MR imaging of optic neuropathy with extended echo-train acquisition fluid-attenuated inversion recovery

Abstract

Background and purpose: XETA, also known as Cube, is a relatively new 3D FSE sequence that can be used to perform whole-brain FLAIR T2-weighted imaging at isotropic high spatial resolution. This high-resolution volumetric imaging, coupled with both fat and fluid suppression, permits ideal evaluation of optic nerve anatomy and signal intensity; therefore, we hypothesized that XETA FLAIR would be useful for the detection of T2 signal-intensity abnormality in the optic nerve. Our purpose was to evaluate the sensitivity of XETA FLAIR for this abnormality and to compare it with the coronal FSE T2 FS.

Materials and methods: After obtaining approval of the institutional review board, 2 CAQ neuroradiologists retrospectively reviewed all patients with a clinical diagnosis of optic neuropathy who had undergone XETA FLAIR and standard orbital imaging from September 2006 to February 2009. Fifteen patients met these criteria and underwent the following sequences: XETA FLAIR, coronal FSE T2 FS, and T1-weighted postgadolinium sequences with FS.

Results: Signal-intensity abnormality was identified on the correct side of the patient's vision loss in all 15 patients on XETA but in only 11/15 patients on the coronal FSE T2-weighted imaging. Reviewer 1 perceived the signal-intensity abnormality better on the XETA versus T2-weighted imaging in 10/15 patients, and reviewer 2, in 9/15 patients. Neither reviewer visualized any of the imaging better by using the conventional coronal FSE T2 FS sequence.

Conclusions: XETA FLAIR was more sensitive than coronal FSE T2 FS for identifying abnormal signal intensity within the optic nerves in patients with optic neuropathy.

Fig 1.

Graph shows signal-intensity abnormality in all patients on XETA on the correct side of the vision loss, but in only 11/15 on T2-weighted imaging. All 9 patients who presented acutely showed enhancement, but the 6 patients who underwent MR imaging after 4 weeks did not have enhancement. Two patients with negative T2 presented in the chronic period. These patients had no enhancement, so they would have been missed on all of our standard orbital sequences without XETA.

Fig 2.

This graph shows the difference in the degree of signal-intensity abnormality. XETA shows grade 2 (obvious T2 hyperintensity) in most patients, whereas the coronal T2 FSE imaging shows only grade 1 (subtle T2 hyperintensity) in most patients and grade 0 (no signal intensity abnormality) in 4 patients.

Fig 3.

A 30-year-old woman presented with acute left optic neuritis. She had a history of contralateral (right) optic neuritis with persistent decreased visual acuity and an ultimate diagnosis of chronic relapsing inflammatory optic neuropathy. A and B, Coronal (A) and axial (B) XETA reformations show obvious swelling and T2 hyperintensity in the left optic nerve (arrow). Of note, this is 1 of the 2 cases with bilateral abnormality. The right optic nerve is atrophic and also hyperintense secondary to chronic optic neuritis. C, The surrounding perineural CSF makes it difficult to perceive the T2 signal-intensity abnormality within the left optic nerve on this standard coronal T2 FSE FS image (arrow). D, Axial T1-weighted postgadolinium image shows enhancement of the left optic nerve (arrow).

Fig 4.

A 39-year-old man with subacute left optic neuritis but persistent decreased visual acuity. This was a clinically isolated syndrome, which carries a risk for the subsequent diagnosis of MS. A, Mildly motion-degraded coronal T2 FSE images do not show any signal-intensity abnormality within the optic nerves (arrows). B, Coronal XETA image easily shows hyperintensity within the intracanalicular portion of the left optic nerve as compared to the right optic nerve (arrows).

Fig 5.

A 51-year-old man with a history of recurrent unilateral optic neuritis with chorioretinal atrophy on the right. A, Coronal XETA reformation nicely shows T2 hyperintensity in the right optic chiasm (arrow) in this unusual case of isolated intracranial segment disease. B, Coronal T2 FSE does not show the signal-intensity abnormality (arrow), likely because the surrounding CSF T2 hyperintensity obscures it.