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Optic nerve metastasis


Key points

  • Definition: Isolated metastasis to the optic nerve is rare and is often overlooked or misdiagnosed initially.

  • Classic clue: Typically, a middle-aged female presents with “a little blurred vision,” further inquiry identifies pain, proptosis, reduced visual acuity, and bitemporal hemianopsia with enhancing abnormality related to the optic nerve (ON) sheath(s). Her past medical history reveals that she first had breast carcinoma 10 years ago with recurrence 5 years ago and now experiences loss of vision.

Imaging

General imaging features

  • Radiographic features considered characteristic of optic nerve meningioma (ONM) have been found in patients with ON metastasis, delaying correct diagnosis.

  • These features include the “tram track” sign. ,

Computed tomography features

  • May show “tram track” sign or central optic nerve lucency on contrast-enhanced computed tomography (CECT).

  • Proptosis (see Figure 21-1, A and C ).

Magnetic resonance imaging features

  • T1: Metastatic carcinoma is characteristically isointense or slightly hyperintense (see Figure 21-1, A and D ).

  • T2: Metastatic carcinoma is hypointense (see Figure 21-1 , B ). ,

    FIGURE 21-1 ■, A, Axial T1 image through optic nerves shows proptosis with prominent ON complexes bilaterally with sheaths showing slightly higher signal than adjacent ONs. B, Coronal T2 image shows signal within the ON sheath to be reduced on the right compared to the fluid on the left. A subtle finding, which in retrospect corresponds to tumor can be seen to enhance on contrasted images. C, Axial T1 Gd shows proptosis with avid abnormal enhancement of both ON sheaths extending smoothly from the globes to the optic chiasm. D, Coronal T1 image shows enlarged ON complexes bilaterally with slightly increased signal in ON sheaths relative to central ONs. E, F, and G, Coronal T1 Gd image shows abnormal enhancement of ON sheaths and central portions of the ONs.

Ultrasound features

  • Ocular ultrasound may show an echogenic mass related to the ON.

  • Melanomas tend to be echolucent.

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