• Neuro-Ophthalmology/Orbit

    The authors of this study published in the July 2010 issue of Multiple Sclerosis examined whether the extent of initial inflammatory demyelination in optic neuritis correlates with the remyelinating capacity of the optic nerve. They analyzed multifocal visual evoked potential (mfVEP) results in patients with acute unilateral optic neuritis and good visual recovery. The results indicate that the extent of the initial inflammatory demyelination appears to be the most important factor in determining the completeness of remyelination, with the first six months after the attack likely the most favorable time for remyelination.

    The authors tested mfVEPs in 40 patients. Average latency recovery was 4.7 (3.3) ms, 8.6 (3.6) ms and 11.3 (3.1) ms at three, six and 12 months, respectively. All patients demonstrated at least some recovery by the end of the follow-up period. Latency recovery ranged from 7 to 17 ms (average = 11.3 (3.1) ms), despite the fact that in a number of cases the baseline latency delay was more than 35 to 40 ms.

    The data demonstrate that the extensive latency delay at baseline significantly improved over time, although recovery slowed after six months. The authors also found that the magnitude of latency recovery was independent of the initial latency delay. They conclude that optic nerve lesions tend to remyelinate at a particular rate irrespective of the size of the initial demyelinated zone, with smaller lesions accomplishing recovery more completely.

    They say the study's results may have implications for clinical trials of remyelination-enhancing therapies and support the concept that earlier initiation of treatment could potentially be more beneficial. They conclude that it is likely that the combined effect of various factors, including degree of the tissue injury during acute inflammation, limitation of oligodendrocyte precursor cell recruitment and their delayed arrival, may limit remyelination in patients with extensive optic nerve lesions.