Imaging of cerebellopontine angle lesions: an update. Part 2: intra-axial lesions, skull base lesions that may invade the CPA region, and non-enhancing extra-axial lesions

Comparison of DWI techniques in patients with epidermoid cyst: TGSE-BLADE DWI vs. SS-EPI DWI

PURPOSE

To compare quantitative values and image quality between single-shot echo-planar imaging (SS-EPI) diffusion-weighted imaging (DWI) and two-dimensional turbo gradient- and spin-echo DWI with non-Cartesian BLADE trajectory (TGSE-BLADE DWI) in patients with epidermoid cyst.

METHODS

Patients with epidermoid cyst who underwent both SS-EPI DWI and TGSE-BLADE DWI were included in this study. Two raters placed ROIs encircling the entire epidermoid cyst on SS-EPI DWI, and then on TGSE-BLADE DWI. Apparent diffusion coefficient (ADC) of the epidermoid cyst was measured within each ROI, then the intraclass correlation coefficient (ICC) between raters was obtained for each DWI. The areas of ROIs placed by the two raters were measured and compared using the Dice coefficient. In the selected slice analysis, one rater selected the most appropriate slice and carefully placed the ROIs slightly smaller than the epidermoid outline to avoid artifacts. Image quality analysis was assessed qualitatively for geometric distortion, susceptibility artifacts, lesion conspicuity, and diagnostic confidence. ADCs for both DWI techniques were compared with theoretical values derived from the diffusion phantom.

RESULTS

Twenty patients with epidermoid cyst were included in this study. The ICC of ADC measured by the two raters for TGSE-BLADE (0.80) was higher than that for SS-EPI (0.59). Dice coefficient of ROI areas was significantly higher with TGSE-BLADE (0.78) than with SS-EPI (0.71, P = 0.007). Selected slice analysis showed that the ADC of epidermoid cyst was significantly higher with TGSE-BLADE DWI than with SS-EPI DWI (P < 0.001). ADCs measured from carefully selected ROIs avoiding artifacts with the two techniques correlated positively (r = 0.87, P < 0.001; ICC 0.75). TGSE-BLADE DWI rated better for image quality than SS-EPI DWI according to all raters. ICCs of measured ADC and theoretical ADCs exceeded 0.99 for both techniques.

CONCLUSIONS

TGSE-BLADE DWI appears more suitable than SS-EPI DWI for evaluating epidermoid cyst.

Epidermoid cyst of the craniovertebral junction-A case report

An epidermoid cyst is a benign tumor in many locations. The symptoms of an epidermoid cyst depend on its location. The brain or spine MRI can confirm the lesion. Removing total decompression is the first choice in treatment with a symptomatic cyst.

Cerebellopontine angle meningioma originating from choroid plexus of the foramen of Luschka: An extremely rare entity and overlook of literature

INTRODUCTION AND IMPORTANCE

Meningiomas without dural attachments are quite a novelty, with such meningiomas in the posterior fossa being even more far and few between. The authors describe an extremely rare cerebellopontine angle (CPA) meningioma lacking a dural attachment arising from the choroid plexus of the foramen of Luschka (CPFOL).

CASE PRESENTATION

A 35-year-old male presented to our center complaining of a generalized and progressive headache for 10 months. A 3 cm × 4 cm well-defined lesion in the left CPA, hypointense in T1 and hyperintense in T2-weighted magnetic resonance imaging (MRI), was noted with no evident dural base or dural attachment. CPFOL was appreciated right at the point where the tumoral base was detected, which implied that the tumor originated from CPFOL. A gross total resection (GTR) was achieved, with the postoperative period remaining uneventful. The histopathologic investigation confirmed a transitional meningioma World Health Organization (WHO) grade I with no atypical features.

CLINICAL DISCUSSION

Meningioma without dural attachment remains a rare phenomenon, with few available in English literature, and such pathology in the posterior fossa is even more unusual. Discriminating between CPFOL and another kind of CPA meningioma is mandatory when dealing with intracranial meningioma surgeries.

CONCLUSION

While managing a space-occupying lesion around CPA, although extremely rare, a meningioma originating from CPFOL is suggested to be included in the differentials with necessary imaging analysis and advised to be imperatively pursued before proceeding for surgical intervention.

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.

Differentiating between adult intracranial medulloblastoma and ependymoma using MRI

AIM

To investigate the value of routine magnetic resonance imaging (MRI) examination combined with diffusion-weighted imaging (DWI) in the differential diagnosis of adult intracranial medulloblastomas and ependymomas.

MATERIALS AND METHODS

MRI images of 18 medulloblastomas and 18 ependymomas in adult patients were analysed retrospectively, and the differences in MRI features of lesions and apparent diffusion coefficient (ADC) of solid lesions between the two groups were recorded. Independent sample t-tests and χ2 tests were used to analyse the differences in MRI signs and maximum ADC (ADC_max), minimum ADC (ADC_min), and mean ADC (ADC_mean) values between the two groups. The receiver operating characteristic (ROC) curve was used to determine the differential diagnostic efficacy and optimal threshold for each ADC value.

RESULTS

Age, tumour location, and tumour enhancement were significantly different between adult medulloblastoma and ependymoma (p<0.05). The ADC_max (0.69 ± 0.11 versus 1.04 ± 0.20 × 10^-3 mm²/s, p<0.001), ADC_min (0.57 ± 0.12 versus 0.96 ± 0.21 × 10^-3 mm²/s, p<0.001), and ADC_mean (0.62 ± 0.11 versus 1.00 ± 0.20 × 10^-3 mm²/s, p<0.001) values were significantly lower in adult medulloblastoma than in ependymoma. The areas under the ROC curves of ADC_max, ADC_min, and ADC_mean were 0.951, 0.957, and 0.966, respectively. The optimal ADC_mean threshold was 0.75 × 10^-3 mm²/s, with a sensitivity of 88.9% and a specificity of 88.9%.

CONCLUSION

Routine MRI examination combined with DWI helps differentiate between intracranial infratentorial medulloblastoma and ependymoma in adults.

Third Ventricular Epidermoid Tumor in a Pediatric Case

Epidermoid tumors, which constitute 0.2 to 1.8% of primary intracranial neoplasms, occur in the third and fifth weeks of fetal development. Epidermoid tumors, which are known to occur most frequently in the cerebellopontine angle, are rarely located intraventricularly. A third ventricular location can be seen in 0.7% of cases. Epidermoid tumors are more common between the ages of 19 and 69, and are very rare in the pediatric period. In this report, we present a third ventricular epidermoid tumor in an 11 years old pediatric patient.

Meningioma Originating From Choroid Plexus of Foramen of Luschka: A Rare Case Report and Tip of Differential Diagnosis

Meningiomas are the most common benign brain tumors, and most of them originate from the dura mater. However, in some cases, they can originate from the choroid plexus, and they are rarely found in the posterior cranial fossa. A 63-year-old female patient presented with dizziness and swallowing difficulty and was found to have a homogeneously enhancing mass in the right posterior cranial fossa. Mass removal was performed through retrosigmoid suboccipital craniotomy, and the mass was confirmed to originate from the choroid plexus. The pathological diagnosis was meningothelial meningioma. The patient had temporary swallowing difficulty but recovered without any neurological sequelae. We report a rare case of a lower cerebellopontine angle meningioma without dural attachment originating from the choroid plexus of the foramen of Luschka.

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.

Evaluation of schwannoma using the 3D-SPACE sequence: comparison with the 3D-CISS sequence in 3T-MRI

Background/aim

The purpose of this study is to compare the diagnostic accuracy and interobserver reliability of the T2-weighted 3D-SPACE (three-dimensional sampling perfection with application-optimized contrasts by using different flip angle evolutions) sequence in comparison with T2-weighted 3D-CISS (three-dimensional constructive interference in steady state) sequences for diagnosis of schwannomas.

Materials and methods

Forty patients with cerebellopontine angle (CPA), internal acoustic canal (IAC), and cochlear schwannoma who had undergone magnetic resonance imaging (MRI) using the 3D-CISS and 3D-SPACE sequences were identified. The sequences were retrospectively evaluated by two radiologists for the qualitative analyses, which were subsequently compared using the Mann–Whitney U test. Following this, kappa values were used for interobserver agreement. P < 0.05 was considered to be of statistical significance.

Results

The interobserver agreement was found to be excellent between the two observers for the interpretation of all qualitative analyses for both sequences (kappa value > 0.8). The 3D-SPACE sequences demonstrated significantly better qualitative scores and fewer artifacts compared with the 3D-CISS sequences (p < 0.05).

Conclusion

Our results demonstrate that 3D-SPACE is superior to 3D-CISS in the imaging process of the schwannoma in terms of image quality, description of the relationship between the lesion and cranial nerve, signal differentiation between lesion and cistern, and signal differentiation between the lesion and adjacent brain.

Advanced Magnetic Resonance Imaging of the Skull Base

Magnetic resonance (MR) imaging is a crucial tool for evaluation of the skull base, enabling characterization of complex anatomy by utilizing multiple image contrasts. Recent technical MR advances have greatly enhanced radiologists' capability to diagnose skull base pathology and help direct management. In this paper, we will summarize cutting-edge clinical and emerging research MR techniques for the skull base, including high-resolution, phase-contrast, diffusion, perfusion, vascular, zero echo-time, elastography, spectroscopy, chemical exchange saturation transfer, PET/MR, ultra-high-field, and 3D visualization. For each imaging technique, we provide a high-level summary of underlying technical principles accompanied by relevant literature review and clinical imaging examples.

The Role of Magnetic Resonance Imaging (MRI) in Diagnostics of Acoustic Schwannoma

Background:

Acoustic neuromas are also called vestibular schwannoma, acoustic neurinoma, vestibular neuroma, and acoustic neurofibroma. These are tumors that evolve from Schwann cell sheath and can be either intracranial or extra-axial. They usually occur adjacent to the cochlear or vestibular nerve. Anatomically, acoustic neuromas tend to occupy the cerebellopontine angle. About 20% of internal carotid artery (ICA) tumors are meningiomas and may occur elsewhere in the brain. Bilateral acoustic neuromas also tend to be exclusively in individuals with type 2 neurofibromatosis.

Objective:

The aim was to asses the role of MRI in evaluation of cerebellopontine angle acoustic schwannomas, the role of the cyber knife treatment in eliminating the tumor with a maximum protection of healthy tissue.

Methods:

MRI, GE 1.5 Tesla unit and standard protocol: Pre-contrast MRI images of the temporal bones and posterior fossa were obtained using Ax 3D Fiesta T2W Hi-resolution; Ax 3D T1 Fat-Suppressed, Thin-slice (2mm) Coronal T2W, Sag 3D FiestaT2W Hi-resolution images. Post-contrast images were obtained using Ax 3D T1 Fat-Suppressed Cor 3D T1 Fat-suppressed sequences. FLAIR sequence axial).

Case report:

A woman 62 years of age, reported sudden tinnitus, dizziness, hearing loss in her left ear. After one years she began to experience vertigo, headache.

Results:

MRI of brain temporal bone with contrast show acoustic schwannoma measuring 20x9 mm on the left cerebellopontine angle extending into and enlarging the left IAC, solid enhancing component is seen the acoustic meatus and peripheral contrast cystic component in the left cerebellopontine angle, after cyber knife treatment MRI result was the solid component of the mass, filling the left internal acoustic canal shows marked post-contrast enhancement and is measured 10x5x4mm, cystic component of it filling the left cerebellopontine angle cistern is enlarged to 25x19x12mm), it extends down till the left lateral aspect of medullary cistern, abutting the CN-XII at its entrance to left hypoglossal canal. After 5 month control show, a 15mm long and 5mm thick neoplastic soft-tissue in the left internal acoustic canal, with post-contrast enhancement, measured up to 12mm at the level of porus acusticus but cystic component of the mass in left cerebellopontine angle cistern is no longer visible in this MRI exam.

Conclusion:

The sensitivity of MRI for correctly diagnosing acoustic schwannoma was 100 % and specificity was 92.86 % with a positive predictive value of 94.12 % and accuracy of 96.67 %. MRI is considered as an excellent noninvasive investigation for pontocerebral angle Schwannoma’s.

Surgical management of choroid plexus papilloma of the cerebellopontine and cerebellomedullary angle: classification and strategy

Choroid plexus papillomas (CPPs) are primary neuroectodermal neoplasms that usually arise in the fourth ventricle in adults. In this study, we present 12 patients with CPP arising from the cerebellopontine angle (CPP-CPA) and/or of the cerebellomedullary angle (CPP-CMA) that were treated in our department. Patients who underwent surgery for the treatment for CPP-CPA/CMA from January 2004 to March 2020 were identified by a computer search of their files from the Department of Neurosurgery, Tübingen. CPPs were classified according to their location into type 1 (tumor portion only in the CPA,), type 2 (tumor portions only in the CMA), and type 3 (tumor portions both in the CPA and CMA). Patients were evaluated for initial symptoms, previous therapies in other hospitals, extent of tumor resection, recurrence rate, and complications by reviewing patient documents. Of approximately 1500 CPA lesions, which were surgically treated in our department in the last 16 years, 12 patients (mean age 42 ± 19 years) were found to have CPP-CPA/CMA. Five were male, and seven were female patients. Gross total resection was achieved in nine cases, and a subtotal resection was attained in three cases. Tumor recurrence in the same location after the first surgery in our hospital was observed in 2 patients after 15 and 40 months of follow-up, and in another patient, distant metastases (C3/4 and L3 levels) were observed. Surgical removal of CPP is the treatment of choice, but additional therapeutic options may be necessary in case of remnant tumor portions, recurrence, or malignant transformation.

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.

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.

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.

Neuroglial ectopia of the vestibular nerve masquerading as a vestibular schwannoma: A case report

Neuroglial ectopia is a rare entity of undetermined clinical significance. Here, we report a unique case of neuroglial ectopia of the vestibular nerve. A 27-year-old pharmacy student with a previous radiological diagnosis of vestibular schwannoma presented to our clinic for surgical evaluation. Magnetic resonance imaging (MRI) of the brain revealed a 17-mm T1 hypo- to isointense, T2 iso- to hyperintense, poorly enhancing left cerebellopontine angle mass extending into the left internal auditory canal compatible by imaging with a vestibular schwannoma. The lesion was resected under MRI guidance. The frozen specimen came back as a benign hypocellular lesion. Histological assessment revealed a peripheral nerve engulfed by glial fibrillary acidic protein-positive, S-100-negative cells, suggestive of neuroglial ectopia. There was no evidence of schwannoma. The main concerns were benign neoplasm with potential for progression or sampling artifact. The patient had an uncomplicated hospital course. This case report demonstrates an unusual case of neuroglial ectopia of the vestibular nerve. The differential diagnoses for a poorly enhancing cerebellopontine angle mass should include neuroglial ectopia.

Staged multi-modality treatment approaches for giant cerebellopontine angle hemangioblastomas

Giant hemangioblastomas (HBs) located in the cerebellopontine angle (CPA) present rare, high risk neurosurgical challenges. En bloc resection has been traditionally recommended for HBs, however this approach may pose unacceptable risk with giant tumors. Alternative treatment strategies have not been well described and the relevant literature is scant. This case review includes an illustrative patient with a giant, symptomatic CPA HB. It was felt that the neurovascular and tumor attributes were favorable for a multi-modality treatment strategy rather than circumferential dissection to remove this formidable tumor. A staged approach consisting of preoperative HB devascularization, debulking and piecemeal resection followed by radiosurgery for a small residuum produced an excellent clinical outcome. Variations of this unconventional multi-modality strategy may reduce the perioperative morbidity of carefully selected patients with giant CPA HBs. A thorough literature review is provided.

Primary Obstruction of the Foramen of Luschka: Anatomy, Histology, and Clinical Significance

BACKGROUND

The foramen of Luschka is a natural aperture between the fourth ventricle and the subarachnoid space at the cerebellopontine angle. Membranous closure of this foramen is referred to as primary obstruction. Available information about this variant and its role in the development of the cysts of the posterior fossa is contradictory.

METHODS

The macroscopic and histologic features of the obstructed foramina were examined in 61 formalin-fixed human brains (122 foramina). Three rhomboid lips of various sizes with lateral recess were used for comparison. Five postoperative cases of diverticulum of the foramen of Luschka were included in this study, with 1 case presented in detail to illustrate anatomic and histologic findings.

RESULTS

Primary obstruction was present in 11 of 122 cases. In 1 case, an enlarged rigid pouch with a thick wall was found. The wall of the membrane in primary obstruction and the rhomboid lip were composed of an inner ependymal, a middle glial, and an outer leptomeningeal layer.

CONCLUSIONS

The rhomboid lip is a remnant of the roof of the fourth ventricle. Imperforation of the foramen of Luschka results in a pouch in the cerebellopontine angle that contains choroid plexus (Bochdalek's flower basket) and communicates with the fourth ventricle. This pouch has the potential to grow to a diverticulum and cause clinical symptoms. Based on our clinical observations, detailed radiologic and surgical-anatomic criteria were proposed to support the differential diagnosis of a diverticulum of the foramen of Luschka. Treatment strategies were also suggested.

Diagnostic Dilemma: Cerebellopontine Angle Lipoma Versus Dermoid Cyst

Both lipomas and dermoid cysts of the cerebellopontine angle are rare tumors. These tumors differ in their embryological origin but share similar features on imaging. Both of these congenital lesions can be found in the cerebellopontine angle (CPA), and symptomatic clinical presentation is dictated by the location of the lesion. This paper demonstrates a unique case in which a CPA lipoma was misidentified as a dermoid cyst, leading to surgical intervention. Further, the paper provides a literature review of CPA lipomas and dermoid cysts to aid readers in further differentiating between these two unique tumors.

Atypical choroid plexus papilloma: clinicopathological and neuroradiological features

Background Atypical choroid plexus papilloma (APP) is a rare, newly introduced entity with intermediate characteristics. To date, few reports have revealed the magnetic resonance (MR) findings. Purpose To analyze the clinicopathological and MR features of APP. Material and Methods The clinicopathological data and preoperative MR images of six patients with pathologically proven APP were retrospectively reviewed. The MR features including tumor location, contour, signal intensity, degree of enhancement, intratumoral cysts, and necrosis; and flow voids, borders, peritumoral edema, and associated hydrocephalus were analyzed. Results The APP were located in the ventricle (n = 4) and cerebellopontine angle (CPA, n = 2). Tumor dissemination along the spinal subarachnoid space was found in one patient. The tumors appeared as milt-lobulated (n = 5) or round mass (n = 1), with slightly heterogeneous signals (n = 5) or mixed signals (n = 1) on T1-weighted and T2-weighted images. Heterogeneous and strong enhancement were found in five cases on contrast-enhanced images. Three of four intraventricular tumors had a partly blurred border with ventricle wall. Four tumors had mild to moderate extent of surrounding edema signals. A slight hydrocephalus was seen in four patients. Incomplete capsule was seen in four tumors at surgery. Histopathologically, mild nuclear atypia was seen in all tumors with a mitotic rate of 2-5 per 10 high-power fields. Conclusion APP should be included in the differential diagnosis when an intraventricular or CPA tumor appearing as a multi-lobulated solid mass with slight heterogeneity, heterogeneous strong enhancement, partly blurred borders, mild to moderate peritumoral edema, or slight hydrocephalus are present.

Meningioma mimics: five key imaging features to differentiate them from meningiomas

There are a wide variety of intracranial mass lesions, both benign and malignant, which can closely mimic meningioma on imaging. We present five characteristic imaging features that can alert the radiologist to consider other differential diagnoses. Of the five imaging characteristics that were rarely seen in meningiomas, but common and specific for meningioma mimics, absence of dural tail is the most common (83.7%). Homogeneous T2 hyperintensity or T2 hypointensity are seen in nearly half of meningioma mimics and osseous destruction and leptomeningeal extension are present in 40.5% and 21.6% of meningioma mimics, respectively. The distinction between meningioma and its mimics is important because a large portion of the meningioma mimics requires substantially different clinical and surgical management.

Evaluating the utility of a scoring system for lipomas of the cerebellopontine angle

BACKGROUND

Cerebellopontine angle (CPA) lipomas are rare, benign, slow-growing masses. Resections are considered in symptomatic patients who are refractory to targeted medical therapies, but at those stages the lipomas have often reached considerable sizes and encompass critical neurovascular structures. The objective of this study is to develop and to evaluate the utility of a scoring system for CPA lipomas. The hypothesis is that CPA lipomas with lower scores are probably best managed with early surgery.

METHODS

The PubMed database was searched using relevant terms. Data on patient and lipoma characteristics were extracted and used to design a scoring system. CPA lipomas were stratified by scores with corresponding managements and outcomes analyzed.

RESULTS

One hundred and seventeen patients with CPA lipomas were identified and 40 CPA lipomas were scored. The remaining CPA lipomas were deficient in data and not scored. No lipomas were scored as 1. Score 2 lipomas (n = 12; 30%) most often underwent serial surveillances (n = 5; 41.6%), with the majority of symptoms remaining unimproved (n = 2; 40%). Patients with score 2 CPA lipomas treated with medical therapies (n = 3; 25%) often experienced symptom resolution (n = 2; 66.6%) (p = 0.0499). Patients with score 2 CPA lipomas undergoing surgical resections (n = 3; 25%) all experienced symptom resolution (n = 3; 100%) (p = 0.0499). Score 3 was most common (n = 16; 40%) and these lipomas were often surgically resected (n = 10; 62.5%). The majority of patients with score 3 CPA lipomas having undergone surgical resections (n = 10; 62.5%) experienced symptom improvement (n = 1; 10%) or resolution (n = 4; 40%).

CONCLUSIONS

Score 2 CPA lipomas are smaller and would be deemed non-surgical in general practice. However, our data suggest that these lipomas may benefit from either medical therapies or early surgical resections. The advantages of early surgery are maximal resection, decreased surgical morbidity, and improved symptom relief.

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

BACKGROUND

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.

METHODS

We review all reported cases of hypervascular lesions of the CPA and discuss the roles of angiography and stereotactic radiosurgery in their management.

RESULTS

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.

CONCLUSIONS

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.

Imaging findings of extraventricular choroid plexus papillomas: A study of 10 cases

Extraventricular choroid plexus papillomas (CPPs) are rare. In this study, we reveal the imaging findings of CPPs located in extraventricular sites. The imaging findings of 11 masses [10 masses on magnetic resonance imaging (MRI) and one mass on computed tomography (CT)] of extraventricular CPP in 10 patients were retrospectively observed. The mass site, size, contour, signal intensity, cystic or solid appearance, calcification, capsules, degree and pattern of enhancement, and hydrocephalus were evaluated based on CT or MRI. The misdiagnosis rate of CPPs in extraventricular sites was 80.0% (8/10). Solitary masses and multiple masses were observed in nine patients (90.0%, 9/10) and one patient (10%, 1/10), respectively. In addition to the typical imaging findings [a lobulated, cauliflower-like or mulberry-like mass that is homogeneous isointense or slightly hypointense on T1-weighted imaging (T1WI) and heterogeneous isointense or slightly hyperintense on T2WI], four masses had round or oval contours and three had cystic components; abnormal signal intensity (mixed hyperintense signals on T1WI and T2WI or slightly hyperintense signals on T1WI or hypo-/hyperintense on T2WI) and low or no enhancements were observed in three and six masses, respectively; absence of hydrocephalus and mild or local hydrocephalus were each observed in four subjects, respectively. Hemorrhage and psammomatous bodies and/or calcification were observed in four and three masses, respectively. In conclusion, in addition to the typical imaging findings, atypical imaging findings, including atypical contours, abnormal signal intensity, low enhancement and absence of hydrocephalus were also observed in extraventricular CPPs.

Is there a role for conventional MRI and MR diffusion-weighted imaging for distinction of skull base chordoma and chondrosarcoma?

BACKGROUND

Chordoma and chondrosarcoma are locally invasive skull base tumors with similar clinical symptoms and anatomic imaging features as reported in the literature.

PURPOSE

To determine differentiation of chordoma and chondrosarcoma of the skull base with conventional magnetic resonance imaging (cMRI) and diffusion-weighted MR imaging (DWI) in comparison to histopathological diagnosis.

MATERIAL AND METHODS

This retrospective study comprised 96 (chordoma, n = 64; chondrosarcoma, n = 32) patients with skull base tumors referred to the Paul Scherrer Institute (PSI) for proton therapy. cMRI signal intensities of all tumors were investigated. In addition, median apparent diffusion coefficient (ADC) values were measured in a subgroup of 19 patients (chordoma, n = 11; chondrosarcoma, n = 8).

RESULTS

The majority 81.2% (26/32) of chondrosarcomas displayed an off-midline growth pattern, 18.8% (6/32) showed clival invasion, 18.8% (6/32) were located more centrally. Only 4.7% (3/64) of chordomas revealed a lateral clival origin. Using cMRI no significant differences in MR signal intensities were observed in contrast to significantly different ADC values (subgroup of 19/96 patients examined by DWI), with the highest mean value of 2017.2 × 10(-6 )mm(2)/s (SD, 139.9( )mm(2)/s) for chondrosarcoma and significantly lower value of 1263.5 × 10(-6 )mm(2)/s (SD, 100.2 × 10(-6 )mm(2)/s) for chordoma (P = 0.001/median test).

CONCLUSION

An off-midline growth pattern can differentiate chondrosarcoma from chordoma on cMRI in a majority of patients. Additional DWI is a promising tool for the differentiation of these skull base tumors.

Epidermoid cysts of the cerebellopontine angle: Clinical features and treatment outcomes

OBJECTIVE

To report clinical characteristics, treatment outcomes and risk of recurrence in patients with surgically treated cerebellopontine angle epidermoids.

METHODS

In 1994-2013, we operated 17 patients, including 7 with tumor limited to the cerebellopontine angle, 7 with cerebellopontine angle tumor penetrating supratentorially, and 3 with cerebellopontine angle tumor extending along skull base to contralateral cerebellopontine angle. All patients were followed-up for the mean duration of 126 months.

RESULTS

On admission cranial nerve symptoms predominated. Total tumor removal was achieved in 5 patients, and incomplete removal (with small tumor remnants left on vessels, nerves, or brainstem) in 12 patients. Postoperatively, preoperative deficits worsened in 2 and new postoperative deficits occurred in 10 patients. The extent of tumor expansion had no effect on postoperative morbidity and risk of recurrence. During long-term follow-up, improvement or resolution of preoperative deficits was seen in 11 of 17 patients, and new postoperative deficits in 8 of 10 patients. Symptomatic recurrences after an average of more than 9 years were noted in 5 patients, 3 of whom were reoperated. Recurrences occurred in some younger patients and always in area of primary tumor. No effect of extent of tumor removal on risk of recurrence was found.

CONCLUSIONS

The extent of tumor removal had no effect on the risk of recurrence, and thus it may be acceptable to leave tumor capsule fragments adhering closely to nerves, vessels, or brainstem. During long-term follow-up, resolution or improvement of present preoperatively and new postoperative neurological deficits may be expected in most patients.

Diagnostic neuroimaging in neuro-ophthalmic disorders

PURPOSE OF REVIEW

Neuroimaging studies are a valuable diagnostic tool in the evaluation of a patient with neuro-ophthalmic disease. This review provides an approach to selecting an appropriate imaging study and interpreting the results.

RECENT FINDINGS

MRI and CT are the imaging studies most commonly employed in neuro-ophthalmology. Each modality has unique strengths that make it particularly suitable in certain clinical situations.

SUMMARY

In the current practice of neuro-ophthalmology, the clinician must be familiar with the uses and limitations of neuroimaging studies so they can be used appropriately to improve diagnostic accuracy.

Role of magnetic resonance imaging in evaluation of cerebellopontine angle schwannomas

The aim of the present study was to evaluate the role of Magnetic Resonance Imaging (MRI) to localize and characterize the MR imaging features of cerebellopontine angle schwannomas and to compare with surgical/histopathological findings. It was a prospective study which included 19 patients, who presented with signs and symptoms s/o any lesion in the CP angle and were referred to the radiology department for MRI. All patients included in the study were subjected to detailed clinical history and physical examination following which MRI was carried out on Philips Gyroscan Achieva 1.5 Tesla unit and the standard protocol consisted of T1WI, T2WI, DWI and FLAIR images in axial, sagittal and coronal planes. Hearing abnormality was the most common presenting complaint in patients with CP angle schwannoma's followed by headache and tinnitus. Vestibulocochlear nerve was the most commonly involved nerve in patients with these lesions followed by involvement of trigeminal nerve. MRI was erroneous in giving provisional diagnosis of schwannoma in one case, which on subsequent surgery and histopathology was found to be a meningioma. The sensitivity of MRI for correctly diagnosing vestibular schwannoma was 100 % and specificity was 92.86 % with a positive predictive value of 94.12 % and accuracy of 96.67 %. MRI is considered as an excellent noninvasive investigation for CP angle schwannoma's. It can identify the site and extension of the lesions as well as the characteristic signal. Apart from diagnosing, MR imaging plays an important role in stratifying patients into appropriate treatment options.

Management of cerebellopontine angle lipomas: need for long-term radiologic surveillance?

OBJECTIVE

To date, only a very limited number of lipomas of the cerebellopontine angle (CPA) have been reported. Our objective was to examine clinical and radiologic features of CPA lipomas and determine the most appropriate management plan.

STUDY DESIGN

Retrospective case series.

SETTING

Tertiary referral center.

PATIENTS

Patients with CPA lipomas were identified through the skull base multidisciplinary meeting database.

INTERVENTIONS

Radiologic surveillance and clinical assessment.

MAIN OUTCOME MEASURES

Tumor growth, assessed through radiologic measurements on serial magnetic resonance imaging, demographics, presenting symptoms, and any correlation between weight gain and lipoma growth were among the examined factors.

RESULTS

Of the 15 patients with CPA lipomas, six were female and nine were male, with an average age at presentation of 50.2 years (range, 31.7-76.4 yr) and an average follow-up time of 51.7 months (range, 6-216 mo). The lipomas were unilateral in all cases, nine on the right (60%) and six on the left (40%) side. None of the lipomas increased in size. All patients were treated conservatively. Sensorineural hearing loss was the main presenting symptom (80%) followed by tinnitus (46.7%) and vertigo (20%). None of the patients suffered from facial nerve dysfunction. There was no correlation between weight gain and tumor growth.

CONCLUSION

CPA lipomas can be diagnosed accurately with appropriate magnetic resonance imaging techniques and be managed conservatively with safety. Cochleovestibular are the most common presenting symptoms, whereas facial nerve involvement is rare. CPA lipomas do not tend to grow and can be monitored on a less regular basis.

Unique presentation of cerebellopontine angle choroid plexus papillomas: case report and review of the literature

Objectives We present the case of a choroid plexus papilloma (CPP) in the cerebellopontine angle (CPA), describe the different appearances of CPPs with a variety of imaging techniques, and discuss the differential diagnosis of CPA tumors.

Participant and Design We report the case of a 52-year-old woman with headache, tinnitus, and unilateral hearing impairment whose preoperative magnetic resonance imaging revealed a heterogeneously enhancing CPA mass that extended into the internal auditory canal.

Main Outcome Measures, Results, and Conclusion The preoperative imaging appearance of the lesion was most consistent with that of a schwannoma. Postoperative histopathologic examination found the tumor to be a CPP with cuboidal epithelial cells overlying fibrovascular stroma. CPPs are rare benign central nervous system neoplasms arising from choroid plexus epithelium. The most common site of presentation is in the fourth ventricle in adults and the lateral ventricles in children. CPPs rarely occur in the CPA, and when they do, clinical-radiologic diagnosis is difficult due to both the rarity of this presentation and to nonspecific radiological features.

Choroid plexus papillomas: advances in molecular biology and understanding of tumorigenesis

Choroid plexus papillomas are rare, benign tumors originating from the choroid plexus. Although generally found within the ventricular system, they can arise ectopically in the brain parenchyma or disseminate throughout the neuraxis. We sought to review recent advances in our understanding of the molecular biology and oncogenic pathways associated with this disease. A comprehensive PubMed literature review was conducted to identify manuscripts discussing the clinical, molecular, and genetic features of choroid plexus papillomas. Articles concerning diagnosis, treatment, and long-term patient outcomes were also reviewed. The introduction of atypical choroid plexus papilloma as a distinct entity has increased the need for accurate histopathologic diagnosis. Advances in immunohistochemical staining have improved our ability to differentiate choroid plexus papillomas from other intracranial tumors or metastatic lesions using combinations of key markers and mitotic indices. Recent findings have implicated Notch3 signaling, the transcription factor TWIST1, platelet-derived growth factor receptor, and the tumor necrosis factor-related apoptosis-inducing ligand pathway in choroid plexus papilloma tumorigenesis. A combination of commonly occurring chromosomal duplications and deletions has also been identified. Surgical resection remains the standard of care, although chemotherapy and radiotherapy may be considered for recurrent or metastatic lesions. While generally considered benign, these tumors possess a complex biology that sheds insight into other choroid plexus tumors, particularly malignant choroid plexus carcinomas. Improving our understanding of the molecular biology, genetics, and oncogenic pathways associated with this tumor will allow for the development of targeted therapies and improved outcomes for patients with this disease.

Diagnostic value of EAAT-1 and Kir7.1 for distinguishing endolymphatic sac tumors from choroid plexus tumors

The endolymphatic sac tumor (ELST) is a low-grade carcinoma originating in the ear. These extremely rare tumors are capable of invading the cerebellopontine angle and might be mistaken for choroid plexus tumors (CPTs) in this region. Currently, these tumors are distinguished by conventional morphologic and immunohistochemical studies for S-100, cytokeratin, and GFAP expression, but all markers are variably expressed by both tumors. Therefore, we examined new promising markers such as EAAT-1 and Kir7.1 in 4 ELSTs and 35 CPTs located in the fourth ventricle or at the cerebellopontine angle in adults. Immunohistochemical expression of Kir7.1 was found in 30 (100%) of 30 and EAAT-1 in 32 (91%) of 35 CPTs tested and was absent in all ELSTs. Expression of GFAP was found in 16 (55%) and S-100 in 29 (100%) of 29 CPTs tested, but both markers were also expressed in 2 of 4 ELSTs examined. Specificity and sensitivity of Kir7.1 (both 100%) and EAAT-1 (100% and 91%, respectively) were superior to the values for S-100 (50% and 100%, respectively) and GFAP (50% and 55%, respectively) for distinguishing CPT from ELST.

Fibrotic nodule arising from the cerebellopontine angle

The authors present an extremely rare case of a fibrotic nodule arising from the cerebellopontine (CP) angle. A 57-year-old male had suffered from hearing disturbance and tinnitus for several years. Computed tomography revealed a high-density mass in the left CP angle with little enhancement after intravenous administration of contrast media. Magnetic resonance imaging (MRI) showed a very hypointense mass on T2-weighted imaging. T1-weighted MRI with gadolinium revealed very faint, delayed enhancement of the tumor. The patient underwent surgical resection of the tumor. Histopathologically the lesion comprised entirely fibrotic tissue consisting of thick collagenous fibers and sclerosing blood vessels with a few intervening viable cells with, partly, the immunophenotype of arachnoid cells. Intracranial fibrotic nodules are extremely rare. This tumor, however, had some radiological features similar to those of other, more common, tumors for example meningiomas or solitary fibrous tumors; it was, therefore, difficult to distinguish it from the others. It is believed that intracranial fibrotic nodules usually have benign, non-neoplastic characteristics, although their natural history is not yet fully understood. It is, therefore, necessary to be able to perform a differential diagnosis that will distinguish this rare condition from other intracranial fibrous neoplasms that occasionally have malignant features.

Intratumoral hemorrhage, vessel density, and the inflammatory reaction contribute to volume increase of sporadic vestibular schwannomas

Vestibular schwannomas show a large variation in growth rate, making prediction and anticipation of tumor growth difficult. More accurate prediction of clinical behavior requires better understanding of tumor biological factors influencing tumor progression. Biological processes like intratumoral hemorrhage, cell proliferation, microvessel density, and inflammation were analyzed in order to determine their role in vestibular schwannoma development. Tumor specimens of 67 patients surgically treated for a histologically proven unilateral vestibular schwannoma were studied. Preoperative magnetic resonance imaging (MRI) scans were used to determine tumor size and to classify tumors as homogeneous, inhomogeneous, and cystic. Immunohistochemical studies evaluated cell proliferation (histone H3 and Ki-67), microvessel density (CD31), and inflammation (CD45 and CD68). Intratumoral hemorrhage was assessed by hemosiderin deposition. The expression patterns of these markers were compared with tumor size, tumor growth index, MRI appearance, patients’ age, and duration of symptoms. No relation between cell proliferation and clinical signs of tumor volume increase or MRI appearance was found. Intratumoral hemosiderin, microvessel density, and inflammation were significantly positively correlated with tumor size and the tumor growth index. Cystic and inhomogeneous tumors showed significantly more hemosiderin deposition than homogeneous tumors. The microvessel density was significantly higher in tumors with a high number of CD68-positive cells. The volume increase of vestibular schwannomas is not based on cell proliferation alone. Factors like intratumoral bleeding, (neo)vascularization, and intensity of the inflammatory reaction also influence tumor volume.

Multifocal choroid plexus papillomas: case report

Choroid plexus papillomas (CPP) are rare tumors of the central nervous system, usually occurring in the ventricular system. Apart from spinal drop metastases, CPPs are generally unique tumors. In this report, the authors present two exceptional adult cases involving multiple benign CPPs located in both intra- and extraventricular locations. The tumors were located in the fourth ventricle and Meckel's cave in one case and the cerebellopontine angle, the frontotemporal region and the fourth ventricle in the other. A review of the literature revealed that these two cases represent the first reported occurrences of multiple choroid plexus papillomas involving Meckel's cave and frontotemporal intraparenchymal locations.