Commonly encountered central nervous system infections in the intensive care unit

Learning objectivesBy reading this article, you should be able to:•Recognise the common clinical features associated with CNS infections in intensive care.•Identify the organisms causing CNS infection in the community, in the immunocompromised patient or returning traveller, and in patients with healthcare-associated ventriculitis and meningitis.•Interpret the results of CSF analysis and neuroimaging appropriately.•Select the most appropriate antimicrobial agent and treatment duration based on the clinical features and results of investigations.Key points•CNS infections account for around 3.9% of infections in the ICU but are associated with significant morbidity and mortality.•Early recognition and initiation of treatment are key to the management of CNS infections and improving outcomes.•Urgent brain imaging should be performed in patients with clinical evidence of increased intracranial pressure before lumbar puncture, but this should not delay treatment with antibiotics, as a delay is associated with increased mortality.•Geographical location and immune status should be considered when determining the likely causative organism.•Autoimmune encephalitis should be considered in all patients presenting with suspected CNS infection, particularly when microbiological tests are negative. By reading this article, you should be able to:•Recognise the common clinical features associated with CNS infections in intensive care.•Identify the organisms causing CNS infection in the community, in the immunocompromised patient or returning traveller, and in patients with healthcare-associated ventriculitis and meningitis.•Interpret the results of CSF analysis and neuroimaging appropriately.•Select the most appropriate antimicrobial agent and treatment duration based on the clinical features and results of investigations. •CNS infections account for around 3.9% of infections in the ICU but are associated with significant morbidity and mortality.•Early recognition and initiation of treatment are key to the management of CNS infections and improving outcomes.•Urgent brain imaging should be performed in patients with clinical evidence of increased intracranial pressure before lumbar puncture, but this should not delay treatment with antibiotics, as a delay is associated with increased mortality.•Geographical location and immune status should be considered when determining the likely causative organism.•Autoimmune encephalitis should be considered in all patients presenting with suspected CNS infection, particularly when microbiological tests are negative. Central nervous system infections account for 3.9% of all infections in adult ICUs, at 3.9% of the total. They are associated with up to 29% mortality and often lead to persistent neurological deficits, including cognitive impairment in 32% of adults who survive meningitis.1Vincent J.L. Sakr Y. Singer M. et al.Prevalence and outcomes of infection among patients in intensive care units in 2017.J Am Med Assoc. 2020; 323: 1478-1487Crossref PubMed Scopus (317) Google Scholar,2Hoogman M. van de Beek D. Weisfelt M. de Gans J. Schmand B. Cognitive outcome in adults after bacterial meningitis.J Neurol Neurosurg Psychiatry. 2007; 78: 1092-1096Crossref PubMed Scopus (159) Google Scholar Diagnosis can be challenging, and timely management is of the utmost importance. Here, we present an overview of the most commonly encountered CNS infections, including meningitis and encephalitis. We aim to provide a framework to assist with diagnosis and management of such infections, often starting with empirical treatment. We also discuss specific subgroups of patients, including the returning traveller, immunocompromised patients, healthcare-associated ventriculitis and meningitis (HAVM), brain abscess and subdural empyema (SE), in addition to the possible alternative diagnoses when microbiology results are negative. CNS infections in children and neonates are beyond the scope of this article. Bacterial meningitis is defined as inflammation of the meninges, particularly the pia and arachnoid mater, associated with the invasion of bacteria into the subarachnoid space.3Hoffman O. Weber J.R. Review: pathophysiology and treatment of bacterial meningitis.Ther Adv Neurol Disord. 2009; 2: 401-412Crossref Scopus (119) Google Scholar It is thought that bacterial invasion into the CNS is preceded by high-grade bacteraemia, with invasion occurring at highly vascularised sites, such as the choroid plexus and leptomeningeal blood vessels. A further source of entry is direct access to the CNS in association with local infection, such as sinusitis, or via dural defects (which can be iatrogenic; traumatic, including after surgery or base of skull fracture; or spontaneous). Bacterial invasion results in endothelial activation and leucocyte infiltration. Whilst this limits bacterial invasion, it may also result in neuronal damage and adverse outcomes.3Hoffman O. Weber J.R. Review: pathophysiology and treatment of bacterial meningitis.Ther Adv Neurol Disord. 2009; 2: 401-412Crossref Scopus (119) Google Scholar The classical symptoms of meningitis are fever, headache, neck stiffness and altered mental status. Up to 95% of patients will present with two out of four of these symptoms.4van de Beek D. de Gans J. Spanjaard L. Weisfelt M. Reitsma J.B. Vermeulen M. Clinical features and prognostic factors in adults with bacterial meningitis.N Engl J Med. 2004; 351: 1849-1859Crossref PubMed Scopus (1181) Google Scholar Additional signs may include focal neurological deficits, such as cranial nerve palsies, aphasia, hemiparesis, seizures, coma and a rash most commonly associated with Neisseria meningitidis infection.4van de Beek D. de Gans J. Spanjaard L. Weisfelt M. Reitsma J.B. Vermeulen M. Clinical features and prognostic factors in adults with bacterial meningitis.N Engl J Med. 2004; 351: 1849-1859Crossref PubMed Scopus (1181) Google Scholar The global burden of disease attributable to meningitis remains high. Incidence depends on geographical location, ranging from 0.5 per 100,000 population in Australia to 207 per 100,000 in South Sudan.5Zunt J.R. Kassebaum N.J. Blake N. et al.Global, regional, and national burden of meningitis, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016.Lancet Neurol. 2018; 17: 1061-1082Abstract Full Text Full Text PDF PubMed Scopus (195) Google Scholar The overall mortality from community-acquired meningitis is around 20% and up to 30% for pneumococcal disease.6McGill F. Heyderman R.S. Michael B.D. et al.The UK joint on the diagnosis and management of meningitis and in Full Text Full Text PDF PubMed Scopus Google Scholar the and the of attributable to meningitis by and J.R. Kassebaum N.J. Blake N. et al.Global, regional, and national burden of meningitis, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016.Lancet Neurol. 2018; 17: 1061-1082Abstract Full Text Full Text PDF PubMed Scopus (195) Google Scholar the most common causative It after J.R. Kassebaum N.J. Blake N. et al.Global, regional, and national burden of meningitis, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016.Lancet Neurol. 2018; 17: 1061-1082Abstract Full Text Full Text PDF PubMed Scopus (195) Google B. van de Beek D. of on bacterial meningitis Full Text Full Text PDF PubMed Scopus Google Scholar It for of of meningitis, in association with such as or is for the of of meningitis in the of pneumococcal meningitis by the of the de Beek D. 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