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Locally produced oligoclonal IgG bands (OCB) are present in the cerebrospinal fluid (CSF) of 95% patients with multiple sclerosis (MS)[2,3]. The most sensitive method for the detection of OCB is isoelectric focusing (IEF) [1]. Occasional patients with clinically definite MS lack evidence for intrathecal IgG synthesis [2,9]. This study was designed to compare brain magnetic resonance imagining (MRI) findings between CSF OCB positive and negative MS patients. The study comprised 22 OB negative patients with clinically definite MS and 22 OCB positive controls matched for age, disease duration, activity and course of MS. In the both groups clinical assessment was performed by using Expanded Disability Status Scale (EDSS) score. T2 weighted MRI of the brain was performed on a Siemens Magnetom (1.0 T). Lesions were countred and sized for 15 anatomically defined locations:7 periventricular (PV) and 8 non-periventricular (NPV) regions. An arbitrary scoring system weighted for lesions size was used to estimate total and regional lesions loads: a)1 point was given for each lesion with a diameter 1-5 mm, b) 2 points for one lesion with a diameter 6-10 mm, c) 3 points for one over 10 mm, and confluent lesions scored one extra point [16]. Atrophy were scored as follows: 0-normal size, 1-mild atrophy, 2-moderate atrophy and 3-severe atrophy. Mean score of total brain MRI loads was lower in OCB negative than in OCB positive MS patients (44 vs. 50) but the difference was not statistically significant. Mean periventricular (32 vs. 23) non-periventricular (26 vs. 19) and infratentorial (11 vs. 9) scores were higher in OCB positive MS group in comparison with OCB negative patients but non-significant (figure 1). There was no correlation between EDSS score and total MRI lesions load in OCB negative MS patients, while in OCB positive group we detected significant correlation between EDSS score and total MRI lesions load (p=0.026) (figure 2). The results of this study demonstrate that by using conventional brain MRI the extent end severity of the pathological process seems to be similar in OCB negative and OCB postive MS patients. On the other hand, we found statistically significant correlation between brain MRI total lesion load and EDSS in the OCB positive MS patients, while this correlation was not detected in OCB negative MS patients. Differences in brain MRI findings between OCB positive nad OCB negative MS patients have been already analyzed [9,12]. In the first, Zeman et al. reported that OCB negative MS patients have lower total MRI brain lesion loads in comparison to OCB positive group, but the differences was not statistically significant [9]. In accordance with these findings Fukazawa et al. also failed to show differences in the distribution, extent shape and number of brain MRI lesions between OCB positive and negative MS patients. [12]. On the other hand, it has been demonstrated that the rate of intrathecal IgG synthesis apparently correlates with plaque volume in the brain, as demonstrated on MRI, in MS patients [17]. However, our results along with those from two above-mentioned previous studies do not support this notion. In conclusion, trend towards lesser MRI lesion load and lack of its correlation with EDSS in OCB negative MS patients, warrants further investigations with new MRI techniques (magnetic resonance spectroscopy and magnetisation transfer), including the thorough exploration of normal-appearing white matter, in OCB negative MS patients.