360° to the Petrous Apex: Comprehensive Surgical Anatomy and Limitations of Open and Endoscopic Endonasal Approaches to the Petrous Apex.

Surgical approaches to the petrous apex region are extremely challenging; while subtemporal approaches and variations represent the milestone of the surgical modules to reach such deep anatomical target, in a constant effort to develop minimally invasive neurosurgical routes, the endoscopic endonasal approach (EEA) has been tested to get a viable corridor to the petroclival junction. Lately, another ventral endoscopic minimally invasive route, i.e., the superior eyelid endoscopic transorbital approach, has been proposed to access the most lateral aspect of the skull base, including the petrous apex region. Our anatomic study aims to compare and combine such two endoscopic minimally invasive pathways to get full access to the petrous apex. Three-dimensional reconstructions and quantitative and morphometric data have been provided. Five human cadaveric heads (10 sides) were dissected. The lab rehearsals were run as follows: (i) preliminary pre-operative CT scans of each specimen, (ii) pre-dissection planning of the petrous apex removal and its quantification, (iii) petrous apex removal via endoscopic endonasal route, (iv) post-operative CT scans, (v) petrous apex removal via endoscopic transorbital route, and (v) final post-operative CT scan with quantitative analysis. Neuronavigation was used to guide all dissections. The two endoscopic minimally invasive pathways allowed a different visualization and perspective of the petrous apex, and its surrounding neurovascular structures. After both corridors were completed, a communication between the surgical pathways was highlighted, in a so-called connection area, surrounded by the following important neurovascular structures: anteriorly, the internal carotid artery and the Gasserian ganglion; laterally, the internal acoustic canal; superiorly, the abducens nerve, the trigeminal root, and the tentorium cerebelli; inferomedially, the remaining clivus and the inferior petrosal sinus; and posteriorly, the exposed area of the brainstem. Used in a combined fashion, such multiportal approach provided a total of 97% of petrous apex removal. In particular, the transorbital route achieved a mean of 48.3% removal in the most superolateral portion of the petrous apex, whereas the endonasal approach provided a mean of 48.7% bone removal in the most inferomedial part. The difference between the two approaches was found to be not statistically significant (p= 0.67). The multiportal combined endoscopic endonasal and transorbital approach to the petrous apex provides an overall bone removal volume of 97% off the petrous apex. In this paper, we highlighted that it was possible to uncover a common path between these two surgical pathways (endonasal and transorbital) in a so-called connection area. Potential indications of this multiportal approach may be lesions placed in or invading the petrous apex and petroclival regions that can be inadequately reached via transcranial paths or via an endonasal endoscopic route alone.

Objectives This study aimed to establish the anatomical landmarks for performing a contralateral transmaxillary approach (CTM) to the petrous apex (PA) and petroclival region (PCR), and to compare CTM with a purely endoscopic endonasal approach (EEA). Design EEA and CTM to the PA and PCR were performed bilaterally in eight human anatomical specimens. Surgical techniques and anatomical landmarks were described, and EEA was compared with CTM with respect to ability to reach the contralateral internal acoustic canal (IAC). Computed tomographic scans of 25 cadaveric heads were analyzed and the "angle" and "reach" of CTM and EEA were measured. Results Entry to the PA via a medial approach was limited by (1) abducens nerve superiorly, (2) internal carotid artery (ICA) laterally, and (3) petroclival synchondrosis inferiorly (Gardner's triangle). With CTM, it was possible to reach the contralateral IAC bilaterally in all specimens dissected, without dissection of the ipsilateral ICAs, pterygopalatine fossae, and Eustachian tubes. Without CTM, reaching the contralateral IAC was possible only if: (1) angled endoscopes and instruments were employed or (2) the pterygopalatine fossa was dissected with mobilization of the ICA and resection of the Eustachian tube. The average "angle" and "reach" advantages for CTM were 25.6-degree greater angle of approach behind the petrous ICA and 1.4-cm more lateral reach. Conclusion The techniques and anatomical landmarks for CTM to the PA and PCR are described. Compared with a purely EEA, the CTM provides significant "angle" and "reach" advantages for the PA and PCR.

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.

The endoscopic endonasal approach (EEA) was recently added to the neurosurgical armamentarium as an alternative approach to the petrous apex (PA) region. However, the maximal extension, anatomical landmarks, and indications of this procedure remain to be established. To investigate the limitations and suggest a classification of PA lesions for endoscopic petrosectomy. Five anatomical specimens were dissected with EEA to the PA. Anatomical landmarks for the surgical steps and maximal limits were noted. Pre- and postprocedural computed tomographic scan and image-guidance were used. Relevant surgical cases were reviewed and presented. We defined 3 types of petrosectomy: medial, inferior, and inferomedial. Medial petrosectomy was limited within the paraclival internal carotid artery (ICA) anteriorly, lacerum ICA inferiorly, abducens nerve superiorly, and petrous ICA laterally. Among those, abducens nerve and petrous ICA are surgical limits. Full skeletonization of the paraclival ICA and removal of the lingual process are essential for better access to the medial aspect of PA. Inferior petrosectomy was defined by the lacerum foramen synchondrosis anteriorly, jugular foramen inferiorly, internal acoustic canal posteriorly, and PA superolaterally. Those are surgical limits except for the foramen lacerum synchondrosis. The connective tissue at the pterygosphenoidal fissure was a key landmark for the sublacerum approach. Clinical cases in 3 types of PA lesions were presented. The EEA provides access to the medial and inferior aspects of the PA. Several technical maneuvers, including paraclival and lacerum ICA skeletonization, sublacerum approach, and lingual process removal, are key to maximize PA drilling.

The purpose of this study was to define the patterns of drainage of the superior petrosal venous complex (SPVC) along the petrous ridge in relation to the Meckel cave and internal acoustic meatus (IAM) and to delineate its effect on the surgical exposures obtained in subtemporal transtentorial and retrosigmoid suprameatal approaches. The patterns of drainage of the SPVC along the petrous ridge were characterized according to their relation to the Meckel cave and the IAM based on an examination of 30 hemispheres. Subtemporal transtentorial and retrosigmoid suprameatal approaches were performed in three additional cadavers to demonstrate the effect of the drainage pattern on the surgical exposures. The SPVC emptied into the superior petrosal sinus (SPS) within a distance of 1 cm from the midpoint of the Meckel cave. The patterns of drainage of the SPVC were classified into three groups. Type I emptied into the SPS above and lateral to the boundaries of the IAM. The most common type, Type II, emptied between the lateral limit of the trigeminal nerve at the Meckel cave and the medial limit of the facial nerve at the IAM, within an area of approximately 13 mm. Type III emptied into the SPS above or medial to the Meckel cave. The ideal SPVC for a subtemporal transtentorial approach (with or without anterior extradural petrosectomy) seems to be a Type I. In SPVC Type III and those Type II cases in which the SPVC is located near the Meckel cave, the amount of working space is significantly limited in a subtemporal transtentorial approach. In contrast, the ideal type of SPVC for a retrosigmoid suprameatal approach would be a Type III, and the SPVC must be divided in the majority of Type I and II cases for a satisfactory surgical exposure along the Meckel cave and middle fossa dura. The proposed modified classification system and its effect on the surgical exposure may aid in planning the approach directed along the petrous apex and may reduce the probability of venous complications.

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.

Accessing the petrous apex (PA) via an endoscopic endonasal approach (EEA) is challenging due to its posterior and lateral anatomical relationship with the paraclival carotid artery. Typically, the EEA requires the mobilization or compression of the vessel and the use of angled-lens endoscopes and instruments. A sublabial contralateral transmaxillary (CTM) corridor has been used to overcome these challenges. Still, it requires extensive osteo-meatal disruption and drilling of the medial pterygoid process, which risks the vidian nerve and increases nasal morbidity. Furthermore, the CTM corridor positions the endoscope in the same horizontal plane as the instruments passing through the nostrils, leading to fencing. The authors propose a novel minimally invasive route to the PA, the precaruncular contralateral medial transorbital (cMTO) corridor, to address these issues. This anatomical study compares the EEA+CTM and EEA+cMTO corridors in accessing the PA. The authors dissected 14 fresh, preinjected cadaveric specimens (28 sides) using neuronavigation to complete EEA, cMTO, and CTM on each side. In addition to qualitative analysis, they measured and compared the working distance between the entry point (nose, orbit, maxilla) and the petrosal process of the sphenoid bone (PPSB), superomedial PA, and foramen lacerum (FL); angle of attack (AoA); area of surgical freedom; endoscope-instrument fencing angle; and visual angle for each approach. The cMTO corridor provided the shortest working distance to the petroclival region (PA = 67.4 ± 4.47 mm, PPSB = 67.57 ± 4.33 mm, and FL = 66.30 ± 4.77 mm) compared to the CTM (PA = 75.85 ± 3.63 mm, PPSB = 76 ± 3.96 mm, and FL = 74.52 ± 4.26 mm) and to the EEA (PA = 85.16 ± 3.16 mm, PPSB = 84.55 ± 3.02 mm, and FL = 83.42 ± 3.21 mm, p < 0.001). Both CTM and cMTO corridors had a similar visual angle to the PA (20.72° ± 2.16° and 21.63° ± 1.84°, respectively), offering a similar but significantly better visualization than EEA alone (44.71° ± 3.24°, p < 0.001). The cMTO corridor provided better instrument maneuverability than the CTM, as evidenced by a significantly greater fencing angle (30.9° ± 4.9°) than with the CTM (21.7° ± 4.02°, p < 0.001). The vertical AoAs for the EEA, cMTO, and CTM corridors were 9.79° ± 1.75°, 10.65° ± 0.82°, and 9.82° ± 1.43°, respectively (p = 0.009), whereas in the horizontal plane, these were 9.29° ± 1.51°, 9.10° ± 0.73°, and 10.49° ± 1.43° (p < 0.001), respectively. Both the CTM and cMTO corridors offered similar areas of surgical freedom (678.06 ± 99.5 mm2 and 673.59 ± 104.8 mm2, p = 0.986), but they were more significant than that provided by the EEA 487.29 ± 112.9 mm2 (p < 0.001). The EEA+cMTO multiport technique may be a better alternative than the EEA+CTM multiport approach for targeting the petroclival region. However, clinical validation is required to confirm these laboratory findings.

Objective The purpose of this study was to dissect these structure existed in petrous portions of the temporal bones and the posterior fossa nearby,to measure the distence of those important stuctures around the superior petrosal venous (SPV), to propose the patterns of drainage of the SPV along the petrous ridge in relation to the Meckel cave and internal acoustic meatus (IAM) and to delineate its effect on the surgical exposures obtained in subtemporal transtentorial and retrosigmoid suprameatal approaches. Methods Ten adult cadaveric heads (20 hemispheres) were studied, and data of SPV and the structures around were measured. The patterns of drainage of the SPV along the petrous ridge were characterized according to their relation to the Meckel cave and the IAM based on an examination of 20 hemispheres. Subtemporal trans-tentorial and retrosigmoid suprameatal approaches were performed in two additional cadavers to demonstrate the effect of the drainage pattern on the surgical exposures. Result The SPV originated from the cerebellopontine angle cistern, and were multibranch. According to SPV relationship with the Meckel cave and internal acoustic meatus (IAM), the patterns of drainage of the SPV were classified into three groups. Type Ⅰ emptied into the SPS above or medial to the Meckel cave. The most common type-Type Ⅱ, emptied between the lateral limit of the trigeminal nerve at the Meckel cave and the medial limit of the facial nerve at the IAM. Type Ⅲ emptied into the SPS above and lateral to the boundaries of the IAM Conclusions The site which the SPV emptied into the superior petrosal sinus (SPS) was relationship tightly with the Meckel cave and IAM. According to SPV relationship with the Meckel cave and internal acoustic meatus (IAM). The proposed modified classification system and its effect on the surgical exposure may aid in planning the approach directed along the petrous apex and may reduce the probability of venous complications. Key words: Superior petrosal vein; Superior petrosal sinus; Retrosigmoid approach; Subtemporal approach

This 59-yr-old man presented with headache, dizziness, diplopia, and right-side hearing impairment for years. The objective degree of hearing impairment was not available. Magnetic resonance imaging (MRI) showed a right petrous apex lesion centered behind the right petrous internal carotid artery and extending lateral to the medial aspect of the right internal auditory canal. A combined endoscopic endonasal and left contralateral transmaxillary (CTM) approach was performed, and gross-total resection was achieved. Peeling the cyst wall from the dura resulted in minor weeping. It was covered with a left-sided, vascularized nasoseptal flap. His dizziness and diplopia improved immediately after the surgery. Histopathology revealed an epidermoid cyst. In this surgical video, we demonstrate the key steps of the CTM approach for access to the petrous apex posterior to the petrous internal carotid artery (ICA). The patient gave informed consent for surgery and video recording.

Chronic suppurative otitis media (CSOM) has a potential for intratemporal complications. Gradenigo syndrome, lateral sinus thrombosis and cavernous sinus thrombosis must be considered when patients present with ear discharge, headache, fever and lateral rectus palsy. Computed Tomography and Magnetic Resonance Imaging are essential in confirming the diagnosis but do not substitute for a good clinical eye in establishing the diagnosis and initiating proper treatment.&#x0D; CASE&#x0D; A 17 year old male with an 11-year history of otorrhea on the right ear was admitted because of on-and-off diffuse headache, drowsiness, occasional sensorial changes, high grade fever and vomiting. Later in the ward, he complained of double vision; anisocoria and lateral rectus palsy were confirmed by active generation test. Associated symptoms included right-sided frontal, orbital and mastoid pain with neck stiffness. Otoscopy showed yellowish foul smelling discharge with a pink, smooth mass partially obstructing the external auditory canal.&#x0D; Leukocytosis was seen with a count of 32.9 x 103/L. Pure tone audiometry revealed moderate conductive hearing loss on the right ear. CT scan with contrast (Figure 1) showed lytic erosion of the underpneumatized right mastoid bone and sigmoid sinus plates with slightly asymmetric right internal auditory canal (IAC). Penicillin G 5 million “IU” every 6 hours and Chloramphenicol 1.5 grams IV every 8 hours were given for 3 weeks, but he continued to deteriorate and two units of PRBC were transfused. Because of his worsening condition, Penicillin G was shifted to Ceftriaxone 2 grams IV BID while Chloramphenicol IV was continued at the same dose. The patient’s headache and fever steadily lessened after 4 weeks but orbital pain and diplopia persisted. On the 50th hospital day, patient underwent Modified Radical Mastoidectomy, right. Intraoperatively, granulation tissue was noted occupying the enlarged mastoid cavity and antrum. A 0.5 cm break at the sigmoid sinus was also occupied by granulation tissue. IV antibiotics was continued 2 weeks postoperatively and after 64 days of hospitalization he was discharged on oral Ciprofloxacin 500mg BID for 1 month with steroid/antibiotic otic drops.&#x0D; Regular follow-up documented gradual lessening of diplopia, headache and orbital pain. Complete resolution of diplopia with normal ophthalmologic findings and a dry mastoidectomy cavity were noted on the fourth month of follow-up.&#x0D; &#x0D; &#x0D; DISCUSSION&#x0D; In the Philippines, the prevalence of Chronic Suppurative Otitis Media (CSOM) is estimated at 2.5 – 29.5%.1 Complications of chronic otitis media can cause grave morbidity and even mortality2 even though the intratemporal and/or intracranial complications of infectious ear disease have become rarer with the advent of broad spectrum antibiotics.3 The spread of infection can occur by osteothrombosis, bone erosion and when present along preformed pathways.2 &#x0D; The triad of Gradenigo syndrome includes otorrhea, retroorbital pain and abducens nerve palsy. Chole and Donald found that the most common presenting symptom in 22 patients from 1976-1995 was otalgia (72%) followed by deep pain, headache and otorrhea (59%). Cranial nerve VI paralysis was only present in 18.2% of the cases.4 Homer and others reported 3 cases with middle ear infection and 6th nerve palsy without petrositis. 5&#x0D; MRI and CT are required to identify the deep seated petrous apex as the site of the inflammatory process.6 While CT scans may demonstrate opacification of the air cells of the petrous apex with cortical bone erosion, MRI is very useful for assessing inflammatory soft tissue lesions around the petrous apex.5 Both CT and MRI are essential to establish opacification of air cells in the petrous apex under suspicion, as opposed to assymetric pneumatization.2 However, acute petrositis cannot always be equated with Gradenigo syndrome.7 A study by Back and others documented 8 cases of radiologically confirmed apical petrositis that did not manifest the classical syndrome of deep facial pain, otitis media and ipsilateral abducens nerve palsy.8 &#x0D; Petrous apicitis is essentially mastoiditis that occurs in the petrous apex.2 Because the trigeminal (CN V) or gasserian ganglion lies in Meckel’s cave on the antero-superior aspect of the petrous tip, damage or irritation to the ganglion may explain the deep facial pain in some patients with apicitis. The petroclinoid ligament extends from the tip of the petrous apex to the clinoid. Below this ligament, the gasserian ganglion (CN V) and abducens nerve (CN VI) travel in the small Dorello's canal. Inflammation extending into the canal produces the triad of symptoms recognized by Gradenigo9: lateral rectus (CN VI) palsy, retroorbital pain (CN V), and otorrhea.&#x0D; Lateral Sinus Thrombophlebitis (LST) or thrombosis of the lateral sinus usually forms as an extension of a perisinus abscess following mastoid bone erosion from cholesteatona, granulation tissue or coalescence which eventually leads to pressure necrosis and mural thrombus formation.2 Classic symptoms of LST include a "picket fence" fever pattern, chills and progressive anemia. Symptoms of septic emboli, headache and papilledema may indicate extension to involve the cavernous sinus4 or sudden intracranial hypertension resulting from decreased venous drainage from the skull.2&#x0D; The diagnostic procedure of choice is MRI with MR angiography. The thrombus can be identified by its signal intensity on MRI and the flow void in the affected sinus is clearly documented on MR angiography.10 Non-contrast CT findings include dense cord sign, dense dural sinuses, diffuse cerebral edema, non hemorrhagic infarct or multifocal haemorrhages.11 Papilledema and anisocoria may be symptoms of progression of lateral sinus thrombophlebitis or development of cavernous sinus thrombosis.4 Fresh thrombi from the lateral sinus can propagate and extend to the cavernous sinus via the superior and inferior petrosal sinus.&#x0D; Cavernous Sinus Thrombosis is usually a late complication of an infection of the central face or paranasal sinuses. Other causes include bacteremia, trauma, and infections of the maxillary teeth or ear, as seen in our patient. CST is generally a fulminant process with high rates of morbidity and mortality. Headache is the most common presenting symptom that usually precedes fever, periorbital edema (which may or may not occur) and cranial nerve dysfunction.&#x0D; This intimate relationship of veins, arteries, nerves, meninges, petrous apex and paranasal sinuses account for the characteristic etiology and presentation of CST. The internal carotid artery with its surrounding sympathetic plexus passes through the cavernous sinus. The third, fourth, and sixth cranial nerves are attached to the lateral wall of the sinus while the ophthalmic and maxillary divisions of the fifth cranial nerve are embedded in the wall.8&#x0D; Other signs and symptoms include chemosis resulting from occlusion of the ophthalmic veins, lateral gaze palsy (isolated cranial nerve VI), ptosis, mydriasis and eye muscle weakness from cranial nerve III dysfunction. These are followed by manifestations of increased retrobulbar pressure (such as exophthalmos) and increased intraocular pressure (such as sluggish pupil and decreased visual acuity). Systemic signs indicative of sepsis are late findings.&#x0D; The complications of Gradenigo syndrome, lateral sinus thrombophlebitis and cavernous sinus thrombosis from chronic suppurative otitis media need immediate diagnosis and aggressive medical treatment with broad spectrum antibiotics against gram positive cocci (Staphylococci and Streptococci), gram negative bacilli (Pseudomonas aeruginosa) and to a lesser extent, Anaerobes. These antibiotics should also cross the blood-brain barrier.&#x0D; Mastoidectomy is required once the patient is neurologically stable.2 In cases of lateral sinus thrombosis, surgical removal of emboli can be done. However, Cummings, Syms and colleagues2 report 6 patients operated on without opening and evacuating the lateral sinus clot who all survived, albeit with a longer 49 day average hospital stay. Once a highly controversial issue, ligation of the internal jugular vein is seldom needed. In the majority of recent cases, anticoagulation has not been found to be necessary.2

The goal of the current study is to describe the transnasal endoscopic anatomy of the cavernous sinus and to provide the surgical approaches to this area. Six silicon-injected adult cadaveric heads (12 sides) were dissected through endoscopic endonasal approach. The cavernous sinus and adjacent structures were exposed; detailed anatomies were demonstrated. High-quality pictures were produced. The cavernous sinus had four walls, namely medial, lateral, posterior and superior walls. Five venous spaces within the sinus were identified by their relation to the carotid artery; those were the medial, lateral, posterosuperior, posteroinferior and anterolateral compartments. Three branches arising from the cavernous segment of internal carotid artery from proximal to distal were meningohypophyseal trunk, inferolateral trunk and McConnell capsular artery. Cavernous sinuses communicated each other by intercavernous sinuses, as well as basilar sinus in middle line, and connected with superior and inferior petrosal sinuses. The third and fourth nerves coursed in superior part of the lateral wall of the cavernous sinus; Meckel's cave located in the posteroinferior part of the lateral wall of the cavernous sinus; V1 sloped to the superior orbital fissure along the lateral wall; the sixth nerve entered the posteroinferior compartment then passed through the internal carotid artery and reached to superior orbital fissure. The approaches to the cavernous sinus included trans-sphenoid-sellar-medial cavernous sinus (medial to the internal carotid artery) and trans-ethmoid-pterygoid-sphenoid-lateral cavernous sinus (lateral to the internal carotid artery). Trans-sphenoid-sellar-medial cavernous sinus approach was able to expose medial compartment and posterosuperior compartment and part of posteroinferior compartment. Trans-ethmoid-pterygoid-sphenoid-lateral cavernous sinus approach was able to expose anteroinferior compartment, lateral cavernous sinus and cranial nerves in lateral wall. An understanding of the complex relationships of the cavernous segment of internal carotid artery and cranial nerves in cavernous sinus is paramount for surgically dealing with the disease involved cavernous sinus and adjacent region.

The petrous apex is one of the most challenging areas of the skull base to access. We present a case of residual petrous apex chordoma posterolateral to the paraclival segment of the internal carotid artery (ICA) resected with combined endoscopic endonasal and contralateral transmaxillary (CTM) approaches, without lateralization of the ICA. This case demonstrates the value of the CTM corridor in resecting petrous apex lesions that are posterolateral to the paraclival segment of the ICA.

Since the petroclival region is deep-seated with close neurovascular relationships, the removal of petroclival tumors still represents a fascinating surgical challenge. Although the classical anterior petrosectomy (AP) offers a meaningful access to this petroclival region, the expanded endoscopic endonasal approach (EEEA) recently leads to overcome difficulties from trans-cranial approaches. Herein, we present an anatomic comparison of AP versus EEEA. We aim to describe the limits of these both approaches helping the choice of the optimal surgical route for petroclival tumors. Six fresh cadaveric heads were harvested and injected with colored latex. Each approach was step-by-step detailed until its final surgical exposure. The AP provided a narrow direct supero-lateral access to the petroclival area that can also reach the cavernous sinus, the retrochiasmatic region and perimesencephalic cisterns. However, this corridor anterior to the internal acoustic meatus passed on each side of the trigeminal nerve. Moreover, tumor extensions toward the foramen jugularis, inside the clivus or behind the internal acoustic meatus were difficult to control. The EEEA brought a straightforward access to the clivus but the petrous apex was hidden behind the internal carotid artery. Several variants were described: a medial transclival, a lateral through the Meckel's cave and an inferior trans-pterygoid route. Elsewhere, tumor extension behind the internal acoustic meatus or above the tentorium could not be satisfactorily assessed. PA and EEEA have their own limits in reaching the petroclival region in accordance with the tumor characteristics. The AP should be preferred for radical removal of middle-sized petrous apex intradural tumors like meningiomas. The EEEA would be of interest for extradural midline tumors like chordomas or for petrous apex cysts drainage.

Endoscopic endonasal approaches to the ventral skull base are categorized based on their orientation in coronal and sagittal planes. For all of these approaches, the sphenoid sinus is the starting point, and provides orientation to important vascular and neural structures. Surgical approaches to the petrous apex include 1) a medial approach, 2) a medial approach with internal carotid artery (ICA) lateralization, and 3) a transpterygoid infrapetrous approach (inferior to the petrous internal carotid artery). The choice of a surgical approach depends on the relationship of the lesion to the internal carotid artery (medial or inferior), degree of medial expansion, and pathology. The purpose of this paper is to discuss the anatomic and technical features of endoscopic surgical approaches to the petrous apex, provide a new classification for approaches that focuses on the relationship of the lesion to the petrous internal carotid artery, and provide outcomes data on our first 20 endoscopic petrous apex approaches. A retrospective clinical outcome study of endoscopic petrous apex surgeries was performed at the University of Pittsburgh Medical Center. The medical records from patients with endoscopic endonasal approaches to isolated petrous apex lesions were reviewed for demographics, diagnoses, presentation, endoscopic approach, and clinical outcomes. Patients with lesions that extended into the petrous apex but were not isolated to the petrous apex were excluded (e.g., clival chordoma with extension into the petrous apex). Twenty patients were included in the analysis: 13 inflammatory cystic lesions (9 cholesterol granulomas and four petrous apicitis) and 7 solid lesions. Chondrosarcoma was the most common solid petrous apex lesion in our series. Twelve of 13 cystic lesions were drained endoscopically (one surgery was aborted early in the series). All drained patients had resolution of presenting symptoms. One patient had closure of the outflow tract without return of symptoms and one patient had revision endoscopic drainage due to scarring and neo-osteogenesis and return of unilateral headache. No carotid injuries and no new cranial neuropathies occurred perioperatively. The advantages and limitations of the medial transsphenoidal approaches (with and without carotid mobilization) and the transpterygoid infrapetrous approach are discussed. The endoscopic endonasal approach to petrous apex lesions is safe and effective for appropriately selected patients in the hands of experienced endoscopic skull base surgeons. If offers advantages of removing the hearing and facial nerve risks from the transtemporal/transcranial approaches and allows for a larger and more natural drainage pathway into the sinuses.

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. 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. 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.