Optic Nerve Lesions

Optic Nerve Glioma (Juvenile Pilocystic Astrocytoma)

A benign, slow-growing tumor (Figure 8.12D), optic nerve glioma arises from astrocytes within the optic nerve. The median age of onset is about 5 years of age, with a slight preponderance for females. Neurofibromatosis type 1 occurs in about 10% of cases and is characterized by bilateral involvement of the optic nerve. The patient presents with progressive propto-sis and visual loss.

Optic Nerve Sheath Meningioma

Optic nerve sheath meningioma is a benign tumor (Figure 8.12E) that arises from the meningoen-dothelial cells of the arachnoid layer. The tumor usually affects middle-aged women. Neurofibro-matosis type 1 is found in about 16% of cases. Presentation is with slowly progressive proptosis and unilateral visual loss. Ultrasonography shows a dif

FIGURE 8.12. Optic nerve disorders (A-C) thyroid optic neuropathy, (D) optic nerve glioma, and (E) optic nerve meningioma. (A) B-scan echogram shows crescent sign (large arrow) due to accumulation of subarachnoid fluid around the optic nerve (small arrow). (B) A-scan echogram reveals double-peaked borders representing a perineural enlargement (between arrowheads) between the optic nerve parenchyma (arrow) and the perineural sheaths. Upon lateral gaze, retrograde "milking" of cerebrospinal fluid in this perineural enlargement occurs, with secondary collapse of the subarachnoid space shown on dynamic A-scan echography as almost visual adherence of the two spikes (between arrowheads). (C) The change of thickening of the intersheath space indicates a fluid retention con-

dition rather than tumefaction of the perineural sheaths. (D) Optic nerve glioma. Echographically, there is widening of the internal lumen of the nerve (nerve proper) showing fusiform topographic pattern (arrow) (upper). The perineural sheath normal double spikes on A-scan are invariably touching (arrows), giving the appearance of a thick, single spike with a double head (lower). (E) Optic nerve meningioma. On A scan, the optic nerve proper appears thinner than normal (owing to meningeal compression), while the inter-sheath space is significantly wider (connected arrows) with a high-reflective internal structure between the inner and the outer peri-neural sheaths. Measurement of the intersheath space is possible and indicative of the pathologic thickening.

FIGURE 8.12. Optic nerve disorders (A-C) thyroid optic neuropathy, (D) optic nerve glioma, and (E) optic nerve meningioma. (A) B-scan echogram shows crescent sign (large arrow) due to accumulation of subarachnoid fluid around the optic nerve (small arrow). (B) A-scan echogram reveals double-peaked borders representing a perineural enlargement (between arrowheads) between the optic nerve parenchyma (arrow) and the perineural sheaths. Upon lateral gaze, retrograde "milking" of cerebrospinal fluid in this perineural enlargement occurs, with secondary collapse of the subarachnoid space shown on dynamic A-scan echography as almost visual adherence of the two spikes (between arrowheads). (C) The change of thickening of the intersheath space indicates a fluid retention con-

dition rather than tumefaction of the perineural sheaths. (D) Optic nerve glioma. Echographically, there is widening of the internal lumen of the nerve (nerve proper) showing fusiform topographic pattern (arrow) (upper). The perineural sheath normal double spikes on A-scan are invariably touching (arrows), giving the appearance of a thick, single spike with a double head (lower). (E) Optic nerve meningioma. On A scan, the optic nerve proper appears thinner than normal (owing to meningeal compression), while the inter-sheath space is significantly wider (connected arrows) with a high-reflective internal structure between the inner and the outer peri-neural sheaths. Measurement of the intersheath space is possible and indicative of the pathologic thickening.

fuse thickening of the optic nerve following its meandering structure.

0 0

Post a comment