Biomedical subjects
Publications and source records attributed to M F Mafee.
Optic nerve meningiomas usually are seen in middle-aged and elderly women, and present as a slowly progressing axial proptosis and loss of vision. CT and MR imaging are the most valuable diagnostic tools to evaluate these tumors. This article reviews the MR imaging and CT characteristics of optic nerve sheath meningiomas and discusses features that may distinguish optic nerve sheath meningiomas from simulating lesions.
Sarcoidosis, a systemic disease of unknown cause, frequently involves the eye, orbit, and central nervous system. The MR imaging findings of orbital and optic pathway sarcoidosis may closely resemble several other orbital and intracranial diseases. This article reviews MR imaging findings of sarcoidosis when it involves the eye, orbit, and visual pathways. Careful review of MR findings and other neuroimaging findings and clinical characteristics will reduce the incidence of mistaking optic nerve and chiasmal sarcoidosis for meningioma or glioma.
Neurofibromas and schwannomas are orbital neoplasms with similar clinical and radiologic features. Solitary or circumscribed neurofibromas and schwannomas demonstrate slow progressive growth with ocular displacement and are amenable to surgical resection. Plexiform and diffuse neurofibromas are diffusely infiltrative in the orbit and periocular region, they are difficult to resect, and they have a high rate of recurrence. Malignant peripheral nerve tumors are rare, but they have a very high rate of recurrence and a low 5-year survival rate because of extension through the superior orbital fissure to the midbrain region. This article describes the clinical and radiologic features of peripheral nerve sheath tumors.
The lacrimal gland region can be involved in a wide spectrum of orbital pathology, including inflammatory, lymphoproliferative, and epithelial tumors. This article focuses on benign and malignant epithelial tumors of lacrimal gland and simulating lesions. The clinical presentations, MR imaging, and pathologic findings of lacrimal gland tumors are reviewed.
Malignant uveal melanomas are the most common primary intraocular malignant tumors in adults. Choroidal hemangiomas are congenital, benign, vascular lesions that may be confused with malignant uveal melanomas on clinical examination. The MR imaging characteristics of uveal melanomas and choroidal hemangiomas are different, making diagnostic differentiation possible with a high degree of accuracy. This article describes the MR imaging features of uveal melanoma, choroidal hemangioma, and other simulating lesions.
The diagnosis of Rb can usually be made by clinical examination; however, patients should also be studied by CT and MR imaging to help determine the extent of the intraocular tumor, document intralesional calcification, confirm the diagnosis, and delineate orbital or intracranial involvement. These imaging techniques should aid the clinician in differentiating Rb from lesions that simulate Rb.
Coats' disease is an idiopathic disorder in which telangiectatic and aneurysmal retinal vessels leak a lipoproteinaceous exudate, with consequent bullous retinal detachment. It is a diagnostic challenge, and CT and MR imaging provide valuable information to differentiate it from other pathologies, particularly from retinoblastoma. Typical, advanced Coats' disease shows on CT a denser substance posterior to the vitreous, which on MR is hyperintense on all pulse sequences. Contrast administration on both CT and MR might give slight linear enhancement at the boundary between vitreous and exudation. Persistent hyperplastic primary vitreous (PHPV) is a unilateral disorder in a microphthalmic eye, seen in full-term infants. PHPV rarely is bilateral in patients with Norrie's disease, Warburg syndrome, or patients with retinal dysplasia. Persistent fetal vasculature leads to fibrosis, resulting in elongation of the ciliary processes, retinal detachment, and spontaneous cataracts. The CT appearance in the disorder is quite variable; however, MR imaging may be superior in demonstrating the enhancing retrolental mass and the elongated ciliary processes.
The child's orbit may be involved with a variety of cysts and cyst-like lesions. Such lesions may represent development anomalies of the globe and orbit, acquired lesions of the orbit, or cystic expansions from contiguous structures. CT and MR imaging are important diagnostic tools that aid the ophthalmologist in establishing the correct diagnosis and defining the extent of these cystic lesions.
The acute onset of orbital and periorbital inflammation presents the clinician with a diagnostic and therapeutic dilemma, the consequence of which may be very serious. The progression from the initial stage of cellulitis to orbital abscess, cavernous sinus thrombosis, brain abscess, meningitis, or visual loss may be quite rapid at times. CT, ultrasonography, and MR imaging play an important role in clinical management of these patients. Indeed, it is the information obtained through orbital imaging that directs the clinician to use the correct therapeutic modality.
Orbital subperiosteal space, a potential space, is an important entity due to its unique anatomy and susceptibility to various pathologic processes. CT scan and MR imaging are important tools in the diagnosis of orbital subperiosteal hematomas, cholesterol granulomas, and infections. MR imaging has emerged as the modality of choice in the evaluation of hematomas and infections of this space due to its multiplanar capability and various imaging sequences giving better information. High-resolution CT scan offers good differentiation in most of these cases. Osseous changes in a cholesterol granuloma is better seen in CT scan, although MR imaging offers better differentiation from epidermoid or dermoid cysts and other subperiosteal process, as well as lacrimal fossa lesions. Subperiosteal abscesses are best evaluated using MR imaging.
Rhabdomyosarcoma is the most common primary orbital malignancy of childhood. It can present insidiously, mimicking other (benign) processes clinically and radiographically. CT and MR imaging are crucial in the diagnostic evaluation, treatment planning, and follow-up monitoring of the disease. Such imaging, especially when contrast is used, can accurately detect and state the extent of tumor involvement.
The clinical, radiologic, and histopathologic features of two main disorders of the orbit are discussed. Group I, Langerhans cell histiocytosis (histiocytosis X, Class I), is caused by proliferation of X histiocytic Langerhans' cells. Group II is juvenile xanthogranuloma, and Class II is related to the proliferation of non-X histiocytic (monocyte-macrophage) cells. The two diseases are of unknown cause and differ in their clinical, radiologic, and histopathologic features.
Fibro-osseous and cartilaginous lesions of the orbit and facial region share overlapping clinical, radiologic, and pathologic features that may lead to diagnostic confusion and possible misdiagnosis. The value of imaging studies in the histopathologic diagnosis of these lesions cannot be overemphasized. The histopathologic diagnosis of such lesions should not be rendered in the absence of radiographic correlation.
Endoscopic third ventriculostomy has become an increasingly popular procedure. This is mainly due to the improvement of the endoscopes. The progress in imaging techniques and Phase-Contrast Cine MRI in particular offers a reliable method of pre-and post-operative assessment of the patients. Two endoscopes, NeuroPEN and Channel Neuroendoscope (Medtronic PS Medical, CA, USA) have been evaluated in our center for third ventriculostomy. These instruments are light, have a good maneuverability and are disposable. The illumination and the quality of the image are excellent. We have performed Phase-Contrast Cine MRI pre-operatively and post-operatively for our patients. It offers a good assessment of the patency of the ventriculostomy and the fluid dynamics of the CSF pathways. Endoscopic third ventriculostomy is the technique of choice for the treatment of obstructive hydrocephalus. This is mainly due to two points: The progress in the endoscopic instrumentation (namely the reduction in size of endoscopes and introduction of disposable models), and the establishment of Phase-Contrast Cine MRI as the gold standard method for the pre- and post-operative evaluation of the CSF dynamics. However, to date, no technique can show the patency of the subarachnoid space, which is the most important predictive factor of surgical outcome.
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Extraskeletal mesenchymal chondrosarcoma is a relatively uncommon entity, an orbital location being extremely rare. A review of the literature revealed 16 reported cases of primary orbital mesenchymal chondrosarcoma demonstrated by plain film and CT. To the best of our knowledge, the MRI features of orbital extraskeletal mesenchymal chondrosarcoma have not been previously reported. We present the case of an 18-year-old man with a 2-year history of progressive proptosis of the right eye who underwent CT, dynamic CT, MRI without and with gadolinium enhancement, and magnetic resonance angiography of the orbits. CT of orbital mesenchymal chondrosarcoma demonstrates a well-defined mass with multiple areas of fine and coarse calcification and shows moderate contrast enhancement. The noncalcified portions of the mass demonstrate signal intensity lower than or equal to gray matter on T1-weighted images and are isointense to the gray matter on T2-weighted images. Dynamic CT reveals delayed contrast enhancement. MRI has proven to be a valuable diagnostic tool in the diagnosis and differentiation of well-defined intraorbital masses. By a combination of CT and MRI, it appears mesenchymal chondrosarcoma can be differentiated from other intraorbital lesions, such as cavernous hemangioma, hemangiopericytoma, orbital amyloidosis and fibrous histiocytoma.
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We performed T1-, T2-, proton density-weighted, and T1-weighted gadolinium-enhanced MRI on 24 patients with retinoblastoma, using a 1.5 T superconducting unit and head and orbital surface coil imaging. All patients underwent a complete ophthalmologic examination, including B-scan ultrasonography. CT was performed on 10 of 24 patients. Pathologic correlation was obtained in 18 patients who required enucleation. Contrast-enhanced T1-weighted MRI with fat suppression was the sequence most sensitive to optic nerve extension and provided the greatest differentiation between tumor and uninvolved extrascleral tissue. Retinoblastoma demonstrated contrast enhancement.