Disorders Chiasm• 3 SECTIONor Nerve Optic Acquired

Sphenoid Meningioma

Key Facts

•Benign tumor that grows from the meninges covering the sphenoid bone

•Middle-aged women most at risk

•Visual loss slowly progressive

•Brain MRI often diagnostic

•Treatment options are surgery and radiation

Clinical Findings

•Slowly progressive visual loss, usually monocular

•May have headache, ophthalmoplegia, ptosis, but visual loss often an isolated manifestation

•Reduced visual acuity and/or visual field (hemianopic defects are common)

•Afferent pupil defect is common

•Optic disc(s) may appear normal, swollen, or pale

Ancillary Testing

• Brain MRI is often diagnostic

Differential Diagnosis

• Intraorbital optic nerve sheath meningioma

•Other intracranial masses (pituitary adenoma, craniopharyngioma, optic glioma, aneurysm)

•Atypical optic neuritis

•Infiltrative (neoplastic) optic neuropathy

Treatment

•Surgical excision

•Radiation

Prognosis

•Untreated tumors often grow slowly, although after menopause growth often slows or stops

•Visual outcome after surgery:

•30% improve

•30% worsen

•40% remain unchanged

•Visual outcome after radiation:

•5% improve

•20% worsen

•75% remain unchanged

•Visual loss from radiation toxicity is rare if proper dosimetry is applied

Fig. 3.22 Sphenoid wing meningioma. Postcontrast axial T1 MRI shows mass (arrow) growing from the sphenoid ridge and compressing the intracranial left optic nerve.

A

B

Fig. 3.23 Sphenoid wing meningioma. (A) Postcontrast coronal T1 MRI shows a mass (arrow) involving the left orbitocranial area. (B) Postcontrast axial T1 MRI shows that the mass has invaded the lateral orbit (arrow).

Meningioma Sphenoid

Disorders Chiasm• 3 SECTIONor Nerve Optic Acquired

Optic Nerve Sheath Meningioma

Key Facts

•Benign tumor that grows from meninges of intraorbital optic nerve

•Painless progressive monocular visual loss

•Young adult women most at risk

•Resistance to retropulsion of ipsilateral eye

•High-resolution orbital imaging with fat suppression and contrast required to detect the lesion

•Biopsy only if clinical and imaging features are atypical

•Radiation sometimes improves vision and often prevents worsening of vision

•Recommended only if visual preservation in the affected eye would be meaningful.

Clinical Findings

•Slowly progressive painless monocular visual loss

•Usually little if any proptosis but may have resistance to retropulsion

•Visual acuity and nerve fiber bundle visual field loss

•Optic disc(s) may be normal, swollen with or without dilated shunt vessels, or pale

•Afferent pupil defect present

Ancillary Testing

•High-resolution, fat-suppressed, contrast T1-weighted MRI shows fusiform or nodular thickening and enhancement of affected intraorbital optic nerve

• Intracranial extension on to medial sphenoid ridge is common

•Imaging findings often diagnostic but dural inflammation (pachymeningitis) can produce similar findings

Differential Diagnosis

•Dural inflammation (pachymeningitis)

•Sino-orbital vasculitis

•Atypical optic neuritis

•Infiltrative (neoplastic) optic neuropathy

•Optic glioma

Treatment

• Observation or radiation

Prognosis

•Without radiation, progressive visual loss occurs in 75% and remains stable in 25%

•Intracranial extension of orbital tumor does not occur unless tumor actually arises on sphenoid bone (sphenoid meningioma)

•Visual outcome after radiation:

•10% improve

•70% maintain stable vision

•20% have further visual loss

•Visual loss caused by radiation toxicity is rare if proper dosimetry is applied

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B

Fig. 3.24 Optic nerve sheath meningioma. (A) Postcontrast coronal T1 MRI shows high signal around the right optic nerve. (B) Postcontrast axial T1 MRI shows that the abnormality affects the orbital and intracanalicular segment of the optic nerve (arrow). These imaging fi ndings can be mimicked by infl ammatory diseases such as sarcoidosis.

Meningioma Sheath Nerve Optic