J Korean Ophthalmol Soc.  2022 Nov;63(11):958-963. 10.3341/jkos.2022.63.11.958.

Optic Chiasmal Enhancement Revealed by Magnetic Resonance Imaging in a Patient with Ethambutol-induced Toxic Optic Neuropathy

• Lim CW
• Kim WJ

• KMID: 2535899
• DOI: http://doi.org/10.3341/jkos.2022.63.11.958

Abstract

Purpose
We report a bitemporal visual field defect accompanied by optic chiasmal enhancement in a patient with ethambutol (EMB)-induced toxic optic neuropathy.
Case summary
A 53-year-old woman presented with bilateral visual disturbance that had gradually worsened over the prior 2 months. She had been prescribed 800 mg EMB daily to treat pulmonary tuberculosis for the past 10 months but had stopped EMB 1 month prior because of visual disturbance. She had been prescribed 600 mg rifampicin and 1,000 mg clarithromycin daily for 11 months. Her visual acuity was 0.2 in the right eye and 0.1 in the left. Color vision was reduced. Automated perimetry demonstrated a bitemporal visual field defect, which was more severe in the left eye. Magnetic resonance imaging (MRI) of the optic chiasm revealed contrast enhancement in the body of the chiasm. The optic nerve of the left eye evidenced a higher signal intensity than did that of the right, consistent with the visual field test results. One month after her initial visit, the visual symptoms deteriorated further. We delivered high-dose, intravenous steroid pulse therapy (methylprednisolone 1,000 mg daily for 3 days). At the 1-year follow-up, the visual acuity was 0.4 in the right eye and 0.1 in the left.
Conclusions
Bitemporal hemianopia may develop in patients with EMB-induced toxic optic neuropathy. Enhancement of the optic chiasm, consistent with the visual field defect, could be observed in MRI.

Keyword

Bitemporal hemianopia; Ethambutol; Optic chiasm; Toxic optic neuropathy