The trans-sylvian trans-petrosal "half & half" approach-a how I do it.

BACKGROUND: Petroclival meningiomas are one of the most challenging tumors to be operated in the realm of neurosurgery. Many approaches have been developed over the years. METHOD: The authors describe the Half & Half (H&H) approach whose main indication is petroclival meningiomas with suprasellar extension. The part of the tumor located above CN III and in the retrochiasmatic space is addressed through a trans-sylvian, while the petroclival portion is through an extradural anterior petrosectomy approach. The wide surgical corridor given by this approach allows extensive tumor resection while avoiding the risk associated with the manipulation of intracavernous neurovascular structures. CONCLUSION: The H&H approach is an effective strategy to maximize the safe resection of petroclival meningiomas.

Combined retrosigmoid and middle fossa approach for a small, superiorly located petroclival meningioma: how I do it.

BACKGROUND: Petroclival meningiomas pose significant surgical challenges because of their deep location and complex surrounding neurovasculature. The use of multiple surgical approaches can optimize safe tumor removal from multiple anatomic compartments. METHOD: We describe a patient with a growing superior petroclival meningioma centered at the posterior clinoid with extension into Meckel's cave that was successfully removed with a combined retrosigmoid and subtemporal middle fossa approach. This strategy avoided the need for anterior petrous bone drilling and tentorial splitting. CONCLUSION: A combined retrosigmoid and subtemporal middle fossa approach can provide safe access to tumors spanning the supra- and infratentorial compartments.

Vestibular schwannoma extending into the tympanic cavity and jugular fossa by invasion of the petrous bone.

Vestibular schwannomas usually originate in the internal acoustic meatus, and gradually extends into the cerebellopontine cistern. Invasive growth into the petrous bone is extremely rare. We describe a case of a vestibular schwannoma that aggressively extended into the petrous bone and extracranial space. This may have arisen because of an unusually peripheral site of origin on the vestibular nerve.

Surgical Considerations in Addressing Cholesterol Granuloma of the Petrous Apex through an Infracochlear Approach.

Cholesterol granuloma of the petrous bone is a foreign body giant cell reaction to cholesterol deposits with symptoms including hearing loss, vestibular dysfunction, and cranial nerve deficit as a result of cystic mass compression. Surgical treatment is often difficult to plan due to limited access to the lesion and possible injury to surrounding structures. We report on a case of petrous apex cholesterol granuloma drainage through an infracochlear approach. A 27-year-old female patient presented with acute diplopia due to left-sided abducens paralysis. Multislice computed tomography (MSCT) and magnetic resonance (MR) imaging described a 3.5-cm well-marginated lesion in petrous bone apex, compressing the left abducens nerve at the point of entry into the cavernous sinus, corresponding to cholesterol granuloma. The patients was surgically treated through a transcanal infracochlear approach, since preserving the external and middle ear conduction mechanisms was paramount for the patient. The patient was discharged on the second postoperative day and diplopia resolved within 5 days postoperatively. Six months after the surgery, her hearing on the left side is normal, and she remains symptom-free. This case underpins the value of preoperative planning when approaching the petrous apex, an anatomically complex area due to abundance of important neurovascular structures crowded in a narrow and confined region.

Anatomic Study of Petrous Bone and Its Surrounding Structures in the Extended Anterior Transpetrosal Approach.

Extended anterior transpetrosal approach (ATPA) includes drilling the petrous bone to achieve maximal exposure of the petroclival region. Injuring of surrounding neurovascular structures, such as the internal carotid artery (ICA), during the procedure may result in severe complications. In this study, we aimed to use computer topographic images to provide comprehensive anatomic information on the petrous bone and surrounding structures to help surgeons during the extended ATPA. Computer topographic angiography images of 110 individuals were reviewed, and measurements were performed on coronal, sagittal, and axial planes following multiplanar reformation. The petrous apex and sagittal midline were used to locate the anterior, middle, and posterior parts of the petrous bone and petrosal segment of the ICA during the ATPA. The thicknesses of the petrous bone were 3.28±0.71, 3.53±0.88, and 7.02±1.11 mm at the petrous apex, trigeminal impression, and internal opening of internal auditory canal (IAC) positions, respectively. The distances between the petrous apex to the trigeminal impression, internal opening of the IAC, auris interna, and labyrinth were 7.39±1.62, 15.95±2.48, 17.39±2.39, and 29.00±3.18 mm, respectively. Furthermore, the petrosal segment of the ICA was located at the above landmarks on the petrous bone. Our findings provide anatomic information on the petrous bone and surrounding structures during the extended ATPA procedure based on fixed anatomic landmarks so as to achieve maximal exposure and reduce the number of complications.

A novel technique for safe percutaneous biopsy of a petrous apex lesion.

Lesions within the skull base are the most challenging targets for percutaneous biopsy due to the likelihood of encountering a critical structure along any needle trajectory. Due to ICA proximity, the petrous apex is considered unsafe. We describe a novel percutaneous CT-guided approach for biopsying a petrous apex lesion via a contralateral mandibular condylar notch (subzygomatic approach). To our best knowledge, this approach has not been reported and can be safely employed with thorough planning.

The mini-combined transpetrosal approach: an anatomical study and comparison with the combined transpetrosal approach.

BACKGROUND: The combined transpetrosal approach (CTPA) is a versatile technique suitable for challenging skull base pathologies. Despite the advantages provided by a wide surgical exposure, the soft tissue trauma, complex and time-consuming bony work, and cosmetic issues make it far from patient expectations. In this study, the authors describe a less invasive modification of the CTPA, the mini-combined transpetrosal approach (mini-CTPA), and perform a quantitative comparison between these two approaches. METHODS: Five human specimens were used for this study. CTPA was performed on one side and mini-CTPA on the opposite side. The surgical freedom, petroclival and brainstem area of exposure, and maneuverability for 6 anatomical targets, provided by the CTPA and mini-CTPA, were calculated and statistically compared. The bony volumes corresponding to each anterior petrosectomy were also measured and compared. Three clinical cases with an operative video are also reported to illustrate the effectiveness of the approach. RESULTS: The question-mark skin incision done along the muscle attachments permits an optimal cosmetic result. Even though the limited incision, the smaller craniotomy, and the less extensive bone drilling of mini-CTPA provide a smaller area of surgical freedom, the areas of exposure of petroclival region and brainstem were not statistically different between the two approaches. The antero-posterior maneuverability for the oculomotor foramen (OF), Meckel's cave (MC) and the REZ of trigeminal nerve, and the supero-inferior maneuverability for OF, MC, Dorello's canal, and REZ of CN VII are significantly reduced by the smaller opening. The bony volume of anterior petrosectomy resulted similar among the approaches. CONCLUSIONS: The mini-CTPA is an interesting alternative to the CTPA, providing comparable surgical exposure both for petroclival region and for brainstem. Although the lesser soft tissue dissection and bony opening decrease the surgical maneuverability, the mini-CTPA may reduce surgical time, potential approach-related morbidities, and improve cosmetic and functional outcomes for the patients.

Lariboisiere Hospital pre-operative surgical checklist to improve safety during transpetrosal approaches.

BACKGROUND: Transpetrosal approaches are technically complex and require a complete understanding of surgical and radiological anatomy. A careful evaluation of pre-operative magnetic resonance imaging and computed tomography scan is mandatory, because anatomical or pathological variations are common and may increase the risk of complications related with the approach. METHODS: Pre-operative characteristics of venous and petrous bone anatomy were analysed and correlated with intraoperative findings, using injected magnetic resonance imaging and thin-slices computed tomography scan. These data regularly checked before each transpetrosal approach were progressively included in the presented checklist. RESULTS: Transpetrosal approaches have been used in 101 patients. Items included in the checklist were petrous bone pneumatization, angle between petrous apex and clivus, dehiscence of petrous carotid artery, dehiscence of geniculate ganglion, distance between superior semicircular canal and middle fossa floor, distance between cochlea and middle fossa floor, sigmoid sinus dominance, transverse sigmoid sinus junction depth to the outer cortical bone, jugular bulb height (high or low), location of the vein of Labbé, characteristics of superior petrosal vein complex. CONCLUSION: The presented checklist provides a systematic scheme of consultation of characteristic of venous and petrous bone anatomy for transpetrosal approaches. In our experience, the use of this checklist reduces the risk of complications related with approach, by minimizing the neglect of crucial information.

How I do it? Resection of residual petrous apex chordoma with combined endoscopic endonasal and contralateral transmaxillary approaches.

BACKGROUND: The petrous apex is one of the most challenging areas of the skull base to access. METHOD: 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. CONCLUSION: This case demonstrates the value of the CTM corridor in resecting petrous apex lesions that are posterolateral to the paraclival segment of the ICA.

Localisation of the petrous internal carotid artery relative to the vidian canal on computed tomography: a case-control study evaluating the impact of petroclival chondrosarcoma.

BACKGROUND: The vidian canal (VC) is normally a reliable anatomical landmark for locating the petrous internal carotid artery (pICA). This study determined the influence of petroclival chondrosarcoma on the relationship between the VC and pICA. METHODS: Nine patients (3 males, 6 females; median age 49) with petroclival chondrosarcoma, and depiction of the pICA on contrast-enhanced CT, were retrospectively studied. CT-based measurements were performed by two observers, both in the presence of the petroclival chondrosarcoma (case) and on the contralateral control side. The antero-posterior (AP) and craniocaudal (CC) measurements from the posterior VC to the pICA, whether the pICA was in the trajectory of the VC, and the coronal relationship of the pICA anterior genu with the VC were recorded. RESULTS: Chondrosarcoma usually displaced the pICA anteriorly (8/9 cases) and superiorly (6/9 cases) relative to the normal side with mean AP and CC measurements of 3.9 mm v 7.2 mm (p = 0.054) and 4.4 mm v 1.4 mm (p = 0.061). The VC trajectory less frequently intersected the pICA cross-section in the presence of chondrosarcoma however it was in the line of the eroded dorsal VC in one case. The anterior genu of the pICA was displaced more laterally by chondrosarcoma but usually remained superior to the VC. CONCLUSION: Petroclival chondrosarcoma variably influences the anatomical relationship between the VC and the pICA, hence requiring an individualised approach. The pICA is usually anterosuperiorly displaced, and the anterior genu remains superior to the VC, however it may be located in the line of the canal.

Three-dimensional imaging for the localization of related anatomical structures during surgery on the internal auditory canal.

BACKGROUND: The Fisch infra-temporal fossa approach (Fisch's method), first proposed in 1970, is commonly used during internal auditory canal (IAC) surgery with an approach that advances through the middle cranial fossa. This study was designed to address the technical difficulties encountered in recognizing and localizing the arcuate eminence with respect to the superior semicircular canal (SSC). METHODS: Forty men and 40 women (18-57 years of age) without space-occupying lesions in the petrous part of the temporal bone were selected for the study. In total, 160 samples were obtained from both sides of the temporal bone. The temporal bone in these 160 samples was scanned using computed tomography, and a three-dimensional coordinate system was established to measure the three-dimensional coordinate values of structures adjacent to the arcuate eminence, the SSC, and the IAC. RESULTS: The results showed that the shape of the arcuate eminence is highly variable. Approximately 23.12% of samples had no obvious arcuate eminence, which prevented the use of Fisch's method to localize the SSC. The arcuate eminence was difficult to identify in 37 samples. CONCLUSIONS: Analysis samples showed that the SSC was located in a fan ring centered at the midpoint of the upper edge of the petrous portion of the temporal bone. The arcuate eminence did not correspond directly with the SSC, as the former was located posterolateral to the latter in 85.83% of samples. The angle between the SSC and the IAC ranged from 0° to 60° degrees, as reported previously by Fisch. However, the angle typically ranged from 10-30° in our study.

Bilateral Petrous Apex Cephalocele Associated with a Wide Sella.

ABSTRACT: Petrous apex cephalocele (PAC) is a rare type of cephalocele. It is usually asymptomatic. It can be unilateral or bilateral. Bilateral cases are less common. They are etiologically and clinically different entities from unilateral ones. A 56-year-old female patient presented to the hospital with the complaint of a severe nonspecific headache. She has been examined in ear nose throat, ophthalmology, and finally neurology clinics. Bilateral PAC was incidentally found in magnetic resonance imaging (MRi) examination. Headache was associated with PAC because no additional pathology could explain the clinical symptomatology. There is a proven relationship between empty sella and PAC. Regarding PAC less than 50 cases are known. Our paper aims to contribute to the literature by exhibiting etiologic and clinic differences between unilateral and bilateral PAC. It highlights the relationship between PAC and broad sella that is a different entity from empty sella and shows this remarkable radiological appearance. The authors presented our case accompanied by clinical and MRi findings.

Pediatric Petrous Apex Lesions: A Radiological Classification and Diagnostic Algorithm.

The petrous apex (PA) is involved in a myriad of pathological conditions, some of which are exclusive in children. Diagnosis may be difficult due to vague clinical presentation, and local examination is challenging owing to its inaccessible location. This is further complicated by multiple unfused sutures and ongoing PA pneumatization in children. Cross-sectional imaging is vital for the evaluation of the PA lesions, due to their precarious location and proximity to the major neurovascular structures. Several classification systems have been proposed for these lesions based on their site of origin, solid or cystic appearance, surgical or non-surgical (no touch lesions) management, and benign or malignant nature. In this article, we emphasize the distinctive role of different cross-sectional imaging modalities in the diagnosis of pediatric PA lesions, with special attention to normal variants that should not be mistaken for pathology. We also propose a radiological classification and algorithmic approach to aid in the precise diagnosis and facilitate appropriate management of the various PA lesions in children.

[Endoscopic transnasal approach in surgical treatment of petrous temporal bone cholesteatoma extending towards the clivus. Three clinical observations and literature review]. / Endoskopicheskii transnazal'nyi dostup v khirurgicheskom lechenii kholesteatom piramidy visochnoi kosti, rasprostranyayushchikhsya v oblast' skata. Tri klinicheskikh nablyudeniya i obzor literatury.

Petrous temporal bone Cholesteatoma is widely described in the literature and accounts for up to 9% of all neoplasms of this localization. These cholesteatomas rarely spread towards the clivus. Isolated clival cholesteatomas are described only as single cases. There is currently no consensus on the choice of surgical approach for resection of similar neoplasms. OBJECTIVE: To demonstrate the possibilities of endoscopic transnasal approach in surgery for clival and petrous cholesteatoma. MATERIAL AND METHODS: This article presents 3 clinical cases: 2 patients with apical cholesteatoma of petrous part of temporal bone extending to the clivus and 1 patient with massive petrous temporal bone cholesteatoma extending towards the clivus according to the classification of Sanna M. All patients underwent endoscopic transnasal surgery. RESULTS AND CONCLUSION: In our opinion, endoscopic transnasal approach is optimal for resection of similar neoplasms. Total and subtotal resection was performed in 2 and 1 case, respectively. However, there are certain limitations of this approach in accessing the most lateral parts of the neoplasm. Nevertheless, endoscopic transnasal approach ensures resection of petrous temporal bone cholesteatoma extending to the clivus without the risk of damage to acoustic-facial cranial nerves. It is especially significant in patients without their baseline dysfunction.

Relationship between lateral angle and shape of internal acoustic canal: cautionary note for diagnosis of sex.

Lateral angle (LA) of the internal acoustic canal (IAC) at its opening at the surface of the petrous portion of the temporal bone is known in literature as a dimorphic measurement useful for sex assessment. However, its reliability is still debated. Moreover, no information is available about the possible relationship between LA and shape and size of the IAC. This study aims at assessing breadth, length and lateral angle of IAC on 100 CT scans belonging to subjects aged between 20 and 70 years, equally divided between males and females. Possible differences in the three measurements according to side and sex were assessed through two-way ANCOVA test, using three cranial measurements (distance between anterior and posterior nasal spine, upper facial height, bizygomatic breadth) as covariates (p < 0.05). Possible correlations among IAC measurements and with age were assessed through Pearson's test (p < 0.05). Results showed a significantly greater IAC breadth on the left side than on the right side; moreover, LA was significantly wider in females than in males and was positively correlated with IAC breadth in both males and females. In addition, LA was negatively correlated with age only in the female group. The study first showed that LA is strictly related to IAC morphology; moreover, it is significantly affected by masculinization of skeletal traits in females. Therefore, caution is suggested in using this measurement for sex assessment.

Prediction of trigeminal nerve position based on the main feeding artery in petroclival meningioma.

The trigeminal nerve is often displaced by petroclival meningioma (PCM) compression, making it difficult to locate during PCM surgery. This study investigated whether the deviated position of the trigeminal nerve could be easily predicted using the main tumor feeding artery. We retrospectively examined 32 patients who underwent surgery for primary PCM. The deviation of the trigeminal nerve was classified as either Type 1 (displacement toward the back of the cerebellar tentorium), Type 2 (toward the back of the superior petrosal sinus), Type 3 (toward the back of the petrous apex dura), Type 4 (toward the inferior aspect of the tumor), or Type 5 (toward the surface of the brain stem). The main feeding artery was determined by preoperative angiography. The trigeminal nerve was classified as Type 2 in 60% of cases where the proximal tentorial artery (TA) was the main feeding vessel. The nerve was Type 5 where the distal portion of the TA was the main feeding vessel (60% of the cases). The nerves were Type 3 and Type 4 where the proximal inferior lateral trunk (ILT) (60%) and distal ILT (75%), respectively, were the main feeding vessels. In 66.7% of the cases where the dorsal meningeal artery was the main feeding vessel, the nerve was Type 3. Type 1 classification applied in all cases where the ascending pharyngeal artery was the main feeding artery. The main feeding artery can be used to predict trigeminal nerve transposition during PCM surgery.

Differences in surgical outcome between petroclival meningioma and anterior petrous meningioma.

BACKGROUND: Petroclival meningiomas (PC MNGs) and anterior petrous meningiomas (AP MNGs) have similar locations. However, these are different tumors clearly divided by the trigeminal nerve. There has never been a study on the comparison of the surgical outcomes of these two meningiomas. In this study, we compared and analyzed the surgical outcome of PC MNGs and AP MNGs. METHODS: The charts of 85 patients diagnosed with PC MNGs of AP MNGs who underwent surgical treatment were retrospectively reviewed. And we analyzed the characteristics of 49 PC MNGs (57.6%) and compared them with those of 36 AP MNGs. RESULTS: Preoperative brainstem edema was observed in 11 patients (22.4%) of the PC MNG group and 1 patient (2.8%) of the AP MNG group (p = 0.024). Total tumor removal was achieved in 21 patients (58.3%) of the AP MNG group, but only 17 patients (34.7%) of the PC MNG group were able to completely (p = 0.047). In addition, sixth cranial nerve palsy occurred in 17 patients (34.7%) of the PC MNG group and 4 patients (11.1%) of the AP MNG group (p = 0.025). CONCLUSIONS: In this study, we found that PC MNGs has a worse surgical outcome than AP MNGs, because PC MNGs were difficult to completely remove and were more likely to damage abducens nerve.

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.

Temporal Bone Pneumatization: Relationship With Sex and Variants of the Ethmoid and Sphenoid Bone.

ABSTRACT: Pneumatization variants of the temporal bone have a crucial importance in several surgical interventions. However, very few data are known about possible correlation with other pneumatization variants.Pneumatization of glenoid fossa, petrous apex, and infralabyrinthine portion of temporal bone was assessed in 200 computed tomography scans, equally divided between males and females (18-92 years). Pneumatization variants of the ethmoid (concha bullosa, agger nasi, pneumatized crista galli) and the sphenoid sinuses (pneumatized pterygoid processes, anterior clinoid processes, dorsum sellae, volume) were recorded as well.Differences in prevalence of each pneumatization type according to sex and side, among different portions of the temporal bone, and between temporal bone and the pneumatized variants of the ethmoid bone and sphenoid sinuses, were assessed through chi-square test (P < 0.05). Differences in sphenoid volume among different pneumatization degrees of the temporal bone were assessed through 1-way analysis of covariance test (P < 0.05).Pneumatization of the petrous apex and the infralabyrinthine portion was significantly more frequent in males than in females, whereas pneumatization of the glenoid fossa was more often observed on the right side (P < 0.05). Variants of the temporal bone are all related one with each other in males, whereas in females only the relationship between pneumatized petrous apex and infralabyrinthine portion was found. Moreover, in females the pneumatized petrous apex was related with pneumatized anterior clinoid process, and the pneumatized infralabyrinthine portion was related with the sphenoid sinus volume.Results may be useful for predicting these important variants in planning surgical interventions of the cranial base.

Subcochlear canaliculus patterns in the pediatric and adult population: radiological findings and surgical implications.

INTRODUCTION: The pneumatization of the different regions of the temporal bone is strictly related to the age and the degree of development of the mastoid and the middle ear. Petrous apex pneumatization is the last step of the development of the petrous bone system. The subcochlear canaliculus is an anatomical cavity, originating in the space between the fustis and the finiculus, and connecting the round window area to the petrous apex. The aim of the present article is analyzing the trend of development of the subcochlear canaliculus pneumatization, classified through CT scan examination, in different age subgroups. MATERIALS AND METHODS: We conducted a retrospective review of patients who underwent temporal bone CT scans between 2014 and 2019. Pediatric and adult patients were included and divided into different age subgroups. The subcochlear canaliculus was examined through coronal view scans at the level of the round window niche and classified into 3 different groups (A, B and C) according to the degree of pneumatization. RESULTS: A total of 270 Petrous bone CT scans was analyzed. The percentage of type A subcochlear canaliculus was significantly higher in the pediatric population if compared to the adult population (p = 0.001326). As far as type B subcochlear canaliculus is concerned, the difference between children and adults was not statistically significant (p = 0.2378). On the other hand, type C subcochlear canaliculus was predominant in the adult population (p = 0.000256). CONCLUSIONS: There is a constant increase in pneumatization of the subcochlear canaliculus from 0 to 19 years and then a progressive decrease. This discovery has relevant surgical implications and has to be borne in mind in particular for cholesteatoma surgery and cochlear implantation surgery in the age groups in which the subcochlear canaliculus is highly pneumatized.