Cerebellopontine Angle Lesions Research Articles

High resolution T2 MRI in the diagnosis of cerebellopontine angle and internal auditory canal lesions

High resolution T2 magnetic resonance imaging (MRI) can provide exquisite detail of internal auditory canal (IAC) and cerebellopontine angle (CPA) lesions. In this retrospective case series, blinded imaging sequences were delivered to three radiologists and compared with previously archived clinical reads that were non-blinded and incorporated both T1+C and T2 sequences together. This article demonstrates high sensitivity and specificity for high resolution T2 MRI particularly with lesions >5mm. This suggests a role for high resolution T2 MRI as an initial screening sequence or as a surveillance sequence.

Intracranial Epidermoid Lesions: our Experience of 38 Cases.

The clinical outcome following surgical resection of intracranial epidermoid lesions is not well documented. We describe a case series evaluating the clinical presentation and outcome following surgery in patients diagnosed with these lesions. A retrospective study conducted over a 4-year period. A total 38 patients who underwent surgery for intracranial epidermoid lesions were identified. Of these, 20 were supertentorial and 18 were infratentorial lesions. 33 patients presented with headache. 10 patients with supratentorial lesions presented with seizures. Patients with suprasellar epidermoid lesions presented with headache and visual problems. 14 of the 18 patients with cerebellopontine angle lesions presented with symptoms of trigeminal neuralgia. Post-operatively, 3 patients with cerebellopontine angle tumors developed facial weakness which was transient in 2 patients but permanent in 1 patient. Visual impairment in patients with suprasellar epidermoid lesions improved post-operatively. Hormonal replacement therapy was required in 2 patients. Recovery of 4 patients was complicated by Cerebrospinal fluid (CSF) leak while meningitis developed in 2 patients. One patient operated for cerebellopontine angle epidermoid died post operatively. Epidermoid lesions can develop anywhere in the cranial cavity. Like other space occupying lesions they often present with symptoms of raised ICP and with specific neurological deficits depending on location of the tumour. Surgical outcome is excellent with low complication rates.

Hypervascular Lesions of the Cerebellopontine Angle: The Relevance of Angiography as a Diagnostic and Therapeutic Tool and the Role of Stereotactic Radiosurgery in Management. A Comprehensive Review

The cerebellopontine angle (CPA) is a narrowed skull base area containing important cranial nerves and vessels and bordering with eloquent areas of the posterior fossa. Tumors of the CPA are a heterogeneous group and can have extradural, intradural/extra-axial, or intra-axial origins. Their vascular supply changes depending on their anatomic origin. Symptomatic, large CPA tumors require surgical resection in order to prevent irreversible, severe neurological damages. However, its tight and strategical location make surgery in the CPA very challenging and require appropriate pre-surgical planning. Pre-surgical diagnosis is of great importance as it allows us to choose the optimal management for the particular patient. This is of further significance when encountering high-risk lesions such as hypervascular tumors. Neurosurgeons should utilize every available pre-surgical diagnostic modalities as well as neo-adjuvant treatments in order to reduce such risks. We review all reported cases of hypervascular lesions of the CPA and discuss the roles of angiography and stereotactic radiosurgery in their management. Three lesions of the CPA can be considered as truly hypervascular: hemangioblastomas, hemangiopericytomas and paragangliomas. All lesions share many radiological features. However, each lesion has a different anatomical origin and hence, has a characteristic vascular supply. Pre-surgical angiography can be utilized as a diagnostic tool to narrow down the differential diagnosis of a vascular CPA lesion, based on the predominant supplying vessel. In addition, pre-surgical embolization at time of angiography will narrow the associated surgical risks. Angiography is a crucial diagnostic and therapeutic tool, helping both in narrowing the presurgical differential diagnosis and in controlling intraoperative bleeding. Because of the high surgical risks associated with resection of vascular tumors in the CPA, noninvasive treatments, such as stereotactic radiosurgery, also may have a crucial role.

Current role of MRI in cerebellopontine angle lesions

Objective The aim of our study is to evaluate the current role of MRI in the diagnosis of cerebellopontine angle lesions. Background MRI is considered the gold-standard method for the diagnosis of cerebellopontine angle lesions. This study aimed to explore an appropriate diagnosis to assess the extent and type of the lesion allowing for proper treatment. Patients and methods This study included 25 patients with symptoms suggestive of neurological disorders. Patients were subjected to different MRI sequences such as precontrast, postcontrast, diffusion MR, and MR spectroscopy. Results Of the 25 patients studied, the final diagnosis by MRI showed acoustic schwannoma in 12 (48.0%) patients, which was the most common lesion, followed by meningioma, was noted in seven (28.0%) patients, epidermoid cyst in one (4.0%) patient, prominent anterior inferior cerebellar artery (AICA) in one (4.0%) patient, paraganglioma in one (4.0%) patient, cystic neurofibroma in one (4.0%) patient, neurofibromatosis type 2 in one (4.0%) patient, and an arachnoid cyst in one (4.0%) patient. Conclusion MRI is the gold-standard method to differentiate the lesions by anatomical site of origin, shape, signal intensity, and behavior after an injection of contrast media.

Evaluation of Magnetic Resonance Imaging Diagnostic Approaches for Vestibular Schwannoma Based on Hearing Threshold Differences Between Ears: Added Value of Auditory Brainstem Responses.

This study investigates the most appropriate audiometric criterion in deciding which patients with asymmetric hearing loss should be referred to MRI to exclude a lesion in the cerebellopontine angle (CPA). Careful selection of patients could improve resource utilization while preventing unnecessary investigations with accompanying burden and costs. Retrospective case review. Tertiary referral center. Of all the patients who were referred to our clinic between 1997 and 2012, the records were reviewed of those who underwent pure-tone audiometry, auditory brainstem response (ABR) testing, and had a Gadolinium-enhanced MRI of the CPA. Regarding interaural pure-tone threshold differences at single or multiple (averaged) frequencies, we assigned multiple possible cut-off values (dB) defining an aberrant result, suggestive for CPA lesions. Results were compared with MRI to calculate sensitivity and specificity for every cut-off value. These were visualized as ROC curves enabling qualitative comparison. Added value of ABR was assessed as well. Sensitivity and specificity of various criteria to decide which patients with asymmetric hearing loss to send to MRI to exclude a CPA lesion. In total, 1016 records were reviewed. Two hundred ninety-four subjects (29%) were diagnosed with a CPA lesion on MRI. Sensitivity and specificity for audiometry results differed greatly depending on the predefined cut-off value for hearing threshold difference (40-95% sensitivity and 20-90% specificity). Best ROC curves were obtained when threshold differences at two or three higher frequencies were averaged. Adding results of ABR to the threshold criterion yielded a slightly better ROC curve, although sensitivity decreased. The best criterion to decide which patient with asymmetric hearing loss should be referred to MRI is based on the average bone conduction threshold difference at multiple (two or three) higher frequencies. The extent of the average threshold difference between ears that is used as a cutoff will mainly depend on treatment modality and (eventually) on resource costs and on the burden of Gadolinium-enhanced magnetic resonance imaging. Results of ABR can have little added value when only patients with a unilateral abnormal ABR at the worse hearing ear are referred to MRI. However, a lower sensitivity must then be accepted.

The meningeal branches of the superior cerebellar artery: a surgical observation study.

OBJECT The tentorial branch of the posterior cerebral artery was first identified in a cadaver dissection study. However, the tentorial branch of the superior cerebellar artery (SCA) has not been clearly described in autopsy or normal anatomical studies. In this study, a dural branch of the SCA that was found during the surgical treatment of trigeminal neuralgia is described. METHODS Between April 2011 and March 2014, 70 patients with idiopathic trigeminal neuralgia underwent microvascular decompression. The records of 58 patients were reviewed to investigate the meningeal branch of the SCA. RESULTS The meningeal branch of the SCA was visualized in 15 of the 58 patients (25.9%). In 4 patients, it was necessary to divide this branch in order to achieve decompression of the trigeminal nerve without eliciting postoperative neurological deficits. CONCLUSIONS This is the first identification of the meningeal branch of the SCA in living subjects, and such branches were rather frequently found. Recognition of this branch is important for the management of lesions in the cerebellopontine angle and tentorial lesions, using either an open microsurgical or endovascular method.

Primary cerebellopontine angle ependymoma with spinal metastasis in an adult patient: A case report.

Subtentorial ependymoma is a common central nervous system tumor in young children, but is uncommon in adults. Ependymoma often arises from the cells lining the fourth ventricle. The present study reports a rare case of primary ependymoma that originated from the cerebellopontine angle, with local extension to the two internal auditory canals and remote spinal metastasis, in an adult male. A 50-year-old male presented with headache, tinnitus and bilateral hearing loss that had persisted for 4 months. Magnetic resonance imaging (MRI) revealed a mass in each of the cerebellopontine angles, which had spread to each internal auditory canal and wrapped the VII/VIII cranial nerve complex. A gross total resection was performed to remove the mass in the right side. Histological examination confirmed that the tumor was a World Health Organization grade II papillary ependymoma. Notably, the patient complained of urine retention post-surgery and massive occupational lesions in T3-T4 and L5-S2 were found on full spinal cord MRI. The patient then received combination therapy consisting of temozolomide, and whole-brain and spinal cord radiation. In the final follow-up examination, performed 13 months after treatment, slight shrinkage of the T3 lesion was observed, and no progression of the left cerebellopontine angle and S5-L2 lesions were identified on MRI. In summary, although this clinical entity is rare, the diagnosis of ependymoma and the possibility of spinal cord metastasis should be considered in subtentorial tumors.

Non-schwannomatosis lesions of the internal acoustic meatus-a diagnostic challenge and management: a series report of nine cases.

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 16years, 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.

Magnetic resonance imaging of cerebellopontine angle lesions

Background: Cerebellopontine angle (CPA) tumors are usually benign, and they are divided into extra-axial, intra-axial, extradural, and petrous axis tumors. CPA pathologies can be asymptomatic or it may present with vertigo, tinnitus, or unilateral hearing loss depending upon the site of tumor origin and displacement of the neurovascular structure. Aim and Objectives: To evaluate the role of magnetic resonance imaging (MRI) aided with contrast-enhanced MRI as an imaging modality for diagnosis of CPA lesions. Materials and Methods: Analysis of 36 patients of CPA lesions over a period of 2 years was done. MRI was performed on Siemens 1.5 Tesla MAGNETOM Avanto Machine. Conclusion: There are spectrums of pathologies, which can present with these symptoms, which includes tumors, vascular malformations, and vascular loop compressing vestibulocochlear nerve or mastoid pathology so it is important to investigate the patient by MRI. Contrast-enhanced MRI is the most sensitive investigation in the evaluation of the CPA lesions, its characteristic, and its extent.

Remote Supratentorial Hemorrhage After Posterior Fossa Surgery: A Brief Case Report

Abstract The supratentorial hemorrhage after posterior fossa surgery is an unusual but delicate complication that carries high mortality and morbidity. A 50 year old woman presented vertigo 6 months of evolution, which worsened in the last 2 months accompanied by ataxia. She showed left cerebellar signs, had no focal motor or sensory deficits. A brain MRI identified cerebellopontine angle lesion with mass effect. The patient was treated on suboccipital craniectomy and resection of right posterior fossa tumor, the histopathological diagnosis was consistent with typical meningioma. (WHO Class I). The postoperative period was satisfactory. A month later, presented clinical symptoms of right-sided hemiparesis, brain CT revealed left frontal supratentorial hematoma, receiving conservative management. Patient was discharged after 10 days. Reports in the literature on this rare complication, detailed cases where the hematoma was presented in hours to days. To our knowledge this is the first report in the literature of supratentorial hemorrhage and posterior fossa surgery one month after the surgical procedure has been performed.

Surgical Approaches to Cerebellopontine Angle: A 17‐Year Experience of Our Skull Base Team

Objectives: We give an overview of the current state of cerebellopontine angle (CPA) surgery, based on the recent evidence, and describe our center’s experience in surgical approaches to these lesions. Methods: Retrospective review of cases who underwent surgery for CPA lesions at our hospital during the past 17 years (1996-2013), with focus on the description of the currently most used technique-extended retrosigmoid. We also conducted a brief review of the literature on CPA surgery, comparing the different approaches, their indications and complications. Results: During this period, 203 patients underwent surgery for CPA. The most frequent indication was vestibular schwannoma (84.7%). Other indications were meningiomas (8.4%), epidermoids (1%), vestibular neurectomies (1.5%), arteriovenous malformations (1%), anterior inferior cerebellar artery–posterior inferior cerebellar artery aneurysms (1%), trigeminal microscopic decompression (0.5%), and other more rare tumors (2%). The most used approach was extended retrosigmoid (71.9%), followed by the translabyrinthine (26.1%) and middle fossa approach (2%). Until 2004, the most used approach was the translabyrinthine; after 2004, the most used was the extended retrosigmoid. Conclusions: Currently, the preferred surgical approach used by our team is the extended retrosigmoid, because it allows a complete exposition of sigmoid sinus from the transverse sinus to the jugular bulb, enhances CPA vision, avoids cerebellar retraction, and is a simple way to get a wide route to the CPA. It also allows good functional outcomes (hearing and facial nerve preservation) in most cases. However, indications for approaches depend on the size of the lesion, its location and the quality of preoperative hearing, as well as a necessary familiarity with all approaches.

Facial nerve function after the extended translabyrinthine approach.

Objective To evaluate facial nerve function after excision of petroclival/anterior cerebellopontine angle (CPA) meningiomas by the extended translabyrinthine (EXTL) approach and compare these with outcomes after the transcochlear and transotic approaches. Design Retrospective chart review. Setting/Participants A search of archived surgical cases at a single institution between January 1, 1995, and January 1, 2012. Main Outcome Measures Facial function measured on the House-Brackmann (HB) scale. Results A total of 16 patients underwent the EXTL approach for primary excision of petroclival meningiomas. Average tumor size was 4.6 cm, and six patients had gross total resection. Average length of follow-up was 36.4 months. Two patients required reoperation for tumor regrowth. Preoperative facial function was HB I or II in all patients with available examinations. Immediate postoperative facial nerve function ranged from HB I to HB VI. In patients with an intact facial nerve at surgery, all but one had long-term facial function of HB I or II. A robust response on intraoperative facial nerve monitoring was prognostic of favorable long-term facial function. Facial function declined in some patients after postoperative radiation or revision surgery. Conclusions The EXTL approach allows excellent exposure of petroclival/anterior CPA lesions and should be favored to improve facial outcomes.

Potential neurotoxic effects of polymethylmethacrylate during cranioplasty

Cranioplasty for the surgical correction of cranial defects is often performed using polymethyl methacrylate (PMMA), or bone cement. Immediately prior to PMMA application, a liquid monomer form (methylacrylate) and a benzoyl peroxide accelerator are mixed resulting in polymerization, an exothermic reaction during which monomer linking and subsequent formation of solid polymer occur. The potential side effects of residual methylacrylate monomer toxicity and thermal damage of neural tissue during PMMA hardening have been described in various in vitro, animal, and cadaveric studies; however, clinically documented in vivo neurotoxicity in humans attributed to either of the above two mechanisms during PMMA cranioplasty is lacking. We present a series of four patients operated for removal of cerebellopontine angle lesions and two operated for the excision of parieto-occipital tumors who sustained cranial neuropathies and encephalopathies with transient or permanent neurological deficits that could not be attributed to surgical manipulation. We hypothesize that these complications most likely occurred due to thermal damage and/or chemical toxicity from exposure to PMMA during cranioplasty. Our case series indicates that even small volumes of PMMA used for cranioplasty may cause severe side effects related to thermal damage or to exposure of neural tissue to methylacrylate monomer.

Transcondylar Fossa Approach for Cerebellopontine Angle and Ventral Brainstem Lesions: Microsurgical Experiences and Avoidance of Complications

To treat the large tumors located in cerebellopontine angle (CPA) and vascular pathologies including aneurysms and dissection located around the ventral brainstem, transcondylar fossa approach (TCFA) has been regarded as less invasive one. Overall 10 patients had large tumors (D> 3 cm) including schwannomas (n = 8) and meningiomas (n = 2) located in the CPA and 17 patients had vascular pathologies including vertebra-basilar artery aneurysms (n = 14) and dissection (n = 3). Anatomical aspects of the condylar fossa, occipital condyle, and adjacent neurovascular structures were evaluated preoperatively and postoperatively using a three-dimensional computed tomography and magnetic resonance imaging. Gross-total removals in tumor patients achieved without resection of the occipital condyle. In 10 patients with saccular aneurysms, the aneurysms were clipped without resection of the occipital condyle and in 4 patients, partial resection of the condyle and jugular tubercle was necessary to obtain proximal control of the vertebral artery. We met two cases with vertebral artery injury and one case with postoperative cerebrospinal fluid. Transcondylar fossa approach was less invasive technique with minimal or no resection of the occipital condyle comparing with other approaches to ventral brainstem. To avoid complications, anatomical knowledge on the joint and the condylar veins should be reviewed.

Retrosigmoid approach for resection of cerebellopontine angle meningioma and decompression of the trigeminal nerve

Cerebellopontine angle (CPA) lesions account for up to 10% of all intracranial tumors. The most common CPA lesions are vestibular schwannomas (70-80%), meningiomas (10-15%) and epidermoid cysts (5%). CPA tumors are estimated to be the secondary cause for up to 9.9% patients with trigeminal neuralgia. We demonstrate a case of medically refractory trigeminal neuralgia caused by a CPA meningioma that was successfully treated via retrosigmoid approach. The patient had immediate and dramatic symptomatic improvement after surgery. Detailed surgical techniques of retrosigmoid craniotomy and tumor dissection are presented in high definition video with narration. The video can be found here: http://youtu.be/55j9QCQEsH8 .

Bone chips, fibrin glue, and osteogeneration following lateral suboccipital craniectomy: a case report

BackgroundSuboccipital craniectomy is a conventional approach for exploring cerebellopontine angle lesions. A variety of techniques have been successfully employed to reconstruct a craniectomy. This is the first report about the histological findings after performing a cranioplasty by using a mixture of autologous bone chips and human allogenic fibrin glue.Case presentationA 53-year-old German woman underwent left lateral suboccipital retrosigmoidal craniectomy for treatment of trigeminal neuralgia in 2008. Cranioplasty was perfomed by using a mixture of autologous bone chips and human allogenic fibrin glue. Due to recurrent neuralgia, a second left lateral suboccipital craniectomy was performed in 2012. The intraoperative findings revealed a complete ossification of the former craniotomy including widely mature trabecular bone tissue in the histological examination.ConclusionA mixture of autologous bone chips and human allogenic fibrin glue seems to provide sufficient bone-regeneration revealed by histological and neuroradiological examinations.

Strategies to Prevent Positioning-Related Complications Associated with the Lateral Suboccipital Approach

The lateral positioning used for the lateral suboccipital surgical approach is associated with various pathophysiologic complications. Strategies to avoid complications including an excessive load on the cervical vertebra and countermeasures against pressure ulcer development are needed. We retrospectively investigated positioning-related complications in 71 patients with cerebellopontine angle lesions undergoing surgery in our department between January 2003 and December 2010 using the lateral suboccipital approach. One patient postoperatively developed rhabdomyolysis, and another presented with transient peroneal nerve palsy on the unaffected side. Stage I and II pressure ulcers were noted in 22 and 12 patients, respectively, although neither stage III nor more severe pressure ulcers occurred. No patients experienced cervical vertebra and spinal cord impairments, brachial plexus palsy, or ulnar nerve palsy associated with rotation and flexion of the neck. Strategies to prevent positioning-related complications, associated with lateral positioning for the lateral suboccipital surgical approach, include the following: atraumatic fixation of the neck focusing on jugular venous perfusion and airway pressure, trunk rotation, and sufficient relief of weightbearing and protection of nerves including the peripheral nerves of all four extremities.

A 30 Year Old Man with An Acute Presentation of A Cerebellopontine Angle Lesion

Schwannomas are slow-growing tumors with symptoms manifesting progressively. We report the case of a patient who manifested a sudden loss of consciousness as clinical presentation of an intracranial schwannoma with no acute hemorrhage or hydrocephalus. A 30-year-old male presented comatose and posturing. Cerebral CT revealed an extra-axial lesion with a heterogeneous enhancement and a cystic component located on the right cerebellopontine angle (CPA), displacing the brain stem. No acute hemorrhage or hydrocephalus was documented. Through a retrosigmoid suboccipital craniotomy, an extended subtotal tumor resection was performed. The patient experienced no functional hearing impairment and resumed his daily-life activities 3 months after surgery. Histopathological examination was compatible with a benign schwannoma. An exuberant lymphoplasmacytic infiltrate was found in many areas, signing the presence of an unusual inflammatory reaction with adjacent important intratumoral edema. We propose that the exuberant inflammatory infiltrate and the associated intratumoral edema acted as determining elements in the increase of mass effect and sudden clinical deterioration.

Lipomas of the cerebellopontine angle and internal auditory canal

To describe the presentation and clinical course of cerebellopontine angle (CPA) and internal auditory canal (IAC) lipomas. Retrospective cohort study at a tertiary academic referral center. All patients presenting with a CPA or IAC mass radiographically consistent with a lipoma on high-resolution magnetic resonance imaging (MRI) were identified. Data including presenting symptomatology, tumor characteristics, management strategy, and patient course were collected. Between 1996 and 2012, 15 patients were diagnosed with a CPA or IAC lipoma at the authors' institution and were included in the analysis. The mean duration of radiological and clinical follow-up was 3.4 years and 5.1 years, respectively. Eight lesions were confined to the IAC, while seven involved the CPA. The median tumor size at diagnosis was 7.2 mm; one patient demonstrated tumor growth on serial MRI while the remaining subjects did not have radiological progression. The most common presenting symptoms were sensorineural hearing loss (40%) and tinnitus (33%); five patients were diagnosed after incidental discovery on MRI. Fourteen patients were managed with observation, while one subject underwent subtotal resection. None of the observed patients reported worsening symptoms at last follow-up. While rare, lipomas should be included in the differential diagnosis of CPA and IAC lesions. Owing to a generally benign clinical course and high morbidity associated with resection, microsurgery should only be considered in cases of definite tumor enlargement with intractable symptoms from mass effect. Careful radiological evaluation is critical for establishing an accurate diagnosis in order to prevent unnecessary morbidity associated with resection.

Anterior Inferior Cerebellar Artery Aneurysms Mimicking Vestibular Schwannomas

Unruptured anterior inferior cerebellar artery (AICA) aneurysms are rare but potentially lethal cerebellopontine angle (CPA) lesions that may be misdiagnosed as vestibular schwannomas when they present with vestibulo-cochlear symptoms. We report two cases of unruptured but symptomatic AICA aneurysms initially referred to us as atypical vestibular schwannomas requiring surgery. Two discriminant MR features are described. One patient refused treatment. The other was successfully treated by coil occlusion. Caution is advised before suspecting a CPA mass to be a purely extra-canalicular schwannoma, given its extreme rarity. Deafness and cerebellar ischemia may be prevented if AICA aneurysms are correctly identified preoperatively. In the absence of specific arterial imaging, two MR features may distinguish them from vestibular schwannomas: (1) the absence of internal auditory canal enlargement and (2) the "blurry dot sign," representing blood flow artefacts on pre- and postcontrast studies.