Imaging of cerebellopontine angle lesions: an update. Part 1: enhancing extra-axial lesions

Quality requirements for MRI simulation in cranial stereotactic radiotherapy: a guideline from the German Taskforce "Imaging in Stereotactic Radiotherapy"

Accurate Magnetic Resonance Imaging (MRI) simulation is fundamental for high-precision stereotactic radiosurgery and fractionated stereotactic radiotherapy, collectively referred to as stereotactic radiotherapy (SRT), to deliver doses of high biological effectiveness to well-defined cranial targets. Multiple MRI hardware related factors as well as scanner configuration and sequence protocol parameters can affect the imaging accuracy and need to be optimized for the special purpose of radiotherapy treatment planning. MRI simulation for SRT is possible for different organizational environments including patient referral for imaging as well as dedicated MRI simulation in the radiotherapy department but require radiotherapy-optimized MRI protocols and defined quality standards to ensure geometrically accurate images that form an impeccable foundation for treatment planning. For this guideline, an interdisciplinary panel including experts from the working group for radiosurgery and stereotactic radiotherapy of the German Society for Radiation Oncology (DEGRO), the working group for physics and technology in stereotactic radiotherapy of the German Society for Medical Physics (DGMP), the German Society of Neurosurgery (DGNC), the German Society of Neuroradiology (DGNR) and the German Chapter of the International Society for Magnetic Resonance in Medicine (DS-ISMRM) have defined minimum MRI quality requirements as well as advanced MRI simulation options for cranial SRT.

Peritumoral Signal on Postcontrast FLAIR Images: Description and Proposed Biomechanism in Vestibular Schwannomas

BACKGROUND AND PURPOSE

Anecdotally, postcontrast FLAIR images of vestibular schwannomas can show peritumoral hyperintense signal, hypothesized to represent gadolinium extravasation. This study assessed the incidence of this phenomenon in a cohort of patients with treatment-naïve sporadic vestibular schwannomas.

MATERIALS AND METHODS

A retrospective review of 20 patients with presumed vestibular schwannoma based on characteristic imaging findings and with dedicated internal auditory canal imaging, including postcontrast T1W1 and postcontrast FLAIR, was performed. Tumor size and location were recorded, as was the presence or absence of a fundal fluid cleft. Images were reviewed for the presence of peritumoral hyperintense signal on FLAIR images (a "halo") and for both subjectively and objectively elevated signal in the ipsilateral cochlea and fundus.

RESULTS

Patients were randomly selected from an institutional vestibular schwannoma registry. Eleven (55.0%) were women. A peritumoral halo was present in 90% of patients, averaging 1.0 (SD, 0.2) mm in thickness. The maximum mean FLAIR signal in the ipsilateral fundus (205.9 [SD, 110.2]) was significantly greater than on the contralateral side (121.6 [SD, 27.8]) (P = .02). Maximum mean ipsilateral intracochlear signal (167.8 [SD, 104.5]) was also significantly greater than on the contralateral side (113.4 [SD, 40.1]) (P = .04).

CONCLUSIONS

A peritumoral halo on postcontrast FLAIR images was present in 90% of our cohort with randomly selected, treatment-naïve sporadic vestibular schwannomas. Although its mechanism is unknown, this signal is hypothesized to represent gadolinium extravasation, given an ipsilateral increased signal in the adjacent internal auditory canal fundus and cochlea.

Anatomy and Pathology of the Skull Base: Malignant and Nonmalignant Lesions

The skull base (SB) is the osseous foundation of the cranial vault. It contains many openings that allow communication between the extracranial and intracranial structures. This communication is crucial in normal physiologic processes yet may also arrow spread of disease. This article provides a comprehensive review of SB anatomy including important landmarks and anatomic variants relevant to SB surgery. We also illustrate the diverse pathologies affecting the SB.

The Vestibulocochlear Nerve: Anatomy and Pathology

The vestibulocochlear nerve is the eighth cranial nerve, entering the brainstem in the medullopontine sulcus after crossing the internal auditory canal and cerebellopontine angle cistern. It is a purely sensitive nerve, originating from the Scarpa's and spiral ganglions, responsible for balance and hearing. It has 6 nuclei located in the lower pons. Magnetic resonance imaging (MRI) is useful for evaluating the vestibulocochlear nerve, although computed tomography may have a complementary role in assessing bone lesions. A heavily T2-weighted sequence, such as fast imaging employing steady-state acquisition (FIESTA) or constructive interference steady state (CISS), is crucial in imaging exams to depict the canalicular and cisternal segments of the vestibulocochlear nerve, as well as the fluid signal intensity in the membranous labyrinth. The vestibulocochlear nerve can be affected by several diseases, such as congenital malformations, trauma, inflammatory or infectious diseases, vascular disorders, and neoplasms. The purpose of this article is to review the vestibulocochlear nerve anatomy, discuss the best MRI techniques to evaluate this nerve and demonstrate the imaging aspect of the main diseases that affect it.

Perfusion-weighted imaging in vestibular schwannoma: the influence that cystic status and tumor size have on perfusion profiles

Objective

The perfusion profile of vestibular schwannomas (VSs) and the factors that influence it have yet to be determined.

Materials and Methods

Twenty patients with sporadic VS were analyzed by calculating parameters related to the extravascular extracellular space (EES)-the volume transfer constant between a vessel and the EES (Ktrans); the EES volume per unit of tissue volume (Ve); and the rate transfer constant between EES and blood plasma (Kep)-as well as the relative cerebral blood volume (rCBV), and by correlating those parameters with the size of the tumor and its structure (solid, cystic, or heterogeneous).

Results

Although Ktrans, Ve, and Kep were measurable in all tumors, rCBV was measurable only in large tumors. We detected a positive correlation between Ktrans and rCBV (r = 0.62, p = 0.031), a negative correlation between Ve and Kep (r = -0.51, p = 0.021), and a positive correlation between Ktrans and Ve only in solid VSs (r = 0.64, p = 0.048). Comparing the means for small and large VSs, we found that the former showed lower Ktrans (0.13 vs. 0.029, p < 0.001), higher Kep (0.68 vs. 0.46, p = 0.037), and lower Ve (0.45 vs. 0.83, p < 0.001). The mean Ktrans was lower in the cystic portions of cystic VSs than in their solid portions (0.14 vs. 0.32, p < 0.001), as was the mean Ve (0.37 vs. 0.78, p < 0.001). There were positive correlations between the solid and cystic portions for Ktrans (r = 0.71, p = 0.048) and Kep (r = 0.74, p = 0.037).

Conclusion

In VS, tumor size appears to be consistently associated with perfusion values. In cystic VS, the cystic portions seem to have lower Ktrans and Ve than do the solid portions.

Unusual imaging characteristics of cystic meningioma in cerebellopontine angle

We report a case of cystic meningioma at the left cerebellopontine angle (CPA). Magnetic resonance imaging demonstrated both solid and cystic components in the tumor. The cystic component appeared slightly hyperintense compared to cerebrospinal fluid on fluid-attenuated inversion recovery (FLAIR) imaging. A hypointense tubular structure was identified in the cystic component on 3D driven equilibrium sequencing. These imaging findings are unusual for cystic meningioma. However, awareness of these unusual imaging features is important to determine appropriate treatment strategies although cystic meningioma at the CPA is extremely rare.

Successful preoperative embolization of a cystic-solid variant of cerebellopontine angle hemangioblastoma

Tumors of the cerebellopontine angle (CPA) represent an heterogeneous group which can arise extradural, intradural-extraaxial or intraaxial compartment. Hemangioblastomas of the cerebellopontine angle (CPA) are extremely rare. Computed tomography (CT) and magnetic resonance imaging (MRI) are often the gold-standard radiological imaging modalities used in characterizing the lesion's features, and its relationship with the surrounding structures. They are vascular lesions and may cause profuse bleeding intraoperatively, that is why angiography remains a crucial diagnostic and therapeutic tool, by reducing both the presurgical differential diagnosis, as well as the intraoperative bleeding by providing capability of embolization of this vascular tumor. We present the case of a 65 year old patient with a cystic-solid variety of HMB at the right CPA, which was successfully treated by a combination of an endovascular preoperative embolization and surgery without major complications or neurological deficits.

Diffuse large B-cell lymphoma: An uncommon diagnosis at the cerebellopontine angle - A case report

Primary central nervous system lymphoma (PCNSL), a rare variant of extranodal non-Hodgkin's lymphoma, has shown an increased incidence over the last 3-4 decades in both immunocompromised and immunocompetent individuals. Only <20 cases of cerebellopontine (CP) angle lymphoma have been reported so far in the literature. Hereby, we report a case of primary lymphoma of the CP angle mimicking vestibular schwannoma and other common pathologies at the CP angle. Hence, while evaluating a lesion at CP angle, PCNSL should always be considered in the differential diagnosis.

Factors Associated with Acute Obstructive Hydrocephalus After Retrosigmoid Approach for Extra-Axial Cerebellopontine Angle Tumors

BACKGROUND

This study aimed to identify the risk factors for acute obstructive hydrocephalus (AOHCP) after extra-axial cerebellopontine angle (CPA) tumor surgery using the retrosigmoid (RS) approach.

METHODS

This retrospective study assessed 154 patients (100 vestibular schwannomas, 34 CPA meningiomas [MNGs], 9 trigeminal schwannomas, and 11 petroclival MNGs) who underwent surgical resection using the RS approach by a single surgeon between August 2010 and September 2019. AOHCP was defined as postoperative ventricular enlargement due to cerebrospinal fluid flow obstruction caused by surgery-related cerebellar injury within 1 week. The radiological characteristics of the tumors were classified, and the surgical outcomes were reviewed. We analyzed the impact of different factors on the development of AOHCP after surgery.

RESULTS

AOHCP developed in 17 (11%) patients, all of whom were treated with external ventricular drain insertion. Multivariate analysis showed that CPA MNGs (odds ratio [OR], 37.98), grade of tumor extension beyond the petroclival junction (grade 1: OR, 16.42; grade 2: OR, 17.47), major fourth ventricle compression (OR, 17.77), and surgery-related hemorrhage (OR, 7.64) were associated with AOHCP. Surgery-related hemorrhage was observed in 17 (11%) patients. 9 (6%) patients underwent ventriculoperitoneal shunt surgery because of persistent HCP.

CONCLUSIONS

An increased risk of AOHCP after the RS approach was observed in patients with extra-axial CPA tumors with clival extension and major fourth ventricle compression. Compulsive and meticulous hemostasis must be achieved because postoperative hemorrhage is associated with AOHCP.

Occurrence and severity of venous air embolism during neurosurgical procedures in semi-sitting versus supine position

BACKGROUND

At our institution, patients undergoing neurosurgical procedures in the posterior cranial fossa are placed either in the semi-sitting or in the supine position. The major risk of the semi-sitting positioning is a venous air embolism (VAE), which may, however, also occur in the supine position.

METHODS

In a prospective single-center study with 137 patients, we evaluated the occurrence of VAEs in patients in the supine and in the semi-sitting position over the period from January 2014 until April 2015. All patients were monitored for VAE by the use of a transesophageal echocardiography (TEE).

RESULTS

50% of the patients experienced a VAE (with 56% of these patients underwent surgery in the semi-sitting and 11% in the supine position). 86% of the VAEs were just detected by the use of a TEE and did not lead to any changes in the end-expiratory (Et)CO₂. We only observed VAEs with a decrease in EtCO₂ in the semi-sitting position. However, none of the patients had any hemodynamic changes due to the VAE.

CONCLUSIONS

The semi-sitting position with TEE monitoring and a standardized protocol is a safe and advantageous technique, taking account of a significant rate of VAEs. VAEs also occur in the supine position, however, less frequently.

Advanced MRI to differentiate schwannomas and metastases in the cerebellopontine angle/internal auditory canal

BACKGROUND AND PURPOSE

Differentiating schwannomas and metastases in the cerebellopontine angles (CPA)/internal auditory canals (IAC) can be challenging. This study aimed to assess the role of diffusion-weighted imaging (DWI) and dynamic contrast-enhanced MRI (DCE-MRI) to differentiate schwannomas and metastases in the CPA/IAC.

METHODS

We retrospectively reviewed 368 patients who were diagnosed with schwannomas or metastases in the CPA/IAC between April 2017 and February 2022 in a single academic center. Forty-three patients had pretreatment DWI and DCE-MRI along with conventional MRI. Normalized mean apparent diffusion coefficient ratio (nADCmean) and DCE-MRI parameters of fractional plasma volume (Vp), flux rate constant (Kep), and forward volume transfer constant were compared along with patients' demographics and conventional imaging features between schwannomas and metastases as appropriate. The diagnostic performances and multivariate logistic regression analysis were performed using the significantly different values.

RESULTS

Between 23 schwannomas (15 males; median 48 years) and 20 metastases (9 males; median 61 years), nADCmean (median: 1.69 vs. 1.43; p = .002), Vp (median: 0.05 vs. 0.20; p < .001), and Kep (median: 0.41 vs. 0.81 minute^-1 ; p < .001) were significantly different. The diagnostic performances of nADCmean, Vp, and Kep were 0.77, 0.90, and 0.83 area under the curves, with cutoff values of 1.68, 0.12, and 0.53, respectively. Vp was identified as the most significant parameter for the tumor differentiation in the multivariate logistic regression analysis (p < .001).

CONCLUSIONS

DWI and DCE-MRI can help differentiate CPA/IAC schwannomas and metastases, and Vp is the most significant parameter.

Cerebellopontine angle ependymoma presenting as isolated hearing loss in an elderly patient: A case report and literature review

Background:

Ependymoma is an uncommon tumor accounting for approximately 1.9% of all adult central nervous system tumors. Ependymomas at the cerebellopontine angle (CPA) are even more rare and only previously described in isolated case reports. Typically, acoustic neuromas and meningiomas represent the bulk of adult CPA tumors. Diagnosis can be challenging, as ependymomas have clinical findings and imaging characteristics that overlap with more common tumor histologies at the CPA.

Case Description:

We present the case of a 70-year-old male patient with progressive, isolated left-sided hearing loss found to have a World Health Organization (WHO) Grade II CPA ependymoma, representing one of the oldest recorded patients presenting with this primarily pediatric malignancy in this unique location. The patient presentation with isolated hearing loss was particularly unusual. When associated with neurologic deficits, CPA ependymomas more characteristically result in facial nerve impairment with fully preserved hearing, while vestibular schwannomas tend to present with isolated hearing loss. The standard of care for pediatric ependymomas is maximal safe resection with adjuvant radiotherapy, but treatment paradigms in adult CPA ependymoma are not well defined particularly for WHO Grade II disease. After resection, he received adjuvant radiation to decrease the risk of local recurrence. Twenty-nine months after resection, the patient remains free of treatment-related toxicity or disease recurrence.

Conclusion:

We review this patient’s clinical course in the context of the literature to highlight the challenges associated with timely diagnosis of this rare tumor and the controversial role of adjuvant therapy in preventing local recurrence in these patients.

Laryngeal schwannoma with extralaryngeal extension mimicking a thyroid tumour

Objective:

A schwannoma is a common benign tumour that can arise anywhere in the body. When it occurs in an unusual location such as the larynx, its differentiation from other tumours can be challenging. Herein, we report a case of a laryngeal schwannoma with extralaryngeal extension that mimicked a thyroid tumour, focusing on its characteristic features on MRI.

Methods:

A 19-year-old male presented with a mass in the left side of the neck and hoarseness for 2 years. Endoscopy showed a submucosal mass in the laryngeal region. MRI found a well-defined solid mass in the thyroid gland, extending to the larynx through the lower edge of the thyroid cartilage. T₂ weighted MRI showed slightly low signal intensity at the central part of the tumour and high signal intensity at the peripheral part of the tumour. Pre-operative imaging suggested that the tumour originated in the thyroid gland. Left thyroidectomy with tumour excision was performed; the tumour was diagnosed as a laryngeal schwannoma with extralaryngeal extension, compressing the thyroid gland. In retrospect, features such as the dumbbell-shape and known as ‘target sign’ on T₂ weighted MRI were typical features of schwannoma. Additionally, the tumour’s extension pattern was similar to previous reports of laryngeal schwannomas with extralaryngeal extension.

Conclusion:

A large laryngeal schwannoma may extend outside the larynx with significant compression of the thyroid gland. Understanding the pattern of extension and familiarity with the features on MRI can improve the preoperative diagnosis accuracy.

Imaging of the Vestibular Schwannoma: Diagnosis, Monitoring, and Treatment Planning

Appropriate imaging strategies for the detection, treatment planning, and posttreatment monitoring of vestibular schwannomas will be discussed. The typical and variant imaging appearances of vestibular schwannomas, as well as the imaging features that should prompt consideration of differential diagnoses, will be illustrated. Understanding the natural history of vestibular schwannomas, optimal measurement and definition of tumour growth helps the radiologist evaluate for the failure of conservative management and requirement for surgery or radiotherapy. In order to determine the success of conservative management, the radiologist is required to understand the natural history of vestibular schwannomas and how tumour growth is defined. Finally, the imaging features which help guide appropriate treatment with surgery or radiotherapy will be highlighted, and the expected posttreatment imaging changes will be described.

Clinical comparison of single-shot EPI, readout-segmented EPI and TGSE-BLADE for diffusion-weighted imaging of cerebellopontine angle tumors on 3 tesla

OBJECTIVE

The complex anatomical structures of cerebellopontine angle (CPA) pose a unique challenge to diffusion weighted imaging (DWI). This study aimed to compare the clinical utility of the prototypic 2D turbo gradient- and spin echo-BLADE-DWI (TGSE-BLADE-DWI) with that of readout-segmented echo-planar DWI (RESOLVE-DWI) and single-shot echo-planar DWI (SS-EPI-DWI) to visualize CPA anatomic structures and identify CPA tumors.

METHODS

A total of 8 volunteers and 36 patients with pathological CPA tumors were enrolled to perform the three DWI sequences at 3 T. Scan time of TGSE-BLADE-DWI, RESOLVE-DWI and SS-EPI-DWI was 5 min 51 s, 5 min 15 s and 1 min 22 s, respectively. Subjective analysis, including visualization of anatomical structures, geometric distortion, ghosting artifacts, lesion conspicuity, diagnostic confidence, and overall image quality of the three DWI sequences were scored and assessed. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and apparent diffusion coefficient (ADC) of CPA tumors were measured and compared.

RESULTS

A total of 39 lesions were identified, TGSE-BLADE-DWI detected all of them, RESOLVE-DWI 36 and SS-EPI-DWI 27. Significant differences were found in all the subjective parameters among the three DWI sequences (all p < 0.001). TGSE-BLADE-DWI was significantly better than RESOLVE-DWI in visualization of CPA anatomical structures, geometric distortion, ghosting artifacts, lesion conspicuity, diagnostic confidence, and overall image quality (all p < 0.01), and RESOLVE-DWI showed significantly superior performance than SS-EPI-DWI in all parameters (all p < 0.001). CNRs and ADCs were not significantly different among the three DWI sequences (p = 0.355, p = 0.590, respectively). No significant differences were detected between TGSE-BLADE-DWI SNR and RESOLVE-DWI SNR (p = 0.058), or TGSE-BLADE-DWI SNR and SS-EPI-DWI SNR (p = 0.155).

CONCLUSION

Compared with RESOLVE-DWI and SS-EPI-DWI, TGSE-BLADE-DWI minimized geometric distortions and ghosting artifacts and demonstrated an improved ability for depicting CPA tumors with better lesion conspicuity.

SUMMARY

Geometric distortions and ghosting artifacts are found at bone-air interfaces using conventional diffusion-weighted imaging (DWI), which is a challenge for imaging cerebellopontine angle (CPA) tumors. Our study validated that geometric distortions and ghosting artifacts were not present on 2D turbo gradient- and spin-echo-BLADE-DWI scans, making this technique useful for visualizing CPA anatomic structures and diagnosing CPA tumors.

Neuroimaging of Dizziness and Vertigo

Dizziness and vertigo are common symptoms in the primary care and emergency settings, resulting in a significant decrease in quality of life and a high cost burden to the US health care system. The etiology of these symptoms is difficult to elucidate owing to a wide range of diseases with overlapping manifestations. The broad differential diagnosis based on whether the disease process is central or peripheral is showcased. Each differential will be categorized into neoplastic, infectious or inflammatory, structural, traumatic, and iatrogenic causes. Computed tomography scans, MRI, and vascular imaging are frequently complimentary in providing diagnoses and guidance in management.

Primary leptomeningeal melanoma: the prognostic significance of its genetic signature and embryological origin

Primary leptomeningeal melanomas are rare, comprising less than one percent of all brain tumours. They are aggressive and radioresistant tumours, with a poor prognosis. The mainstay of treatment is complete surgical resection and chemotherapy with limited success. Distinguishing a primary leptomeningeal melanoma from the more common metastatic disease can be difficult, and often requires the use of ancillary molecular testing. Primary central nervous system melanomas, including uveal melanomas, frequently exhibit mutations in GNAQ and GNA11, rare in the cutaneous and mucosal counterparts.A case of a primary leptomeningeal melanoma of the cerebellopontine angle is described. Molecular studies identified a GNA11 p.Q209L and a KIT p.M541L missense variant, with losses of chromosomes 1p and 3p demonstrated with cytogenetic studies. Complete surgical resection was not possible and leptomeningeal metastatic disease rapidly ensued despite immunotherapy. Further understanding of the molecular signature may translate to improved diagnosis, prognostication and development of targeted therapies.

Objective improvement in adults with cerebellopontine angle arachnoid cysts after surgical treatment

BACKGROUND

Intracranial arachnoid cysts are extra-axial benign lesions mainly found in the middle cerebral fossa. Rare case series report various cranial nerve dysfunctions associated with cerebellopontine angle (CPA) cysts and there is no consensus with regard to their surgical management; some reports claiming that subjective improvement in adults with intracranial arachnoid cysts cannot justify surgical treatment.

METHODS

This retrospective study included all 12 consecutive adult patients treated by microsurgical fenestration for symptomatic CPA arachnoid cysts between 2010 and 2019 and using a retrosigmoid approach. Demographic, clinical, surgical, and radiological data were collected from medical files.

RESULTS

The main symptoms were audiovestibular in 9 patients (75%) complaining of dizziness and 6 patients (50%) with hearing loss. In addition, 3 patients (25%) reported tinnitus, 3 patients (25%) presented vasovagal syncope, and 1 patient (8.3%) reported facial pain. Surgery improved 5 patients (83%) with pre-operative hearing loss, 7 patients (78%) reporting dizziness, and all patients with vasovagal syncope. All of the patients recovered from at least one symptom. No recurrence was observed with a mean follow-up of 5.5 years.

CONCLUSION

Although most arachnoid cysts are asymptomatic, the CPA location may lead to cranial nerve impairments. Microsurgical fenestration seems to be a simple, safe, and effective technique.

Predominantly Solid Hemangioblastoma Presenting as an Extra-Axial Cerebellopontine Angle Lesion

Hemangioblastomas (HBs) are typically intra-axial, highly vascular tumors of the central nervous system and account for up to 2.5% of all intracranial tumors and up to 12% of posterior fossa neoplasms. Extra-axial HBs are rarely described in the literature. The radiological appearances of cerebellopontine angle (CPA) extra-axial HB can lead to a diagnostic conundrum as they may mimic the appearance of dural metastasis, vestibular schwannoma, or meningioma. Here, we describe a patient who presented with an extra-axial CPA HB and explore the literature of the condition.

[Acoustic neuromas : Differential diagnoses]

CLINICAL ISSUE

Acoustic neuromas in adults are the most common infratentorial tumors that originate from the Schwann's cells of the vestibular part of the eighth cranial nerve and are clinically noticeable through neurological deficits, such as unilateral hypoacusis, tinnitus, dizziness and unilateral facial nerve palsy. Due to the widespread use of computed tomography (CT) and magnetic resonance imaging (MRI), acoustic neuromas can now be diagnosed with a high rate of sensitivity and specificity; however, there are a number of possible differential diagnoses, such as meningioma, epidermoid and metastases as well as a number of less common diagnoses, such as peripheral nerve sheath tumors, sarcoidosis/neuritis and lipomas, which are sometimes difficult to distinguish from acoustic neuromas. Particularly smaller findings can often only be differentiated with the aid of a histopathological investigation.

PRACTICAL RECOMMENDATIONS

Small intrameatal and asymptomatic acoustic neuromas, some of which are discovered as incidental findings, do not require immediate treatment and should instead be monitored by MRI. Larger findings that are symptomatic and thus cause a number of severe neurological symptoms that are stressful for the patient, should be surgically removed. In cases where surgical treatment is not possible or for smaller symptomatic findings, radiotherapy can also be considered as an alternative.

Noncystic cerebellopontine angle hemangioblastoma: A case of an atypical location

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Cerebellopontine angle hemangioblastoma is a rare condition.

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Magnetic resonance imaging evaluation is important for the differential diagnosis of hemangioblastoma.

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Surgical planning in hemangioblastoma surgery is a central key point.

Introduction

Extra-axial cerebellopontine angle (CPA) hemangioblastoma is a rare condition in which the correct differential diagnosis from other CPA lesions can affect the best treatment choice. These are benign tumors that are highly vascularized and mostly present in the cystic form. About twenty-six cases have been reported in the literature with this same location and with a noncystic aspect.

Presentation of case

We report a case of a 63-year-old male with a complaint of progressive headache associated with imbalance and difficulty walking. Neurological examination showed discreet facial paresis, left dysmetria and mild gait ataxia. Magnetic resonance imaging (MRI) showed a solid mass with isointensity on T1-weighted sequences; hypointensity and a heterogeneous appearance on T2-weighted sequences; and intense homogeneous contrast enhancement located in the left CPA region extending superiorly to the tentorial notch. The first diagnosis was meningioma, but during the microsurgical suboccipital retrosigmoid approach, it was observed that the lesion was extremely bloody with several vessels on its surface. We achieved gross total resection, and the pathology confirmed hemangioblastoma.

Discussion

Although it is rare, hemangioblastoma should be one of the differential diagnoses when dealing with CPA solid lesions with high contrast enhancement and heterogeneity on T2-weighted MRI. Analysis of the radiological characteristics allows a greater chance of confirmation and is one of the main tools for surgical planning.

Conclusion

Correct preoperative evaluation and the possibility that hemangioblastoma may arise from the CPA can avoid trans-operative risks mainly related to bleeding and can improve results.

Current imaging tools for vestibular schwannoma

PURPOSE OF REVIEW

Of the tumors found in the cerebellopontine angle (CPA), vestibular schwannomas are by far the most common. Modern diagnostic imaging enables excellent visualization of the CPA and detection of very small tumors while optimizing patient comfort and time. This review addresses the current imaging tools available for diagnosis of vestibular schwannomas.

RECENT FINDINGS

The current gold-standard imaging study for vestibular schwannomas is a gadolinium-enhanced T1-weighted MRI. The yield of this expensive study is only about 3-4% given the low incidence of vestibular schwannomas, thus there is utility in screening with noncontrast T2-weighted MRI, which is a quicker and more economical study.

SUMMARY

Vestibular schwannomas are best evaluated with gadolinium-enhanced T1-weighted MRI, which can detect tumors as small as 2-3 mm. Recent studies have found that the reported sensitivity and specificity of noncontrast MRI is almost equivalent to that of gadolinium-enhanced T1-weighted MRI. As such, this modality is increasingly being adopted by institutions for both diagnosis and surveillance of vestibular schwannomas and shows promise for broader implementation. Newer protocols, such as FLAIR and DTI may provide additional information and further aid preoperative counseling and surgical planning in the future.

Historadiological Correlation of Cerebellopontine Angle Tumors: Series of 122 Cases

Cerebellopontine angle (CPA) tumours, are diverse pathologically with regard to the site of tumour origin and displacement of the neurovascular structures. In general CPA tumours are divided into acoustic and non-acoustic tumours. The aim of the present study was to see the spectrum of lesions at cerebellopontine angle and their historadiological correlation. A retrospective analysis of 122 cases of CPA tumors diagnosed in the Department of Pathology, IHBAS was done from January 2004 to August 2019. There were 56 males and 66 females in the age group of 8-68 years. Clinical history ranged from 10 days to 5 years. Clinical symptoms included hearing deficit, visual loss, facial nerve dysfunction, nausea, vomiting, headache, seizures, unsteadiness and disequilibrium. Historadiological correlation was found in 112 cases (91%).In our series of CPA tumors, nonacoustic tumors were more frequent than in previous studies. We found that presence of intrameatal fraction is not exclusive only for schwannomas. There can be a rare occurrence of medullobastoma/small round cell tumor in CP angle. The final pathological verification can at times give unexpected results. Immunohistochemistry did not have a significant role in diagnosis of cerebellopontine angle tumors.

Additional diagnostic role of MRI spectroscopy, diffusion and susceptibility imaging in differentiation of CPA masses: our experience with emphasis on schwannomas and meningiomas

Background

CPA masses are uncommon lesions and usually have quite distinctive imaging features. Still, diagnosis can be challenging in some cases, carrying a significant impact on the choice of treatment and surgical approach. The purpose of this study was to validate the usefulness of MRI spectroscopy, diffusion, and susceptibility in the characterization of CPA masses with the emphasis on the two commonest lesions: schwannomas and meningiomas.

Results

The study included a total of 27 cases: schwannomas (n = 12), meningiomas (n = 7), epidermoid cysts (n = 2), two chondrosarcomas (n = 2), arachnoid cyst (n = 1), glomus tumor (n = 1), a meningeal metastasis (n = 1), and an endolymphatic sac tumor (n = 1). DWI revealed: eight lesions showed low ADC (<1 × 10−3 mm2/s), 15 lesions with intermediate ADC values (1–1.8 × 10−3 mm2/s), and 4 lesions had high ADC (>1.8 × 10−3 mm2/s.) Meningiomas showed low to intermediate ADC values while schwannomas showed intermediate to high ADC values. A cut-off ADC value of (1 × 10−3 mm2/s) is statistically significant in the differentiation of meningioma from schwannoma. A myoinositol peak was in all 12 schwannomas and single meningioma while 6 meningiomas displayed alanine peak, with a very good statistical significance. Remaining lesions revealed non-specific spectra. SWI made in 18 lesions revealed signal voids in three schwannomas and glomus.

Conclusions

Though MRI features of CPA masses are distinctive in most clinical settings; MRI spectroscopy, diffusion, and susceptibility can provide highly informative additional data in problematic cases. An intermediate to high ADC value plus myoinositol peak and signal voids of micro-bleeds are highly suggestive of schwannomas. This is in contrary to meningiomas displaying low to intermediate ADC and an alanine peak with no micro-bleeds. The less common lesions revealed non-specific data.

Intracranial Leiomyoma Associated with Epstein-Barr Virus: A Cerebellopontine Angle Mass Presenting with Trigeminal Neuralgia

BACKGROUND

Primary intracranial leiomyoma is a rare smooth muscle tumor often associated with Epstein-Barr virus (EBV), with <30 cases reported worldwide. These tumors commonly occur in patients with immunocompromised status, especially those with human immunodeficiency virus. In the present report, we have described the case of an EBV-associated leiomyoma at the cerebellopontine angle. The patient had presented with trigeminal neuralgia, which, to the best of our knowledge, is the first reported anatomical location and presentation for this tumor type.

CASE DESCRIPTION

A 41-year-old male patient had presented with right-sided facial pain in the V1 and V2 dermatomes and previous workup and imaging studies. The patient had undergone treatment of a presumed right-side cerebellopontine angle meningioma as determined by the magnetic resonance imaging characteristics (no biopsy). The patient subsequently underwent right-sided retrosigmoid craniotomy and gross total resection of the tumor. The postoperative period was uneventful with resolution of the trigeminal neuralgia. Histopathologic examination revealed spindle cell neoplasm with histopathologic and immunohistochemical features consistent with leiomyoma. The tumor cells were positive for smooth muscle actin and desmin and were negative for S100, SOX-10, epithelial membrane antigen, glial fibrillary acidic protein, progesterone receptor, CD31, CD34, and E-cadherin.

CONCLUSIONS

Primary intracranial leiomyomas are rare tumors associated with EBV infection that occur in immunocompromised patients. These lesions should be considered in the differential diagnosis for patients with known immunocompromised status (e.g., human immunodeficiency virus), and tissue biopsy should be considered.

Surgical management of primary and secondary pilocytic astrocytoma of the cerebellopontine angle (in adults and children) and review of the literature

Glial tumors in the cerebellopontine angle (CPA) are uncommon and comprise less than 1% of CPA tumors. We present four cases of pilocytic astrocytoma of the CPA (PA-CPA) that were treated in our department. Patients who received surgical treatment for PA-CPA from January 2004 to December 2019 were identified by a computer search of their files from the Department of Neurosurgery, Tübingen. Patients were evaluated for initial symptoms, pre- and postoperative facial nerve function and cochlear function, complications, and recurrence rate by reviewing surgical reports, patient documents, neuroradiological data, and follow-up data. We identified four patients with PA-CPA out of about 1500 CPA lesions (~ 0.2%), which were surgically treated in our department in the last 16 years. Of the four patients, three were male, and one was a female patient. Two were adults, and two were children (mean age 35 years). A gross total resection was achieved in three cases, and a subtotal resection was attained in one case. Two patients experienced a moderate facial palsy immediately after surgery (House–Brackmann grade III). In all cases, the facial function was intact or good (House–Brackmann grades I–II) at the long-term follow-up (mean follow-up 4.5 years). No mortality occurred during follow-up. Three of the patients had no recurrence at the latest follow-up (mean latest follow-up 4.5 years), while one patient had a slight recurrence. PA-CPA can be safely removed, and most complications immediately after surgery resolve in the long-term follow-up.

[Update on diagnostics and microsurgical treatment of vestibular schwannoma]

Vestibular schwannomas are primary benign tumors of the cerebellopontine angle originating either from the superior or the inferior vestibular nerve. Hearing deterioration is the leading symptom, which is why the widespread name for this tumor is acoustic neuroma. Due to the widespread availability of magnetic resonance imaging (MRI), the diagnosis of vestibular schwannoma is frequently made in an early stage of the disease. In these cases a wait and scan policy is recommended. If the tumor grows, the therapeutic options are stereotactic radiotherapy or microsurgical tumor operation. Young patient age, functional hearing ability, persistent dizziness, cystic tumor consistence and large space-occupying tumor size are in favor of surgery via the retrosigmoid, transmeatal approach. In experienced hands excellent results in terms of functional preservation of the facial nerve and the cochlear nerve and radical tumor resection can be obtained.

Lateral Semi-sitting Position: A Novel Method of Patient's Head Positioning in Suboccipital Retrosigmoid Approaches

Background

The most common methods of positioning patients for suboccipital approaches are the lateral, lateral oblique, sitting, semisitting, supine with the head turn, and park bench. The literature on the positioning of patients for these approaches does not mention the use of lateral semisitting position. This position allows utilization of the benefits of both semisitting and lateral position without causing any additional morbidity to the patient.

Aims

The aim of the present study is to highlight the advantages of the lateral semisitting position while operating various cerebellopontine angle (CPA) and posterior fossa lesions.

Materials and Methods

The position involved placing the patient in a lateral position with torso flexed to 45° and head tilted toward opposite shoulder by 20°. The most common approach taken was retrosigmoid suboccipital craniotomy.

Results

The advantages of lateral semisitting position were early decompression of cisterna magna, and the surgical field remained relatively clear, due to gravity-assisted drainage of blood and irrigating fluid. We could perform all the surgeries without the use of any retractors. The position allowed better delineation of surrounding structures resulting in achieving correct dissection plane and also permitted early caudal to cranial dissection of tumor capsule, thereby increasing chances of facial nerve preservation. Importantly, there is less engorgement of the cerebellum as the venous outflow is promoted. We have not experienced any increased rate of complications, such as venous air embolism, tension pneumocephalus with this lateral semisitting position.

Conclusions

Lateral semisitting position is a relatively safe modification, which combines the benefits of semisitting and lateral position, and avoids the disadvantages of sitting position in operating CPA tumors. This position can provide quick and better exposure of the CPA without any significant complications.

A case report on cystic meningioma in cerebellopontine angle and recommendations for management

RATIONALE

Cystic meningioma located at the cerebellopontine angle (CPA) is an extremely rare occurrence. It is frequently misdiagnosed preoperatively. Little is known about the clinical features and outcome of this rare disease.

PATIENT CONCERNS

A 70-year-old male presenting with progressive headache and gait disturbance.

DIAGNOSIS

According to the symptoms, signs, and Gd-enhanced magnetic resonance images (MRI), a preoperative diagnosis of hemangioblastoma located in left CPA was made. Finally, the histological examination revealed a meningioma.

INTERVENTIONS

A complete resection, including the part of the solid mass together with cyst, was performed.

OUTCOMES

The postoperative course of the patient was uneventful, and no residual or recurrent tumor was found during the 24-month follow-up period.

LESSONS

Cystic meningioma should be included in the differential diagnosis of a CPA mass with atypical radiologic features, such as a large cyst and enhanced mural nodule. By summarizing the related literature, we found that the most common pathological subtype of CPA cystic meningioma is the clear cell subtype, which belongs to WHO grade II. Gross total resection including the enhanced cyst wall is extremely important. A close follow-up is necessary because of the high recurrence rate in this subset of meningioma.

Choroid plexus papilloma presenting as an occipital mass with neck pain: Case report

RATIONALE

Choroid plexus papillomas are rare benign central nervous system neoplasms arising from choroid plexus epithelium. They are most often located in the lateral ventricle, followed by the fourth and third ventricles and, rarely, in the cerebellopontine angle.

PATIENT CONCERNS

We report an uncommon case of a 17-year-old boy who presented with neck pain that had lasted for more than 1 month, with accompanying pain and numbness in his upper extremities. His conditions included slight dizziness, nausea, diplopia, paresthesia, and an unsteady gait. Magnetic resonance imaging (MRI) showed huge cerebellopontine angle tumor that extended to the front medulla oblongata.

DIAGNOSIS

Choroid plexus papilloma (WHO I) was diagnosed in this patient.

INTERVENTIONS

The patient was referred for neurosurgical intervention. The very large neoplasm was subtotally resected.

OUTCOMES

The symptoms of the patient were gradually alleviated after surgery and subsequent radiotherapy treatment, but unfortunately, follow-up of 2 years later revealed that the disease was recurrent and the young man passed away.

LESSONS

Neck pain is related to many factors. The case provided an awareness of the origin of severe intracranial disease. It is mandatory to take a thorough clinical assessment with a holistic approach.

Primary central nervous system lymphoma at the cerebellopontine angle mimicking a trigeminal schwannoma: A unique case report and literature review

Primary central nervous system lymphoma (PCNSL) is an uncommon extranodal manifestation of non-Hodgkin's lymphoma with those presenting at the cerebellopontine angle (CPA) being rare presentations with limited reported cases in the literature. We report a 60-year old female presenting with PCNSL of the left CPA radiologically mimicking a trigeminal schwannoma with corresponding clinical signs. Imaging showed a left CPA lesion that was biopsied and confirmed as diffuse large B-cell lymphoma. Given its rarity, PCNSL should be considered in the differential diagnosis for all CPA tumours.

Focal hyperintensity in the dorsal brain stem of patients with cerebellopontine angle tumor: A high-resolution 3 T MRI study

Focal hyperintensity (FHI) in the dorsal brain stem on T2-weighted images of patients with cerebellopontine angle (CPA) tumor was thought to indicate degeneration of the vestibular nucleus and to be specific to vestibular schwannoma. The purpose of this study was to evaluate FHI by using high-resolution 3 Tesla magnetic resonance imaging (3 T MRI) and the relation to clinical characteristics. We retrospectively reviewed the clinical data and MRI of 45 patients with CPA tumors (34 vestibular schwannomas and 11 other tumors). FHI in the dorsal brain stem was found in 25 (55.6%) patients (20 vestibular schwannomas and 5 other tumors). For the vestibular schwannomas, the factors contributing to positive FHI were age (p = 0.025), max CPA (p =  < 0.001), hearing ability (P = 0.005), and canal paresis (p =  < 0.001) in the univariate analysis. Multivariate regression analysis showed that max CPA (p = 0.029) was a significant factor of positive FHI. In other CPA tumors, these factors were not significant predictors. With the use of 3 T MRI, FHI was observed more frequently than previously reported. Our results suggest that FHI is not a specific indicator of vestibular schwannoma and is related to not only vestibular function but also other factors.

The diagnostic challenge of dizziness: computed tomography and magnetic resonance imaging findings

Dizziness is a prevalent symptom in the general population, accounting for a considerable share of physician office visits, and most causes are clinically treatable. It is also a common indication for neuroimaging studies, in order to identify a specific etiology and exclude surgical causes. Here, we illustrate the main peripheral and central causes of dizziness, discussing their possible differential diagnoses, as well as their most important image aspects.

Clinical Features and Surgical Outcomes in Patients with Cerebellopontine Angle Hemangioblastomas: Retrospective Series of 23 Cases

OBJECTIVES

Hemangioblastomas in the cerebellopontine angle (CPA) are uncommon and have rarely been reported. They may be easily misdiagnosed because of the atypical location and clinical and imaging features. The present study aimed to characterize clinical and radiologic features, treatment strategies, and outcomes in these rare lesions and to investigate various factors that may affect postoperative outcomes.

METHODS

The medical records of patients with CPA hemangioblastomas who underwent surgery from 2003-2016 at the West China Hospital were reviewed retrospectively and statistically analyzed.

RESULTS

Twenty-three patients (14 males and 9 females) presented with CPA hemangioblastomas. Eight patients (34.8%) had von Hippel-Lindau (VHL) syndrome. Gross total resection was achieved in 22 patients (95.6%). The mean follow-up was 45.1 ± 36.2 months (range 3-144 months). After surgery, the symptoms improved in 18 cases (78.3%), remained unchanged in 3 cases (13%), and were aggravated in 2 cases (8.7%). Four patients showed local recurrence during follow-up (17.4%). Patients with cystic hemangioblastomas had a better neurologic improvement (P = 0.041) compared with patients with solid tumors. Furthermore, patients with maximal diameter of tumors >3 cm (P = 0.035) or solid tumors (P = 0.018) showed a higher incidence of postoperative complications. The local recurrence was correlated with VHL disease (P = 0.027).

CONCLUSIONS

Although hemangioblastomas of the CPA are challenging lesions to treat surgically, they can be removed safely when these lesions are appropriately diagnosed and treated. Patients with VHL disease are more likely to have a local recurrence. A regular follow-up is recommended to detect the local and distant recurrence, even if the clinical course is benign and the tumor is totally resected.

Radiological indeterminate vestibular schwannoma and meningioma in cerebellopontine angle area: differentiating using whole-tumor histogram analysis of apparent diffusion coefficient

PURPOSE

To assess the role of whole-tumor histogram analysis of apparent diffusion coefficient (ADC) maps in differentiating radiological indeterminate vestibular schwannoma (VS) from meningioma in cerebellopontine angle (CPA).

MATERIALS AND METHODS

Diffusion-weighted (DW) images (b = 0 and 1000 s/mm²) of pathologically confirmed and radiological indeterminate CPA meningioma (CPAM) (n = 27) and VS (n = 12) were retrospectively collected and processed with mono-exponential model. Whole-tumor regions of interest were drawn on all slices of the ADC maps to obtain histogram parameters, including the mean ADC (ADC_mean), median ADC (ADC_median), 10th/25th/75th/90th percentile ADC (ADC₁₀, ADC₂₅, ADC₇₅ and ADC₉₀), skewness and kurtosis. The differences of ADC histogram parameters between CPAM and VS were compared using unpaired t-test. Multiple receiver operating characteristic (ROC) curves analysis was used to determine and compare the diagnostic value of each significant parameter.

RESULTS

Significant differences were found on the ADC_mean, ADC_median, ADC₁₀, ADC₂₅, ADC₇₅ and ADC₉₀ between CPAM and VS (all p values < 0.001), while no significant difference was found on kurtosis (p = 0.562) and skewness (p = 0.047). ROC curves analysis revealed, a cut-off value of 1.126 × 10^-3 mm²/s for the ADC₉₀ value generated highest area under curves (AUC) for differentiating CPAM from VS (AUC, 0.975; sensitivity, 100%; specificity, 88.9%).

CONCLUSIONS

Histogram analysis of ADC maps based on whole tumor can be a useful tool for differentiating radiological indeterminate CPAM from VS. The ADC₉₀ value was the most promising parameter for differentiating these two entities.

Audiologic evaluation of vestibular schwannoma and other cerebellopontine angle tumors

CONCLUSION

Otologic accompanying symptoms, audiogram patterns, and hearing levels according to tumor size differed in patients with CPA tumors classified as VS and non-VS types.

OBJECTIVES

The diagnosis of CPA tumors is often delayed. Late-diagnosed tumors can grow until they compress and damage vital structures. This study evaluated the otologic symptoms and results of audiologic tests in patients with vestibular schwannomas (VS) and other types of CPA tumors.

METHODS

This study included 171 patients with otologic symptoms who were diagnosed with CPA tumors, including 116 with VS and 55 with other types of CPA tumors. Factors analyzed retrospectively included tumor type, size, and location and the results of audiometric examinations.

RESULTS

The most common chief complaint in patients diagnosed with CPA tumors was asymmetrical hearing loss, with most frequent accompanying symptoms being tinnitus in patients with VS and dizziness in those with other types of CPA tumor. The most frequent patterns of hearing loss were the descending type in patients with VS and the flat type in patients with non-VS tumors (p < 0.05). Pure tone thresholds tended to increase more in patients with VS than non-VS tumors according to tumor size, and pure tone averages were significantly higher in patients with VS than non-VS tumors of 11-25 mm in size (p < 0.05).

Cerebellopontine angle tumors in infants and children

OBJECTIVE

Cerebellopontine angle (CPA) and cerebellomedullary fissure (CMF) tumors are rare in children and information is scarce in the literature. This retrospective study reports their histological distribution and tumor origin, and describes surgical resections and post-operative outcome based upon the authors' consecutive personal series.

METHODS

Clinical data of infants and children 16 years old or younger of age treated from 2001 to 2012 by a single surgeon was retrospectively reviewed. All had histologically verified CPA/CMF tumors and underwent radical tumor resection through craniotomy except for two children who had a stereotactic biopsy for malignant tumors (glioblastoma and primitive neuroectodermal tumor (PNET)). Tumors' pathological distributions, tumors' origin, surgical approaches, and patients' outcome were reviewed.

RESULTS

There were 44 infants and children with the age at diagnosis ranging from 11 weeks to 16 years; 32 were predominantly in the CPA and/or CMF whereas 12 showed an extension to the fourth ventricle. Pathology showed 14 ependymomas, 12 benign gliomas (11 pilocytic astrocytomas, 1 ganglioglioma), 4 atypical teratoid rhabdoid tumors (ATRTs), 4 epidermoids, 3 primitive neuroectodermal tumors (PNETs), 3 meningiomas, 3 nerve sheath tumors, and 1 glioblastoma. The anatomical site of tumor origin was the lateral recess of the fourth ventricle in 13 patients, the ventral cerebellar hemisphere in 8, the cerebellar peduncle in 7, and the brain stem in 6. Others were from embryonal nest, cranial nerve, or meninges. For 42 tumor resections, 38 were approached through a posterior fossa craniotomy and 4 through a temporal craniotomy and transtentorial approach. At tumor resection, 26 had a gross total or near total resection, 12 subtotal resection, and 4 partial resection. There were no mortalities. The most significant morbidity was ninth and tenth nerve palsy; 15 patients had unilateral vocal cord palsy or dysphagia. Of these, nine were treated with nasogastric (NG) feeding tube, five with a combination of gastrostomy (G-tube) and tracheotomy, and one with G-tube. All had successful removal of NG feeding from 1 month to 2 years (average 6 months). The tracheostomy and G-tube were removed between 4 months and 2 years (average 14 months) in all.

CONCLUSION

A plethora of tumor types occur in childhood at the CPA/CMF and our review indicated 50 % were benign in histology. High rates of lower cranial nerve morbidity were experienced but their dysfunctions were often recovered or compensated in 2 years. However, one should be cognizant of these complications and conduct resection with appropriate surgical approach, intraoperative monitoring, and surgical microscope.