A Prospective Study of Serum Uric Acid in Optic Neuritis

Abstract

Abstract: : Purpose: Uric acid a natural antioxidant has been shown to be lower than in healthy controls in patients with established multiple sclerosis (MS). However, usually it is still within the normal range. In this study we investigated whether uric acid is decrease after onset of optic neuritis (ON), which often is the first manifestation of MS. Methods: Over a 3 year period, all patients attending the eye casualty department in Leicester with a recent onset of optic neuritis were invited to enter the study. A careful medical history was taken. All patients had a 24-2 visual field test on a Humphrey visual field analyser and they also had visual evoked potential (VEP) and an MRI scan of the brain. Results: 26 Patients (22 female and 6 male) were entered into the study, with an age range of 24 to 47 years of age (mean 31 years of age). Evidence of demyelination was revealed in 15 of the 20 patients (75%) who underwent MRI. 6 patients failed to attend for an MRI scan. 7 patients were known to suffer from MS and 4 had experienced a previous episode of ON. One patient with atypical symptoms was found to have a pituitary tumour. 13 patients (50%) were found to have reduced serum uric acid levels ranging from 135 to 186 µmol/L (normal range: 200 to 350 µmol/L). Of these, 6 patients were presenting with a first episode of ON, with no history of MS. Conclusions: Serum uric acid in optic neuritis is often below the lower limit of normal, which suggests a significantly decreased antioxidant reserve. Interestingly it can be low at the first manifestation of MS and, therefore, does not reflect longstanding inflammation and demyelination. Possibly the below normal levels reflect the short interval between the onset of symptoms and uric acid measurement, in contrast to previous reports in which they were low normal. Uric acid may be an important marker to distinguish optic neuritis from other conditions mimicking optic neuritis.

Keywords: neuro-ophthalmology: optic nerve • optic disc • clinical (human) or epidemiologic studies: pre