Serum and cerebrospinal fluid brain damage markers neurofilament light and glial fibrillary acidic protein correlate with tick-borne encephalitis disease severity-a multicentre study on Lithuanian and Swedish patients.

BACKGROUND AND PURPOSE: Our aim was to examine the correlation between biomarkers of neuronal and glial cell damage and severity of disease in patients with tick-borne encephalitis. METHODS: One hundred and fifteen patients with tick-borne encephalitis diagnosed in Lithuania and Sweden were prospectively included, and cerebrospinal fluid (CSF) and serum samples were obtained shortly after hospitalization. Using pre-defined criteria, cases were classified as mild, moderate or severe tick-borne encephalitis. Additionally, the presence of spinal nerve paralysis (myelitis) and/or cranial nerve affection were noted. Concentrations of the brain cell biomarkers glial fibrillary acidic protein (GFAP), YKL-40, S100B, neurogranin, neurofilament light (NfL) and tau were analysed in CSF and, in addition, NfL, GFAP and S100B levels were measured in serum. The Jonckheere-Terpstra test was used for group comparisons of continuous variables and Spearman's partial correlation test was used to adjust for age. RESULTS: Cerebrospinal fluid and serum concentrations of GFAP and NfL correlated with disease severity, independent of age, and with the presence of nerve paralysis. The markers neurogranin, YKL-40, tau and S100B in CSF and S100B in serum were detected, but their concentrations did not correlate with disease severity. CONCLUSIONS: Neuronal cell damage and astroglial cell activation with increased NfL and GFAP in CSF and serum were associated with a more severe disease, independent of age. Increased GFAP and NfL concentrations in CSF and NfL in serum were also indicative of spinal and/or cranial nerve damage. NfL and GFAP are promising prognostic biomarkers in tick-borne encephalitis, and future studies should focus on determining the association between these biomarkers and long-term sequelae.

Long-term neurological and neurocognitive impairments after tick-borne encephalitis in Lithuania - a prospective study.

BACKGROUND: The aim of this study was to characterise long-term neurological and neurocognitive sequelae after tick-borne encephalitis (TBE) in adults. METHODS: 98 prospective consecutive TBE patients, classified by disease severity, were included. Immediate outcomes were evaluated with Glasgow Outcome Scale (GOS) and Rankin Scale (RS). After 6 and 18 months, long-term disability was evaluated using Modified Rankin Scale (MRS) and neurocognitive assessment was performed with Matrics Consensus Cognitive Battery (MCCB), measuring processing speed, attention/vigilance, working memory, verbal learning, visual learning, reasoning/problem solving and social cognition. The MCCB results were compared to healthy age, gender and education-matched controls. RESULTS: Mild, moderate, and severe TBE was diagnosed in 53.1%, 38.8%, and 8.2% of cases, respectively. At discharge, 25.5% of the patients had major or moderate impairments (GOS) and various levels of disability in 34.7% (RS). Up to 18 months from the onset of TBE, over 20% remained with slight to moderate disability (MRS). GOS, RS and MRS scores correlated with disease severity. At 6 months after the onset, TBE patients scored significantly lower than controls in processing speed, verbal, and visual learning. Two latter domains were significantly more impaired in patients with mild TBE. Patients aged 18-39 performed significantly worse in attention/vigilance and working memory, whereas aged 60+ in verbal learning. A year later, significant improvement was observed in six of seven cognitive domains. CONCLUSIONS: Long-term neurological sequelae persist in a substantial proportion of TBE patients with significant impairment in several cognitive domains, especially in younger patients and even after mild TBE.