Bilateral radiation optic neuropathy following concurrent ch
Published in the journal Neuro-ophthalmology the authors describe a case of RON in glioblastoma after radio-sensitisation with temozolomide with sequential involvement of both optic nerves.

This case provides a timeline for clinical and imaging findings with RON and specifically resolution of nerve enhancement. The authors also highlight the potential of an increase in incidence of RON in glioblastoma with advances in survival seen with greater use of second-line chemotherapy and even re-radiation.

A 64-year-old woman underwent complete resection of a right temporal mass that was confirmed pathologically to be a glioblastoma (Figure 1). She then underwent concurrent chemotherapy with temozolomide and radiation to her resection bed, receiving 46 gray (Gy) of photon radiation to the T2 abnormality and 14 Gy to the T1 abnormality for a total dose of 60 Gy in 30 fractions.

The right optic nerve received a maximum dose of 53.9 Gy, average 49.2 Gy over the whole nerve. The left optic nerve received a maximum of 52.2 Gy, average 33.4 Gy for the whole nerve. After 1 month, she received 12 cycles of monthly maintenance chemotherapy with temozolomide and was enrolled in a clinical trial of scalp-applied grids to deliver alternating electric field current to the tumour field.

After 9 cycles of maintenance chemotherapy (about 36 weeks following radiation), she experienced gradually worsening bilateral vision loss. Examination showed visual acuity of 20/30 right eye and 20/25 left eye with early cataract in both eyes, no afferent pupillary defect and normal appearing optic discs.

Humphrey visual fields revealed superior arcuate scotoma in both eyes more pronounced on the left with mean deviation (MD) of –4.50 db and –6.74 db in right. Subsequently, her visual loss continued to progress in both eyes. Five months later, her examination demonstrated visual acuity of 20/50 right eye and 20/25 left eye. Visual fields revealed dense superior altitudinal defect in the right eye with MD of −15.58 db and dense superior arcuate defect in the left eye with MD of −10.73 db.

36 weeks after beginning of concurrent radiation and temozolomide, there was enhancement of the left optic nerve before optic nerve after exiting the optic canal; the optic tracts and intracanalicular and orbital regions of the nerve were unaffected. This enhancement increased at 45 weeks and was accompanied by enhancement of the right optic nerve. Subtle enhancement of the left side optic chiasm was present. After a further 9 weeks, enhancement diminished, more so on the left.

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