NMO spectrum disorders comprise the major portion of CNS inflammatory diseases in Thai patients: A cross sectional study.

BACKGROUND: Neuromyelitis optica (NMO) is more prevalent than multiple sclerosis (MS) in the Asian population. AQP4-IgG as a specific biomarker for NMO has not been systematically validated in Thai patients.

OBJECTIVE: To identify the proportion of central nervous system demyelinating disease of Thai patient in one of referral center and examine its clinico-serological correlation with AQP4-IgG status.

METHOD: Cross sectional collected sera from patients who visited or were admitted to Prasat Neurological Institute from November 2009 to August 2010 were tested for serum AQP4-IgG levels. Patient information was reviewed and diagnoses of MS and clinical isolated syndrome (CIS) were made using the Revised McDonald criteria 2005. Diagnosis of NMO was made using the Revised NMO criteria 2006 (except for AQP4-IgG status) and NMO spectrum disorder (NMOSD) criteria 2007.

RESULTS: Sixty-one patients were identified including 12 with NMO, 25 with limited form of NMO, 16 with relapsing remitting MS (RRMS), and 8 with CIS. AQP4-IgG was found in 65% of patients in the NMOSD group. In the MS/CIS group, 2 were AQP4-IgG seropositive. Pleocytosis was significantly higher in the NMOSD group than the MS/CIS group. Cranial MRI revealed that the size and degree of brain lesions were similar in all study groups. However, spinal MRI showed that the MS/CIS groups had a higher prevalence of short segment myelitis and a higher abundance of white matter (p<0.05) than NMOSD group. AQP4-IgG seropositive samples correlated with female patients and the presence of optic neuritis.

CONCLUSION: NMOSD is more common than MS in Thai patients. Moreover, AQP4-IgG is highly specific for NMOSD. Spinal MRI can effectively distinguish NMOSD from MS patients. AQP4-IgG seropositivity is highly correlated with females and the presence of optic neuritis.