Relapsing Seronegative Limbic Encephalitis During Pregnancy: A Rare Case with Bilateral Hippocampal Atrophy and Favorable Maternal-Fetal Outcome

We report a rare case of a 24-year-old primigravida who developed relapsing seronegative autoimmune limbic encephalitis (LE) during pregnancy. The initial episode occurred at 24 weeks of gestation, presenting with altered consciousness and a generalized tonic-clonic seizure, following a herpes labialis outbreak. Brain MRI revealed bilateral mesial temporal hyperintensities. Extensive workup, including cerebrospinal fluid analysis, HSV PCR, and autoimmune antibody panel (anti-NMDAR, LGI1, GABA-B, AMPAR, GAD65), was negative. The patient responded well to intravenous immunoglobulin (IVIG). However, she experienced a relapse near term, requiring emergency cesarean section. Postpartum MRI showed bilateral hippocampal atrophy. Despite seizure control, persistent cognitive symptoms remained. This case underscores the diagnostic complexity of seronegative LE in pregnancy and highlights that IVIG can be a safe and effective treatment option, even in the absence of confirmatory biomarkers. Our case also adds to the scarce literature on cognitive sequelae and long-term management in such scenarios.