Current Otorhinolaryngology Reports (2019) 7:65–72 https://doi.org/10.1007/s40136-019-00230-4 OTOLOGY: TUMORS OF THE EAR AND LATERAL SKULL BASE (G DANESI, SECTION EDITOR) The Transpetrosal Approaches System in Posterior Fossa Meningiomas Surgery: Rationale and Results Roberto Pareschi 1 & Giovanni Danesi 2 & Roberto Stefini 3 & Rachele Bivona 2 & Catalina Iglesias Valera 2 Published online: 1 February 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Purpose of Review This is a retrospective review of 90 patients with a posterior fossa meningioma (PFM) treated between 1996 and 2017 in our two tertiary skull base centers. Patients underwent surgical resection via different approaches. We aimed to show how different surgical approaches may help to reach gross total resection (GTR) and low morbidity, especially on facial nerve function. Recent Findings PFM is a real surgical challenge with high morbidity and mortality due to the surrounding structures, their common large size at diagnosis, and their potentially invasive behavior. Total resection is the only way to cure people affected. We successfully treated 90 cases of PFM and evaluated different surgical approaches. Summary GTR is the aim of the surgery as the extent of resection influences the rate of recurrence, which in turn influences the prognosis. Seventy percent (p < 0.001) of surgical patients achieved a GRT with low morbidity and no mortality. Keywords Posterior fossa meningioma . Transpetrosal approaches . Combined petrosal . Gross total resection . Meningioma surgery . Cerebellopontine angle tumors Introduction Meningiomas account for 20 to 25% of all intracranial tumors and 10% are seen in the posterior fossa. Posterior fossa meningioma (PFM) is the second most common tumor in the cerebellopontine angle, accounting for 10 to 15% of neoplasms in this area [1]. PFM is a real surgical challenge with high morbidity and potential mortality due to the surrounding vital structures, the encasement of nerves and vessels, the common large size at diagnosis, and their potentially invasive behavior. The decision on the necessity of complete surgical resection remains critical. They are benign tumors commonly This article is part of the Topical Collection on OTOLOGY: Tumors of the Ear and Lateral Skull Base * Roberto Pareschi rpareschi@inwind.it 1 Ospedale Nuovo di Legnano, ENT & Skull Base Department, via Papa Giovanni Paolo II, Legnano 20025, MI, Italy 2 Ospedali Riuniti di Bergamo, ENT & Skull Base Department, Bergamo, Italy 3 Ospedale Nuovo di Legnano, Neurosurgical Unit, via Papa Giovanni Paolo II, Legnano 20025, MI, Italy seen in adults, which usually present after a long asymptomatic period. The natural history of these lesions suggests progressive growth with progressive neurological deterioration until death [1, 2]. Though they make up a relatively small proportion of cerebellopontine angle (CPA) tumors, PFM is particularly interesting because their management issues differ somewhat from acoustic nerve tumors. Management problems can be much less or much greater depending on the point of the petrous bone (PB) from which they arise [3]. The aim of this report is to present our experience and surgical strategies in the management of PFM. Patients and Methods The study was approved by the respective Ethics Committee and patient consents were obtained. This is a retrospective review of all our patients with posterior fossa meningiomas treated between 1996 and 2017 in our two tertiary skull base centers (Legnano and Bergamo, Italy) as we share the same philosophy in terms of management and surgical treatment. Epidemiological and clinical data, surgical and histological reports, preoperative and 66 Curr Otorhinolaryngol Rep (2019) 7:65–72 postoperative images, complications, data on adjuvant therapy, and follow-up information were reviewed. Between 1996 and 2017, 90 patients were treated for a posterior fossa meningioma and were included in the present analysis. They were 19 male and 71 female with age ranging from 23 to 74 years old. Meningiomas were divided into three groups according to their correlation with the internal auditory canal (IAC): retromeatal, perimeatal, and premeatal. The foramen magnum, jugular foramen, and tentorial meningiomas were excluded from this survey along with intrameatal tumors with a CPA protrusion less than 10 mm. Statistical analysis was performed using SPSS version 17.0 for Windows (SPSS Inc., Chicago, IL); categorical variables were compared using the chi-square, P values of less than 0.05 were regarded as statistically significant. Classification Tumor location was determined after a careful examination of the preoperative radiological images (CT-MRI) along with the intraoperative remarks. The meningiomas were classified into retromeatal, perimeatal, and premeatal, according to the relationship between the main dural attachment and the IAC. The site of the displacement of the acoustic-facial bundle, depending on the dural origin of the tumor, was the utmost important factor determining the surgical complexity and the surgeryrelated morbidity. We distinguished 21 meningiomas with a main dural attachment posterior to the internal auditory canal (retromeatal meningiomas), 19 meningiomas in the contest of IAC and 50 meningiomas with dural attachment anterior to the internal auditory canal (premeatal meningiomas) (Table 1). Retromeatal meningiomas (posterior PB meningiomas) originate from the dura of the posterior PB, between the posterior wall of the IAC and the groove of the sigmoid sinus. They occupy the posterior part of the cerebellar-pontine angle (PCA) usually dislocating anterosuperiorly the acoustic-facial bundle. Eight meningiomas of this group presented an inframeatal extension encroaching the jugular foramen. In two cases, the tumor extended extracranially into the neck. In 18 cases, the dural attachment involved the tentorium with a transtentorial extension. Perimeatal meningiomas arise from the dura in the contest of IAC and they do not dislocate anteriorly or posteriorly. Table 1 Meningiomas’ classification Surgical Approaches The selection of surgical approach (Table 2) was tailored according to the location and the extension of the tumor and on the basis of patient factors, such as age, general health, preoperative cranial nerve dysfunction, and preoperative hearing. We focused our attention on the location of the tumor’s main insertion site, the involvement of the adjacent structures, and the tumor size. Prediction of the nerve displacement, with particular attention to the acoustic-facial bundle, was a key factor in our decision. For retromeatal meningiomas, the surgical approaches were: retrosigmoid (RS), translabyrinthine (TLab), petrooccipital-transigmoid (POTS), and retrolabyrinthinesubtemporal (RLabST). – The RS approach was indicated in all cases with a normal or socially useful preoperative hearing (class A or B of Tokyo Classification)3. The size and the intrameatal extension of the tumor did not influence the choice of this approach. A standard lateral RS approach with the patient in park-bench position was used in this group. The RS approach is a versatile type of craniotomy extending from the sigmoid and the transverse sinus to the occipital squama. Opening of the dura and retraction of cerebellum gives wide access to the CPA after early drainage of the cerebellomedullary cistern. Retrolabyrinthine meatotomy allows exposure of the IAC for the removal of the Table 2 Selection of surgical approach according to the location and the extension of the tumor Retromeatal Retromeatal 21/90 Perimeatal 19/90 Premeatal 50/90 Premeatal meningiomas (anterior PB meningiomas) arise from the dura around the porus trigeminalis (petrous apex (PA) meningiomas) or from the dura of the petroclival (PC) junction or directly from the clivus (PC meningiomas). They occupy the anterior part of the CPA and dislocate posteroinferiorly the acoustic-facial bundle immediately behind the dura of the posterior PB. Premeatal meningiomas are more difficult to remove because the cranial nerves are located between the surgeon and the tumor. Fifteen meningiomas of this group presented a tentorial or a transtentorial extension, with the invasion of the Meckel cave in 11 cases, and in nine cases, the invasion of the cavernous sinus, upper clivus, and middle cranial fossa was evident. Petrous apex 19/50 Petro-clival 25/50 Clival 6/50 Premeatal Perimeatal RS 9 TLabTAp 20 TLab POTS RLabST 7 3 2 TC TLab+FAR lateral Combined petrosal 18 1 11 TLab 19 Curr Otorhinolaryngol Rep (2019) 7:65–72 – – – – intrameatal extension of the tumor with a high rate of hearing preservation. The TLab approach is indicated in all the cases with a significant deterioration of the hearing or anacusia (class C, D, or E of Tokyo classification) [3] or in elderly patients with huge symptomatic tumors. The access to this approach is the mastoid and the target is the IAC and CPA. After a wide conservative mastoidectomy is performed, the occipital pre- and retrosigmoid dura along with the dura of the temporal lobe are exposed thus allowing for the retraction of sigmoid sinus with a significant widening of the surgical field. The posterior wall of the external auditory canal, the tympanic cavity, the cochlea, and the facial nerve are left in place. The posterior labyrinth is completely drilled out together with the bone that is lateral, superior, and inferior to the IAC. The canalicular dura is completely uncovered until the fundus and the facial nerve entering in the fallopian canal is evident. Once the approach is performed, the jugular bulb is the inferior limit and the temporal dura with the superior petrous sinus are the superior limits. The presigmoid dura is transected and the CPA is widely exposed. The POTS approach has been developed for removing tumors situated in the jugular foramen together with their local extension into the adjacent parts of the skull base, the CPA, and the parapharyngeal space (PPS). POTS approach involves a posterolateral exposure and an anteromedially directed surgical axis which allows the surgeon to leave the external and middle ear complex, together with the facial nerve, entirely undisturbed. Single-stage removal of intra- and extradural lesions extending from the CPA to the PPS can be achieved with minimal risk of cerebrospinal fluid (CSF) leak. In essence, the POTS approach is the combination of a retrolabyrinthine petrosectomy and retrosigmoid craniotomy. The external ear canal, tympanic cavity, and facial nerve are left in situ [4]. The RLabST is one of the most minimal of the transpetrosal approaches of the posterior fossa. After a wide conservative mastoidectomy is performed, the sigmoid sinus is skeletonized inferiorly through the infralabyrinthine air cells to the jugular bulb. Complete skeletonization of the facial nerve is unnecessary. All three semicircular canals are, therefore, skeletonized but preserved. Removal of the bone plates on the middle and posterior fossa dura mater and the sigmoid sinus completes the extradural part of the retrolabyrinthine approach. This approach provides exposure of the CPA but does not give the surgeon adequate visualization of the anterior brain stem or petroclival region [5]. For perimeatal meningiomas, the TLab surgical approach was performed. 67 – – – – For premeatal meningiomas, the surgical approaches performed were mainly the translabyrinthine/transapical approach (TLabTAp) and the transcochlear approach (TC), only one case initially treated with a TLab surgery then requested a far-lateral approach; in 11 cases, combined petrosal approaches were performed. The TLabTAp is an anterior extension of the TLAb in which the internal auditory canal is exposed 360° around its circumference. The cornerstone of this approach is the posteroinferior transposition of the acoustic-facial bundle in continuity with the intracisternal tract that, for premeatal meningiomas, is usually located in the interface between the posterior PB dura and tumor. This maneuver respects the functional integrity of the facial nerve (if it is not infiltrated by the tumor) allowing for the complete drilling out of the bone and the exposure of the dura around the porus trigeminalis (PA). The posteroinferior dislocation of the acoustic-facial bundle opens a corridor to the anterior CPA through which the removal of large PA and PC meningiomas is possible. The limit of this access is the midline extension of the tumor. An extension beyond this line should be treated by a TC. The TC represents the widest available access to the posterior fossa. It allows for the exposure of the omolateral CPA, prepontine area, and contralateral CPA. This approach is indicated for giant PA, PC, or clival meningiomas, extending beyond the midline and between the clivus and the pons. Compared with the TLabTAp, it presents some additional surgical steps: (1) the removal of the outer ear canal and tympanic cavity with closure of the external ear canal; (2) total petrosectomy extended to the middle and lower clivus located medially to the cochlea and the vertical tract of the petrous internal carotid artery (ICA); (3) the postero-inferior transposition of the intratemporal facial nerve along with its intrameatal tract. This maneuver does not allow the functional integrity of the facial nerve. After surgery, a grade III facial palsy (according to the House Brackmann Classification [6]) is the best result that can be obtained and this is the most important drawback of this approach. Combined petrosal approaches actually describe numerous surgical approaches to the petroclival area well suited for these tumors. The transtentorial step was necessary in ten of them where the dura of the middle fossa above the superior aspect of the petrosal bone and the tentorium over the trigeminal nerve are resected. Indications to transtentorial approach are: lesion extending from PF to the midbrain, lesion extending from middle fossa to PF, and lesions arising from the tentorium. Transpetrous approaches have important advantages when compared to the RS approaches: 68 Table 3 Main tumors’ residuals Curr Otorhinolaryngol Rep (2019) 7:65–72 Transtentorial 18 Jugular foramen 8 Gasser 1 Cavernous sinus 1 1) The wide surgical field, a shorter working distance between the craniectomy and the tumor and a better orientation towards the lateral and ventral brain stem, limiting the brain retraction. 2) The early resection of the osteo-dural insertion of the meningioma, with coagulation of the tumor’s feeding vessels. 3) The early identification and control of the facial nerve before any dissection or removal of the tumor, and increased protection of the anatomical and functional integrity of the facial nerve (except for the TCA) 4) After the dura is opened or resected, the next step is to obtain an optimal internal debulking, followed by the peripheral dissection, with special attention to the identification and preservation of the neurovascular structures. The main disadvantages of the transpetrous approaches are that they require a dedicated long-lasting training together with a deep knowledge of the complex anatomy of the PB. Moreover, the intrapetrous otoneurological structures are at risk for damage during the approach. Results Ninety patients underwent surgical resection via different approaches as the tumors extended into different directions, mainly towards the petrous apex. Extension and Surgical Approach Twenty-one (23.3%) patients harbored a retromeatal tumor whereas a perimeatal meningioma was found in 19 patients (21.1%) and a premeatal meningioma in 50 patients (55.5%) of which 19 extended to the petrous apex (38%) cases, petro-clival region in 25 (5%) cases, and the clivus in six (12%) cases (Table 1). A transtentorial extension was evident in 18/90 cases (20%) and the jugular foramen was involved in 8/90 cases (8.8%); the gasser ganglion and the cavernous sinus were respectively involved in one case (1%) (Table 3). Those represent the main tumors’ residuals. For the retromeatal meningiomas, a RS approach was performed in nine cases (42.8%), a TLab approach in seven cases (33%), the POTS approach in three cases (14%), and RLabST in two cases (9%). For the perimeatal meningiomas, a TLab approach was performed in all the cases. For the premeatal meningiomas, the TLabTAp approach was performed in 20 cases (40%), the TC approach in 18 cases (36%), and a combined petrosal approach was performed in 11 cases (22%) of which a transtentorial phase was necessary in ten cases (Table 2). Preoperative Symptoms Preoperative symptoms were significantly related to tumor location. Trigeminal symptoms (dysesthesia and neuralgia) and abducent nerve palsy were more frequent in premeatal and perimeatal groups, hearing and vestibular symptoms predominantly occurred in association with retromeatal and perimeatal tumors. Others symptoms like headache and cerebellar signs had a similar distribution between the premeatal and retromeatal groups. (Table 4). Tumor Resection The extent of tumor resection was defined by the intraoperative findings using the Simpson classification [7]. These findings were confirmed by the postoperative MRI with gadolinium at 3 months’ and 1-year’ time. The Simpson grades 1 and 2, with no evidence of persistence at the postoperative MRI, corresponded to a GTR. Simpson grade 3, 4, or 5, confirmed by the evidence of residual tumor at the postoperative MRI, are related to a non-total resection (near total or partial resection). GTR was achieved in 69/90 patients, 77% (p < 0.001). More specifically, in retromeatal meningiomas, a total resection was obtained in 20/21 cases (95%). In perimeatal meningiomas, GTR was obtained in all cases (19/19). In premeatal meningiomas, GTR was lower, 38/50 (76%) patients, reflecting the more difficult surgical treatment of these tumors. A grade 3 (NTR) was evident in 4/90 patients (4%), and grades 4–5 (PTR) in 9/90 patients (10%) (Table 5). Table 4 Preoperative symptoms Trigeminal signs Cerebellar signs VI C.N. palsy Hearing loss, tinnitus, vertigo Hydrocephalus Headache Retromeatal Premeatal Perimeatal 1/21 (4.7%) 6/21 (28.5%) 0/21 (0%) 8/21 (38%) 1/21 (4.7%) 4/21 (19%) 18/50 (36%) 7/50 (14%) 2/50 (4%) 12/50 (24%) 2/50 (4%) 6/50 (12%) 6/19 (31.5%) 0/19 (0%) 0/19 (5.2%) 12/19 (63.1%) 0/19 (0%) 1/19 (5.2%) Curr Otorhinolaryngol Rep (2019) 7:65–72 69 Table 5 Extent of tumor resection Description Retromeatal Premeatal Perimeatal Simpson grade 1–2 GTR (p < 0.001) 20/21 (95.2%) 38/50 (76%) 19/19 (100%) Simpson grade 3 NTR 0/21 (0%) 4/50 (8%) 0/19 (0%) Simpson grade 4–5 PTR 1/21 (4.7%) 8/50 (16%) 0/19 (0%) The consistency, bleeding, and adherence of the tumor to the brain stem and to vessels prevented their total removal, permitting only brain-stem decompression. According to the surgical approach, a GTR (Simpson Grade 1–2) was achieved in 69/90 (77%). (Table 6). Morbidity Previous studies have emphasized the less important morbidity regarding auditory and facial function in retromeatal meningiomas compared with anteriorly based tumors (Table 7). Retromeatal tumors represented the more accessible tumors in our series. A postoperative HB grades I–II was achieved in all cases except one TLab approach (p < 0.001). Fourteen out of 21 patients were eligible for hearing preservation. A postoperative class A–B (Tokyo classification) was obtained in 12 out of 14 patients (85.7%). Premeatal meningiomas and especially the petroclival and clival tumors are still considered the most challenging due to their proximity to vital neurovascular structures. Until the mid-1980s, these tumors were regarded as unresectable. However, after pioneering efforts in skull base field, the surgical resectability started to increase. The several variations of transtemporal approaches introduced in the 1990s allowed a high resectability rate of premeatal tumors but surgical morbidity is still a major issue. In premeatal meningiomas, the cranial nerves, notably the acoustic-facial bundle, are displaced between the tumor and the surgeon and this is related with an increased rate of postoperative neuropathies. Moreover, the transtemporal approaches have an intrinsic important morbidity causing deafness and, in particular, the TC approaches, a partial facial nerve palsy grades II–III HB. In the present analysis, for premeatal meningiomas, HB grades I–II were obtained in 25/50 (50%) patients. More specifically, the rate of HB grades I–II was 80% (p < 0.001) for Table 6 GTR according to approach GTR according to the approach TLabTAp TC RS POTS TLab+FL TLab RLabST Combined petrosal 18/20 (90%) 13/18 (72.2%) 9/9 (100%) 1/3 (33.3%) 0/1 (0%) 19/26 (73%) 2/2 (100%) 7/11 (63.6%) TLabTAp approach, none for the TC approach, and in 9/11 (81.8%) out of combined petrosal approaches. For patients who underwent the TC approach, the best VII C.N. function we could achieve was an HB grade III in 15 out of 18 patients (83.3%); in perimeatal and retromeatal meningiomas, HB grades I–II were obtained in a high percentage (Table 8). Hearing preservation was attempted only in 11 patients with a very small premeatal meningioma, with the largest diameter of maximum 2.5 cm. This goal was achieved managing the tumor by a combined petrosal approach. Additionally, we reported 9/90 (10%) cases of IV, V, and VI C.N. palsy, and 4/90 (4.4%) cases of lower cranial nerves palsy (Table 7). In one case, we reported an ab-ingestis pneumonia and no cases of perioperative death, cerebrospinal fluid leakage, or meningitis occurred. Discussion The objective of this study is to present surgical outcomes and support an anatomic classification for PFM based on their localization. The extent of tumor resection has often been used as a predictor of recurrence, as usually small pieces of tumor may remain attached nearby. Prognostic factors for the recurrence of this tumor are well described in literature, such as the growth rate. Interestingly, the reported growth rate is different in untreated and resected tumors. As a matter of fact, Jung HW et al. [8], have shown that the growth rate in petroclival meningiomas is 0.81 cm 3 /yr. (volume) and 0.81 mm/yr. (diameter) after surgery as compared to 1.16 mm/yr. (diameter) and 1.10 cm3/yr. (volume) for unresected tumors. It is clear that a good resection is important, as the extent of resection influences the rate of recurrence, which in turn influences the prognosis. However, deliberate residuals must be Table 7 Postoperative morbidity None CN’s IX–X–XI–XII CN’s IV–V–VI CN VII Trigeminal signs Cerebellar signs Retromeatal Premeatal Perimeatal 17/21 (80.9%) 3/21 (14.2%) 0/21 (0%) 1/21 (4.7%) 0/21 (0%) 0/21 (0%) 12/50 (24%) 1/50 (2%) 9/50 (18%) 25/50 (50%) 2/50 (4%) 1/50 (2%) 17/19 (89.4%) 0/19 (0%) 0/19 (0%) 2/19 (10.5%) 0/19 (0%) 0/19 (0%) 70 Table 8 Postoperative facial nerve function Curr Otorhinolaryngol Rep (2019) 7:65–72 HB in retromeatal TLab POTS RLabST RS I–II HB 6/7 (85.7%) 3/3 (100%) 2/2 (100%) 9/9 (100%) III HB IV–V–VI HB (p < 0.001) 1/7 (14.2%) 0/7 (0%) 0/2 (0%) 0/2 (0%) 0/2 (0%) 0/2 (0%) 0/9 (0%) 0/9 (0%) HB in perimeatal I–II HB TLab 17/19 (89.4%) III HB IV–V–VI HB (p < 0.001) 2/19 (10.5%) 0/19 (0%) HB in premeatal TLabTAp TC TLab+FL Combined petrosal I–II HB 16/20 (80%) 0/18 (0%) 0/1 (0%) 9/11 (81.8%) III HB (p < 0.001) 2/20 (10%) 15/18 (83.3%) 0/1 (0%) 0/11 (0%) IV–V–VI HB 2/20 (10%) 3/18 (16.6%) 1/1 (100%) 2/11 (18.1%) taken into account, as when the pia mater, jugular foramen, cavernous sinus, and Gasser ganglion are infiltrated, pieces of tumor are expressly left in situ. Meningiomas in posterior fossa can grow and spread to different locations [9•]. We easily divided them into three groups according to their relation to IAC, as we observed that they commonly can grow and develop nearby the IAC, with progression towards the petrous apex or the CPA. Premeatal tumors, which are located anterior to the IAC, exert mass effect on the brain stem and trigeminal ganglion. They mainly presented with symptoms attributable to involvement of the fifth cranial nerve. As has been reported before [10•], cranial nerve compression from meningioma can result in a spectrum of facial numbness to trigeminal neuralgia. Perimeatal tumors are more likely to present with hearing loss and vestibular symptoms. This is coherent with prior papers that found normal hearing in only 20% of patients with tumors nearby these regions [11]. Even though the facial nerve also crosses in this Fig. 1 Rate of GTR, NTR, and PTR region, it was relatively skimped in all tumor groups, with no patient presenting with facial weakness. Probably it can be explained with a relatively earlier appearance of vestibular symptoms (hearing loss, vertigo, and tinnitus) due to their impact on daily activities. The facial nerve typically requires more compression before facial motor deficits can be noticeable, the same finding in acoustic neuromas [11]. Retromeatal tumors presented primarily with symptoms secondary to mass effect or hydrocephalus rather than focal deficits, consistent with others findings as headache, ataxia, and vertigo. Similar findings are present in literature [12]. For years, skull base meningiomas have been considered unresectable, but recent reviews have shown that they can be operated upon with good outcome comparable to the convexity meningiomas [13]. Even though technical advancement of surgery now permits total excision of many skull base lesions, radical removal of meningiomas is not always possible. Lesions of CPA and the surrounding skull base present a great Curr Otorhinolaryngol Rep (2019) 7:65–72 challenge to the skull base surgeon in consideration of the regional anatomy. Many surgical techniques have been developed for accessing these regions both for better exposure of the site and to allow a low rate of morbidity by preserving facial nerve function and hearing. Even if GTR remains the gold standard for patients, the complete removal within the restrictions of acceptable morbidity is not always achievable. Few studies have looked at morbidity or mortality compared across all approaches [14]. Our aim was to share our experience in the treatment of various diseases. The literature reports that skull base meningiomas are believed to have a high rate of recurrence and worse prognosis compared with intracranial meningiomas, although the only statistically significant finding is that increasing age is associated with poor outcomes. Surgeons’ experience has contributed to dispelling that belief. GTR in our findings was the most common extent of resection (Fig. 1). We achieved a rate of GTR of 77% (p < 0.001) with morbidity of about 89% for retromeatal and perimeatal tumors. This is consistent despite of the most recent literature as many series demonstrated high GTR rate but concomitant high morbidity rates [15]. Speaking of which, common finding is that the retrosigmoid approach is perhaps one of the most commonly used surgical approaches for removing skull base meningiomas [16]. However, in deciding which surgical approach fits better to the patient, considerations must be given to tumor invasion of the cavernous sinus and IAC, to their tentorial attachments, and to their forward expansion towards the jugular foramen. Moreover, this approach leads to residual tumor that is usually treated via conservative treatment, such as radiotherapy. However, it should be emphasized that CPA meningiomas with WHO grade II or higher levels of morphological evidence have a higher risk of recurrence in a relatively shorter period of time [17]. So GTR is extremely important for these patients. Since radiosurgery does not guarantee the prevention of the recurrence of tumors, complete surgical resection is still the main strategy to prevent tumor recurrence. The surgeon’s choice of surgical approach depends mainly on the characteristics of the tumor and personal preferences. In our centers, many different approaches were chosen based on our understanding of the following: tumor origin, growth direction, form and size, and the main symptoms related to the invaded vital structures. Indeed, some other authors suggest that the retrosigmoid approach has limitations, such as a restricted angle of view, high venous pressures, and suboptimal brain relaxation [18]. In comparison, transpetrous approaches help to get a wide surgical field, a shorter working distance between the craniectomy and the tumor, and a better orientation towards the lateral and ventral brain stem, limiting the brain retraction. Moreover, it is possible to early identify and control the facial nerve 71 and to early resect the osteo-dural insertion of the meningioma, with coagulation of the tumor’s feeding vessels. Our classification based on tumors’ location according to the IAC helped us find out the best surgical approach in order to achieve a GTR. Different surgical approaches and careful microneurosurgical technique can be used to achieve improved surgical and functional outcomes. Resection is obviously related to surgical risk which often depends on tumor site. Many related morbidities worry both patients and surgeons. According to literature, one concern is undoubtedly facial nerve function, which is always taken into account in almost all papers [9•]. Thanks to different surgical approaches, HB grades I–II were achieved for the 69% of our patients. Choosing a different approach for the three categories led us to achieve a low rate of morbidity, particularly in retromeatal and perimeatal groups. Ninety percent of patients in these groups lacked complications. Premeatal tumors are the most concerning due to their anatomical correlations with facial nerve function affected in half of the patients. However, despite of the high surgical risks in treating these tumors, we eventually achieved a 24% lack of complications in the premeatal group. Last, hearing function, interestingly is not as deeply considered as facial nerve function in the literature. Transcochlear and translabyrinthine approaches require a sacrifice of hearing but often the decision to proceed with these approaches is made because of large tumor extension involving the IAC, petrous ridge, clivus, or cavernous sinus, or because of brain-stem compression or basilar artery involvement. Moreover, as previously shown, these approaches let us achieve a very high rate of GTR accounting about 73% for TC and TLab approach themselves, which get stronger the huge worth of these approaches. Conclusions Total resection is the only way to cure patients affected by PCM. GTR is the aim of surgery as the extent of resection influences the rate of recurrence, which in turn influences the prognosis. We aimed to show how different surgical approaches may help to reach GTR and low morbidity, especially on facial nerve function. In this study, we reviewed a large sample size of 90 patients with FCM. Though generally considered challenging to resect tumors at this location, different approaches bore satisfactory results with an excellent extension of resection, preservation of cranial nerves, and low complication rates in our two centers. Compliance with Ethical Standards Conflict of Interest The authors declare that they have no conflicts of interest. 72 Human and Animal Rights and Informed Consent This article does not contain any studies with human or animal subjects performed by any of the authors. Curr Otorhinolaryngol Rep (2019) 7:65–72 10.• Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. References Papers of particular interest, published recently, have been highlighted as: • Of importance 1. Castellano F, Ruggiero G. Meningiomas of the posterior fossa. Acta Radiol Suppl. 1953;104:1–177. 2. Martinez R, Vaquero J, Areitio E, Bravo G. Meningiomas of the posterior fossa. Surg Neurol. 1983;19(3):237–43. 3. Thomas NW, King TT. Meningiomas of the cerebellopontine angle. A report of 41 cases. Br J Neurosurg. 1996;10:59–68. 4. Mazzoni A. The petro-occipital trans-sigmoid approach for lesions of the jugular foramen. Skull Base. 2009;19(1):48–56. 5. Ramachandra P, Tummala MD, Ernesto Coscarella MD, Jacques J, Morcos MD. F.R.C.S. Transpetrosal approaches to the posterior fossa. Neurosurg Focus. 2005;19(2):E6. 6. House JW, Brackmann DE. Facial nerve grading system. Otolaryngol Head Neck Surg. 1985;93:146–7. 7. Simpson D. The recurrence of intracranial meningiomas after surgical treatment. J Neurol Neurosurg Psychiatry. 1957;20:22–39. 8. Jung HW, Yoo H, Paek SH, Choi KS. Long-term outcome and growth rate of subtotally resected petroclival meningiomas: experience with 38 cases. Neurosurgery. 2000;46(3):567–74. 9.• Rogers L, et al. Meningiomas: knowledge base, treatment outcomes, and uncertainties: a RANO review. J Neurosurg. 2015;122(1):4–23. Response Assessment in Neuro-Oncology (RANO) subcommittees are developing a paper on systemic 11. 12. 13. 14. 15. 16. 17. 18. therapies for meningioma and a separate article proposing standardized end point and response criteria for meningioma. Magill ST, Rick JW, Chen WC, Haase DA, Raleigh DR, Aghi MK, et al. Petrous face meningiomas: classification, clinical syndromes and surgical outcomes. World Neurosurg. 2018. https://doi.org/10. 1016/j.wneu.2018.03.194. PFMs present with distinct clinical syndromes based on their location along the petrous face: anterior with trigeminal symptoms, middle with auditory/ vestibular symptoms, and posterior with symptoms of mass effect/hydrocephalous. Surgical resection is associated with excellent long-term survival and a low rate of recurrence, which can be managed with radiotherapy. Roser F, Nakamura M, Dormiani M, Matthies C, Vorkapic P, Samii M. Meningiomas of the cerebellopontine angle with extension into the internal auditory canal. J Neurosurg. 2005;102(1):17–23. Velho V, Agarwal V, Mally R, Palande DA. Posterior fossa meningioma “our experience” in 64 cases. Asian J Neurosurg. 2012;7(3): 116–24. Anil Nanda and Prasad Vannemreddy. Recurrence and outcome in skull base meningiomas: do they differ from other intracranial meningiomas? SKULL BASE/VOLUME 18, NUMBER 42008. Michael L. DiLuna and Ketan R. Bulsara. Surgery for petroclival meningiomas: a comprehensive review of outcomes in the skull base surgery era. SKULL BASE/VOLUME 20, NUMBER 52010. Joseph P. Roche et al., Treatment of lateral skull base and posterior cranial fossa lesions utilizing the extended middle cranial fossa approach. Otology. Neurology. 2017;38(5). He X, Liu W, Wang Y, et al. Surgical management and outcome experience of 53 cerebellopontine angle meningiomas. Cureus. 2017;9(8):e1538. https://doi.org/10.7759/cureus.1538. Couldwell WT, Cole CD, Al-Mefty O. Patterns of skull base meningioma progression after failed radiosurgery. J Neurosurg. 2007;106(1):30–5. Sanai N, McDermott MW. A modified far-lateral approach for large or giant meningiomas of the posterior fossa. J Neurosurg. 2010;112: 907–12.