The clinical significance of mirror patterns of cerebrospinal fluid oligoclonal immunoglobulin G bands (IgG-OCBs) in peripheral neuropathy disorders.

Background: CSF (cerebrospinal fluid) oligoclonal immunoglobulin G bands (IgG-OCBs) analysis plays a crucial role in diagnosis of various neurological disorders. However, the clinical significance of mirror pattern bands remains unclear, and their precise application is not well understood.

Methods: We retrospectively reviewed a total of 7597 IgG-OCB records detected using isoelectric focusing from May 2020 and August 2023 at Huashan Hospital. Among these, 121 mirror pattern bands (62 type IV and 59 type V) were identified in patients with neurological disorders. Basic clinical data, including discharge diagnosis, gender, and age, were collected. Additionally, CSF and serum immunological parameters, as well as monoclonal protein (M protein) detection, were reviewed.

Results: Although mirror pattern bands are rarely observed in neurological diseases, approximately half of these patterns were found in patients with peripheral neuropathy (PN). In the type IV group, 40.74 % of cases were associated with immune-mediated PN, while type V pattern was predominantly observed in cancer-related/lymphoproliferative PN, comprising 63.33 % of the cases. Patients with cancer-related or lymphoproliferative PN showed significantly higher IgG-CSF concentrations (p = 0.017) and 24-h intrathecal IgG synthesis rate (p = 0.022), indicating a stronger humoral immune response. Additionally, both patients with immune-mediated PN and cancer-related/lymphoproliferative PN exhibited abnormal intrathecal synthesis rate and moderate to severe blood-brain barrier impairment. Furthermore, the type V group also exhibited a high prevalence of M protein positivity.

Conclusions: The differential immunological responses and distinct patterns of OCBs observed in our study underscore the critical role of OCB analysis in the diagnostic workup of PN.