Clinical and neurophysiological findings in oligoclonal band negative multiple sclerosis patients

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 b