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Third neuron retroorbital

Fig. 19.5. The differential diagnosis of optic atrophy in children

Fig. 19.6. a Lesion of the right optic tract with an incongruous, homonymous quadrantic hemianopia to the left. Optic discs: The disc of the right eye has temporal pallor with a shallow excavation, while the disc of the left eye has a bow-tie pattern of pallor, evident in both the nasal and temporal disc quadrants. This finding is easily missed, when a direct ophthalmoscope is not used. b Visual field testing (static perimetry with the Humphrey Field Analyzer), of the central visual field, i.e., within 30° of eccentricity. c MRI. Shown

Fig. 19.6. a Lesion of the right optic tract with an incongruous, homonymous quadrantic hemianopia to the left. Optic discs: The disc of the right eye has temporal pallor with a shallow excavation, while the disc of the left eye has a bow-tie pattern of pallor, evident in both the nasal and temporal disc quadrants. This finding is easily missed, when a direct ophthalmoscope is not used. b Visual field testing (static perimetry with the Humphrey Field Analyzer), of the central visual field, i.e., within 30° of eccentricity. c MRI. Shown is the case of an 11-year-old patient with a circumscribed cortical lesion (zone of ischemia) and associated degeneration of the retro-geniculate optic radiations and optic tract on the right side. This finding reliably marks the damage as having been either intrauterine or neonatal in origin. Family members reported that the child could not catch a ball approaching from the left side. The vertical arrow indicates the tract hypoplasia; the left arrow indicates the middle cerebral artery

Fig. 19.7. a Optic nerve glioma (MRI). It is important to note that the nerve itself is enlarged, in contrast to the appearance of an optic sheath meningioma. Kinking or sharp angulation of the optic nerve is also very characteristic. Gliomas of the optic nerve frequently occur in the setting of neurofibromatosis type 1 (NF1). Depending on the location of the tumor, optic disc swelling may be seen at the time of discovery. In later stages, a partial or complete optic atrophy will be apparent. b Lisch nodules are typical in NF1, but may not be apparent during childhood

Fig. 19.7. a Optic nerve glioma (MRI). It is important to note that the nerve itself is enlarged, in contrast to the appearance of an optic sheath meningioma. Kinking or sharp angulation of the optic nerve is also very characteristic. Gliomas of the optic nerve frequently occur in the setting of neurofibromatosis type 1 (NF1). Depending on the location of the tumor, optic disc swelling may be seen at the time of discovery. In later stages, a partial or complete optic atrophy will be apparent. b Lisch nodules are typical in NF1, but may not be apparent during childhood

Optic Disc Elevation

The differential diagnosis of optic disc elevation in children includes several specific entities. A more detailed discussion of the various etiologic sources of disc elevation, independent of the patient's age, can be found in Chap. 8.

Optic Disc Drusen

During childhood, drusen are not usually calcified, making their identification difficult. Echographic detection of drusen is simple and noninvasive, when the drusen are calcified, and visible drusen are autofluorescent, providing a simple verification of the diagnosis. Superficially located drusen are easily identified by direct ophthalmoscopy, and they have an unmistakable appearance. It is often helpful to examine multiple members of the patient's family, since drusen develop as an autosomal dominant trait. They can also be found linked to a number of hereditary retinal degenerations.

Optic Nerve Gliomas

Optic nerve gliomas (■ Fig. 19.7 a) frequently occur in the setting of neurofibromatosis type 1 (NF1). Common signs and symptoms of NF1 include cafe-au-lait spots in the skin (at least six light brown, well-demarcated, macular skin marks) and Lisch nodules (pigmented iris hamartomas, consisting of epithelioid cells of neurectodermal origin; ■ Fig. 19.7 b), although they do not necessarily present during childhood. Lisch nodules are almost always absent in infants, are present in 50% of cases by age 5 years, and in 90% by age 20 years. NF1 is inherited as an autosomal dominant trait, and the spontaneous mutation rate is high.

Optic Nerve Sheath Meningioma

Disc elevation (infrequently) can be the presenting finding of an optic nerve sheath meningioma in children ( ■ Fig. 19.8 a). Neuroradiologic imaging almost always allows a clear and decisive differentiation between optic nerve gliomas and sheath meningiomas. Sheath meningio-mas frequently occur in patients with neurofibromatosis type 2 (NF2), which is inherited as an autosomal dominant trait. NF2 commonly presents as an acoustic neuroma and is not infrequently bilateral. Initial findings can also include retinal pigment epithelial hamartomas (■ Fig. 19.8 c) and a variety of lens opacities (■ Fig. 19.8 b).

Craniosynostoses

Premature or disordered closure of cranial sutures can present as optic nerve compression, with or without optic disc edema. Visually evoked potential (VEP) testing and ophthalmoscopy are frequently helpful in determining a correct diagnosis.

jl Note

Absence of optic disc edema does not rule out a com-pressive lesion of the optic nerve, as for instance in children presenting with open fontanels or already established optic atrophy.

Congenital Optic Disc Anomalies

■ Table 19.7 provides a summary of congenital optic disc anomalies (see Chap. 8). It is important to recognize that the appearance of the anomaly gives no absolute indication of the visual potential of the eye. The swinging flashlight test is of help in identifying anomalies associated with severe impairment of visual potential. But if there is any doubt about the visual potential of such an eye, a trial of occlusion therapy should always be attempted, so as to minimize the risk of amblyopia.

Fig. 19.8. a Optic nerve sheath meningioma (CT scan). The optic nerve itself has not changed, but it has been surrounded by tumor. Calcification of the tumor is a very characteristic sign, and best visualized with CT scan. Calcification may be absent in particular in larger tumors. Depending on the location of the tumor, optic disc swelling may be seen. Optic nerve sheath meningiomas also occur in the context of neurofibromatosis type 2 (NF2). b Additional ocular findings in NF2 include unilateral lens opacities, e.g., lens fiber haziness. c Retinal pigment epithelial hamartoma in a patient with NF2. These hamartomas may also occur as an isolated finding

Table 19.7. Developmental anomalies of the optic disc

Optic nerve hypoplasia

Morning-glory optic disc anomaly

Optic disc coloboma

Peripapillary staphyloma

Megalopapilla

Optic nerve pit

Tilted disc

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