Clinical and neurophysiological findings in oligoclonal band negative multiple sclerosis patients
Authors: Mesaros Sarlota , Drulovic Jelena , Levic Zvonimir 
Published: July 2008

Besides magnetic resonance imaging, the presence of locally produced oligoclonal IgG bands (OCB) in the cerebrospinal fluid (CSF) is the most consistent laboratory abnormality in patients with multiple sclerosis (MS). The most sensitive method for the detection of CSF OCB is isoelectric focusing (IEF) [6]. Occasional patients with clinically definite MS lack evidence for intrathecal IgG synthesis [7, 8]. This study was designed to compare clinical data and evoked potential (EP) findings between CSF OCB positive and OCB negative MS patients. The study comprised 22 OCB negative patients with clinically definite MS [11] and 22 OCB positive controls matched for age, disease duration, activity and course of MS. In both groups clinical assessment was performed by using Expanded Disability Status Scale (EDSS) score [12] and progression rate (PR). All patients underwent multimodal EP: visual (VEPs), brainstem auditory (BAEPs) and median somatosensory (mSEPs). The VEPa were considered abnormal if the P100 latency exceeded 117 ms or inter-ocular difference greater than 8 ms was detected. The BAEPs were considered abnormal if waves III or V were absent or the interpeak latencies I-III, III-V, or I-V were increased. The mSEPs were considerd abnormal when N9, N13 and N20 potentials were absent or when increased interpeak latencies were recorded. The severity of the neurophysiological abnormalities was scored for each modality as follows normal EP score 0; every other EP abnormality except the absence of one of the main waves, score 1; absence of one or more of the main waves, score 2 [13]. Both mean EDSS score (4.0 vs. 3.5) and PR (0.6 vs. 0.5) were similar in OCB positive and OCB negative group, (p>0.05). In the first group males were predominant, but without statistical significance (Table 1). Disease started more often with the brainstem symptoms in the OCB positive than in OCB negative MS group (p=0.028), while there was no differences in other initial symptoms between the groups (Graph 2). The frequency of (multimodal) EP abnormalities was higher in the OCB positive group but the differences were not statistically significant, except for bilateral SEP abnormalities (p=0.012). The severity of the AEPs abnormalities was similar in both groups while for the VEPs and SEPs abnormalities were more pronounced in the OCB positive group but not significantly (Table 2). The male preponderance of OCB negative MS patients in our study is in accordance with previous studies [14, 15]. This finding could be potentially ascribed to the well known gender-related differences in both humoral and cellular immune responses [17]. We found no statistically significant differences in either disability or PR between the two patient groups, although OCB negative MS patients had lower EDSS score and PR than OCB positive cases. In accordance with these findings, Fukazawa et al. also failed to show differences in disability between OCB negative and positive MS patients. On the other hand, few studies reported that OCB negative MS patients have a better prognosis [16 18]. The only clinical difference between two groups of patients that we found was that the disease more often started with brainstem symptoms in OCB positive MS patients (p=0.028). OCB positive MS patients had more often bilateral SEPs abnormalities (p=0.012). There was no statistically significant differences between two groups of patients in the severity of trimodal EPs abnormalities and the frequency of BAEPs and VEPs abnormalities although OCB negative patients had trend towards less pronounced EP disturbancies. In conclusion, our results did not reveal significant difference in clinical and neurophysiological(y) parameters between two groups of patients. However, they indicate a trend towards better prognosis of the disease in OCB negative MS patients.