Orbital Schwannoma and Neurofibroma: Role of Imaging

Solitary neurofibroma confined to inferior rectus muscle tendon: a case report

The present study reports a case of solitary neurofibroma attached to the Inferior Rectus (IR) muscle tendon in a 24-year-old healthy woman and reviews the relevant literature regarding the clinical presentation, diagnosis, and management of this uncommon tumor. The patient underwent successful surgical resection of the tumor, leading to the resolution of associated symptoms (left lower eyelid protrusion and redness). Pathological examination confirmed the diagnosis of neurofibroma based on characteristic histopathological and immunohistochemical markers. This case report underscores the rarity of solitary neurofibromas and primary neoplasms of orbit and ocular adnexa. We also discuss the background of solitary neurofibromas originating from orbit and ocular adnexa. The successful management of this case through surgical resection highlights the importance of accurate diagnosis and tailored treatment strategies. To the best of our knowledge, this is the first reported solitary neurofibroma confined solely to the IR tendon.

Orbital schwannoma with hyposmia as the only presentation: Case report and a literature review on differential diagnosis

Orbital schwannoma is a rare benign tumor, originating from the Schwann cells of the orbital peripheral nerve sheath. Orbital schwannoma is easily misdiagnosed if the patient shows atypical presentations and atypical appearance on MRI imaging. A 56-year-old male experienced hyposmia for 1 year and was misdiagnosed with cavernous hemangioma pre-operation. This case was treated by surgery through the endoscopic trans-nasal approach. After operation, the patient had no recurrence or complications. Preoperative diagnosis for these cases remains difficult. Combined imaging modalities including computed tomography (CT) and magnetic resonance imaging (MRI) can help in differential diagnosis. Surgery is the main treatment modality for treating orbital schwannoma. Outcomes in most cases are favorable without complications or recurrence.

Imaging characteristics of orbital peripheral nerve sheath tumors: Analysis of 34 cases

BACKGROUND

Peripheral nerve sheath tumors (PNSTs), a rare group of neoplasms in the orbit, comprise only 4% of all orbital tumors. At present, there are very few studies detailing the features of these tumors identified using imaging technology.

AIM

To compare the differences in location, morphology, magnetic resonance imaging (MRI) signal intensity/computed tomography (CT) value, and enhancement degree of tumors of different pathological PNSTs types.

METHODS

Clinical, pathological, CT, and MRI data were analyzed retrospectively in 34 patients with periorbital sheath tumors diagnosed using histopathology from January 2013 to August 2021.

RESULTS

Among 34 cases of orbital peripheral nerve sheath tumors, 21 were schwannomas, 12 were neurofibromas, and 1 was a plexiform neurofibroma. Common clinical symptoms presented by patients with these types of tumors include eyelid swelling, exophthalmos, and limited eye movement. Schwannomas mostly occur in the intramuscular space with small tumor volume and rare bone involvement. Neurofibromas develop in the extrapyramidal space with larger tumor volume and more bone involvement. Radiologically, schwannomas and neurofibromas are characterized by regular morphology and uneven density and signal. One case of plexiform neurofibroma showed tortuous and diffuse growth along the nerve, with a worm-like appearance on imaging.

CONCLUSION

Different pathological types of orbital peripheral nerve sheath tumors have unique imaging characteristics. Comprehensive consideration of the patient's clinical and imaging manifestations is of great value in the diagnosis of orbital peripheral nerve sheath tumors.

Orbital schwannoma management: a case report, literature review, and potential paradigm shift

PURPOSE

To present a case of orbital schwannoma and assess the literature on treatment modalities.

METHODS

A MEDLINE literature search for cases of orbital schwannomas was performed using the PubMed search tool using the search terms "orbital schwannoma" and "orbital neurilemmoma." Papers were included if they were peer-reviewed, published in English, discussed management, and included the search terms. Each article was rated using the scale developed by the British Centre for Evidence-Based Medicine. In addition, we present a case report of an orbital schwannoma.

RESULTS

A total of 428 articles were found. 102 met the criteria for inclusion. Only two articles met Level 1 evidence and 16 were important to the clinical care process. We report a case of a biopsy-proven orbital schwannoma managed conservatively with observation over a 4-year period due to risk of cosmetic disfigurement with tumor removal. There has been no change in tumor size and no associated complications during follow up.

CONCLUSIONS

There is a paucity of data on the natural history of orbital schwannomas. Based on our review of the literature, we recommend observation for asymptomatic or minimally symptomatic orbital schwannomas with minimal growth over an extended period of time. For rapidly growing tumors or large tumors affecting key structures causing visual loss, diplopia, aesthetic disfigurement, or patient discomfort, a more aggressive approach may be necessary.

MRI-Based Radiomics for Differentiating Orbital Cavernous Hemangioma and Orbital Schwannoma

Aim: The purpose of this work was to develop and evaluate magnetic resonance imaging (MRI)-based radiomics for differentiation of orbital cavernous hemangioma (OCH) and orbital schwannoma (OSC).

Methods: Fifty-eight patients (40 OCH and 18 OSC, confirmed pathohistologically) screened out from 216 consecutive patients who presented between 2015 and 2020 were divided into a training group (28 OCH and 12 OSC) and a validation group (12 OCH and 6 OSC). Radiomics features were extracted from T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI). T-tests, the least absolute shrinkage and selection operator (LASSO), and principal components analysis (PCA) were used to select features for use in the classification models. A logistic regression (LR) model, support vector machine (SVM) model, decision tree (DT) model, and random forest (RF) model were constructed to differentiate OCH from OSC. The models were evaluated according to their accuracy and the area under the receiver operator characteristic (ROC) curve (AUC).

Results: Six features from T1WI, five features from T2WI, and eight features from combined T1WI and T2WI were finally selected for building the classification models. The models using T2WI features showed superior performance on the validation data than those using T1WI features, especially the LR model and SVM model, which showed accuracy of 93% (85–100%) and 92%, respectively, The SVM model showed high accuracy of 93% (91–96%) on the combined feature group with an AUC of 98% (97–99%). The DT and RF models did not perform as well as the SVM model.

Conclusion: Radiomics analysis using an SVM model achieved an accuracy of 93% for distinguishing OCH and OSC, which may be helpful for clinical diagnosis.

Orbital Schwannoma

Orbital schwannomas are rare neoplasms of the orbit. The presenting symptoms are often nonspecific. Classic imaging characteristics seen on magnetic resonance imaging (MRI) and orbital ultrasound can be useful to help aid in the diagnosis of orbital schwannoma. When diagnosed, the goal of treatment is complete surgical excision. The location of the tumor within the orbit dictates which surgical approach would provide the best exposure. When complete excision is achieved, recurrence rates are very low. This article addresses the etiology, patient population, presentation, natural history, and differential diagnosis of orbital schwannomas. Imaging characteristics and histopathologic subtypes are reviewed. Treatment goals, approaches, and specialties involved in the management of these patients is discussed. Finally, a representative case is presented.

Differentiate cavernous hemangioma from schwannoma with artificial intelligence (AI)

Background

Cavernous hemangioma and schwannoma are tumors that both occur in the orbit. Because the treatment strategies of these two tumors are different, it is necessary to distinguish them at treatment initiation. Magnetic resonance imaging (MRI) is typically used to differentiate these two tumor types; however, they present similar features in MRI images which increases the difficulty of differential diagnosis. This study aims to devise and develop an artificial intelligence framework to improve the accuracy of clinicians' diagnoses and enable more effective treatment decisions by automatically distinguishing cavernous hemangioma from schwannoma.

Methods

Material: As the study materials, we chose MRI images as the study materials that represented patients from diverse areas in China who had been referred to our center from more than 45 different hospitals. All images were initially acquired on films, which we scanned into digital versions and recut. Finally, 11,489 images of cavernous hemangioma (from 33 different hospitals) and 3,478 images of schwannoma (from 16 different hospitals) were collected. Labeling: All images were labeled using standard anatomical knowledge and pathological diagnosis. Training: Three types of models were trained in sequence (a total of 96 models), with each model including a specific improvement. The first two model groups were eye- and tumor-positioning models designed to reduce the identification scope, while the third model group consisted of classification models trained to make the final diagnosis.

Results

First, internal four-fold cross-validation processes were conducted for all the models. During the validation of the first group, the 32 eye-positioning models were able to localize the position of the eyes with an average precision of 100%. In the second group, the 28 tumor-positioning models were able to reach an average precision above 90%. Subsequently, using the third group, the accuracy of all 32 tumor classification models reached nearly 90%. Next, external validation processes of 32 tumor classification models were conducted. The results showed that the accuracy of the transverse T1-weighted contrast-enhanced sequence reached 91.13%; the accuracy of the remaining models was significantly lower compared with the ground truth.

Conclusions

The findings of this retrospective study show that an artificial intelligence framework can achieve high accuracy, sensitivity, and specificity in automated differential diagnosis between cavernous hemangioma and schwannoma in a real-world setting, which can help doctors determine appropriate treatments.

[Orbital hemangiomas: capabilities of modern neuroradiological diagnostics]

MATERIAL AND METHODS

In the period from 2010 to 2016. 14 patients with cavernous hemangioma (CH) and 2 patients with capillary hemangioma (CapH) of the orbit were examined. The age of CH patients varied from 17 to 67 years (median, 53 years); 8 females and 6 males. The age of CapH patients was 35 and 54 years. All patients underwent surgery with subsequent histological verification. CT-perfusion was performed in 10 CH patients and 2 CapH patients according to a developed low-dose protocol (80 kV, 200 mAs, t_scan=40 s) with allowance for a target localizer (80 kV, 120 mAs) and at a maximum radiation dose of not more than 4.0 mZv. Neoplasm microcirculation was quantitatively assessed by calculating hemodynamic parameters: blood flow velocity (BFV), blood volume (BV), and mean transit time (MTT). MRI without and with contrast enhancement was performed in 11 CH patients and 2 CapH patients according to the ophthalmologic protocol (Signa GE, 3.0 T) accepted at the Institute: without contrast enhancement - T1, T2, and T2-FLAIR modes, T1 and T2 with a Fat Sat technique at a scan thickness of 3 mm, and DWI MRI; contrast enhancement - T1 (three projections) mode, including the Fat Sat technique. SWAN (n=2) and non-contrast MR perfusion ASL (n=3) were also used. Diffusion-weighted images (DWI) were processed with calculation of the apparent diffusion coefficient (ACD).

RESULTS

In all CH patients, CT-perfusion revealed low perfusion parameters of blood flow: BV_CH=0.86±0.37 mL/100 g, BFV_CH= 4.89±2.01 mL/100 g/min with a high mean transit time MTT_CH=10.13±3.05 s compared to the same parameters of blood flow in the normal white matter: CBV_NormWM=1.63±2.22 mL/100 g, CBFV_NormWM=9.72±3.13 mL/100 g/min, and MTT_NormWM=6.76±2.78 s. In CapH cases, significantly increased blood flow velocity and volume values and a low MTT value in the tumor were observed: BV_CapH=10.30±4.10 mL/100 g, BFV_CapH=119.72±53.13 mL/100 g/min, and MTT_CapH=4.35±1.79 s. In the case of orbital hemangiomas, optimal MRI modes were T1 and T2 with the Fat Sat technique, a scan thickness of 3 mm, and intravenous contrast enhancement. The revealed pattern of contrast agent accumulation by CH, initially in the central part and then in the periphery, may be a useful radiographic sign in the differential diagnosis with other orbital tumors.

CONCLUSION

Modern CT- and MRI-based diagnostics of orbital hemangiomas provides not only the exact location, size, and spread of the lesion but also reveals the characteristic structural features of these tumors, and the use of perfusion techniques visualizes hemodynamics of the tumors. CT-perfusion-based hemodynamic parameters of cavernous hemangiomas typical of this type of hemangiomas may be used in the differential diagnosis with other tumors of this location. The use of contrast enhancement and the Fat Sat technique with a scan thickness of not more than 3 mm is optimal for MRI diagnostics of orbital hemangiomas.

Cranial Nerve Schwannomas: Diagnostic Imaging Approach

Schwannomas are benign nerve sheath tumors that may arise along the complex course of the cranial nerves (CNs), anywhere in the head and neck. Sound knowledge of the CN anatomy and imaging features of schwannomas is paramount for making the correct diagnosis. In this article, we review approaches to diagnosing CN schwannomas by describing their imaging characteristics and the associated clinical presentations. Relevant anatomic considerations are highlighted by using illustrative examples and key differential diagnoses categorized according to regions, which include the anterior skull base, orbit, cavernous sinus, basal cisterns, and neck. The clinical presentations associated with CN schwannomas vary and range from no symptoms to symptoms caused by mass effect or CN deficits. Individuals with the inherited disorder neurofibromatosis type 2 are predisposed to multiple schwannomas. When a lesion follows the course of a CN, the radiologist's roles are to confirm the imaging features of schwannoma and exclude appropriate differential considerations. The characteristic imaging features of CN schwannomas reflect their slow growth as benign neoplasms and include circumscribed margins, displacement of local structures, and smooth expansion of osseous foramina. These neoplasms exhibit various degrees of solid enhancement, often with internal cystic spaces on magnetic resonance (MR) and computed tomographic (CT) images and heterogeneous high signal intensity specifically on T2-weighted MR images. Clinical and/or imaging evidence of end-organ compromise of the involved CN may exist and aid in the identification of the nerve of origin. With a detailed understanding of the course of the CNs, the diagnostic features of CN schwannomas, and the correlation between these data and the associated clinical presentations of these tumors, the radiologist can have a key role in the diagnosis of CN schwannomas and the treatment planning for affected patients. (©)RSNA, 2016.

Uncommon primary tumors of the orbit diagnosed by computed tomography-guided core needle biopsy: report of two cases

Computed tomography-guided percutaneous biopsy is a safe and effective alternative method for evaluating selected intra-orbital lesions where the preoperative diagnosis is important for the therapeutic planning. The authors describe two cases of patients with uncommon primary orbital tumors whose diagnosis was obtained by means of computed tomography-guided core needle biopsy, with emphasis on the technical aspects of the procedure.

Tumor pathology of the orbit

The term orbital tumor covers a wide range of benign and malignant diseases affecting specific component of the orbit or developing in contact with them. They are found incidentally or may be investigated as part of the assessment of a systemic disorder or because of orbital signs (exophthalmos, pain, etc.). Computed tomography, MRI and Color Doppler Ultrasound (CDU), play a varying role depending on the clinical presentation and the disease being investigated. This article reflects long experience in a reference center but does not claim to be exhaustive. We have chosen to consider these tumors from the perspective of their usual presentation, emphasizing the most common causes and suggestive radiological and clinical presentations (progressive or sudden-onset exophthalmos, children or adults, lacrimal gland lesions, periorbital lesions and enophthalmos). We will describe in particular muscle involvement (thyrotoxicosis and tumors), vascular lesions (cavernous sinus hemangioma, orbital varix, cystic lymphangioma), childhood lesions and orbital hematomas. We offer straightforward useful protocols for simple investigation and differential diagnosis. Readers who wish to go further to extend their knowledge in this fascinating area can refer to the references in the bibliography.

Differentiation between benign and malignant orbital tumors at 3-T diffusion MR-imaging

INTRODUCTION

To differentiate between malignant and benign orbital tumors at 3-T diffusion MR imaging.

METHODS

A retrospective study was conducted on 47 patients (34 males and 13 females aged 4-74 years) with orbital masses. They underwent echo-planar diffusion-weighted MR imaging of the orbit with b-factor of 0, 500, and 1,000 s/mm(2) at 3-T MR unit. Apparent diffusion coefficient (ADC) maps were reconstructed, and the ADC value of the orbital mass was calculated.

RESULTS

The mean ADC value of the malignant orbital tumors (0.84 ± 0.34 × 10(-3) mm(2)/s) was significantly lower (P = 0.001) than that of the benign orbital tumors (1.57 ± 0.33 × 10(-3) mm(2)/s). The selection of an ADC value of 1.15 × 10(-3) mm(2)/s as a threshold value for differentiating malignant orbital tumors from benign lesions has a sensitivity of 95%, a specificity of 91%, and an accuracy of 93%. There was a significant difference in the ADC value between well- and poorly differentiated malignancies (P = 0.005).

CONCLUSION

Apparent diffusion coefficient value at 3 T is an additional noninvasive imaging parameter that can be used for the differentiation of malignant orbital tumors from benign lesions, the characterization of some orbital tumors, as well as the grading of orbital malignancy.

Evaluation of MR imaging findings differentiating cavernous haemangiomas from schwannomas in the orbit

Objective

It is important to distinguish between orbital cavernous haemangioma and schwannoma because the treatments of choice for the two tumours are different. The aim was to evaluate MR imaging findings distinguishing the two tumours.

Methods

Magnetic resonance imaging including T1- and T2-weighted imaging and contrast-enhanced MR imaging was performed in 43 patients with cavernous haemangiomas and 16 patients with schwannomas confirmed by pathology. Location, configuration, margins, signal intensity, homogeneity and enhancement pattern of the tumour were retrospectively evaluated.

Results

There was a significant difference between cavernous haemangiomas and schwannomas regarding the location, configuration and margins of the mass, signal intensity and homogeneity on T1- and T2-weighted imaging, the spread pattern of contrast enhancement, the enhancement pattern and the type of time–intensity curve (P < 0.05). Markedly homogeneous hyperintensity signal on T2-weighted imaging and the spread pattern of the contrast enhancement favoured cavernous haemangioma rather than schwannoma (P < 0.01).

Conclusion

Cavernous haemangiomas and schwannomas have different MR imaging features that could be helpful in the differentiation between the tumours. The spread pattern of the contrast enhancement on dynamic contrast-enhanced MR imaging is the most reliable finding distinguishing cavernous haemangiomas from schwannomas.

A patient with swelling of the eyelid: ancient schwannoma of the supraorbital nerve (2010:6b)

We present a case of swelling of the eyelid and supraorbital anesthesia caused by an intraorbital tumor. The differential diagnosis based on imaging consisted of aneurysmal bone cyst, schwannoma, neurofibroma, dermoid cyst, and cavernous hemangioma. The surgical and pathological diagnosis was an ancient schwannoma of the orbit, a rare entity.

Value of MR imaging in the differentiation of benign and malignant orbital tumors in adults

Purpose

To prospectively evaluate magnetic resonance (MR) imaging including dynamic contrast-enhanced MR imaging in the differentiation of benign from malignant orbital masses and to evaluate which MR imaging features are most predictive of malignant tumors.

Materials and methods

The study was approved by the institutional review board and signed informed consent was obtained. Nonenhanced, static, and dynamic contrast-enhanced MR imaging was performed in 102 adult patients with an orbital mass. Diagnosis was based on histologic findings. MR imaging features of benign and malignant orbital lesions were evaluated correlated with histological findings. Multivariate logistic regression analysis was employed to identify the best combination of MR imaging features that might be predictive of malignancy.

Results

Nonenhanced, static, and dynamic enhancement MR imaging was significantly superior to two other models in prediction of malignancy (p < 0.05). Multivariate logistic regression analysis identified that the most discriminating MR imaging features were isointense mass on T2-weighted imaging and a washout-type time–intensity curve for both observers.

Conclusion

Nonenhanced, static, and dynamic enhancement MR imaging improved differentiation between benign and malignant orbital masses in adult patients.

Inferior oblique schwannoma: diagnosis and management

INTRODUCTION

Orbital schwannoma accounts for less than 5% of orbital tumours and few cases arising in the superior orbit are reported in the literature.

PURPOSE

To present, to our knowledge, the first report of inferior oblique-associated orbital schwannoma.

METHODS

Interventional case report with clinical photographs, MRI imaging, intra-operative photographs and histology.

RESULTS

A 68 year-old man presented with decreased right vision and double vision in downgaze. Examination revealed a right 3 mm ptosis, hypertropia and limitation of depression. Exploration and excision, via anterior orbitotomy, and histological examination confirmed a schwannoma located within the right inferior oblique muscle. Vision normalised post-operatively and there has been no clinical or radiological recurrence of the lesion at 2 years.

CONCLUSIONS

This rare case highlights that schwannoma may occur in association with the inferior oblique complex and we suggest that schwannomas should now be considered in the differential diagnosis when patients present with a clinically-suspected or radiologically-proven orbital mass.