (847.84 mm³ vs. 138.91 mm³ , P < .005). MITA also offered greater angles of approach for all targets.

CONCLUSIONS

This study suggests that the MITA may be indicated to supplement the exposure provided by a transpterygoid EEA. This technique, associated with low potential morbidity, offers an alternative to internal carotid lateralization while managing extradural lesions that are adjacent to the petrous ICA.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:339-343, 2019.

Delayed complications from expanded endonasal surgery for intracranial tumors

PURPOSE OF REVIEW

Delayed complications after endoscopic endonasal approaches to the skull base, defined as complications greater than 1 month postoperatively, are uncommon. These complications are divided into categories including sinonasal, neuroanatomic, endocrine and vascular. This review highlights the most up-to-date advancements and reviews the management of delayed complications for skull base patients.

RECENT FINDINGS

Over the last 10 years, the field of endoscopic endonasal skull base surgery has expanded with new data highlighting the long-term patient outcomes. The majority of patients experience increased quality of life (QOL) after these interventions. However, delayed complications including alterations to sinonasal function, delayed encephaloceles from the bony skull base defect and resulting endocrinopathies can significantly impact patient's QOL. Awareness of these complications and their current management is valuable for endoscopic surgeons.

SUMMARY

Endonasal approaches to the skull base are safe and well tolerated in properly selected patients. This article highlights the delayed complications that require recognition and management by skull base surgeons to ensure the best possible care for patients.

Endoscopic endonasal approach to the vidian nerve and its relation to the surrounding structures: an anatomic cadaver study

PURPOSE

The aim of this study was to investigate the neurovascular structures and their relevant anatomy with the endonasal endoscopic transpterygoid approach on fresh human cadavers. In addition, the relationship between the vidian nerve, ICA and surrounding structures were investigated METHODS: This study was carried out at an otolaryngology department of a tertiary medical center between June 2014 and June 2015. Ten fresh human cadavers were included in this study. Pterygopalatine fossa was explored via an endoscopic endonasal transpterygoid approach. Same surgical dissection procedures were performed on all cadavers: maxillary antrostomy, anterior and posterior ethmoidectomy, sphenoidotomy, transpterygoid pterygopalatine fossa and vidian canal dissection.

RESULTS

Mean distance between the anterior nasal spine and ethmoidal crest was 60.35 ± 1.31 mm (range 59-64 mm). Mean distance between the sphenopalatine foramen and superior border of choana was 18.30 ± 1.38 mm (range 17-22 mm). Mean distance between the vidian canal and sphenopalatine foramen was 6.30 ± 0.47 mm (range 5.5-7 mm). Mean distance between the vidian canal and anterior nasal spine was 64.6 ± 1.71 mm (range 62-67 mm). Foramen rotundum was located superior lateral to the vidian canal in all specimens. Mean distance between foramen rotundum and vidian canal was 9.45 ± 0.60 mm (range 8.5-10.5 mm). Course of the greater palatine nerve was always medial to the descending palatine artery. The mean length of the vidian nerve from the petrous ICA to the point the nerve exits the vidian canal (vidian canal length) was 17.90 ± 1.59 mm (range 16-20 mm).

CONCLUSIONS

The distances between the vidian canal and surrounding neurovascular structures would help the skull base surgeon in this narrow and complex area.

Landmarks to Identify Petrous Apex Through Endonasal Approach Without Transgression of Sinus

Objectives  The use of nasopharyngeal landmarks to localize the petrous apex has not been previously described. We describe a purely endoscopic endonasal corridor to localize the petrous apex without transgressing any of the paranasal sinuses. Methods  Anatomical dissections of four formalin preserved cadaveric heads (eight petrous apices) were performed to evaluate the feasibility of a nonsinus-based approach and illustrate the surgical landmarks and measurements that are useful for surgery in this area. Results  The Eustachian tubes, fossa of Rosenmüller (FR), and posterior end of the middle and inferior turbinates are constant landmarks, which can be identified without opening any nasal sinuses. The petrous apex is located on an extended straight line connecting the upper end of the torus tubarius (TT) and the roof of the FR. The distance from upper end of TT to the roof of FR measured 9.875 (±0.99) mm, and the distance from roof of the FR to the petrous apex measured 9.75 (±1) mm. Conclusion  With well-defined landmarks, the inferior, medial petrous apex can be reached using the endoscopic endonasal approach without crossing the sinus cavities.

Petrous Apex Cholesterol Granulomas: Outcomes, Complications, and Hearing Results From Surgical and Wait-and-Scan Management

OBJECTIVE

1. To analyze the surgical outcomes in the management of petrous apex cholesterol granulomas (PACG) with a brief literature review.2. To evaluate the importance of wait-and-scan management option.

STUDY DESIGN

Retrospective review.

SETTING

Quaternary referral center for otology and skull base surgery.

SUBJECTS AND METHODS

Charts of 55 patients with at least 12 months of follow-up were analyzed for demographic, clinical, audiometric, and radiological features. Patients were divided into surgical group (SG) (n = 31) and wait-and-scan (n = 24) (WS) group. Surgical approach was chosen as per hearing status and PACG extension and relation to nearby neurovascular structures and included either drainage by transmastoid-infralabyrinthine approach (TM-IL)/transcanal-infracochlear approach (TC-IC) or resection by infratemporal fossa type B approach (ITF-B). The combination of ITF-B with trans-otic (TO) approach or TO approach solely was used in unserviceable hearing cases. Postoperative outcomes and complications were evaluated in SG.

RESULTS

Postoperative symptom relief was observed in 24 patients (77.4%). Diplopia and paresthesia recovered in each case and improvement in headache, dizziness, tinnitus, and hearing loss was observed in 87.1% cases. Serviceable hearing was preserved in 24 of 26 cases. Postoperative complication rate was 32.2% including incidences of profound hearing loss, facial nerve paresis, carotid artery injury and intraoperative CSF leaks. Revision surgery was required in 3 (9.6%) cases, after TM-IL approach.

CONCLUSION

Surgical drainage is preferable to more aggressive resection procedures, with the latter reserved for recurrent lesions or lesions with severe hearing loss/involvement of critical neurovascular structures. ITF-B approach provides adequate cyst and neurovascular control for resection, while avoiding brain retraction. An initial wait-and-scan approach can be used in most patients where symptoms and imaging justify so.

Analysis of the far-medial transoral endoscopic approach to the infratemporal fossa

OBJECTIVES/HYPOTHESIS

To demonstrate anatomic relationships of the far-medial transoral endoscopic assisted approach (FMT-EAA) to the infratemporal fossa (ITF) and define the corridor dimensions, surgical freedom, and limitations associated with this approach.

STUDY DESIGN

Cadaveric study.

METHODS

Twenty ITFs (10 specimens) were dissected with the assistance of 0 °, 30 °, and 45 ° rod-lens endoscopes. Image guidance was used to confirm and measure the corridors' structural boundaries and document the anatomical relationships encountered in this approach.

RESULTS

Access to the ITF via the FMT-EAA can be divided into two secondary surgical corridors: the superomedial and inferolateral triangles, each of which provides access to different areas. The superomedial triangle is bounded medially by the lateral pterygoid plate and posterolateral maxillary sinus wall, superiorly by the greater sphenoid wing, and inferolaterally by the lateral pterygoid muscle. The inferolateral triangle is bounded superiorly by the lower head of the lateral pterygoid muscle, inferiorly by the medial pterygoid muscle, and laterally by the mandible. Using a standard 19-mm endoscope, the FMT-EAA achieves a mean surgical freedom of 231 mm and 161 mm in the vertical and horizontal planes, respectively.

CONCLUSIONS

FMT-EAA adequately exposes critical structures of the ITF. This technique is a viable option for the management of selected ITF lesions, either alone or in combination with alternative minimally invasive approaches to the region.

LEVEL OF EVIDENCE

NA Laryngoscope, 128:2273-2281, 2018.

Reconstruction of Dural Defects in Endoscopic Transnasal Approaches for Intradural Lesions Using Multilayered Fascia with a Pressure-Control Spinal Drainage System

OBJECTIVE

Nasoseptal flap reconstruction is a widely accepted method for reducing cerebrospinal fluid (CSF) leakage after endoscopic transnasal surgeries (ETSs). However, this method is associated with nasal complications and is difficult to apply repeatedly in recurrent cases. Therefore, alternative methods are needed.

METHODS

Layers of autologous fascia lata were placed on the inside and outside of the dural defect to sufficiently cover it, and the grafts were compressed with an inflated balloon. A lumbar drainage system with a pressure-control valve was used for 72 hours postoperatively. We retrospectively analyzed data on patients with skull base lesions showing intracranial extensions that required wide opening of the ventral dura in ETS. Fifty cases (47 skull base tumors and 3 others) were included, 28 of which were recurrent cases.

RESULTS

In 21 cases (42%), the nasal septum was not intact because of the previous ETS. Seventeen patients (34%) had a history of radiotherapy and 9 (18%) had undergone multisession radiotherapies. None of the 50 patients required additional surgery for postoperative CSF rhinorrhea, and 2 had intermittent CSF leakage that resolved with prolonged lumbar drainage placement for a week. Previous multisession radiotherapy was the only significant risk factor for the need of prolonged drainage (P = 0.029).

CONCLUSIONS

The multilayer closure method with a pressure-control spinal drainage system is a simple, safe, and effective method for preventing postoperative CSF leakage, which can be readily applied to dural defects in any parts of the skull base regions and in patients with various conditions.

Investigating the application of diving endoscopic technique in determining the extent of pituitary adenoma resection via the trans-nasal-sphenoidal approach

The aim of the present study was to investigate the advantages and disadvantages of the diving endoscopic technique in pituitary adenoma surgery, and the application value in determining the extent of tumor resection. A total of 37 patients with pituitary adenoma initially underwent tumor resection under an endoscope-assisted microscope via standard trans-nasal-sphenoidal approach, and tumor cavity structure was observed by applying the diving endoscopic technique. Surgery was subsequently performed again under a microscope or endoscope. The diving endoscopic technique allowed surgeons to directly observe the structure inside a tumor cavity in high-definition. In the present study, 24 patients had pituitary macroadenomas or microadenomas that did not invade the cavernous sinus, and were considered to have undergone successful total resection. Among these patients, no tumor residues were observed through the diving endoscopic technique. Some white lichenoid or fibrous cord-like tissues in the tumor cavity were considered to be remnants of tumors. However, pathology confirmed that these were not tumor tissues. For tumors that invaded the cavernous sinus in 13 patients, observation could only be conducted under the angulation endoscope of the diving endoscope; i.e., the operation could not be conducted under an endoscope. The present study suggests that the diving endoscopic technique may be used to directly observe the resection extent of tumors within the tumor cavity, especially the structure of the tumor cavity inside the sella turcica. The present study also directly validates the reliability of pituitary adenoma resection under endoscope-assisted microscope. In addition, the diving endoscopic technique also allows the surgeon to observe the underwater environment within the sella turcica.

Radiographic Analysis of the Vidian Canal and Its Utility in Petrous Internal Carotid Artery Localization

BACKGROUND

Endoscopic endonasal surgery of the skull base requires expert knowledge of the anatomy and a systematic approach. The vidian canal is regarded as a reliable landmark to localize the petrous internal carotid artery (pICA) near the second genu, which can be used for orientation in deep skull base approaches. There is controversy about the relationship between the vidian canal and the pICA.

OBJECTIVE

To further establish the vertical relationship between the vidian canal and the pICA to aid in surgical approaches to the skull base.

METHODS

We utilized a collection of institutional review board-approved computed tomographic (CT) angiograms (CTAs). Fifty CTAs were studied bilaterally for 100 total sides. The vidian canal was visualized radiographically to determine whether it terminates below, at, or above the level of the pICA.

RESULTS

Sixty-six of 100 vidian canals terminated inferior to the pICA (66%), which was the most common relationship observed. The average distance inferior to the pICA was 1.01 mm on the right, 1.18 mm on the left, and 1.09 mm of the total 66 sides. Less commonly, the vidian canal terminated at the level of the pICA canal in 34 sides (34%). The vidian canal was not observed to terminate superior to the pICA in any of the 50 CTAs studied.

CONCLUSION

The vidian canal terminates inferior to the pICA most commonly, but often terminates at the level of the pICA. Careful drilling clockwise inferior to superior around the vidian canal should allow for safe pICA localization in most cases.

Endoscopic transpterygoid approach to a mass in a child

The endoscopic transterygoid approach to the petrous apex is a feasible/alternative approach in carefully selected patients with specific favorable anatomy, even children. This approach, unlike traditional approaches, spares cochlear and vestibular function. We report a case of a six-year-old boy with embryonal rhabdomyosarcoma of the petrous apex that was diagnosed via the endoscopic transpterygoid approach.

Surgical Anatomy of the Eustachian Tube for Endoscopic Transnasal Skull Base Surgery: A Cadaveric and Radiologic Study

OBJECTIVE

The endoscopic endonasal approach to the anatomically complex lateral skull base presents technical challenges. The use of the eustachian tube as a landmark to identify the petrous internal carotid artery has recently been reported, and this study aims to define the anatomic relationship between the eustachian tube and its surrounding structures using cadaveric dissection and radiologic analysis.

METHODS

To clarify the relationship of the eustachian tube with its surrounding structures, we performed endoscopic and microscopic dissection of 4 adult cadaveric heads and analyzed computed topography scans from 20 patients.

RESULTS

The eustachian tube is divided into the osseous and cartilaginous parts. The cartilaginous part can be further subdivided into the posterolateral, middle, and anteromedial parts, based on its relationship to the skull base. The eustachian tube is closely related to the pterygoid process of the sphenoid bone, the foramen lacerum, and the petrosal apex and is directed away from the oblique sagittal plane almost parallel to the vidian canal at 12.2° ± 6.2° (mean ± standard deviation). The relationship between the course of the vidian canal and the eustachian tube can aid the estimation of the anatomic course of the horizontal segment of the petrous carotid artery.

CONCLUSIONS

The eustachian tube is a useful landmark for predicting the course of the internal carotid artery when accessing the lateral skull base regions via an endonasal route. A profound understanding of the relationship between the eustachian tube and the surrounding skull base structures is important for endoscopic endonasal skull base surgeries.

Contralateral transmaxillary corridor: an augmented endoscopic approach to the petrous apex

OBJECTIVE The endoscopic endonasal approach (EEA) has been shown to be an effective means of accessing lesions of the petrous apex. Lesions that are lateral to the paraclival segment of the internal carotid artery (ICA) require lateralization of the paraclival segment of the ICA or a transpterygoid infrapetrous approach. In this study the authors studied the feasibility of adding a contralateral transmaxillary (CTM) corridor to provide greater access to the petrous apex with decreased need for manipulation of the ICA. METHODS Using image guidance, EEA and CTM extension were performed bilaterally on 5 cadavers. The anterior wall of the sphenoid sinus and rostrum were removed. The angle of the surgical approach from the axis of the petrous segment of the ICA was measured. Five illustrative clinical cases are presented. RESULTS The CTM corridor required a partial medial maxillectomy. When measured from the axis of the petrous ICA, the CTM corridor decreased the angle from 44.8° ± 2.78° to 20.1° ± 4.31°, a decrease of 24.7° ± 2.58°. Drilling through the CTM corridor allowed the drill to reach lateral aspects of the petrous apex that would have required lateralization of the ICA or would not have been accessible via EEA. The CTM corridor allowed us to achieve gross-total resection of the petrous apex region in 5 clinical cases with significant paraclival extension. CONCLUSIONS The CTM corridor is a feasible extension to the standard EEA to the petrous apex that offers a more lateral trajectory with improved access. This approach may reduce the risk and morbidity associated with manipulation of the paraclival ICA.

Expanding the endoscopic transpterygoid corridor to the petroclival region: anatomical study and volumetric comparative analysis

OBJECTIVE The endoscopic endonasal transmaxillary transpterygoid (TMTP) approach has been the gateway for lateral skull base exposure. Removal of the cartilaginous eustachian tube (ET) and lateral mobilization of the internal carotid artery (ICA) are technically demanding adjunctive steps that are used to access the petroclival region. The gained expansion of the deep working corridor provided by these maneuvers has yet to be quantified. METHODS The TMTP approach with cartilaginous ET removal and ICA mobilization was performed in 5 adult cadaveric heads (10 sides). Accessible portions of the petrous apex were drilled during the following 3 stages: 1) before ET removal, 2) after ET removal but before ICA mobilization, and 3) after ET removal and ICA repositioning. Resection volumes were calculated using 3D reconstructions generated from thin-slice CT scans obtained before and after each step of the dissection. RESULTS The average petrous temporal bone resection volumes at each stage were 0.21 cm³, 0.71 cm³, and 1.32 cm³ (p < 0.05, paired t-test). Without ET removal, inferior and superior access to the petrous apex was limited. Furthermore, without ICA mobilization, drilling was confined to the inferior two-thirds of the petrous apex. After mobilization, the resection was extended superiorly through the upper extent of the petrous apex. CONCLUSIONS The transpterygoid corridor to the petroclival region is maximally expanded by the resection of the cartilaginous ET and mobilization of the paraclival ICA. These added maneuvers expanded the deep window almost 6 times and provided more lateral access to the petroclival region with a maximum volume of 1.5 cm³. This may result in the ability to resect small-to-moderate sized intradural petroclival lesions up to that volume. Larger lesions may better be approached through an open transcranial approach.

Role of endoscopic transnasal surgery for skull base chondrosarcoma: a retrospective analysis of 19 cases at a single institution

OBJECTIVE Skull base chondrosarcoma is one of the most intractable tumors because of its aggressive biological behavior and involvement of the internal carotid artery and cranial nerves (CNs). One of the most accepted treatment strategies for skull base chondrosarcoma has been surgical removal of the tumor in conjunction with proactive extensive radiation therapy (RT) to the original tumor bed. However, the optimal strategy has not been determined. The goal of this study was to evaluate the early results of endoscopic transnasal surgery (ETS). METHODS The authors retrospectively analyzed 19 consecutive patients who underwent ETS at their institution since 2010. Adjuvant stereotactic radiosurgery (SRS) was performed only for the small residual tumors that were not resected to avoid critical neurological complications. Histological confirmation and evaluation of the MIB-1 index was performed in all cases. The Kaplan-Meier method was used to determine the actuarial rate of tumor-free survival. RESULTS The median tumor volume and maximal diameter were 14.5 cm³ (range 1.4-88.4 cm³) and 3.8 cm (range 1.5-6.7 cm), respectively. Nine patients (47%) had intradural extension of the tumor. Gross-total resection was achieved in 15 (78.9%) of the 19 patients, without any disabling complications. In 4 patients, the surgery resulted in subtotal (n = 2, 11%) or partial (n = 2, 11%) resection because the tumors involved critical structures, including the basilar artery or the lower CNs. These 4 patients were additionally treated with SRS. The median follow-up duration was 47, 28, and 27 months after the diagnosis, ETS, and SRS, respectively. In 1 patient with an anterior skull base chondrosarcoma, the tumor relapsed in the optic canal 1 year later and was treated with a second ETS. Favorable tumor control was achieved in all other patients. The actuarial tumor control rate was 93% at 5 years. At the final follow-up, all patients were alive and able to perform independent activities of daily living without continuous neurological sequelae. CONCLUSIONS These preliminary results suggest that ETS can achieve sufficient radical tumor removal, resulting in comparative resection rates with fewer neurological complications to those in previous reports. Although the follow-up periods of these cases were relatively short, elective SRS to the small tumor remnant may be rational, achieving successful tumor control in some cases, instead of using proactive extensive RT. Thus, the addition of RT should be discussed with each patient, after due consideration of histological grading and biological behavior. To determine the efficacy of this strategy, a larger case series with a longer follow-up period is essential. However, this strategy may be able to establish evidence in the management of skull base chondrosarcoma, providing less-invasive and effective options as an initial step of treatment.

Pneumatization Patterns of the Petrous Apex and Lateral Sphenoid Recess

Introduction  The petrous apex poses a challenge for surgical intervention due to poor access. As intraoperative image guidance and surgical instrumentation improve, newer endoscopic approaches are increasingly favored. This study aims to provide normative data on the anatomy of the lateral sphenoid sinus recess and petrous apex. These normative data could assist in determining the efficacy of a transnasal transsphenoidal approach to lesions of the anteroinferior petrous apex. Methods  This is a retrospective study investigating normative data on all maxillofacial computed tomography (CT) scans performed at a level I trauma center over a 6-month period. All appropriate images had the pneumatization pattern of the petrous apex and lateral recess of the sphenoid sinus reviewed by a single otologist and graded bilaterally. These were then analyzed in SPSS; Pearson correlation analyses and χ ² test were used. Results  A total of 481 patients were identified, yielding a total of 962 temporal bones and sphenoid sinuses for analysis. Eighty-eight percent of sides analyzed had a nonpneumatized lateral recess. The petrous apex was nonpneumatized in 54% of sides analyzed. There was a correlation noted between the degree of pneumatization of the petrous apex and pneumatization of the lateral recess of the sphenoid. Conclusion  This study is the first to provide normative data comparing pneumatization of the petrous apex and sphenoid sinus. These data may support future work evaluating the utility of an endonasal approach to the petrous apex.

Anatomical variants of sphenoid sinuses pneumatisation: a CT scan study on a Northern Italian population

Sphenoid bone may be affected by different variants of pneumatisation, which have a relevant importance from a clinical and surgical point of view. The description of such variants in different populations may give useful information. However, few articles describe the variability of sphenoid pneumatised structures and none of them focuses on Northern Italian population. Variants of pneumatisation of sphenoid bone were described in a sample of 300 Northern Italian patients who underwent a CT scan. More than fifty-seven percent of patients showed a form of anatomical variant: the most common form was the pneumatised pterygoid processes (39.6%), followed by dorsum sellae (32.9%) and clinoid processes (20.3%), without statistically significant differences between males and females (p > 0.01). In 26.3% of patients, a combined pneumatisation of these three structures was observed, being the combination pterygoid processes-dorsum sellae the most frequent (11.3%). In 9.3%, all the three sphenoid structures were affected. This article is the first description of the prevalence of different variants of pneumatisation in a Northern Italian population: the occurrence of such forms has to be acknowledged for their possible clinical and surgical consequences.

Expanded Endonasal Endoscopic Approaches to the Skull Base for the Radiologist

The cranial base is a complex 3-D region that contains critical neurovascular structures. Pathologies affecting this region represent some of the most challenging lesions to manage due to difficulty with access and risk of significant postoperative morbidity. With the development of expanded endonasal endoscopic approaches, skull base surgeons use the nose and paranasal sinuses as a corridor to access selected ventral skull base lesions. This review discusses high-resolution imaging in the evaluation of patients with skull base lesions considered for endonasal endoscopic surgery, summarizes various expanded endonasal endoscopic approaches, and provides examples of commonly used expanded endonasal endoscopic procedures.

The endoscopic anatomy of the middle ear approach to the fundus of the internal acoustic canal

OBJECTIVE The application of the endoscope in the lateral skull base increases the importance of the middle ear cavity as the corridor to the skull base. The aim of this study was to define the middle ear as a route to the fundus (lateral end) of the internal acoustic canal and to propose feasible landmarks to the fundus. METHODS This was a cadaveric study; 34 adult cadaveric temporal bones and 2 dry bones were dissected with the aid of the endoscope and microscope to show the anatomy of the transcanal approach to the middle ear and fundus of the internal acoustic canal. RESULTS In the middle ear cavity, the cochleariform process is one of the key landmarks for accessing the fundus of the internal acoustic canal. The triangle formed by the anterior and posterior edges of the overhang of the round window and the cochleariform process provides a landmark to start drilling the bone to access the fundus of the internal acoustic canal. CONCLUSIONS The external acoustic canal and middle ear cavity combined, using endoscopic guidance, can provide a route to the fundus of the internal acoustic canal. A triangular landmark crossing the promontory has been described for reaching the meatal fundus. This transcanal approach requires an understanding of the relationship between the middle ear cavity and the fundus of the internal acoustic canal and provides a potential new area of cooperation between otology and neurosurgery for accessing pathology in this and the bordering skull base.

Endoscopic Management of Middle Ear and Temporal Bone Lesions

Tantamount to the management of temporal bone neoplasms is the ability to visualize the pathology and its relationship with the numerous critical structures housed therein. Transcanal endoscopic ear surgery provides the surgeon with an unparalleled view of the entire middle ear. This article presents the latest information on the usefulness of transcanal endoscopic ear surgery in the management of middle ear and temporal bone neoplasms.

Required Reading: The Most Impactful Articles in Endoscopic Endonasal Skull Base Surgery

OBJECTIVE

Endoscopic endonasal skull base surgery has become widely accepted in neurosurgery and otolaryngology over the last 15 years. However, there has yet to be a formal curation of the most impactful articles for an introductory curriculum to its technical evolution.

METHODS

The Science Citation Index Expanded was used to generate a citation rank list (October 2015) on articles relevant to endoscopic skull base surgery. The top 35 cited articles overall, as well as the top 15 since 2009, were identified. Journal, year, author, study population, article format, and level of evidence were compiled. Additional surgeon experts were polled and made recommendations for significant contributions to the literature.

RESULTS

The top 35 publications ranged from 98 to 467 citations and were published in 10 different journals. Four articles had more than 250 citations. A period of frequent contribution occurred between 2005 and 2009, when 21/35 reports were published. 18/35 articles were case series, and 13/35 were technical reports. There were 11/35 articles focused primarily on pituitary surgery and 10/35 on extrasellar lesions. The top 15 articles since 2009 had 8/15 articles focused on extrasellar lesions. Polled surgeons consistently identified the most prominently cited articles, and their recommendations drew attention to cerebrospinal fluid leak as well as extrasellar management.

CONCLUSIONS

Identification of the most cited works within endoscopic endonasal skull base surgery shows greater anatomic access and safety over the last 2 decades. These articles can serve as an educational tool for novices or midlevel practitioners wishing to obtain a greater understanding of the field.

Subtemporal Retrolabyrinthine (Posterior Petrosal) versus Endoscopic Endonasal Approach to the Petroclival Region: An Anatomical and Computed Tomography Study

Background The petroclival region seats many neoplasms. Traditional surgical corridors to the region can result in unacceptable patient morbidity. The combined subtemporal retrolabyrinthine transpetrosal (posterior petrosal) approach provides adequate exposure with hearing preservation; however, the facial nerve and labyrinth are put at risk. Approaching the petroclival region with an endoscopic endonasal approach (EEA) could minimize morbidity. Objective To provide an anatomical and computed tomography (CT) comparison between the posterior petrosal approach and EEA to the petroclival region. Methods The petroclival region was approached transclivally with EEA. Different aspects of dissection were compared with the posterior petrosal approach. The two approaches were also studied using CT analysis. Results A successful corridor medial to the internal auditory canal (IAC) was achieved with EEA. Wide exposure was achieved with no external skin incisions, although significant sinonasal resection was required. The posterior petrosal was comparable in terms of exposure medially; however, the dissection involved more bone removal, greater skill, and a constricting effect upon deeper dissection. Importantly, access lateral to the IAC was obtained, whereas EEA could not reach this area. Conclusion An EEA to the petroclival region is feasible. This approach can be considered in lesions medial to the IAC.

Ectopic Esthesioneuroblastoma of the Sphenoclivus: A Rare Entity

Esthesioneuroblastoma is a rare malignant neoplasm of oflactory neuroepithelium and usually located at the olfactory cleft at superior nasal cavity. Ectopic localization of esthesioneuroblastoma is even rarer and usually posed with a diagnostic dilemma and delay in the diagnosis and management, We report a rare case of ectopic esthesioneuroblastoma of the sphenoclivus with the presentation of intermittent unilateral epistaxis, intermittent intractable headache without anosmia. Nasal endoscopy findings showed a pulsatile mass at the anterior face of the sphenoid sinus with extension posteriorly towards the clivus region and occupying the floor of the sphenoid sinus. Endonasal transclival endoscopic excision of tumour was performed which involved otorhinolaryngology surgeon and neurosurgeon with intraoperative navigation imaging and frozen section. The histopathological findings was esthesioneuroblastoma. Due to its rarity and unusual presentation, the diagnosis of ectopic esthesioneuroblastoma is difficult and can be misdiagnosed with the other type of malignancy. Therefore, the histopathological result is important in confirming the type of tumour and can lead to the next step of management.

Endoscopic transsphenoidal anterior petrosal approach for locally aggressive tumors involving the internal auditory canal, jugular fossa, and cavernous sinus

OBJECTIVE Reports about endoscopic endonasal surgery for skull base tumors involving the lateral part of petrous apex remain scarce. The authors present their experience with the endoscopic transsphenoidal anterior petrosal (ETAP) approach through the retrocarotid space for tumors involving the internal auditory canal, jugular fossa, and cavernous sinus. METHODS The authors performed the ETAP approach in 10 patients with 11 tumors (bilateral in 1 patient) that extensively occupied the lateral part of petrous apex, e.g., the internal auditory canal and jugular fossa. Eight patients presented with diplopia (unilateral abducens nerve palsy), 3 with tinnitus, and 1 with unilateral hearing loss with facial palsy. After wide anterior sphenoidotomy, the sellar floor, clival recess, and carotid prominence were verified. Tumors were approached via an anteromedial petrosectomy through the retrocarotid triangular space, defined by the cavernous and vertical segments of the internal carotid artery (ICA), the clivus, and the petrooccipital fissure. The surgical window was easily enlarged by drilling the petrous bone along the petrooccipital fissure. After exposure of the tumor and ICA, dissection and resection of the tumor were mainly performed under direct visualization with 30° and 70° endoscopes. RESULTS Gross-total resection was achieved in 8 patients (9 tumors). In a patient with invasive meningioma, the tumor was strongly adherent to the ICA, necessitating partial resection. Postoperatively, all 8 patients who had presented with abducens nerve palsy preoperatively showed improvement within 6 months. In the patient presenting with hearing loss and facial palsy, the facial palsy completely resolved within 3 months, but hearing loss remained. Regarding complications, 3 patients showed mild and transient abducens nerve palsy resolving within 2 weeks, 3 months, and 6 months. Postoperative CSF rhinorrhea requiring surgical repair was observed in 1 patient. No patient exhibited hearing deterioration, facial palsy, or symptoms of lower cranial nerve palsy after surgery. CONCLUSIONS The ETAP approach can offer a simple, less invasive option for invasive skull base tumors involving petrous regions, including the internal auditory canal, jugular fossa, and cavernous sinus. The ETAP approach can reach more extensive areas in the extradural regions around the petrous bone. The authors' results indicate that the transsphenoidal retrocarotid route is sufficient to approach the petrosal areas in select cases. Further expansion of the surgical field is not always necessary. However, experience with intradural lesions remains limited, and the extent of tumor resection largely depends on tumor characteristics. Application of the ETAP approach should thus be carefully determined in each patient, taking into consideration the size of the retrocarotid window and tumor characteristics.

The Inferolateral Transorbital Endoscopic Approach: A Preclinical Anatomic Study

BACKGROUND

In recent years, transorbital endoscopic approaches are increasing in popularity as they provide several corridors to reach lateral areas of the ventral skull base through the orbit. The aim of this study is to investigate the feasibility of the inferolateral transorbital endoscopic approach (ILTEA) by detailing the step-by-step dissection, anatomic landmarks, and target anatomic areas.

METHODS

Seven cadaveric specimens (14 sides) were dissected in the Laboratory of Endoscopic Anatomy of the University of Brescia. Step-by-step dissection of ILTEA was performed to identify the main anatomic landmarks and corridors. Skin incision, dural incision, and boundaries of craniectomy were measured. Neuronavigation was used to check landmarks, track boundaries of surgical volumes, and measure orbital dislocation.

RESULTS

The study on the 14 ILTEAs defined 1 anatomic area ("waterline door") that leads to 4 corridors: Meckel's cave corridor, carotid foramen corridor, petrous corridor, and transdural middle fossa corridor. Crucial anatomic landmarks were identified and analyzed. Orbital dislocation was <10 mm.

CONCLUSIONS

ILTEA provides the surgeon with a direct route to the region of the "waterline door," lateral areas of the ventral skull base, and middle cranial fossa. In addition, it allows an optimal view of the intracranial and extracranial portions of the maxillary and mandibular nerves. Further anatomic and clinical studies are needed to validate ILTEA in surgical practice.

Cholesterol Granuloma Development following Temporal Bone Surgery

OBJECTIVE

To describe the clinical presentation and management of patients with cholesterol granulomas (CGs) that develop following temporal bone surgery.

STUDY DESIGN

Case series with chart review.

SETTING

Two independent tertiary academic referral centers.

SUBJECTS AND METHODS

A multicenter retrospective review was performed to identify all patients between 2001 and 2014 who were diagnosed with a CG that developed following temporal bone surgery. Patients with a history of idiopathic petrous apex CGs were excluded, as were those with <6 months of follow-up after diagnosis. Demographic and clinical data were recorded at presentation, and the main outcome measure was symptom evolution over time.

RESULTS

A total of 20 patients met inclusion criteria (median age, 55.0 years; 70.0% female), and their cases were analyzed. Diagnosis was made, on average, 149.5 months (median, 94.5; range, 13.0-480.0) following a temporal bone operation, which was for chronic ear disease in 75.0% of cases. The most common presenting symptoms were otalgia (55.0%) and otorrhea (40.0%). In patients initially managed with observation, 71.4% required no surgical intervention through a mean of 56.8 months (median, 30; range, 12.0-178.0) of follow-up. For those who initially underwent surgical excision, durable symptom relief was achieved in 66.7% of cases.

CONCLUSION

Postoperative CG formation in the temporal bone is a rare occurrence that can be encountered years following surgery. The present study suggests that conservative management can be appropriate for many cases in which patients are relatively asymptomatic.

A new multilayer reconstruction using nasal septal flap combined with fascia graft dural suturing for high-flow cerebrospinal fluid leak after endoscopic endonasal surgery

This study aimed to evaluate the usefulness and reliability of a new endoscopic multilayer reconstruction using nasal septal flap (NSF) to prevent high-flow cerebrospinal fluid leak after endoscopic endonasal surgery. This study was a retrospective review on 97 patients who underwent multilayer reconstructions using NSF combined with fascia graft dural suturing after endoscopic endonasal surgery between July 2012 and March 2014. Patients were divided into two groups, third ventricle opening group and nonopening group, based on the presence of a direct connection between the third ventricle and the paranasal sinus after tumor removal. Furthermore, we compared this procedure with our previous reconstruction after resection of craniopharyngioma. Finally, we checked the patients who had postoperative prolonged discomfort of the nasal cavity for over a year. Postoperative cerebrospinal fluid (CSF) leak occurred in three patients (3.1 %): one from the third ventricle opening group and the remaining two from the nonopening group. External lumbar drain was performed after surgery in only seven patients (7.2 %). The incidence of postoperative CSF leak was similar in both groups, whereas the rate of craniopharyngioma in the third ventricle opening group was significantly higher. The incidence of postoperative CSF leak after resection of craniopharyngioma was not statistically significant but obviously higher in the previous group (12.2 %) compared with that in the present group (2.3 %). Twelve patients (12.4 %) had postoperative nasal discomfort of the nasal cavity for over a year. Multilayer reconstruction using NSF combined with fascia graft dural suturing is a more reliable method for preventing postoperative high-flow CSF leakage after endoscopic endonasal surgery even if there is a direct connection between the third ventricle and the paranasal sinus. However, we should pay close attention especially to prolonged discomfort of the nasal cavity after harvesting NSF.

Comparative analysis of the anterior transpetrosal approach with the endoscopic endonasal approach to the petroclival region

OBJECTIVE The endoscopic endonasal approach (EEA) offers direct access to midline skull base lesions, and the anterior transpetrosal approach (ATPA) stands out as a method for granting entry into the upper and middle clival areas. This study evaluated the feasibility of performing EEA for tumors located in the petroclival region in comparison with ATPA. METHODS On 8 embalmed cadaver heads, EEA to the petroclival region was performed utilizing a 4-mm endoscope with either 0° or 30° lenses, and an ATPA was performed under microscopic visualization. A comparison was executed based on measurements of 5 heads (10 sides). Case illustrations were utilized to demonstrate the advantages and disadvantages of EEA and ATPA when dealing with petroclival conditions. RESULTS Extradurally, EEA allows direct access to the medial petrous apex, which is limited by the petrous and paraclival internal carotid artery (ICA) segments laterally. The ATPA offers direct access to the petrous apex, which is blocked by the petrous ICA and abducens nerve inferiorly. Intradurally, the EEA allows a direct view of the areas medial to the cisternal segment of cranial nerve VI with limited lateral exposure. ATPA offers excellent access to the cistern between cranial nerves III and VIII. The quantitative analysis demonstrated that the EEA corridor could be expanded laterally with an angled drill up to 1.8 times wider than the bone window between both paraclival ICA segments. CONCLUSIONS The midline, horizontal line of the petrous ICA segment, paraclival ICA segment, and the abducens nerve are the main landmarks used to decide which approach to the petroclival region to select. The EEA is superior to the ATPA for accessing lesions medial or caudal to the abducens nerve, such as chordomas, chondrosarcomas, and midclival meningiomas. The ATPA is superior to lesions located posterior and/or lateral to the paraclival ICA segment and lesions with extension to the middle fossa and/or infratemporal fossa. The EEA and ATPA are complementary and can be used independently or in combination with each other in order to approach complex petroclival lesions.

Upper Nasopharyngeal Corridor for Transnasal Endoscopic Drainage of Petroclival Cholesterol Granulomas: Alternative Access in Conchal Sphenoid Patients

Background Cholesterol granulomas arising at the petrous apex can be treated via traditional open surgical, endoscopic, and endoscopic-assisted approaches. Endoscopic approaches require access to the sphenoid sinus, which is technically challenging in patients with conchal sphenoidal anatomy.

Clinical Presentation A 55-year-old woman presented with intermittent headaches and tinnitus. Formal audiometry demonstrated moderately severe bilateral hearing loss. CT of the temporal bones and sella revealed a well-demarcated expansile lytic mass. MRI of the face, orbit, and neck showed a right petrous apex mass measuring 22 × 18 × 19 mm that was hyperintense on T1- and T2-weighted images without enhancement, consistent with a cholesterol granuloma. The patient had a conchal sphenoidal anatomy.

Operative Technique Herein, we present an illustrative case of a low-lying petroclival cholesterol granuloma in a patient with conchal sphenoidal anatomy to describe an alternative high nasopharyngeal corridor for endoscopic transnasal transclival access.

Postoperative Course Postoperatively, the patient's symptoms recovered and no complications occurred. Follow-up imaging demonstrated a patent drainage tract without evidence of recurrence.

Conclusion In patients with a conchal sphenoid sinus, endoscopic transnasal transclival access can be gained using a high nasopharyngeal approach. This corridor facilitates safe access to these lesions and others in this location.

Morphometric Analysis of Bone Resection in Anterior Petrosectomies

Introduction The anterior petrosectomy is a well-defined skull base approach to lesions such as petroclival meningiomas, posterior circulation aneurysms, petrous apex lesions (chondrosarcomas, cholesteatomas), ventrolateral brainstem lesions, clival chordomas, trigeminal neurinomas, and access to cranial nerves III, IV, V, and VII. Methods and Materials Fourteen anterior petrosectomies on eight cadaveric heads were performed in a skull base dissection laboratory. Predissection and postdissection thin-cut computed tomography scans were obtained to compare the bone resection. A computer program was used (InVivo5, Anatomage, San Jose, California, United States) to measure the bone resection and the improved viewing angle. Results The average bone removed in each plane was as follows: anterior to posterior plane was 10.57 mm ± 2.00 mm, superior to inferior was 9.39 mm ± 1.67 mm, and lateral to medial was 17.46 mm ± 4.64 mm. The average increased angle of view was 13.01 ± 2.35 degrees (Table 1). The average volume was 1786.94 ± 827.40 mm(3). Conclusions Anterior petrosectomy is a useful approach to access the ventrolateral brainstem region. We present a cadaveric study quantitating the volume of bone resection and improvement in the viewing angle. These data provide useful preoperative information on the utility of this skull base approach and the gain in the viewing angle after bony removal.

Endoscopic endonasal surgery for sinonasal and skull base lesions in the pediatric population

Endoscopic endonasal skull base surgical techniques, initially developed in adult patients, are being utilized with increasing frequency in pediatric patients to treat sinonasal and skull base lesions. This article reviews the current state of endoscopic endonasal approaches to the skull base to both treat disease and reconstruct the skull base in pediatric patients. Sinonasal and skull base embryology and anatomy are reviewed as a foundation for understanding the disease processes and surgical techniques. Selected skull base pathologies and conditions that involve the pediatric skull base are also reviewed.

Endoscopic endonasal translacerum approach to the inferior petrous apex

OBJECTIVE

The surgical approach to lesions involving the inferior petrous apex (IPA) is still challenging. The purpose of this study is to demonstrate the anatomical features of the IPA and to assess the applicability of an endoscopic endonasal approach through the foramen lacerum (translacerum approach) to the IPA.

METHODS

The surgical simulation of the endoscopic endonasal translacerum approach was conducted in 3 cadaver heads. The same technique was applied in 4 patients harboring tumors involving the IPA (3 chordomas and 1 chondro-sarcoma).

RESULTS

By removing the fibrocartilaginous component of the foramen lacerum, a triangular space was created between the anterior genu of the petrous portion of the carotid artery and the eustachian tube, through which the IPA could be approached. The range of the surgical maneuver reached laterally up to the internal auditory canal, jugular foramen, and posterior vertical segment of the petrous portion of the carotid artery. In clinical application, the translacerum approach provided sufficient space to handle tumors at the IPA. Gross-total and partial removal was achieved in 3 and 1 cases, respectively, without permanent surgery-related morbidity and mortality.

CONCLUSIONS

The endoscopic endonasal translacerum approach provides reliable access to the IPA. It is indicated alone for lesions confined to the IPA and in combination with other approaches for more extensive lesions.

Endoscopic endonasal surgical management of chondrosarcomas with cerebellopontine angle extension

OBJECT

Skull base chondrosarcomas are slow-growing, locally invasive tumors that arise from the petroclival synchondrosis. These characteristics allow them to erode the clivus and petrous bone and slowly compress the contents of the posterior fossa progressively until the patient becomes symptomatic, typically from cranial neuropathies. Given the site of their genesis, surrounded by the petrous apex and the clival recess, these tumors can project to the middle fossa, cervical area, and posteriorly, toward the cerebellopontine angle (CPA). Expanded endoscopic endonasal approaches are versatile techniques that grant access to the petroclival synchondrosis, the core of these lesions. The ability to access multiple compartments, remove infiltrated bone, and achieve tumor resection without the need for neural retraction makes these techniques particularly appealing in the management of these complex lesions.

METHODS

Analysis of the authors' database yielded 19 cases of skull base chondrosarcomas; among these were 5 cases with predominant CPA involvement. The electronic medical records of the 5 patients were retrospectively reviewed for age, sex, presentation, pre- and postoperative imaging, surgical technique, pathology, and follow-up. These cases were used to illustrate the surgical nuances involved in the endonasal resection of CPA chondrosarcomas.

RESULTS

The male/female ratio was 1:4, and the patients' mean age was 55.2 ±11.2 years. All cases involved petrous bone and apex, with variable extensions to the posterior fossa and parapharyngeal space. The main clinical scenario was cranial nerve (CN) palsy, evidenced by diplopia (20%), ptosis (20%), CN VI palsy (20%), dysphagia (40%), impaired phonation (40%), hearing loss (20%), tinnitus (20%), and vertigo/dizziness (40%). Gross-total resection of the CPA component of the tumor was achieved in 4 cases (80%); near-total resection of the CPA component was performed in 1 case (20%). Two patients (40%) harbored high-grade chondrosarcomas. No patient experienced worsening neurological symptoms postoperatively. In 2 cases (40%), the symptoms were completely normalized after surgery.

CONCLUSIONS

Expanded endoscopic endonasal approaches appear to be safe and effective in the resection of select skull base chondrosarcomas; those with predominant CPA involvement seem particularly amenable to resection through this technique. Further studies with larger cohorts are necessary to test these preliminary impressions and to compare their effectiveness with the results obtained with open approaches.

The Endoscopic Endonasal Approach for Removal of Petroclival Chondrosarcomas

Chondrosarcomas of the skull base are rare, locally invasive tumors that typically arise in the petroclival region, from degenerated chondroid cells located within the synchondrosis. Given their usually slow growth rate, they are capable of reaching sizable dimensions, promoting bone erosion and significant displacement of neurovascular structures before causing symptomatology that will eventually lead to diagnosis; cranial neuropathies and headaches are common complaints. This article discusses the pertinent surgical anatomy, patient selection criteria, technical nuances and complication management of the endonasal resection of skull base chondrosarcomas.

Endoscopic transnasal approach for resection of locally aggressive tumors in the orbit

OBJECT

In recent years, application of endoscopic transnasal surgery (ETS) has been expanded to orbital lesions, and preliminary results have started to be published for medially located soft mass lesions. However, reports on experience with endoscopic intraorbital surgery aimed at resection of invasive skull base tumors remains quite limited. This report presents the authors' experience with ETS for locally aggressive tumors involving the orbit.

METHODS

ETS was performed for 15 cases of aggressive tumors involving the orbit: 5 meningiomas (meningothelial, n = 3; atypical, n = 1; anaplastic, n = 1), 4 chordomas, 2 chondrosarcomas, and 4 others (metastasis from systemic myxofibrosarcoma, schwannoma, inverted papilloma, and acinic cell carcinoma, n = 1 each). Among these, 9 tumors were located outside the periorbita and 6 inside the periorbita. In 6 intraperiosteal tumors, 5 were intraconal lesions, of which 3 arose in the muscle cone (anaplastic meningioma, optic sheath meningioma, and metastatic myxofibrosarcoma), and 2 meningothelial meningioma had invaded from the sphenoid ridge or the cavernous sinus into the muscle cone through the optic canal and the superior orbital fissure. A case of schwannoma originated around the cavernous sinus and pterygopalatine fossa and extended extraconally into the periorbita. Intraoperatively, ethmoid air cells and the lamina papyracea were removed, and extraperiosteal tumors were safely approached. For intraperiosteal tumors, the periorbita was widely opened, and the tumors were approached through the surgical window between the rectus and oblique muscles.

RESULTS

Gross-total resection was achieved for 12 of the 15 tumors, including 2 intraconal lesions. After surgery, exophthalmos resolved in all 8 patients with this symptom, and diplopia resolved in 5 of 6 patients. Improvement of visual symptoms was reported by 4 of 5 patients with loss of visual acuity or constriction of the visual field. Postoperatively, 1 patient showed mild, transient worsening of existing facial dysesthesia, and another showed transient ptosis and mild hypesthesia of the forehead on the affected side. All those symptoms resolved within 3 months. No patients showed enophthalmos, worsening of diplopia or visual function, or impairment of olfaction after surgery.

CONCLUSIONS

ETS appears acceptable as a less-invasive alternative for treating aggressive tumors involving the orbit. For extraperiosteal tumors, gross-total removal can generally be achieved without neurological complications. For intraperiosteal tumors, surgical indications should be carefully discussed, considering the relationship between the tumor and normal anatomy. Wide opening of the periorbital window is advocated to create a sufficient surgical pathway between the extraocular muscles, allowing a balance between functional preservation and successful tumor resection.

Nuances in the treatment of malignant tumors of the clival and petroclival region

Introduction Malignancies of the clivus and petroclival region are mainly chordomas and chondrosarcomas. Although a spectrum of malignancies may present in this area, a finite group of commonly encountered malignant pathologies will be the focus of this review, as they are recognized to be formidable pathologies due to adjacent critical neurovascular structures and challenging surgical approaches.

Objectives The objective is to review the literature regarding medical and surgical management of malignant tumors of the clival and petroclival region with a focus on clinical presentation, diagnostic identification, and associated adjuvant therapies. We will also discuss our current treatment paradigm using endoscopic, open, and combined approaches to the skull base.

Data Synthesis A literature review was conducted, searching for basic science and clinical evidence from PubMed, Medline, and the Cochrane Database. The selection criteria encompassed original articles including data from both basic science and clinical literature, case series, case reports, and review articles on the etiology, diagnosis, treatment, and management of skull base malignancies in the clival and petroclival region.

Conclusions The management of petroclival malignancies requires a multidisciplinary team to deliver the most complete surgical resection, with minimal morbidity, followed by appropriate adjuvant therapy. We advocate the combination of endoscopic and open approaches (traditional or minimally invasive) as required by the particular tumor followed by radiation therapy to optimize oncologic outcomes.

Endoscopic versus Open Approach to the Infratemporal Fossa: A Cadaver Study

Introduction Various lateral and anterior approaches to access the infratemporal fossa (ITF) have been described. We provide our observations regarding the endoscopic transpterygoid and preauricular subtemporal approaches, listing their respective advantages and limitations through cadaveric dissection. Methods A cadaver study was performed on five adult specimens. An endoscopic transpterygoid approach to the ITF was completed bilaterally in three specimens, and an open preauricular ITF approach was performed bilaterally in two specimens. Results After completing the cadaveric dissections, we studied differences between the endoscopic transpterygoid approach and open preauricular subtemporal approaches in regard to exposure and ease of dissection of different structures in the ITF. Conclusions In comparison with a lateral approach, the endonasal endoscopic transpterygoid approach provides better visualization and more direct exposure of median structures such as the nasopharynx, eustachian tube, sella, and clivus. We concluded that the endoscopic transpterygoid approach can be utilized to resect benign lesions and some select group of malignancies involving the infratemporal and middle cranial fossae. Open approaches continue to play an important role, especially in the resection of extensive malignant tumors extending to these regions.

Anterior Petrosectomy: Consecutive Series of 46 Patients with Attention to Approach-Related Complications

Objective Anterior petrosectomy(AP) was popularized in the 1980s and 1990s as micro-neurosurgery proliferated. Original reports concentrated on the anatomy of the approach and small case series. Recently, with the advent of additional endonasal approaches to the petrous apex, the morbidity of AP remains unclear. This report details approach-related morbidity around and under the temporal lobe. Methods A total of 46 consecutive patients identified from our surgical database were reviewed retrospectively. Results Of the 46 patients, 61% were women. Median age of the patients was 50 years (mean: 48 ± 2 years). Median follow-up of this cohort was 66 months. Most procedures dealt with intradural pathology (n = 40 [87%]). Approach-related morbidity consisted of only two patients (4%) with new postoperative seizures. There were only two significant postoperative hemorrhages (4%). Cerebrospinal fluid leakage occurred in two patients (4%) requiring reoperation. Conclusion Approach-related complications such as seizures and hematoma were infrequent in this series, < 4%. This report describes a contemporary group of patients treated with open AP and should serve as a comparison for approach-related morbidity of endoscopic approaches. Given the pathologies treated with this approach, the morbidity appears acceptable.

Endoscopic Endonasal Infrapetrous Transpterygoid Approach to the Petroclival Junction for Petrous Apex Chondrosarcoma: Technical Report

Chondrosarcomas of the skull base are rare tumors that present difficult management considerations due to the pathoanatomical relationships of the tumor to adjacent structures. We present the case of a 25-year-old female patient presenting with a chondrosarcoma of the right petrous apex extending inferiorly, medial to the cranial nerves. The tumor was resected via an endoscopic endonasal infrapetrous transpterygoid approach that achieved complete resection and an excellent long-term outcome with no complications. Technical nuances and potential pitfalls of the case are discussed in depth including measures to protect the carotid artery while performing the required drilling of the skull base to access the lesion.

Use of the pedicled nasoseptal flap in the endoscopic management of cholesterol granulomas of the petrous apex

BACKGROUND

Nowadays the endoscopic approach represents a useful alternative to traditional surgical approaches in the treatment of cholesterol granulomas (CGs) of the petrous apex (PA). Recently the nasoseptal flap (NSF) has been employed to permit long-term patency of drainage site. The purpose of this study is to report our experience with the NSF in the endoscopic management of CG and to analyze the advantages, limitations, and outcomes of the technique.

METHODS

A retrospective analysis was carried out on 10 patients affected by CG of the PA who had been treated endoscopically, using the NSF.

RESULTS

An endoscopic transpterygoid approach was used for 6 patients and the remaining 4 were treated using the transclival approach. A NSF was used in all 10 cases. In 6 cases the flap was ipsilateral to the lesion whereas in 4 it was contralateral. In 90% of our patients no evidence of disease was observed after a mean follow-up period of 35.7 months, with resolution of their symptoms. One patient presented a recurrence because of a technical error (inadequate placement of the flap in the cavity), and has been retreated endoscopically.

CONCLUSION

The pedicled NSF seems to be helpful in avoiding the concentric growth of the granulomatous cyst epithelium while assuring ventilation and drainage of the cyst. However, bigger studies with longer-term follow-up are needed to confirm these findings. Correct and meticulous placement of the flap inside the cystic cavity is the most critical issue for the success of the procedure.

Endoscopic transnasal interseptal approach for invasive clival tumors: development of an approach method regarding maximal preservation of the nasal anatomy

Asian people frequently show small noses, narrow nasal apertures, and congestive mucosa on the turbinates and septum. To reduce the risk of nasal morbidity with increased radicality for skull base tumors in these patients, we developed endoscopic transnasal interseptal approach (ETISA) in transsphenoidal surgery for invasive clival tumors (ICTs). Indication for ETISA is radical resection for tumors occupying deep ventral skull base regions, confined posterior to the level of the middle turbinates. After removing ethmoidal air cells, the middle turbinates are laterally deflected. A linear incision is made vertically on each side of the septal mucosa, which is separated from the bony septum as far as the sphenoid rostrum. The blades of an adjustable speculum are inserted submucosally, and the bony septum is temporarily displaced. The surgical pathway is widely maintained from the entrance to the deep surgical field without sacrificing the nasal mucosa and turbinates. Thirty-two consecutive patients with clival tumors (18 chordomas, 11 chondrosarcomas, 3 others) were treated. Bilateral middle turbinectomy was routinely performed in the initial 3 patients, but in only 4 of the remaining 29 (3 unilaterally, 1 bilaterally). Tumor was sufficiently resected in 29 patients (90.6%; gross total removal n = 25, subtotal resection n = 4). As complications, 6 patients showed mild and transient worsening of cranial nerve symptoms. Nasal complications arose in 3 patients, persisting > 3 months in 2 (5.7%). This approach allows fine bimanual handling and swift delivery of surgical equipment while reasonably preserving the nasal anatomy, which is useful in endoscopic transsphenoidal surgery for ICT.