Evoked Potential Studies (EP) P-EV001. Visual evoked potential findings in Neuromyelitis optica spectrum disorders

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Introduction . Neuromyelitis optica is an inflammatory, demyelinating syndrome of central nervous system that is characterised by severe attacks of optic neuritis and myelitis. It has a high morbidity and mortality. Five years after initial presentation, more than 50% of patients with NMO will be blind in one or both eyes or require ambulatory help. Methods . A total of 68 patients with neuromyelitis optica spectrum disorders (NMOSD) admitted to neuromedical ward of Yangon General Hospital were prospectively studied for visual acuity, and visual evoked potential were performed. Results . Visual acuity was ranged from normal to blindness. Visual impairment were classified into mild, moderate, severe and blindness according to WHO classification. At admission, among 68 patients, 4.4% of the patients had moderate vision impairment, 1.5% had severe vision impairment, 50.0% had blindness, and 44.1% had no vision impairment. Among 136 eyes examined, 43 (31.6%) had no visually evoked response. Out of 93 eyes (68.4%) in which VEP responses were detected, 61 (65.6%) had P100 wave latency within normal limits, while remaining 32 (34.4%) had increased wave latency. Latency values among study population were found to be ranging between 84.7 ms and 164.6 ms and the average latency of P100 was 111.8 ± 19.5 ms. Among 93 eyes in which visual response was evoked, it was found that 14 eyes (15.1%) had reduced P100 wave amplitude with normal latency. Conclusion . In Neto et al. study (2013), reduced P100 wave amplitude with normal latency in 65% of the 20 eyes in which the visual response was evoked .This pattern was called the ‘NMO pattern’. So regarding these data, such an NMO pattern was not evident in present study. Because most of patients have severe vision impairment and latency is prolonged in most of the patients.