Acute central nervous system infections in adults-a retrospective cohort study in the NHS North West Region

Background: Over the last 15 years, bacterial meningitis has received considerable attention, including national guidelines, whilst viral central nervous system (CNS) infections have been relatively neglected. A recent pilot study suggested that management of patients with suspected viral encephalitis was often suboptimal.

Aim: To examine the relative incidence, clinical features and management of suspected acute CNS infections in adults across the NHS North West Region.

Design: A multicentre cross-sectional retrospective cohort study at 10 hospitals across the region over 3 months (from September to December 2007). Following a screen of all patients who had cerebrospinal fluid (CSF) analysis or received intravenous aciclovir and/or third-generation cephalosporin, those with clinical features suspicious of a CNS infection were included. Management was compared with the national meningitis and regional encephalitis guidelines.

Results: Three hundred and eighty-five patients were screened; 217 patients had a suspected CNS infection and 44 (20%) had a CNS infection: 18 aseptic meningitis (one herpes simplex virus [HSV]-2), 13 purulent meningitis (four Streptococcus pneumoniae) and 13 encephalitis (three HSV-1). The median (range) time from admission to suspicion of CNS infection and to LP was longer for patients with encephalitis than meningitis [4 (0.3–312) vs. 0.3 (0.1–12) h, P < 0.001, and 23 (4–360) vs. 12 (2–48) h, P = 0.042, respectively]; and the median time to treatment was longer for aciclovir than cephalosporin [7 (0.5–312) vs. 3 (0.3–312) h, P = 0.002].

Discussion: Encephalitis was as common as purulent meningitis, and HSV as common as Streptococcus