Lyme neuroborreliosis with encephalitis; a systematic literature review and a Scandinavian cohort study

Background: Lyme neuroborreliosis (LNB) presenting with encephalitis is rare and scarcely described. Objectives: To describe the available literature on LNB encephalitis and to characterize this patient group through a Scandinavian retrospective cohort study. Data sources: Medline, Embase, Scopus, Cochrane library. Study eligibility criteria: There was no discrimination on study type, time of publication or language. Participants: Review: All articles with definite LNB and confirmed/possible encephalitis. Cohort: LNB cohorts from Denmark, Sweden and Norway 1990–2019 were screened for patients with encephalitis. Methods: Review: Adhering to PRISMA guidelines; two authors extracted reviews and assessed quality of studies. Cohort: Data on demography, symptoms, cerebrospinal fluid findings, differential diagnostic examinations, treatment, residual symptoms, 1-year mortality were registered. Results: Review: 2330 articles screened on title/abstract, 281 full texts, yielding 42 articles (case reports/series or cohort studies), including 45 patients from 18 countries spanning 35 years. Altered mental status ranged from personality changes and confusion to unconsciousness. Common focal symptoms were hemiparesis, ataxia and dysarthria; seven patients had seizures. Median time from symptom onset to hospital was 2 weeks (IQR 2–90 days). Of 38 patients with available follow-up after median 12 months (IQR 5–13), 32 had fully or partially recovered, two had died. Cohort: Thirty-five patients (median age 67 years, IQR 48–76) were included. The encephalitis prevalence was 3.3% (95% CI 2.2–4.4%) among 1019 screened LNB patients. Frequent encephalitis symptoms were confusion, personality changes, aphasia, ataxia. EEGs and neuroimaging showed encephalitis in 93.8% and 20.6%, respectively. Median delay from symptom onset to hospital was 14 days (IQR 7–34), with further 7 days (IQR 3–34) delay until targeted therapy. At follow-up (median 298 days post-treatment; IQR 113–389), 65.6% had residual symptoms. None had died. Conclusions: This study shows that encephalitis is an uncommon, but likely overlooked clinical manifestation of LNB. As the high frequency of residual symptoms may be related to prolonged treatment delay, prompt LNB testing of patients with encephalitis in Borrelia burgdorferi-endemic areas should be considered.