Analysis of autoantibody spectrum and human herpesvirus 6 in adult patients with ‘early’ versus ‘late’ diagnosis of ‘possible limbic encephalitis’

•High prevalence of ‘neuronal’ or onconeuronal autoantibodies in adult patients with “early diagnosis” of possible limbic encephalitis.•Anti-LGI1 as most frequent autoantibody in the cohort with early diagnosis of limbic encephalitis.•Human herpesvirus type 6 (HHV-6) DNA was not present in patients’ CSF. New onset temporal seizures are increasingly encountered in adult patients. Many of those fulfill diagnostic criteria for possible or definite limbic encephalitis (LE). LE is associated with autoantibodies (autoABs) against neuronal surface structures (‘neuronal’ autoABs), ‘onconeuronal’ or GAD65. AutoABs can emerge in a paraneoplastic setting. However, by far not all patients with possible/definite LE have an oncological history. AutoABs have also found to arise in the context of viral encephalitis. Rare associations between autoAB-positive LE and human herpes virus 6 (HHV-6) infection have been as well reported. Our present analysis was dedicated to learn about potentially different autoAB spectra and HHV-6 detection rates in adult-onset temporal seizure patients with possible LE and largely different time spans between first seizure events and referral to a tertiary epileptological center due to pharmacoresistent seizures. We scrutinized serum/CSF samples obtained from adults with ‘early diagnosis’ of possible LE (≤ 30 months after first seizure event; n = 94) versus a patient group with ‘late diagnosis’ of possible LE (≥ 97 months; n = 45) for the presence of autoABs and HHV-6 DNA. AutoABs were detected in CSF and/or serum samples (n = 20) in 21.3 % of the early diagnosis patients with the highest abundance of anti-LGI1 (n = 8), significantly more frequent than in the late diagnosis group (autoAB positive: n = 4 (8.9 %); *p < 0.05, Fisher’s Exact Test). Quantitative PCR revealed viral HHV-6 DNA in only one serum sample of the early diagnosis cohort but no evidence in corresponding CSF samples or in any sample of the late diagnosis group. The present data demonstrate a higher incidence of distinct autoABs in adults with early diagnosis of possible LE. The distinct spectra of autoABs have to be taken into account in the differential diagnosis of possible LE patients with short versus more sustained duration of temporal seizure activity.