The orbit is divided into the ocular compartment or globe, the muscle cone, and intraconal and extraconal spaces (Fig 1). Differential diagnosis. Clinical presentation: Incidental finding. The optic nerve may be in the center of the lesion, or may be eccentrically positioned. These are usually asymptomatic, but when the ophtomologist inspects the eye, there is the impression of papilledema, i.e. Other common calcifications are at the optic nerve head within the eye, also called 'optic disc drusen'. 2 Optic nerve sheath meningiomas can have multiple appearances on imaging; tubular expansion of the meninges surrounding the optic nerve is most common, but globular, fusiform, and focal optic nerve enlargement also exist. ONSM occurs more commonly in middle aged women. Rare reports of calcified optic nerve gliomas also exist. pseudo-papilledema. This was regarded as an incidental finding. A patient with bilateral idiopathic optic nerve sheath inflammation, described by Margo et al, 8 did not experience a beneficial response to corticosteroids. Six extraocular muscles control ocular movements; all but the inferior oblique muscle constitute the muscle cone. Radiology is essential for a differential diagnosis of the intraconal orbital mass and to determine the extent and tissue involved. Crossref, Medline, Google Scholar; 5 Zimmerman CF, Schatz NJ, Glaser JS. Trauma to the optic nerve and tissue death can also cause optic nerve calcification. Radiology 1984; 150:409-415. Radiol Clin North Am 1999; 37:37-58. Extraglobal calcifications are most often of vascular origin (arteriosclerosis, phlebolith, encapsulated venous malformation, and AVM). 2 What is the clinical diagnosis? These changes are appreciated more along the … 3 Nonetheless, the … CT scan with contrast of the orbit and brain revealed dural optic sheath calcification with areas of relatively symmetrical parenchymal intracranial calcification and with normal serum investigations. chlear nerve, CN IX = glossopharyngeal nerve, CN X = vagus nerve, CN XI = accessory nerve, CN XII = hypoglossal nerve, CPA = cerebel-lopontine angle, IAC = internal auditory canal, ICA = internal carotid artery RadioGraphics 2016; 36:1463–1477 Published online 10.1148/rg.2016150199 Content Codes: 1From the Departments of Radiology (A.D.S., Malignant Tumors . Radiologically, it manifests as uveal enhancement, retinal detachment, and calcifications in the retina (, Figs 6,, 7) (, 9). 5.-lnhomogeneous calcification in optic nerve head and adjacent MRI typically shows homogeneous, intermediate T1 and T2 signals. I All authors: Department of Radiology, ... Calcifications are seen occasionally [4]. Most importantly, the optic nerve cannot be seen separately from the mass (figs. According to a recent meta-analysis and subse-quently reported large bi-institutional series, primary ONSMs accounts for approximately one third of primary optic nerve tumors and 5% to 10% of orbital tumors.1-3 of optic nerve thickening with enhancement and calcification within the tumor was not seen; instead, an elongating gadolinium enhancing band-like area adjacent to the superomedial aspect of the left optic nerve sheath was identified. 6 A, B). However, calcification in a meningioma is typically a tubular thickening involving the perimeter of the nerve, whereas in our cases, the full thickness of the nerve was calcified. Nerve Sheath Meningioma Optic nerve sheath meningioma (ONSM) is a term applied to primary and secondary meningiomas of the optic nerve. 4 In general, they are more common in Caucasians than African-Americans 4. Case: 1. Optic nerve calcification is a rare radiological finding, with only a short differential diagnosis, many of which have only been described in isolated case reports 1-4. Tumours of eye like retinoblastoma and optic nerve meningioma too are known to show calcifications. 5.-Partly calcified optic nerve sheath meningioma posterior to lamina cribrosa. Calcification of the trochlea. CT scan is more sensitive than MRI in identifying calcification. The ONSD measurements were analyzed by using the Statis-tical Package for the Social Sciences, Version 17.0 (SPSS, Chicago, Illinois). 1996 The Royal College of Radiologists, Clinical Radiology, 51, 359-361. Unlike optic nerve meningiomas, gliomas cannot be separated from the optic nerve itself Optic diameters were measured on the MR images in a blinded fashion. Conclusion and importance It is crucial to differentiate an optic nerve sheath meningioma from idiopathic calcification of the optic nerve. Calcification is a common characteristic in optic nerve sheath meningioma. The optic nerve sheath demonstrates changes in diameter with CSF pressure changes as there is a layer of subarachnoid space between the nerve and its sheath, which expands due to raised intracranial pressure. They are typically seen in patients with age-related macular degeneration 7. The calcified lesions involving the optic nerve includes optic nerve sheath meningioma, optic nerve head drusen, idiopathic dural optic nerve sheath calcification , , calcified optic nerve gliomas and metaplastic dural ossification . Idiopathic calcification of the dural optic sheath is very rare entity. Fig. Calcification of the Trochlea. Several types of calcium deposits can develop in the optic nerve. Calcium deposits may develop within protein deposits in the optic nerve known as drusen. High calcium levels do not cause or contribute to optic nerve drusen, which may run in families. High calcium levels in the blood can cause metastatic calcification in the optic nerve. A supplementary computed tomography angiography (CTA) exposed scattered dural calcification, which included the optic nerves. MR is preferred imaging modality for tumor assessment, but CT is useful for looking for calcifications. Fusiform enlargement, kinking, and tortuosity of the optic nerve and enlargement of the optic canal are typical features on CT and MRI. 1 Metaplastic dural ossification has been described as well. A full-thickness biopsy specimen of the more severely involved optic nerve revealed chronic inflammation of the optic nerve sheath with vasculitic changes and necrobiotic granulomas. OPTIC NERVE AND SHEATH: DEVELOPMENTAL ABNORMALITIES ANTHONY A. MANCUSO AND MARY FRAN SMITH KEY POINTS Magnetic resonance imaging is the study of choice for complete and definitive imaging evaluation of congenital abnormalities of the optic nerve. The authors reviewed a large number of high-resolution CT scans and divided enlargement into three groups: tubular, fusiform, and excrescent. Septo-optic dysplasia is a condition that may have a broad spectrum of abnormalities involving the optic nerve, … The main differential diagnosis is calcification within an optic nerve sheath meningioma (3,4). Imaging usually shows a sausageshaped enlargement of the optic nerve and chiasm with kinking or buckling - of the nerve Enhancement may range from none to intense homogeneous CT: isodense, no calcifications, enlargement of bony optic canal MRI: iso to hypointense onT1WI, hyperintense on T2WI . Optic nerve glioma results in tortuous thickening of the optic nerve/sheath complex that is most commonly tubular, but may also be fusiform or excrescent. Unlike optic nerve sheath meningiomas, gliomas do not show calcification on CT. On MRI, they appear hypo- or isointense on T1- and hyperintense on T2-weighted images and enhance to a variable degree ( Fig. In the case reported by Jacoby et aI., there was no association with acoustic neuromas but there was an optic nerve sheath meningioma. Orbital Calcifications. part of the globe include phthisis bulbi, neoplasm (optic nerve glioma, meningioma, and retinoblastoma), hamartoma (tuberous sclerosis), and systemic disease with hypercal-5 6 Fig. Normally, the intraorbital segment of the optic nerve is slack and compliant; the ends fixed within the neural canal and the annulus. Optic Glioma The differential diagnosis for calcified lesions involving the optic nerve includes optic nerve sheath meningioma, optic nerve head drusen and idiopathic dural optic nerve sheath calcification. A, Axial section of right orbit after IV contrast administration shows swollen sclera and thickened dilated optic nerve sheath secondary to the inflammatory process (arrow). Optic sheath hydrops is pathologic enlargement of the CSF space within the optic nerve/sheath complex; when diffuse, it implies that elevated intracranial pressures are being transmitted to the optic nerve/sheath complex (Fig. They can also be familial and inherited as a dominant trait 1,4. CT demonstrates punctuate calcification in the anterior, medial and superior corner of the orbit. These findings were inconsistent with bilateral optic nerve sheath This is a 50-year-old man who underwent CT for headache. Eye movements stress and strain the nerve and the peripapillary eye wall. CT may show calcification. Optic disc drusen are identified radiographically in up to 0.3-3.7% of the population and are frequently bilateral 1,4,5. Involvement of the optic nerve by optic gliomas and optic nerve sheath meningiomas is well known. However, nonneoplastic processes such as increased intracranial pres­ sure, optic neuritis, Grave ophthalmopathy, and orbital pseudotumor may also alter the appearance of the optic nerve/ sheath on computed tomography. ... Radiology Resident, Indiana University School of Medicine. A large number of entities have been described associated with sheath may spread along the longitudinal axis of the nerve, be locally exophytic, Optic nerve/sheath enlargement: a differential approach based on high-resolution CT morphology. Optic nerve sheath meningioma presents a typical appearance of a calcified optic nerve sheath quite similar to that seen in our cases. uncommon, benign neoplasms originating from the meningothelial cells of the meninges surrounding the optic nerve. 55.1). The calcification was localized to the optic nerve sheaths with no abnormal enhancement or optic nerve signal intensity abnormality on MR imaging. The mean width of the optic nerve sheath was calculated separately for the controls and patients with IIH within each age group. Primary ONSMs account for approximately one third of primary optic nerve tumors and 5% to 10% of orbital tumors [1,2]. This review has focussed on imaging appearances of intra-ocular calcifications, a small process in a small organ that nevertheless has a wide impact on the entire organs. Optic nerve gliomas constitute 80 per cent of all primary optic nerve tumours. Optic nerve sheath meningioma (ONSM) is a term applied to primary and secondary meningioma of the optic nerve. Link, Google Scholar; 4 Mafee MF, Goodwin J, Dorodi S. Optic nerve sheath meningiomas: role of MR imaging. The key imaging finding of optic nerve sheath meningioma is a homogeneously enhancing mass that surrounds the optic nerve. dilated right optic nerve sheath representing uni­ lateral hydrops secondary to orbital contusion and implicating secondary optic CSF flow ob­ struction. The key imaging finding of ONSM is a homogeneously enhancing mass that surrounds the optic nerve. Optic nerve meningiomas are benign tumours arising from the arachnoid cap cells of the optic nerve sheath and represent ~20% of all orbital meningiomas, the majority of which are direct extensions from intracranial meningiomas.   These tumours ty... 20/15 vision in both eyes and normal optic nerve function and appearance, the patient underwent B-scan ultrasonography and MRI. Calcification of the trochlea. Differential considerations for ON include optic nerve glioma (marked enlargement of the nerve) and optic nerve sheath meningioma (calcification and thickened enhancement of the nerve sheath but a normal nerve) References. The muscle cone converges at the orbital apex, forming a tendinous ring (annulus of Zinn). optic nerve meningioma; optic nerve head drusen; idiopathic dural optic nerve sheath calcification; calcified optic nerve glioma; metaplastic dural ossification unilateral cerebellar hemispheric calcification with a pattern and location similar to that seen in our two cases. Dystrophic calcification of the optic nerves has been reported after trauma with hemorrhage, but a previous head injury could also be ruled out. Meningioma of the optic nerve sheath infiltrating the posterior globe and hemangioblastoma (von Hippel–Lindau disease) may also produce intraglobal calcifications. Through this ring enters the optic nerve, The calcification was localized to the optic nerve sheaths with no abnormal enhancement or optic nerve signal intensity abnormality on MR imaging. Calcifications are seen occasionally [4]. Most importantly, the optic nerve cannot be seen separately from the mass (figs. 2A and 2B) [4]. CT is especially valuable in demonstrating intracranial extension of orbital gliomas [4-6]. Enlargement of the optic canal is often demonstrable on CT (fig. 2C), obviating con­ ventional tomography. A number of entities can mimic an optic nerve meningioma and result in enlargement of the optic nerve. Thickening, calcification, and increased pressure in the poSAS in patients with meningiomas presumably stiffen the optic nerve sheath. A wide variety of neoplastic and non-neoplastic processes can cause the intraorbital optic nerve and sheath to be enlarged on CT. It is usually unilateral but can be bilateral but features of intracranial dural septal calcification are not associated. The CSF space within the optic nerve/sheath complex communicates directly with the anterior suprasellar cistern. The pathology literature describes an entity known as 2A and 2B) ... optic nerve/ sheath with lower absorption nerve (arrow) encased by thickened sheath. CMV-induced retinitis most commonly begins in one eye and progresses to involve the contralateral eye.
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