Clinical Significance and Distribution of Cerebrospinal Fluid Type IV Oligoclonal Band Pattern in Neurological Disorders: A Retrospective Analysis

Background and Objectives: To characterize the clinical features and cerebrospinal fluid (CSF) findings of patients exhibiting a type IV oligoclonal band (OCB) pattern, defined by the presence of identical IgG bands in both CSF and serum. Methods: This retrospective observational study included all consecutive adult patients with a type IV pattern detected during routine CSF analysis at Geneva University Hospitals in 2023. Demographic, clinical, and laboratory data were collected through chart review. Results: A total of 178 patients were included. The mean age was 60.2 years (SD 16.5), and 51.7% were female. The type IV pattern was most frequently observed in non-inflammatory neurological diseases (NIND) (n=103, 57.9%). Other inflammatory neurological diseases accounted for 37 cases (20.7%), multiple sclerosis was identified in 8 patients (4.5%), and peripheral nervous system disorders were present in 20 patients (11.2%). Systemic inflammatory comorbidities were observed in 40 patients (22.5%). An elevated albumin quotient was present in 73 patients (41%) and was most common among those with CNS infections, aseptic meningitis, CNS neoplastic diseases, and peripheral nervous system disorder. Repeated CSF analyses demonstrated temporal fluctuations in the type IV pattern in some patients, without corresponding changes in diagnosis. Discussion: The type IV pattern is predominantly associated with NIND and is relatively uncommon in multiple sclerosis. Although it may reflect systemic immune activation and/or blood brain barrier dysfunction in certain inflammatory conditions, its clinical significance remains nonspecific. These findings support cautious interpretation of the type IV pattern in routine clinical practice.