Acta Neurologica Belgica

, Volume 112, Issue 2, pp 209–211

Diffusion MRI and tensor tractography in ischemic optic neuropathy

Authors

  • C. Cauquil
    • Department of NeurologyCentre Hospitalo-Universitaire de Bicêtre, Assistance Publique–Hôpitaux de Paris
    • Université Paris-Sud 11
  • R. Souillard-Scemama
    • Department of NeuroradiologyCentre Hospitalo-Universitaire de Bicêtre, Assistance Publique–Hôpitaux de Paris
  • M. Labetoulle
    • Department of OphtalmologyCentre Hospitalo-Universitaire de Bicêtre, Assistance Publique–Hôpitaux de Paris
    • Université Paris-Sud 11
  • D. Adams
    • Department of NeurologyCentre Hospitalo-Universitaire de Bicêtre, Assistance Publique–Hôpitaux de Paris
    • Université Paris-Sud 11
    • INSERM U788
  • D. Ducreux
    • Department of NeuroradiologyCentre Hospitalo-Universitaire de Bicêtre, Assistance Publique–Hôpitaux de Paris
    • Université Paris-Sud 11
    • INSERM U788
    • Department of NeurologyCentre Hospitalo-Universitaire de Bicêtre, Assistance Publique–Hôpitaux de Paris
    • INSERM U788
Case Report

DOI: 10.1007/s13760-012-0013-5

Cite this article as:
Cauquil, C., Souillard-Scemama, R., Labetoulle, M. et al. Acta Neurol Belg (2012) 112: 209. doi:10.1007/s13760-012-0013-5

Abstract

Ischemic optic neuropathies (IONs) are among the most prevalent diseases causing visual impairment in middle-aged and elderly people. While arteritic ION is an ocular emergency and requires early diagnosis and immediate treatment with systemic high-dose corticosteroids to prevent further visual loss, treatment options for non-arteritic ION remain limited. We describe the case of a woman with unilateral right-sided non-arteritic posterior ischemic optic neuropathy. The diagnosis was made on clinical and radiographic grounds. Diffusion-weighted sequences and apparent diffusion coefficient maps revealed markedly restricted diffusion in the right optic nerve. It was very helpful to precise the posterior topography of the optic nerve lesion. Furthermore, we reported the diffusion tensor tractography study which appears to be an objective tool to assess the incomplete visual recovery. These MRI techniques including tensor tractography remain to be evaluated in large cohort of ION patients’ particularly in future therapeutic trials.

Keywords

Ischemic optic neuropathyAIONPIONDiffusion MRTensor tractography

Introduction

Ischemic optic neuropathies (IONs) are the most frequent acute optic neuropathy in patients older than 50 years [1]. ION is classified into anterior and posterior according to the affected part of the optic nerve [1]. While anterior ION (AION), by far the most common type, presents with sudden, painless visual loss associated with a swollen optic nerve head, posterior ION (PION) is characterized by acute vision loss without disc edema but with subsequent optic disc atrophy. To date, treatment for non-arteritic ION remains limited, while arteritic ION is an ocular emergency which requires corticosteroids to prevent further visual loss [1]. Hitherto, no treatment of known value is available for non-arteritic ION; systemic steroid therapy helping to improve vision only in a minority of these patients [1]. Currently, more tools are needed in order to individually predict spontaneous evolution. In this report, we describe the clinical and neuroradiological features of PION. MR imaging was very helpful: diffusion sequences to highlight the posterior topography of the optic nerve lesion and MR tractography to objectively evaluate the incomplete visual recovery.

Case report

A 71-year-old woman presented with sudden-onset right-sided visual loss associated with headaches during the following days. Right vision acuity was limited to light perception. A relative afferent pupillary defect was found while fundus examination, intraocular pressure and fluorescein angiography were normal. Medical history was only significant for hypertension and dyslipidemia. The routine laboratory workup including ESR, CRP and lumbar puncture was normal. The suspected diagnosis was acute PION. Initial MRI showed high-signal intensity of the posterior part of the right optic nerve on T2-WI sequences and restricted diffusion with a 43% reduced-ADC signal (0.8 × 10−3 vs. 1.4 × 10−3 within the left optic nerve; Fig. 1a). On the fiber tracking of the optic nerves, no significant asymmetry was observed. MR angiography, cervical and transcranial Doppler, echocardiography, EKG and Holter cardiac monitoring did not disclose abnormalities except moderate atherosclerosis. Since in a recent publication, systemic steroids had a beneficial effect on visual function in non-arteritic PION [1], and since giant cell arteritis was not formally excluded, aspirin and a systemic corticosteroid were administered for 4 weeks. Following treatment, headaches disappeared within 48 h. In addition, the patient reported relative visual improvement (right acuity 20/200 on day 15). Temporal biopsy showed no inflammation. Six months later, she unfortunately still had a similar reduction in right visual acuity, while fundoscopy showed right temporal disc pallor. MRI revealed the persistence of a high-signal intensity of the right optic nerve on diffusion-WI (associated with ADC value measured at 1.2 × 10−3). The fiber tracking revealed a significant loss of fibers in the right optic nerve compared to the contralateral nerve (Fig. 1b, c). Non-arteritic PION was retained as the final diagnosis, because of the initial clinical presentation and MRI features.
https://static-content.springer.com/image/art%3A10.1007%2Fs13760-012-0013-5/MediaObjects/13760_2012_13_Fig1_HTML.jpg
Fig. 1

Diffusion-weighted MRI and optic nerves tractography. a Initial diffusion weighted-MR sequence disclosed a hypersignal in the right optic nerve (arrow) (with a b factor of 500 s/mm²) (associated with a low ADC value measured at 0.8 × 10−3 vs. 1.4 × 10−3 in the left optic nerve). b, c Fiber tracking of the optic nerves at sixth month showed significant loss of fibers in the right optic nerve compared to the contralateral normal optic nerve fiber pattern on axial (b) and coronal (c) planes [while initial tracking was normal (not shown)]

Discussion

High-signal intensity on diffusion imaging in the optic nerve has been previously described in rare patients with ION in the setting of hypotension, infection, thrombocythemia or in spontaneous non-arteritic cases [28]. In our case of PION, MR imaging was very helpful, including (1) diffusion sequences to confirm optic nerve infarction and precise topography, and (2) tractography to objectively assess the incomplete recovery.

These MRI techniques including tensor tractography remain to be evaluated in large cohort of ION patients’ to help for their management and perhaps predict recovery in future therapeutic trials [1].

Conflict of interest

None.

Copyright information

© Belgian Neurological Society 2012