The clinical significance of an intrathecal monoclonal immunoglobulin band

Background: Intrathecal oligoclonal band synthesis occurs in 95% of patients with clinically definite MS but may also occur in the context of CNS infection and other inflammatory conditions. By contrast, the significance of an intrathecal synthesis of a monoclonal band remains uncertain. Previously, an association between a single intrathecal band and CNS lymphoma has been reported but a relationship has also been shown with diagnoses more usually associated with an oligoclonal pattern. At present, it is not known whether a single band will convert to an oligoclonal response with time. Methods: Data were obtained from patients who had CSF and serum analyzed by isoelectric focusing (IEF) at the authors’ institutions over a 6-year period. Clinical details were acquired for those who underwent repeat lumbar puncture after an initial CSF examination revealed an intrathecal monoclonal immunoglobulin G band. Results: Of the 31 patients identified as having an initial intrathecal monoclonal band, clinical details were available for 27. Of those, 9 were found on subsequent lumbar puncture to have developed an intrathecal oligoclonal response. Conclusions: Among those subjects who developed oligoclonal bands, there was a propensity for either a diagnosis of MS or clinically isolated syndromes due to demyelination. In the 18 subjects who either reverted to having normal CSF IEF or continued to exhibit only the monoclonal band, no cases of MS were encountered. Importantly, one of these had cerebral lymphoma.