Origin and significance of leucine-rich glioma-inactivated 1 antibodies in cerebrospinal fluid.

BACKGROUND

Whether antibodies against leucine-rich glioma-inactivated 1 (LGI1-Abs) in cerebrospinal fluid (CSF) are partially transferred from serum and the impact of CSF-LGI1-Ab positivity on clinical features and prognosis are unclear. Therefore, we aim to investigate the differences in serum titers, clinical features, and outcomes between LGI1-Ab CSF-positive and LGI1-Ab CSF-negative patients.

METHODS

Retrospective analysis of serum titers and clinical features according to CSF LGI1-Ab status. In addition, univariate and multivariate logistic regression were performed to identify predictors of worse outcomes.

RESULTS

A total of 60 patients with anti-LGI1 encephalitis and positive serum LGI1-Abs were identified, of whom 8 (13.3%) patients were excluded due to the absence of CSF LGI1-Ab testing. Among the remaining 52 patients, 33 (63.5%) were positive for LGI1-Abs in CSF. CSF-positive patients were more likely to have high serum titers (≥ 1:100) than CSF-negative patients (p = 0.003), and Spearman's correlation analysis showed a positive correlation between CSF and serum titers in CSF-positive patients (r = 0.405, p = 0.019). Psychiatric symptoms and hyponatremia were more frequent in CSF-positive patients (p < 0.05). Both univariate and multivariate logistic regression analyses showed that CSF LGI1-Ab positivity and delayed immunotherapy are independent risk factors for incomplete recovery (modified Rankin Scale (mRS) > 0 at last follow-up).

CONCLUSIONS

LGI1-Ab CSF-positive patients have higher serum titers, and their CSF titers are positively correlated with serum titers, indicating a possible peripheral origin of CSF LGI1-Abs. CSF-positive patients more often present with psychiatric symptoms, hyponatremia, and worse outcomes, suggesting more severe neuronal damage.