Optic neuritis. Doppler ultrasonography compared with MR and correlated with visual evoked potential assessments

To establish the role of Doppler ultrasonography (US) in the examination of patients with acute unilateral optic neuritis.

Twenty-five patients with a clinical diagnosis of optic neuritis were prospectively evaluated and 18 of them were included in the study. The inclusion criteria were MR findings of unilateral disease and age below 50 years. All patients were examined with MR in order to objectively detect, localize and measure the optic nerve lesions and in order to exclude patients with unidentifiable optic nerve involvement. Evaluation with US was performed to determine nerve morphology, nerve swelling, and resistance to flow in the central retinal artery. The patients' contralateral optic nerve served as an internal control. The US findings were correlated to the degree of visual impairment, both initially and at follow-up. Visual evoked potential (VEP) assessments were also performed in 16 patients.

A statistically significant difference was found in the optic nerve diameter and in the resistance to flow in the central retinal artery between the affected and unaffected eyes. Patients with a prolonged impairment of visual acuity initially had a more swollen nerve and an increased resistance to flow in the affected optic nerve. Prognostic information was also gathered solely by evaluating the unaffected nerve diameter: patients who normally had thinner optic nerves had a more severe form of optic neuritis. VEP assessments were positive in all patients investigated.

Doppler US can be used together with a VEP assessment as an indicator of the disease process in acute optic neuritis. These methods offer a potential for monitoring patients over time.