Intraosseous Schwannoma of the Petrous Apex

Intraosseous Schwannoma of the Frontal Bone: A Case Report and Review of the Literature

Intraosseous schwannoma is a rare diagnosis, particularly so in the skull. Accordingly, little data exists to unify common features of this disease. Here, we present the fourth known case of a primary intraosseous schwannoma of the frontal bone: a 46-year-old male with severe, progressive headache and an osteolytic frontal bone lesion. Gross total resection of the lesion was performed with excellent clinical outcome. Histological analysis confirmed the diagnosis. The limited existing literature on this topic was reviewed to identify emerging trends surrounding presenting symptoms and treatment. Early literature suggests symptoms are often nonspecific, except for lesions of the petrous apex. No cases of recurrence have been demonstrated after gross total resection, though incomplete resection has been associated with recurrence. This diagnosis appears to be becoming a more often-considered differential for osteolytic, expansile skull lesions.

Imaging Features of Intraosseous Schwannoma: A Case Series and Review of the Literature

To characterize the imaging features of patients with pathologically confirmed intraosseous schwannoma (IOS), institutional pathology and imaging databases were searched for IOS cases over a period of 17 years. A musculoskeletal radiologist evaluated all imaging studies. Additionally, a literature search was performed to identify IOS cases that had imaging findings of at least two modalities. Six patients (one female, five males, mean age of 50 ± 14 years) with IOS were identified, with all lesions localized to the lumbosacral region. Radiographic imaging was available in four patients, while all patients underwent CT and MR imaging. Radiographs depicted lytic lesions, and CT depicted heterogeneous expansile lesions with centrally hypodense areas and peripheral sclerosis. All cases involved extra-osseous extension, producing a mass effect on adjacent soft tissues and nerve roots. On MRI, the neoplasms displayed iso- to- slightly- low signal intensity on T1-weighted images and hyperintense signal intensity on T2-weighted images with heterogeneous enhancement. The literature review resulted in 102 IOS cases, which to the best of our knowledge, is the largest review on IOS, and the imaging findings of the previously published cases were the same as our cases. IOSs are rare benign neoplasms that should be considered in the differential diagnosis of well-defined expansile lytic lesions with sclerotic borders. This is particularly important in middle-aged adults with mandibular, sacral, or vertebral body mass.

Intraosseous schwannoma in the clivus mimicking chordoma treated with endoscopic endonasal surgery: A case report

Background:

Intraosseous schwannomas are extremely rare and they have not yet been reported to occur in the clivus. We report a schwannoma in the clivus mimicking chordoma and review intraosseous schwannomas of the skull.

Case Description:

A 62-year-old man presented with gradually worsening hoarseness with dysphagia and atrophy of the left tongue, trapezius muscle, and sternocleidomastoid muscle. Magnetic resonance imaging showed that the tumor was mainly located in the clivus, and a computed tomography (CT) scan revealed an osteolytic lesion with expansion of the clivus and preservation of the bony cortex. Endoscopic endonasal surgery was performed to diagnose and treat symptoms. The tumor was subtotally removed without any complications. The histopathological findings revealed typical schwannoma, which showed Antoni A and Antoni B patterns positive for S100 protein. Based on the preoperative imaging, intraoperative and histopathological findings, the tumor was considered to be an intraosseous schwannoma in the clivus, and no recurrence was observed after 1 year of postoperative follow-up.

Conclusion:

Even though the intraosseous schwannoma in the clivus is uncommon, it should be considered as a differential diagnosis if an expansive lesion without destruction of the cortical bone is shown on CT as well as iso-hyperintensity on T2-weighted magnetic resonance imaging.

Pediatric Petrous Apex Lesions: A Radiological Classification and Diagnostic Algorithm

The petrous apex (PA) is involved in a myriad of pathological conditions, some of which are exclusive in children. Diagnosis may be difficult due to vague clinical presentation, and local examination is challenging owing to its inaccessible location. This is further complicated by multiple unfused sutures and ongoing PA pneumatization in children. Cross-sectional imaging is vital for the evaluation of the PA lesions, due to their precarious location and proximity to the major neurovascular structures. Several classification systems have been proposed for these lesions based on their site of origin, solid or cystic appearance, surgical or non-surgical (no touch lesions) management, and benign or malignant nature. In this article, we emphasize the distinctive role of different cross-sectional imaging modalities in the diagnosis of pediatric PA lesions, with special attention to normal variants that should not be mistaken for pathology. We also propose a radiological classification and algorithmic approach to aid in the precise diagnosis and facilitate appropriate management of the various PA lesions in children.

Intraosseous schwannomas involving the sacrum: Characteristic imaging findings and review of the literature

Background and purpose Sacral intraosseous schwannomas represent a rare subset of schwannomas. The existing literature detailing the radiographic appearance of intraosseous schwannomas is limited. The aim of this study is to formally characterize the radiological appearance of sacral intraosseous schwannomas to differentiate them from other lytic lesions. Materials and methods Imaging studies of 13 pathologically proven intraosseous schwannomas were reviewed from multiple institutions by fellowship-trained radiologists. A PubMed search was performed and identified four papers pertaining to the imaging characteristics of sacral intraosseous schwannomas. The results of these papers were compared to findings from our cases. Results All tumors had heterogeneous signals and were predominately solid but cystic components with fluid-fluid levels were present. The tumors caused a mass effect but none infiltrated the surrounding soft tissues. Post-contrast T1-weighted images revealed heterogeneous enhancement in all 13 tumors and four possessed non-enhancing cysts. A literature review identified 16 other cases of sacral intraosseous schwannomas forming a total of 29 cases examined. Conclusions Sacral intraosseous schwannomas should be considered in the differential diagnosis for both radiologists and pathologists when dealing with large expansile, lytic lesions, with well-defined sclerotic margins involving the sacrum. This is particularly important in middle-aged adults presenting with pathology centered around S2-3.

[Tumors of the inner ear and adjacent structures]

Tumors of the inner ear and adjacent structures often present with hearing loss, tinnitus and vertigo due to compression of the traversing cranial nerves. More than 90% of the tumors of the inner ear with or without expansion into the cerebellopontine angle are histologically diagnosed as vestibular schwannomas. Less common tumorous lesions include ectopic meningiomas located in the petrous bone, glomus tympanicum paragangliomas or endolymphatic sac tumors (ELST) originating in the vestibular recess. Most tumors are sporadic, but hereditary disorders have to be considered. Bilateral vestibular schwannomas are indicative of neurofibromatosis type 2 and ELST in conjunction with other abdominal tumors indicates von Hippel-Lindau disease. The neuropathological diagnostics and grading guides the subsequent therapy of these mostly benign lesions.