Diagnostic Outcomes of ‘Optico-Spinal Demyelination’: A 10 Year Prospective Cohort Study from the United Kingdom (P6.136)

Objective: To identify the natural history of non-MS optico-spinal demyelination. Background: Patients with non-MS ‘demyelination’ can be challenging to classify. With the availability of Aquaporin-4 antibody testing, many patients with relapsing spinal cord and optic nerve syndromes can be classified as NMO spectrum disorders. Despite this, a number of patients remain who have ‘isolated optico-spinal demyelination’ whose natural history is uncertain. Methods: This is a prospective longitudinal cohort study. From 2003 to 2005 cases of non-MS optico-spinal demyelination (defined in 2003 as optic neuritis, myelitis (any lesion length) and brain MRI not suggestive of MS) were reported via the British Neurological Surveillance Unit (n= 128). Some were typical for NMO and MS (n=61) as per criteria in 2005. After excluding these, 67 patients were classified as optico-spinal demyelination - unclassified (OSD-U) (52[percnt]). Patients and their physicians were contacted in 2011 and 2015 to ascertain most recent diagnosis. AQP4 antibodies were tested in all. Results: By 2015 (10 years follow up) outcomes of 64 of the 67 patients were obtained. A definite diagnosis was made based on clinical, radiological or serum AQP4 IgG in 50 (75[percnt]) patients. 39 were classified as NMOSD (58[percnt]), 11as MS (17[percnt]) 14 remained as OSD-U (21 [percnt]). 3 (4[percnt]) patients were untraceable. 7 of the 14 OSD -U are being treated with azathioprine, one with Rebif and 6 are not on treatment. Conclusions: At 10 years from recruitment into study and a median of 12 years after onset of disease 75[percnt] of unclassifiable optico-spinal demyelinating disorders had a definite diagnosis. 17[percnt] developed MS and 58[percnt] developed NMOSD. 21[percnt] still remained unclassifiable. Whether the last group comprise a distinct disease entity or will turn out to be typical MS or NMOSD (perhaps associated with new serum markers) on longer follow up remains to be seen. Disclosure: Dr. Hamid has nothing to disclose. Dr. Panicker has nothing to disclose. Dr. Elsone has nothing to disclose. Dr. Mutch has nothing to disclose. Dr. Das has nothing to disclose. Dr. Boggild has nothing to disclose. Dr. Jacob has nothing to disclose.