Aim: To determine the frequency and clinical and laboratory features of patients with multiple sclerosis characterized by uncommon cerebrospinal findings, ie, negative oligoclonal band or increased number of mononuclear cells in cerebrospinal fluid.
Methods: The retrospective analysis included medical records of 233 patients (158 women and 75 men) admitted to the Department of Neurology, Ljubljana Medical Center, between January 1, 1990, and December 31, 1999 and discharged with the diagnosis of multiple sclerosis. We determined clinical features and cerebrospinal fluid parameters of patients with oligoclonal band-negative multiple sclerosis and > or =15 mononuclear cells/mm( 3) in cerebrospinal fluid and compared them with patients with oligoclonal band-positive multiple sclerosis and expected number of mononuclear cells in cerebrospinal fluid, respectively. There were 26 patients with oligoclonal band-negative finding and 26 with > or =15 mononuclear cells/mm(3) in cerebrospinal fluid. The two groups of patients did not overlap, except for one patient, who had 19 mononuclear cells/mm(3) and was oligoclonal band-negative.
Results: The diagnosis was delayed in oligoclonal band-negative multiple sclerosis patients, their cerebrospinal fluid contained less leukocytes, and lower concentration of IgG. The patients with > or =15 leukocytes/mm( 3) in cerebrospinal fluid were diagnosed earlier and had increased cerebrospinal fluid protein and IgG concentrations.
Conclusion: Multiple sclerosis with negative oligoclonal band or increased count of leukocytes in cerebrospinal fluid were found in approximately 10% of patients with the disease. Because of the absence of oligoclonal band and less active cerebrospinal fluid, the diagnosis in these patients may be delayed.