Baseline magnetic resonance imaging of the optic nerve provides limited predictive information on short-term recovery after acute optic neuritis

Abstract

Background: In acute optic neuritis, magnetic resonance imaging (MRI) may help to confirm the diagnosis as well as to exclude alternative diagnoses. Yet, little is known on the value of optic nerve imaging for predicting clinical symptoms or therapeutic outcome.

Purpose: To evaluate the benefit of optic nerve MRI for predicting response to appropriate therapy and recovery of visual acuity.

Methods: Clinical data as well as visual evoked potentials (VEP) and MRI results of 104 patients, who were treated at the Department of Neurology with clinically definite optic neuritis between December 2010 and September 2012 were retrospectively reviewed including a follow up within 14 days.

Results: Both length of the Gd enhancing lesion (r = -0.38; p = 0.001) and the T2 lesion (r = -0.25; p = 0.03) of the optic nerve in acute optic neuritis showed a medium correlation with visual acuity after treatment. Although visual acuity pre-treatment was little but nonsignificantly lower if Gd enhancement of the optic nerve was detected via orbital MRI, improvement of visual acuity after adequate therapy was significantly better (0.40 vs. 0.24; p = 0.04). Intraorbitally located Gd enhancing lesions were associated with worse visual improvement compared to canalicular, intracranial and chiasmal lesions (0.35 vs. 0.54; p = 0.02).

Conclusion: Orbital MRI is a broadly available, valuable tool for predicting the improvement of visual function. While the accurate individual prediction of long-term outcomes after appropriate therapy still remains difficult, lesion length of Gd enhancement and T2 lesion contribute to its prediction and a better short-term visual outcome may be associated with detection and localization of Gd enhancement along the optic nerve.

Figure 1. Gd enhancement and T2 lesion of the right optic nerve.

Optic nerve MR imaging of a representative patient with ON. (A) Coronar fat-saturated T1-weighted MRI sequences of the intraorbital and (B) canalicular part of the optic nerve after application of 0.1mmol/kg gadolinium. The arrows highlight the Gd enhanced right optic nerve. (C) Signalalteration of the intraorbital and (D) canalicular part of the optic nerve in coronar fat-saturated T2 turbo spin-echo MRI sequences. The arrows highlight the hypertense T2 lesion of the right optic nerve.

Figure 2. Patients with Gd enhancement of the optic nerve show significant higher visual improvement.

(A) Mean improvement of visual acuity of patients with or without either T2 lesion or Gd enhancement of the optic nerve in orbital MRI. Error bars indicate standard error of the mean. * indicates significant difference with p = 0.04 as determined via Mann-Whitney rank sum test. Improvement of visual acuity was defined as difference between visual acuity before and after adequate treatment. (B) Mean visual acuity of patients with or without T2 lesion or Gd enhancement of the optic nerve in orbital MRI before and after adequate therapy. Error bars indicate standard error of the mean. No significant differences were found between the single groups.