Petrous apex cholesterol granulomas: endonasal versus infracochlear approach

Radiological Classification and Management Algorithm of Petrous Apex Cholesterol Granuloma

Background: Petrous apex cholesterol granulomas (PACGs) are benign inflammatory cystic lesions of the temporal bone. Usually, asymptomatic patients may develop symptoms as the lesions expand. The diagnosis is based on both CT and MRI scans and the management relies on "wait and scan" or surgery. This paper aims at evaluating surgical outcomes and proposing a CT-based classification and a management algorithm. Methods: Patients with PACGs who were surgically treated between 2014 and 2024 were included. Symptoms, imaging, approach type and complications were considered. CT scans were classified as Type A (preserved apex cellularity), Type B (erosion of the apex cellularity), and Type C (involvement of the noble structures bone boundaries). The possible connection of the lesion with the infracochlear, perilabyrinthine and sphenoidal cellularity was assessed. Results: Nineteen patients with symptoms like diplopia, headache and sensorineural hearing loss were included. According to our classification, 1/19 patients was Type A, 4/19 were Type B and 14/19 were Type C. Five patients underwent a total resection, seven a subtotal and seven a surgical drainage. Only two complications were recorded, and 17/19 patients showed symptom regression and stability during follow-up. Conclusions: While the management of PACGs is still controversial, according to our classification and surgical outcomes, Type A, being mostly asymptomatic, should be managed with "wait and scan", Type B should undergo surgery when symptoms are present, while Type C should always undergo surgery because of their invasiveness and potential complications. When possible, a drainage should be attempted; otherwise, a surgical resection is chosen, and its completeness depends on the preoperative general and hearing status.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Endoscopic Endonasal and Endoscopic-Assisted Transmaxillary Transpterygoid Approaches

Introduction  The endoscopic endonasal transpterygoid approach (EETPA) with or without the addition of the endoscopic-assisted sublabial anterior transmaxillary approach (ESTA) has become increasingly utilized for lesions posterior to the pterygopalatine fossa (PPF), including infratemporal fossa (ITF), lateral recess of the sphenoid sinus, Meckel's cave, petrous apex, and parapharyngeal space. The main goal of this study is to develop an educational resource to learn the steps of the EETPA for trainees. Methods  EETPA and ESTA were performed in 12 specimens by neurosurgery trainees, under supervision from the senior authors. One EETPA and one ESTA were performed on each specimen on opposite sides. Dissections were supplemented with representative cases. Results  After a wide unilateral sphenoidotomy, ethmoidectomy, and partial medial maxillectomy, the anteromedial bone limits of the PPF were identified and drilled out. The pterygoid progress was modularly removed. By enlarging the opening of the posterior and lateral walls of the maxillary sinus through EETPA and ESTA, respectively, the neurovascular and muscular compartments of the PPF and ITF were better identified. The EETPA opens direct corridors to the PPF, medial ITF, middle cranial fossa, cavernous sinus, Meckel's cave, petrous apex, and internal carotid artery. If a more lateral exposure of the ITF is needed, the ESTA is an appropriate addition. Conclusion  Despite the steep learning curve of the EETPA, granular knowledge of its surgical anatomy and basic surgical steps are vital for those advancing their learning in complex endoscopic approaches to the ventral skull base when expanding the approach laterally in the coronal plane.

Cyst-to-Mastoid Antrum Diversion as an Alternate Pathway for Management of Small Symptomatic Petrous Apex Cholesterol Granuloma Without Anteromedial Expansion Using an Extradural Middle Fossa Approach: A Technical Case Report

BACKGROUND AND IMPORTANCE

Cholesterol granuloma (CG) is the most common petrous apex (PA) cystic lesion. Posterolateral expansion of a PA CG (PACG) compresses the internal auditory canal (IAC), leading to vestibulocochlear (VC) and facial nerve dysfunction. Even small, symptomatic PACGs are managed surgically. The preferred strategy is not complete removal, but drainage and aeration. PACG with anteromedial expansion using an endoscopic endonasal approach provides natural drainage into the nasal sinus without risking VC and facial dysfunction. Endoscopic endonasal approach is inappropriate for small PACGs without anteromedial expansion because of potential damage to the petrous internal carotid artery. Small PACGs without anteromedial expansion are managed using extradural middle fossa (EMF) approach, which lacks a natural drainage pathway, thus necessitating an artificial drainage pathway for PACG aeration to prevent recurrence. We introduced EMF approach for CG decompression and cyst-to-mastoid antrum (MA) diversion for managing small, symptomatic PACGs without anteromedial expansion.

CLINICAL PRESENTATION

A 48-year-old woman presented with headache, vertigo, tinnitus, and left hemifacial spasm with preserved hearing because of IAC compression caused by a small PACG without anteromedial expansion. Using the EMF approach, the CG and IAC were safely decompressed. Effective and long-standing artificial drainage for CG aeration was established by anterior petrosectomy and silicone tubing from the CG into the MA. Surgery resolved the symptoms, which have not recurred in 3 years.

CONCLUSION

Granuloma decompression and cyst-to-MA diversion using silicone tubing using the EMF approach is a safe and effective surgical management for small, symptomatic PACG without anteromedial expansion.

Contralateral Transmaxillary Approach to Petrous Apex Granuloma with Lateral Maxillotomy: 2-Dimensional Operative Video

The endoscopic endonasal approach (EEA) has proven to be a valuable tool to access the petrous apex (PA).¹ Although lesions located medial to the PA can be easily accessed through an EEA with minimal risk to the internal carotid artery (ICA), more laterally seated lesions represent a surgical challenge. The contralateral transmaxillary approach is an effective extension of the normal EEA to the PA, allowing a more lateral trajectory and thereby reducing the risks connected to paraclival ICA manipulation.^2-4 This is a 47-year-old female presenting with tinnitus, hearing loss, and right facial twitching. The preoperative audiogram showed a 60 dB sensorineural hearing loss, and magnetic resonance imaging demonstrated an expansive lesion of the PA with high signal intensity in T1- and T2-weighted sequences. A high-riding jugular bulb ruled out the use of an infracochlear infralabyrinthine approach, and a middle cranial fossa approach was felt to render a high risk of recurrence due to the potential for incomplete resection. Ultimately, a contralateral transmaxillary approach was selected. Due to the extreme lateral position of the lesion, the maxillotomy was created in the lateral wall of the maxillary sinus to allow a coaxial approach to the PA. Postoperatively, the patient did not report new neurologic deficits. Anatomic pathology was consistent with cholesterol granuloma (Video 1). In the surgical management of PA granulomas, recognizing relevant anatomic structures such as the paraclival ICA, cochlea, jugular bulb, and vestibule preoperatively is of paramount importance to tailor the surgical approach and reduce its risks.

Combined endoscopic endonasal and transorbital multiportal approach for complex skull base lesions involving multiple compartments

PURPOSE

This study defines the specific areas that connect the surgical corridors of the endoscopic endonasal (EEA) and transorbital approach (TOA) to identify adequate clinical applications and perspectives of this combined multiportal approach.

METHODS

Consecutive patients who underwent combined EEA and TOA procedures for various pathologies involving multiple compartments of the skull base were enrolled.

RESULTS

A total of eight patients (2 chondrosarcomas, 2 meningiomas, 2 schwannomas, 1 glioma, and 1 traumatic optic neuropathy) were included between August 2016 and April 2021. The cavernous sinus (CS) was targeted as the connection area of the combined approach in four patients with tumors infiltrating the middle cranial fossa (MCF) and central skull base through the CS. For two patients with MCF tumors extending into the infratemporal fossa (ITF), the horizontal portion of the greater sphenoid wing and the foramen ovale were utilized as the connection area. In the remaining 2 patients, connection was achieved through the optic canal (OC). Gross total and near total resection was achieved in 5 patients with tumors, and circumferential removal of bone composing the OC was performed in one patient with traumatic compressive optic neuropathy. Postoperative complications included one cardiac arrest due to underlying cardiovascular disease and one case of oculomotor nerve palsy.

CONCLUSIONS

The combined EEA and TOA procedure is a useful strategy for complex lesions involving multiple compartments of the skull base. Herein, we identified the specific areas connecting the two surgical approaches, allowing a common path for EEA and TOA procedures.

Endoscopic Endonasal Surgical Strategy for Skull Base Chordomas Based on Tumor Growth Directions: Surgical Outcomes of 167 Patients During 3 Years

Background

Skull base chordomas (SBCs) are rare malignant bone tumors with dismal long-term local control. Endoscopic endonasal surgeries (EESs) are increasingly adopted to resect SBCs recently. Gross total resection (GTR) favors good outcomes. However, the SBCs often invade the skull base extensively and hide behind vital neurovascular structures; the tumors were challenging to remove entirely. To improve the GTR, we established a surgical strategy for EES according to the tumor growth directions.

Methods

A total of 112 patients with SBCs from 2018 to 2019 were classified into the derivation group. We retrospectively analyzed their radiologic images and operation videos to find the accurate tumor locations. By doing so, we confirmed the tumor growth directions and established a surgical strategy. Fifty-five patients who were operated on in 2020 were regarded as the validation group, and we performed their operations following the surgical strategy to verify its value.

Results

In the derivation group, 78.6% of SBCs invade the dorsum sellae and posterior clinoid process region. 62.5% and 69.6% of tumors extend to the left and right posterior spaces of cavernous ICA, respectively. 59.8% and 61.6% of tumors extend to the left and right posterior spaces of paraclival and lacerum ICA (pc-la ICA), respectively. 30.4% and 28.6% of tumors extended along the left and right petroclival fissures that extend toward the jugular foramen, respectively. 30.4% of tumors involved the foramen magnum and craniocervical junction region. The GTR was achieved in 60.8% of patients with primary SBCs in the derivation group. Based on the tumors’ growth pattern, pituitary transposition and posterior clinoidectomy techniques were adopted to resect tumors that hid behind cavernous ICA. Paraclival ICA transposition was used when the tumor invaded the posterior spaces of pc-la ICA. Lacerum fibrocartilage resection and eustachian tube transposition may be warranted to resect the tumors that extended to the jugular foramen. GTR was achieved in 75.0% of patients with primary SBCs in the validation group.

Conclusion

Besides the midline clival region, the SBCs frequently grow into the eight spaces mentioned above. The surgical strategy based on the growth pattern contributes to increasing the GTR rate.

Endoscopic endonasal and transorbital approaches to petrous apex lesions

OBJECTIVE

The petrous apex (PA) is one of the most challenging areas in skull base surgery because it is surrounded by numerous critical neurovascular structures. The authors analyzed the clinical outcomes of patients who underwent endoscopic endonasal approach (EEA) and transorbital approach (TOA) procedures for lesions involving PA to determine the perspectives and proper applications of these two approaches.

METHODS

The authors included patients younger than 80 years with lesions involving PA who were treated between May 2015 and December 2019 and had regular follow-up MR images available for analysis. Patients with meningioma involving petroclival regions were excluded. The authors classified PA into three regions: superior to the petrous segment of the internal carotid artery (p-ICA) (zone 1); posterior to p-ICA (zone 2); and inferior to p-ICA (zone 3). Demographic data, preoperative clinical and radiological findings, surgical outcomes, and morbidities were reviewed.

RESULTS

A total of 19 patients with lesions involving PA were included. Ten patients had malignant tumor (chondrosarcoma, chordoma, and osteosarcoma), and 6 had benign tumor (schwannoma, Cushing's disease, teratoma, etc.). Three patients had PA cephalocele (PAC). Thirteen patients underwent EEA, and 5 underwent TOA. Simultaneous combined EEA and TOA was performed on 1 patient. Thirteen of 16 patients (81.3%) had gross- or near-total resection. Tumors within PA were completely resected from 13 of 16 patients using a view limited to only the PA. Complete obliteration of PAC was achieved in all patients. Postoperative complications included 2 cases of CSF leak, 1 case of injury to ICA, 1 fatality due to sudden herniation of the brainstem, and 1 case of postoperative diplopia.

CONCLUSIONS

EEA is a versatile surgical approach for lesions involving all three zones of PA. Clival tumor spreading to PA in a medial-to-lateral direction is a good indication for EEA. TOA provided a direct surgical corridor to the superior portion of PA (zone 1). Patients with disease with cystic nature are good candidates for TOA. TOA may be a reasonable alternative surgical treatment for select pathologies involving PA.

Endoscope Assisted Subcochlear Approach for Symptomatic Petrous Apex Effusion

ABSTRACT

Petrous apex effusions are rare disorders and usually occur in the petrous apex (PA) having well-aerated cells and it may present with several symptoms or can be diagnosed incidentally on imaging methods obtained for another reason. If there are persistent symptoms despite the conservative treatment in symptomatic patients, a surgical attempt can be considered. In patients with favorable hearing levels and with the well-pneumatized petrous bone, PA cells may be effectively drained through subcochlear or supracochlear approaches by preserving patient's hearing levels. In this case report, the authors presented a severe symptomatic patient with petrous apex effusion who did not respond to conservative treatment and petrous apex drainage was performed via the subcochlear approach.

Mucosal Grafting Reduces Recurrence After Endonasal Surgery of Petrous Apex Cholesterol Granulomas

OBJECTIVES/HYPOTHESIS

The endoscopic endonasal approach (EEA) is increasingly utilized for management of petrous apex cholesterol granuloma (PACG). Surgical goals include drainage and marsupialization of the cyst. Various techniques have been described to try to reduce the rates of recurrence. We studied the effect of mucosal grafting on recurrence.

STUDY DESIGN

Retrospective Cohort study.

METHODS

Patients who underwent EEA for PACG at two tertiary care centers between 1999 and 2018 were identified and divided into two cohorts: Mucosal versus no mucosal reconstruction. Surgical approach, reconstructive method, and recurrence were recorded. Primary endpoint was symptomatic or radiographic recurrence.

RESULTS

Thirty-four patients were identified undergoing 37 surgeries. Four patients developed recurrences of which three elected to undergo revision. Some form of mucosa was used to line the drainage tract in 20 cases. A free mucosal graft was used in 8, and a small customized nasal septal flap (miniflap) in 12. All four recurrences occurred in cases where no mucosa was used, demonstrating decreased recurrences with mucosal reconstruction (P < .05). There was no difference found between free mucosal grafts and miniflaps.

CONCLUSIONS

Utilization of mucosa to partially line a circumferentially de-epithelialized drainage pathway after EEA for PACG reduce recurrence rates.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:E2513-E2517, 2021.

Surgical anatomy of the transcanal infracochlear approach

PURPOSE

The objective of this study is to describe the detailed surgical anatomy of the infracochlear approach to prevent complications and to compare the postauricular transcanal microscopic and endoscopic approaches to reach the petrous apex.

METHODS

Cadaver heads were dissected using a binocular surgical microscope, endoscopes, and an electric drill. The dimensions of the access field that could be reached and manipulated with surgical instruments and straight drill via postauricular transcanal microscopic and endoscopic approaches were evaluated.

RESULTS

Both postauricular microscopic and transcanal endoscopic approaches were considered to be inapplicable in cases with a tympanic cavity located jugular bulb closer than 3 mm to the cochlea. This relationship was seen in 3 (9%) sides of the cadavers. In 4 specimens (12%), a cochlear aqueduct with an open lumen was detected. Both postauricular microscopic and transcanal endoscopic approaches reached a nearly identic dissection area. Detailed anatomy of the approach and measurements about the topography of the third portion of the facial nerve from the tympanic cavity were presented.

CONCLUSION

Both traditional microscopic postauricular and endoscopic transcanal approaches provided comparable access areas to the inferior petrous apex with wide exposure, and radiologic measurements were compatible. A tympanic cavity located jugular bulb in close relation with cochlea was the only instance that restricted the applicability of this technique.

Experience With the Endoscopic Contralateral Transmaxillary Approach to the Petroclival Skull Base

OBJECTIVES/HYPOTHESIS

The contralateral transmaxillary (CTM) approach is a new surgical approach that improves the surgical trajectory relative to the petrous segment of the internal carotid artery (ICA). Here, we present our clinical experience with the CTM approach to the petroclival region of the skull base.

STUDY DESIGN

Retrospective review.

METHODS

A retrospective review of 29 patients who underwent a CTM approach for skull base pathology from 2015 to 2020 was performed. Assessment of gross total resection (GTR) was based on postoperative imaging.

RESULTS

The male:female ratio was 15:14, with an average age of 52 years (range = 19-78 years). Diagnoses included: 12 chondrosarcomas, 11 chordomas, two meningiomas, one schwannoma, one metastasis, one petrous apicitis, and one arachnoid cyst. CTM was performed in addition to a transclival approach and ipsilateral transpterygoid approach in all patients. Reconstruction of surgical defects included a vascularized flap in all but two patients: 24 nasoseptal flaps and three lateral nasal wall flaps. The reconstructive flap was on the same side as the CTM approach in 22 of 28 (79%) patients. There were no ICA injuries. In a subset of patients with chondromatous tumors, GTR of the targeted area was achieved in 16 of 22 (73%) evaluable chondromatous tumors. With a median follow-up of 13 months, 64% of these patients are without disease or dead of other causes; the remainder are alive with disease.

CONCLUSIONS

The CTM approach improves the degree of resection of skull base tumors involving the petroclival region using an endoscopic endonasal approach and may minimize risk to the ICA.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:294-298, 2021.

Cholesterol Granulomas: A Comparative Meta-Analysis of Endonasal Endoscopic versus Open Approaches to the Petrous Apex

Petrous apex cholesterol granulomas (PACG) are rare disorders that can lead to patient morbidity and must, occasionally, be drained by either endoscopic endonasal (EN) or open procedures (OP). The objective of our study was to complete a review of the literature to compare the EN and OP approaches on multiple levels, notably on safety and effectiveness. Ovid MEDLINE and Embase were used to perform a thorough literature review of all cases of PACG treated by either EN or OP dating from January 1948 to August 2017. In total, 49 articles were selected including 23 for EN (n=76) and 26 for OP (n=210). Differences were found in the incidence of preoperative hearing loss (HL) (EN 18.4%, OP 57.3%; p<0.001), headache (EN 48.7%, OP 31.2%; p=0.007), and disequilibrium (EN: 14.5%, OP 26.1%; p=0.04). Differences in lesion proximity to the sphenoid sinus (EN 23.6%, OP: 1.0%; p<0.001), clivus (EN 11.8%, OP 4.7%; p=0.03), otic capsule (EN 0.0%, OP 5.2%; p=0.03), internal auditory canal (EN 2.6%, OP 10.9%; p=0.01), and internal carotid artery (ICA) (EN 9.2%, OP 2.8%; p=0.02) were found on preoperative imaging. The EN procedure had better hearing improvement rates (EN 85.7%, OP 23.4%; p<0.001), lower complication rates (EN 7.9%, OP 17.6%; p=0.04), shorter median follow-up (EN:13.5 months, OP:37.2 months; p<0.001), and shorter time to recurrence (EN 3 months, OP 22.6 months; p=0.002) than the known OP. No differences were found in age, preoperative size, recurrence rate, operative time, stent placement, or improvement of other symptoms. Endoscopic nasal approaches, when feasible, should be favored to open procedures for PACG drainage given their better hearing improvement and less complication rates.

A Comparative Study Between Traditional Microscopic Surgeries and Endoscopic Endonasal Surgery for Skull Base Chordomas

BACKGROUND

Skull base chordomas (SBCs) are rare clinically aggressive neoplasms, developing local recurrences after surgical resection. Although SBCs have traditionally been resected by craniotomy or microscopic transsphenoidal surgery (TSS), the recent development of the endoscopic endonasal approach (EEA) has revolutionized treatment strategies through minimally invasive techniques. This study aimed to evaluate clinical outcomes after traditional microsurgeries or EEAs for SBCs.

METHODS

The present retrospective study investigated 66 patients with primary SBCs who underwent surgery between 1977 and 2019. Resection was performed via EEA in 17 cases, craniotomy in 23, transoral approach in 8, TSS in 12, staged surgery in 4, and others in 2. The median follow-up period for progression-free survival (PFS) was 19.5 months.

RESULTS

There were no significant differences in preoperative tumor volume or resection rate among these approaches. The incidence of postoperative cranial nerve palsy was significantly lower in EEA than that in craniotomy (P < 0.05). Although total resection was observed in 4 cases of EEA expanding into the superior and inferior part of the clivus, no cases of transoral approach or TSS achieved total resection for both parts. No significant difference in PFS was found among these approaches. Multivariate analysis showed that being female and the absence of radiotherapy were significantly associated with shorter PFS (P < 0.05 and P < 0.001, respectively). The resection rate was not associated with PFS.

CONCLUSIONS

EEA is a less invasive surgical approach for SBCs. The development of surgical instruments and postoperative radiotherapy will further improve patients' outcomes.

[The infracochlear approach for diagnostic petrous apicotomy]

Diagnostic and therapeutic approaches to the petrous apex involve sub-/transtemporal, retrosigmoidal, infratemporal and-lesser invasive-e. g. infracochlear, infralabyrinthine or under favourable anatomic conditions, transsphenoidal surgical pathways. For diagnostic purposes, minimally invasive approaches should be preferred due to their lesser morbidity. This article illustrates the infracochlear approach to the petrous apex in the case of a diagnostic indication in a patient with an incidental, asymptomatic tumorous lesion of the right petrous apex with bony erosion. After the bone of the floor of the ear canal and the hypotympanum was removed, the carotid artery and the jugular bulb were identified using a diamond burr. The route to the petrous apex is triangled by the cochlea superiorly, the jugular bulb posteriorly, and the carotid artery anteriorly. After opening the petrous apex lesion, biopsies were taken. The defect in the floor of the ear canal and the hypotympanum was reconstructed with cartilage and temporalis fascia. The patient recovered quickly from surgery without vertigo or hearing loss. Histological evaluation showed a chondrosarcoma. The patient opted for primary radiation therapy (C12, 63 Gy). The infracochlear approach is minimally invasive and can offer access to the petrous apex with minimal morbidity. The pathway, however, is narrow and deep and bounded by the jugular bulb and the carotid artery. The available space can be estimated from preoperative CT scans and, if possible, with 3D reconstructions. Navigation can additionally enhance safety.

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.

A morphometric study of the structures bordering the infra-cochlear corridor - Relevant for endoscopic/microscopic ear surgery

Application of surgical endoscope, used alone or in combination with the surgical microscope, for the operative management of ear and temporal bone conditions may allow improved access and clearance of disease. Preservation of normal structures may also be improved.

As the use of this tool is increasing, the need for better understanding of the anatomy of the ear is becoming evident. This is particularly so for endoscopic surgery aiming at removal of lesions involving the infra-cochlear corridor and/or petrous apex.

Human temporal bone-derived labyrinth casts (molds), originally made for endolymphatic duct and sac analysis which genuinely represent the membranous labyrinth and its adjacent soft tissues, were morphometrically analyzed in terms of the anatomic relations between structures in and around the infra-cochlear corridor. The distance between the petrous carotid artery (PCA) and the basal turn of the cochlea, the distance between PCA and infra-cochlear vein (ICV)/cochlear aqueduct (CA), and the distance between the lower surface of basal cochlear turn and the point where the carotid artery and jugular vein (JV) meet close to the jugular foramen, were measured to be around 1.3 mm, 6 mm and 8 mm respectively, thus constituting an approximate 6 × 8 mm² infra-cochlear corridor. This analysis and further study with larger samples might be helpful for operation via this corridor led to the petrous apex where cholesterol granuloma, cholesteatoma and other lesions are not uncommon.

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.

Quantitative imaging analysis of transcanal endoscopic Infracochlear approach to the internal auditory canal

PURPOSE

A transcanal endoscopic infracochlear surgical approach to the internal auditory canal (IAC) in a human temporal bone model has previously been described. However, the proportion of patients with favorable anatomy for this novel surgical technique remains unknown. Herein, we perform a quantitative analysis of the transcanal endoscopic infracochlear corridor to the IAC based on computed tomography.

MATERIALS AND METHODS

High resolution computed tomography scans of adult temporal bones were measured to determine the accessibility of the IAC when using an endoscopic transcanal, cochlear-sparing surgical corridor.

RESULTS

This approach to the IAC was feasible in 92% (35 of 38) specimens based on a minimum distance of 3mm between the basilar turn of the cochlear and the great vessels (jugular bulb and carotid artery).

CONCLUSIONS

Infracochlear access to the IAC is feasible in the majority of adult temporal bones and has implications for future hearing preservation drug delivery approaches to the IAC.

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.

Quantification and comparison of neurosurgical approaches in the preclinical setting: literature review

There is a growing awareness of the need for evidence-based surgery and of the issues that are specific to research in surgery. Well-conducted anatomical studies can represent the first, preclinical step for evidence-based surgical innovation and evaluation. In the last two decades, various reports have quantified and compared neurosurgical approaches in the anatomy laboratory using different methods and technology. The aim of this study was to critically review these papers. A PubMed and Scopus search was performed to select articles that quantified and compared different neurosurgical approaches in the preclinical setting. The basic characteristics that anatomically define a surgical approach were defined. Each study was analyzed for measured features and quantification method and technique. Ninety-nine papers, published from 1990 to 2013, were included in this review. A heterogeneous use of terms to define the features of a surgical approach was evident. Different methods to study these features have been reported; they are generally based on quantification of distances, angles, and areas. Measuring tools have evolved from the simple ruler to frameless stereotactic devices. The reported methods have each specific advantages and limits; a common limitation is the lack of 3D visualization and surgical volume quantification. There is a need for a uniform nomenclature in anatomical studies. Frameless stereotactic devices provide a powerful tool for anatomical studies. Volume quantification and 3D visualization of the surgical approach is not provided with most available methods.

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.

Endoscopic Transnasal Approach for Cholesterol Granuloma of the Petrous Apex

Cholesterol granulomas are rare round or ovoid cysts. They contain cholesterol crystals surrounded by foreign bodies of giant cells and are characterized by chronic inflammation. Large cholesterol granuloma can compress surrounding tissue especially cranial nerves. There are several types of surgery for the resection of cholesterol granuloma. We describe 4 cases of cholesterol granuloma operated on via transnasal endoscopic approach. In this report, we describe radiologic and pathologic features of this lesion and explain the advantages and disadvantages of transsphenoidal endoscopic approach for these rare lesions.

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 transsphenoidal drainage of an aggressive petrous apex cholesterol granuloma: unusual complications and lessons learnt

OBJECTIVES

This case report describes the endoscopic transsphenoidal management of a cholesterol granuloma situated in a technically challenging part of the petrous apex, and the associated peri- and post-operative complications that arose. The literature on diagnosis and management of petrous apex cholesterol granulomas is reviewed.

METHOD AND RESULTS

Surgical intervention was attempted on three occasions, each time via an endoscopic, transsphenoidal approach with image guidance. The procedure was abandoned on the first occasion as there was a significant risk to the carotid artery; only a small drainage ostium was created because of the proximity of the carotid artery. The second attempt, complicated by copious bleeding from the clival venous plexus, was arrested prematurely. Successful drainage was achieved at the third attempt, but recovery was complicated by tension pneumocephalus.

CONCLUSION

The transnasal route is less invasive than a lateral labyrinthine or cochlear approach, and spares cochlear and vestibular function. However, this approach is not without risk. It is important to consider the natural anatomical variance of vasculature when planning surgical intervention for a lesion situated in a technically challenging part of the petrous apex. Additional magnetic resonance venography is recommended to circumnavigate the venous plexus, thereby avoiding an unexpected breach.

Clival chordomas: A pathological, surgical, and radiotherapeutic review

BACKGROUND

The purpose of this study was to discuss the optimal management of patients with clival chordomas and provide an up-to-date review of the field.

METHODS

A schematic description of the anatomy of the clivus and its surrounding structures is provided based on the modular classification of the surgical corridors used in endoscopic skull base surgery. Postoperative radiotherapy (RT) techniques are described.

RESULTS

The optimal treatment is gross total resection. Recent advances in endoscopic endonasal skull base surgery have allowed very high rates of macroscopic and radiographic complete tumor resection in spite of the challenging location of these lesions. When the tumor location or extension is too lateral or inferior to be effectively resected with an endoscopic approach, an open approach or a combination of endoscopic and open approaches in stages should be considered. Postoperative RT is usually indicated because the likelihood of recurrence is high in spite of complete surgical resection. The main site of recurrence is local and late recurrences are relatively common. The probability of cure is approximately 50% at 10 years and significantly increases when complete tumor resection has been achieved.

CONCLUSION

The preferred treatment for patients with clival chordoma is gross total resection (via endoscopic endonasal surgery when possible) followed by postoperative RT. Treatment at experienced multidisciplinary cranial base centers is key to minimize complications and to enhance the probability of total removal of the tumors.