Evaluation of traumatic optic neuropathy in patients with optic canal fracture using diffusion tensor magnetic resonance imaging: a preliminary report.

OBJECTIVE To investigate the role of diffusion tensor magnetic resonance imaging (DT-MRI) in the evaluation of traumatic optic neuropathy (TON). METHODS Six patients with TON underwent DT-MRI prior to decompression surgery. DTV 2 and Volume One 1.44 software were used to measure the fractional anisotropy (FA) and the mean apparent diffusion coefficient (ADC) of the optic nerves. White matter fiber bundle tracking was used to display optic nerves. RESULTS Visual acuity was improved in 1 of the 6 patients after surgery. The mean FA of the injured eye declined significantly with regard to that of the normal eye (0.2438 ± 0.0670 vs. 0.4524 ± 0.0531; t = 8. 711; p = 0. 000). The mean ADC on the injured side increased significantly compared with that on the normal side [(1.4172 ± 0.1208) × 10(-3) mm(2)/s vs. (1.0866 ± 0.1179) × 10(-3) mm(2)/s; t = -5.316; p = 0. 003). The continuity of the intracanalicular segment of the optic nerve was interrupted in 3 patients without improved postoperative visual acuity. In 1 patient with improved postoperative visual acuity, the fiber bundle of the optic nerve was somewhat less dense in the injured eye than in the normal eye. CONCLUSIONS DT-MRI provides valuable information for evaluating the fibers of optic nerves in TON.