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Introducción: los quistes epidermoides son el tercer tumor más común del ángulo pontocerebeloso (APC). Es infrecuente detectar simultáneamente un colesteatoma infiltrativo del oído medio (OM). Caso clínico: paciente de 51 años acude a urgencias por cefalea hemicraneal intensa, pulsátil secundaria a hidrocefalia aguda, requirió ventriculostomía. En la resonancia magnética nuclear (RMN) cerebral contrastada se reporta una masa en el APC sugestivo de quiste epidermoide y simultáneamente un colesteatoma infiltrativo del OM. La paciente fue intervenida primero con resección de colesteatoma del OM; en un segundo tiempo resección del quiste epidermoide del APC por vía translaberíntica. El posoperatorio la evolución clínica fue satisfactoria. Discusión: los quistes epidermoides del APC son histopatológicamente idénticos al colesteatoma del OM y pueden ser secundarios a estos. Conclusión: se debe individualizar el manejo sin descartar la posibilidad de tener las dos enfermedades de manera simultánea.

Introduction: cysts are the third most common tumor of the cerebellopontine angle (CPA). It is rare to simultaneously detect an infiltrative cholesteatoma of the middle ear (OM). Clinical case: a 51-year-old patient attended the emergency department due to intense throbbing hemicranial headache secondary to acute hydrocephalus, requiring ventriculostomy. Contrast-enhanced cerebral magnetic resonance imaging (MRI) reported a mass in the APC suggestive of an epidermoid cyst and simultaneously an infiltrative cholesteatoma of the OM. The patient underwent first surgery with resection of the OM cholesteatoma; in a second stage, resection of the epidermoid cyst of the APC through a translabyrinthine approach. The postoperative clinical evolution was satisfactory. Discussion: APC epidermoid cysts are histopathologically identical to OM cholesteatoma and may be secondary to them. Conclusion: management must be individualized without ruling out the possibility of having both diseases simultaneously.

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Surgical ventriculoperitoneal shunting remains standard treatment for communicating hydrocephalus, despite persistently elevated infection and revision rates. A novel minimally invasive endovascular cerebrospinal fluid (CSF) shunt was developed to mimic the function of the arachnoid granulation which passively filters CSF from the central nervous system back into the intracranial venous sinus network. The endovascular shunt is deployed via a femoral transvenous approach across the dura mater into the cerebellopontine angle cistern. An octogenarian with intractable hydrocephalus following subarachnoid hemorrhage underwent successful endovascular shunting, resulting in swift intracranial pressure reduction from 38 to <20 cmH2O (<90 min) and resolution of ventriculomegaly. This first successful development of a percutaneous transluminal venous access to the central nervous system offers a new pathway for non-invasive treatment of hydrocephalus and the potential for intervention against neurological disorders.

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El artículo publicado por Sawamura Y. y Abe H. hace más de dos décadas representó una técnica revolucionaria para las cirugías contemporáneas de reanimación facial con axones del nervio hipogloso.1 Estos procedimientos se realizan cuando no es posible neurotizar al nervio facial con un cabo proximal del propio nervio. Esta situación se observa luego de la exéresis de tumores del ángulo pontocerebeloso, en la que se daña al VII par en su trayecto cisternal. La dificultad de realizar la neo anastomosis del hipogloso con el facial en su porción extracranal reside en la distancia anatómica en la que se encuentran

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Abstract Introduction: Arachnoid cyst in the internal auditory canal is a quite rare pathology but due to its compressive action on the nerves in this district should be surgically removed. Several surgical techniques have been proposed but no surgeons have used the minimally assisted endoscope retrosigmoid approach for its removal. Objective: To investigate the feasibility of using a minimally invasive endoscope assisted retro-sigmoid approach for surgical removal of arachnoid cysts in the internal auditory canal. Methods: Minimally invasive endoscope assisted retrosigmoid approach allows to access to the internal auditory canal through a minimally invasive retrosigmoid approach that combines the use of a microscope and an endoscope. It is performed in six steps: soft tissue step, bone step, dura step, cerebellopontine angle step (performed using an endoscope and a microscope), microscope-endoscope assisted arachnoid cysts removal and closure. We tested minimally invasive endoscope assisted retrosigmoid approach for removal of arachnoid cysts in the internal auditory canal on two human cadaveric heads (specimens) of subjects affected from audio-vestibular disorders and with arachnoid cysts in the internal auditory canal confirmed by magnetic resonance imaging. Results: The mass was completely and successfully removed from the two specimens with no damage to the nerves and/or vessels in the surgical area. Conclusion: The results of our study are encouraging and support the feasibility of using minimally invasive endoscope assisted retrosigmoid approach for removal of arachnoid cysts in the internal auditory canal. While further clinical in-vivo studies are needed to confirm the accuracy and safety of using the minimally invasive endoscope assisted retrosigmoid approach for this specific surgery, our group has successfully used the minimally invasive endoscope assisted retrosigmoid approach in the treatment of microvascular compressive syndrome, schwannoma removal and vestibular nerve resection.

Resumo Introdução: O cisto aracnóide no conduto auditivo interno é uma doença bastante rara, mas, devido à sua ação compressiva sobre os nervos deste local, ele deve ser removido cirurgicamente. Várias técnicas cirúrgicas foram propostas, mas ninguém utilizou a abordagem retrosigmoide minimamente invasiva assistida por endoscopia para a sua remoção. Objetivo: Investigar a viabilidade do uso da abordagem retrosigmoide minimamente invasiva assistida por endoscopia para remoção cirúrgica de cistos aracnóides no conduto auditivo interno. Método: A abordagem retrosigmoide minimamente invasiva assistida por endoscopia permite o acesso ao conduto auditivo interno através de uma abordagem retrosigmóide minimamente invasiva que combina o uso de um microscópio e um endoscópio. É realizada em seis etapas: do tecido mole, óssea, dura-máter, do ângulo pontocerebelar (realizado com um endoscópio e um microscópio), remoção e fechamento assistidos por endoscópio-microscópico. Testamos a abordagem retrosigmoide minimamente invasiva assistida por endoscopia para remoção de cistos aracnóides no conduto auditivo interno em duas cabeças de cadáveres humanos (espécimes) de indivíduos afetados por distúrbios auditivos-vestibulares e com cistos aracnóides no conduto auditivo interno confirmado por imagem de ressonância magnética. Resultados: A lesão foi removida completamente e com sucesso nos dois espécimes sem dano aos nervos e/ou vasos na área cirúrgica. Conclusão: Os resultados do nosso estudo são encorajadores e apoiam a viabilidade do uso da abordagem retrosigmoide minimamente invasiva assistida por endoscopia para remoção de cistos aracnóides no conduto auditivo interno. Embora mais estudos clínicos in vivo sejam necessários para confirmar a precisão e a segurança do uso da abordagem retrosigmoide minimamente invasiva assistida por endoscopia para essa cirurgia específica, nosso grupo utilizou com sucesso a abordagem retrosigmoide minimamente invasiva assistida por endoscopia no tratamento da síndrome compressiva microvascular, remoção de schwannoma e ressecção do nervo vestibular.

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INTRODUCTION: Arachnoid cyst in the internal auditory canal is a quite rare pathology but due to its compressive action on the nerves in this district should be surgically removed. Several surgical techniques have been proposed but no surgeons have used the minimally assisted endoscope retrosigmoid approach for its removal. OBJECTIVE: To investigate the feasibility of using a minimally invasive endoscope assisted retro-sigmoid approach for surgical removal of arachnoid cysts in the internal auditory canal. METHODS: Minimally invasive endoscope assisted retrosigmoid approach allows to access to the internal auditory canal through a minimally invasive retrosigmoid approach that combines the use of a microscope and an endoscope. It is performed in six steps: soft tissue step, bone step, dura step, cerebellopontine angle step (performed using an endoscope and a microscope), microscope-endoscope assisted arachnoid cysts removal and closure. We tested minimally invasive endoscope assisted retrosigmoid approach for removal of arachnoid cysts in the internal auditory canal on two human cadaveric heads (specimens) of subjects affected from audio-vestibular disorders and with arachnoid cysts in the internal auditory canal confirmed by magnetic resonance imaging. RESULTS: The mass was completely and successfully removed from the two specimens with no damage to the nerves and/or vessels in the surgical area. CONCLUSION: The results of our study are encouraging and support the feasibility of using minimally invasive endoscope assisted retrosigmoid approach for removal of arachnoid cysts in the internal auditory canal. While further clinical in-vivo studies are needed to confirm the accuracy and safety of using the minimally invasive endoscope assisted retrosigmoid approach for this specific surgery, our group has successfully used the minimally invasive endoscope assisted retrosigmoid approach in the treatment of microvascular compressive syndrome, schwannoma removal and vestibular nerve resection.

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Resumen: Las lesiones del ángulo pontocerebeloso (APC) representan el 6 al 10% de las neoplasias intracraneales, siendo los schwannomas vestibulares y meningiomas los más comunes. Sin embargo, hasta el 15% pueden ser otras lesiones, entre ellas las derivadas a partir de restos de células melanocíticas presentes en las leptomeninges. El diagnóstico diferencial de las patologías tumorales del APC es extenso, siempre teniendo en cuenta las lesiones más comunes. Sin embargo, cuando las características radiológicas no son las esperadas, el enfoque debe orientarse hacia las lesiones inusuales, poniendo en contexto las diferentes estirpes celulares que pueden dar origen a las neoplasias en esta localización, como las neoplasias melanocíticas. Se presenta el caso de un masculino de 74 años con síndrome cerebeloso de tórpida evolución, al cual se le realiza RM de cerebro contrastada, identificando una lesión de base dural en el APC izquierdo, con hiperintensidad de señal en T1 e hipointensidad en T2, atípico para las lesiones más comunes en esta región, que sugiere su contenido melanocítico.

Abstract: Cerebellopontine angle tumors (CPA) represent approximately 6 to 10% of intracranial tumors. Vestibular Schwannomas and meningiomas are the most common, however up to 15% can be of other origin, including from melanocytes derived from the neural crest. The differential diagnosis of CPA pathologies is extensive, always taking into account the most common ones. However, if the radiological characteristics are not the expected, the approach should be directed towards unusual lesions, putting into context the different cell lines that can give rise to the neoplasm at this location, such as melanotic neoplasms. We present a case of a 74-year-old male, who presented with a cerebellar syndrome. Due to an atypical clinical evolution, a contrast enhanced head MRI was performed, revealing a dural based tumor on the left CPA, which was hyperintense on T1 and hypointense on T2 weighted sequences, which is not expected from the common lesions at this region and suggested it's melanotic content.

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AIM: The present study aimed to report a case of orofacial pain secondary to acoustic neuroma (AN). METHODS AND RESULTS: A 66-year-old female presented with unilateral facial pain and odontalgia. The pain was described as throbbing, dull, and constant. Tinnitus, hearing loss, dizziness, and others symptoms were also present. Due to the characteristics of the pain and clinical or radiographic findings, other possible diagnoses, such as temporomadibular disorder, tooth-related pain, sinusitis, and primary headaches, were excluded. Somatosensory tests for allodynia and hyperalgesia showed extraoral and intraoral hypersensitivity. Magnetic resonance imaging revealed a lesion located on the right cerebellopontine angle extending into and obliterating the internal auditory canal and compressing the middle cerebral peduncle, the pons, and the cisternal segment of cranial nerve V. The patient was diagnosed with a brainstem tumor compatible with AN and trigeminal neuralgia secondary to cranial nerve V compression. CONCLUSION: Although uncommon, intracranial tumors should be considered during orofacial pain evaluation to avoid iatrogenic treatment and delayed diagnosis.

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Intermediate nerve schwannomas (INS) are extremely rare lesions in literature. They have been described mimicking facial nerve schwannomas, but not vestibular schwannomas (VS). We aimed to review the previously published cases, as well as the evidence to believe that they are far more common, though usually misdiagnosed as facial or VS. We performed a review of PubMed/Medline and Embase of "intermediate nerve schwannoma," "facial nerve schwannoma," "greater superficial petrosal nerve schwannoma," "geniculate ganglion schwannoma," and "chorda tympani schwannoma" to identify all cases of INS, following the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) statement. Furthermore, 2 cases operated at our center are shown to exemplify the proposed hypotheses. No article was excluded from review. Thirteen cases of INS, 11 cases of chorda tympani schwannoma, and 18 cases of greater superficial petrosal nerve schwannoma were found in literature. In facial nerve schwannomas, the predilection of schwannomas for sensory nerves, and the ability to preserve the motor facial nerve during tumor resection support the hypothesis of intermediate nerve as the nerve of origin. For VSs, the different arachnoidal arrangement of medial VS, the sharing of pia mater by the intermediate nerve and vestibular nerve, and the medial Obersteiner-Redlich zone of the intermediate nerve, support the hypothesis of intermediate nerve origin of some VS. The correct identification of the intermediate nerve as a nerve of origin of cerebellopontine angle schwannomas is of uttermost importance, especially when mistaken for VS, as this may account for the heterogeneity of facial and cochlear outcomes after surgery.

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BACKGROUND: Vestibular schwannoma (VS) is the most common benign tumor originating in the cerebellopontine angle. In most cases, tumors tend to grow and deserve proper treatment. Sometimes they stabilize, and rarely they decrease in size spontaneously. METHODS: We evaluated retrospectively the images of patients with spontaneous tumor regression. We describe the common neuroimage findings of patients with spontaneous tumoral regression. RESULTS: Four patients with diagnosis of VS were followed with magnetic resonance imaging (MRI). There were some relevant features in MRI: a heterogeneous contrast enhancement in the outer layer of the tumor and presence of a cerebrospinal fluid column between the tumor and the entrance of the internal auditory canal. The percentage of tumor diameter reduction ranged from 20% to 40%. CONCLUSIONS: Some MRI features may demonstrate a spontaneous involution of VS and may be closely followed in asymptomatic or oligosymptomatic patients.

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Introducción: La cirugía de los schwannoma vestibulares constituye un desafío para los neurocirujanos. Debido a que se trata de un tumor benigno la resección completa de la lesión implica la curación del paciente. Sin embargo, este objetivo no siempre es fácil de lograr preservando la función de los nervios facial y acústico, especialmente en tumores de gran tamaño. Objetivos: Presentar detalles técnicos de la cirugía de resección de un schwannoma vestibular de gran tamaño (IVa) en el que se pudo preservar la función facial. Materiales y métodos: Se presenta el caso de una paciente femenina de 36 años que consultó por hipoacusia izquierda. En la RM preoperatoria se evidenciaba una lesión ocupante de espacio del ángulo pontocerebeloso izquierdo compatible con schwannoma vestibular con compresión del tronco encefálico y sin efecto de masa sobre el IV ventrículo (grado IVa). Mediante un abordaje suboccipital retromastoideo en posición de decúbito lateral se realizó la resección de la lesión en forma completa asistida por monitoreo del nervio facial. En todo momento se pudo preservar el plano aracnoideo que separaba el tumor de los nervios adyacentes. Resultados: Se logró una resección macroscópicamente completa con preservación de la función del nervio facial. La paciente permaneció internada por 96 hs en el postoperatorio sin complicaciones derivadas del procedimiento. Conclusión: La preservación del plano aracnoideo es un detalle técnico de mucha importancia para disminuir las posibilidades de lesión de los nervios facial y auditivo en la cirugía de resección de los schwannoma vestibulares.

Introduction: The surgery of vestibular schwannomas is a challenge for neurosurgeons.Because it is a benign tumor, complete resection of the lesion involves healing the patient. However, this objective is not always easy to achieve, preserving the function of both the facial and acoustic nerves, especially when dealing with large tumors. Objective: The objective of the video is to present some technical details of a large vestibular schwannoma (IVa) surgery in which the facial function could be preserved. Materials and methods: We present the case of a 36-year-old female patient who consulted for left hearing loss. The preoperative MRI showed a space- occupying lesion of the left pontocerebellar angle, which was compatible with vestibular schwannoma, with compression of the brainstem but with no mass effect on the IV ventricle (grade IVa). By means of a retromastoid suboccipital approach in the lateral prone position, the lesion was completely resected assisted by neurophysiological monitoring of the facial nerve. At all times, the arachnoid plane separating the tumor from the adjacent nerves was preserved. Results: A macroscopically complete resection was achieved preserving the facial nerve function. The patient stayed hospitalized for 96 hours during the postoperative period without any complication from the procedure. Conclusion: Preserving the arachnoid plane is a very important technical detail to reduce the possibilities of injury of the facial and auditory nerves in the vestibular schwannoma resection surgery.

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La neuralgia del trigémino es característica en personas mayores de 50 años, comprometiendo principalmente el territorio V2 y V3 de dicho nervio de manera unilateral y la carbamezepina es el fármaco con mayor efectividad, pero no siempre responden. La presentación atípica y los signos de alarma ponen en consideración el estudio con resonancia magnética cerebral, pues obliga a descartar una causa secundaria, siendo necesario el análisis de neuroimágenes. Debido a esto, presentamos un caso de quiste epidermoide con neuralgia secundaria, que se presenta con signos de alarma y se deben considerar los estudios complementarios.

Classic trigeminal neuralgia (TN) is most common after 50 years of age, predominantly unilateral within the distribution of the V2 and V3 branches of the trigeminal nerve. Carbamazepine is the most effective medication, although not all patients respond to it. In consideration physicians should arrange a brain magnetic resonance imaging study when facing TN patients with atypical presentation and alarm signs, as secondary causes must be ruled out. We present a case of epidermoid cyst with secondary TN which presented with "red flag" signs. Image studies were therefore mandatory.

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Introducción: El recorrido del "loop subarcuato" de la arteria cerebelosa anteroinferior (ACAI) presenta múltiples variaciones que condicionan además su principal eferencia, la arteria subarcuata (ASA). El espectro de variaciones de este complejo ha sido referido en la literatura de forma inconexa y desorganizada. Material y Métodos: Se propuso una clasificación sistematizada de las variantes del complejo ACAI-ASA, basada en la interacción del hueso petroso y la ACAI en el periodo embrionario. La misma fue aplicada en una serie de pacientes estudiados mediante secuencia CISS (constructive interference in steady state) de resonancia magnética para categorizar las relaciones presentes en el ángulo pontocerebeloso (APC). Resultados: Se evaluaron 84 pacientes, incluyendo 161 APC. Todos los grados propuestos fueron identificados en la serie evaluada. Las proporciones encontradas en la gradación propuesta se mantuvieron en el rango de las publicaciones aisladas. Conclusión: La clasificación propuesta para el complejo ACAI-ASA permitió distinguir y objetivar consistentemente el espectro de variaciones.

Introduction: The pathway of the anterior inferior cerebellar artery's (AICA) "subarcuate loop" can vary extensively. This variability also affects its main branch, the subarcuate artery (SAA). The spectrum of variations observed with this combination of vessels is inadequately described in the literature. Methods and Materials: A systematized classification system for AICA-SAA complex variants was proposed, based upon interactions between the petrosal bone and the AICA in embryos. This classification scheme then was applied to a series of patients assessed by magnetic resonance CISS (constructive interference in steady state) sequences, to categorize the cerebellopontine angle (CPA) relationships. Results: Eighty-four patients were evaluated, encompassing 161 CPA. All the proposed grades were identified in the evaluated series. The proportions found with the proposed gradation system were within the range of previous publications. Conclusions: The AICA-SAA complex classification system that we proposed allowed for consistently distinguishing and objectifying the spectrum of variations seen in the subarcuate loop.

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INTRODUCTION: The cerebellopontine angle (CPA) is a subarachnoid space in the lateral aspect of the posterior fossa. In this study, we propose a complementary analysis of the CPA from the cerebellopontine fissure. METHODS: We studied 50 hemi-cerebelli in the laboratory of neuroanatomy and included a description of the CPA anatomy from the cerebellopontine fissure and its relationship with the flocculus and the 5th, 6th, 7th, and 8th cranial nerves (CN) origins. RESULTS: The average distance from the 5th CN to the mid-line (ML) was 19.2 mm, 6th CN to ML was 4.4 mm, 7-8 complex to ML was 15.8 mm, flocculus to ML was 20.5 mm, and flocculus to 5th CN was 11.5 mm, additionally, and the diameter of the flocculus was 9.0 mm. The angle between the vertex in the flocculus and the V CN and the medullary-pontine line was 64.8 degrees. DISCUSSION: The most common access to the CPA is through the retrosigmoid-suboccipital region and this approach can be done with the help of an endoscope. The anatomy of origins of neural structures tends to be preserved in cases of CPA lesions. CONCLUSION: Knowledge of the average distances between the neural structures in the cerebellar-pontine fissure and the angular relationships between these structures facilitates the use of surgical approaches such as microsurgery and endoscopy.

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We report a case of a 16-year-old female patient harboring neurofibromatosis type 2 who presented with bilateral hearing impairment, which was on the left side, as well as facial paresis (House-Brackmann grade III) and ataxic gait. A magnetic resonance imaging (MRI) exam evidenced bilateral lesions in the cerebellopontine angles (CPAs) with extension into the internal acoustic meatus, and an additional lesion in the right CPA with radiological characteristics of an epidermoid cyst. The patient was submitted to microsurgical resection, confirming a collision of a vestibular schwannoma and an epidermoid cyst in the right CPA. In the present case report, we describe the first case reported in the literature with preoperative diagnostic work-up, intraoperative findings, postoperative course of the patient, as well as a detailed literature review of these specific coinciding pathologies, denoting the importance of further genomic studies regarding multiple central nervous system (CNS) lesions.

Relatamos o caso de uma paciente de 16 anos de idade com neurofibromatose tipo II com deficiência auditiva bilateral, pior no ouvido esquerdo, assim como paresia facial (HouseBrackmann grau III) e ataxia. Estudo de ressonância magnética comprovou lesão bilateral nos ângulos cerebelopontinos (ACPs) com extensão ao meato acústico interno, e uma lesão adicional no ACP direito com características radiológicas de um cisto epidermoide. A paciente foi submetida a ressecção microcirúrgica, confirmando a colisão de um schwannoma vestibular com um cisto epidermoide no ACP direito. No presente estudo, descrevemos o primeiro caso relatado na literatura com trabalho diagnóstico pré-operatório, resultados intraoperatórios, evolução da paciente no pós-operatório, assim como revisão detalhada da literatura específica sobre essas patologias, demonstrando a importância de mais estudos genômicos sobre as múltiplas lesões do sistema nervoso central (SNC).

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Los Schwannomas del acústico son tumores benignos de crecimiento lento de la división superior del nervio vestibular, con una incidencia de 1,9 por cada 100.000 habitantes. En la actualidad, la tecnología de la neuroimagen en conjunto con la exploración audiológica clínica e instrumentada permiten el diagnóstico en estadios tempranos e incluso como hallazgo clínico, por tal motivo solo el 6 % a nivel mundial se cataloga como tumor grande al momento del diagnóstico. Se presenta el caso de una mujer de 16 años con cefalea, mareo, vómito, hipoacusia, parálisis facial y diadococinesia, por lo que se realizaron estudios de neuroimagen en los que se evidenció masa ocupativa a nivel ángulo pontocerebeloso; por las dimensiones se cataloga según la clasificación de Koss como estadio IV. Se confirmó diagnóstico mediante estudio histopatológico.

Acoustic schwannomas are benign tumors of slow growth in the top division of the vestibular nerve, with an incidence of 1.9 per 100,000 inhabitants. Currently, imaging technology together with the clinical examination audiological and implemented allow diagnosis at an early stage and even as a clinical finding, on that ground only 6 % worldwide are categorized as large tumor at diagnosis. For a woman of 16 with headache, dizziness , vomiting , hearing loss, facial paralysis and diadochokinesia occurs, so neuroimaging studies in which a space- occupying mass level cerebellopontine angle were made evident ; by the dimensions it is classified as classified as stage IV Koss . Diagnosis was confirmed by histopathology.

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Medulloblastoma is the most common central nervous system tumor in children. Extraaxial medulloblastomas, especially tumors with no connection to the brain stem or cerebellum are extremely rare. We report a case of a 3-year-old patient, who presented with a history of subacute headache and vomiting. After performing a head computed tomography scan, a mass was detected in the left cerebello-pontine angle, along with concomitant hydrocephalus. The treatment was total resection of the tumor. Despite the fact that extra-axial medulloblastomas are extremely rare, this differential diagnosis should be included in the management of pediatric patients who present with posterior fossa tumors.

Meduloblastoma é o tumor do sistema nervoso central mais comum em crianças. Meduloblastomas extra-axiais, especialmente tumores sem conexão com o tronco encefálico ou cerebelo, são extremamente raros. Relatamos o caso de uma paciente de 3 anos de idade, que apresentou um histórico de cefaleia subaguda e vômitos. Por meio de um exame de tomografia computadorizada, foi identificada uma massa no ângulo ponto-cerebelar esquerdo, acompanhada de hidrocefalia. O tratamento foi resseção total do tumor. Apesar de meduloblastomas extra-axiais serem extremamente raros, este diagnóstico diferencial deve ser incluído no manejo de pacientes pediátricos que apresentem tumores da fossa posterior.

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Vestibular schwannomas (VS) are the most common lesions of cerebellopontine angle (CPA) corresponding to 76-91 % of the cases. Usually, these lesions present typical CT and MRI findings. Non-schwannomatous tumors restricted to the internal auditory meatus (IAM) are rare and their preoperative radiological diagnosis may be difficult. This article describes nine surgically treated intrameatal non-schwannomatous lesions (NSL) and reviews the literature. In the last 16 years, a total of 471 patients with diagnosis of VS were operated on in our department. Preoperatively, 42 patients had diagnosis of intrameatal schwannomas, but surgery revealed in nine cases NSL (3 meningiomas, 3 arachnoiditis/neuritis, 1 cavernoma, 1 vascular loop, and 1 arachnoid cyst). Most frequent symptoms presented by patients with NSL were hearing loss 89 % (8/9) of patients, tinnitus 78 % (7/9), and vertigo 33 % (3/9). Almost all lesions (8/9) presented MRI findings of isointense signal in T1W with contrast enhancement. The only exception was the arachnoid cyst with intracystic bleeding, which was hyperintense in T1W that is not enhanced with contrast. This series shows an occurrence of 21.4 % of non-schwannomatous tumors in 42 cases of lesions restricted to the IAM. Whenever a solely intrameatal enhanced tumor is detected, it is necessary to think about other diagnostic possibilities rather than VS. Therapeutic management may be changed, specially if radiosurgical treatment is considered.

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