EM@3AM: Bacterial Meningitis

Author: Mounir Contreras Cejin, MD (EM Resident Physician, UTSW – Dallas, TX); Zachary Aust, MD (Assistant Professor of EM/Attending Physician, UTSW – Dallas, TX) // Reviewed by Sophia Görgens, MD (EM Resident Physician, Zucker-Northwell NS/LIJ, NY); Cassandra Mackey, MD (Assistant Professor of Emergency Medicine, UMass Chan Medical School); Alex Koyfman, MD (@EMHighAK); Brit Long, MD (@long_brit)

Welcome to EM@3AM, an emDOCs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.

Epidemiology

• Community acquired acute bacterial meningitis is most commonly caused by S. pneumoniae and N. meningitidis.^{1, 2}
• Listeria monocytogenes is most commonly seen in infants under 3 months, adults over the age of 50, pregnant as well as immunocompromised patients.^1-3
• Healthcare-associated acute bacterial meningitis is caused by staphylococci and aerobic gram-negative bacilli, it usually follows a neurosurgical procedure or head trauma.⁴
• Bacterial meningitis continues to carry a high mortality rate between 10-30% with approximately 10% of survivors having neurologic deficit.³
• Table 1 highlights the most common organisms in each age group.^1-3

Table 1.

Pathophysiology

• Bacterial meningitis is an infection of the arachnoid space that causes inflammation of the leptomeninges.²
• It usually starts with nasopharyngeal colonization followed by mucosal invasion.²
• Upon crossing the blood-brain barrier, bacterial proliferation ensues as the CSF contains low levels of complement and immunoglobulins.²
• Recruitment of leukocytes to the area and subsequent release of cytokines causes an inflammatory process that compromises the permeability of the blood-brain barrier resulting in edema and increase intracranial pressure.²

History and Exam

• Emergency physicians must consider meningitis in a variety of patients, as it may present as mild as a slight headache and fever or as severe as coma and shock.²
• Acute bacterial meningitis should be considered in anyone with fevers, nuchal rigidity, altered mental status or headache but it has been estimated that the classic triad is seen in less than 50% of adult patients.^1-3
• 99%-100% of patients will present with headache plus at least one symptom from the classic triad.
  • Fever being present in 79-95% (most sensitive).³
  • Nuchal rigidity in 83% to 94% (can persist for more than 1 week after treatment and resolution of infection).³
  • Altered mental status (typically confusion or lethargy) in 78% to 83% of patients.³
• Kernig and Brudzinski signs have poor sensitivity.^{3, 5}
• Jolt accentuation has more reliability in meningitis than Kerning and Brudzinski, but it should not be used to rule out meningitis due to varying sensitivities.
  • Exacerbation of a headache with horizontal rotation of the neck at a frequency of 2-3 per second.⁶
  • Studies have shown that all three maneuvers have limited diagnostic value and should not be used to rule out meningitis.^{3, 5}
• Other presenting features include:
  • Focal neurological deficits in 10% to 35% of patient with Listeria monocytogenes.³
  • Seizure in 15% to 30%.³
  • Palpable purpura with septic arthritis in those with Neisseria meningitidis.^1-3
  • Nausea and vomiting.³
  • Papilledema and photophobia have been reported in the literature.³
  • Typical signs and symptoms may be subtle in geriatric and immunocompromised patients.²

ED Evaluation

Labs

• CBC with differential
  • Cell counts may be normal or depressed in the elderly and immunocompromised¹
• Serum electrolytes
• Two sets of blood cultures (even if antibiotics have already been started)^{1, 2}
• Lactate
• CSF analysis via lumbar puncture is essential to make a definitive diagnosis, but there are some considerations before performing the procedure (see section on imaging).^1-3

Imaging

• Imaging can be in the form of a CT scan or an MRI.²
• The goal is to identify those at risk of brain herniation during a lumbar puncture.⁷
• Up to 30% of patients with bacterial meningitis will herniate even without an LP.²
• Risk of herniation is more likely related to the severity of disease.²
• The Infectious Disease Society of America has guidelines recommending when a CT head should precede a lumbar puncture.^{3, 7, 8}
  • Altered level of consciousness
  • Altered mental status
  • Focal neurologic deficit
  • Immunocompromised state
  • History of CNS disease
  • New onset seizure (less than 1 week prior to presentation)
  • Papilledema
  • History of head trauma.
• CT should generally be obtained prior to LP when the exam is concerning for a focal neurologic deficit, cerebral mass lesion, impending herniation, ongoing seizure, or increased intracranial pressure (e.g., papilledema).
• More than 50% of neuroimaging studies in acute meningitis reveal no specific abnormalities and thus neuroimaging should not delay LP or antibiotic therapy.²

CSF analysis

• CSF opening pressures obtained in the lateral recumbent position of adult patients are considered normal when the range is between 5 to 20 cm H₂^{2, 6}
• Labs: cell count and differential, protein, glucose, Gram’s stain and bacterial culture.¹
• CSF of immunocompromised patients – consider adding PCR for HSV or other viral pathogens, antigen testing (bacterial or Cryptococcal) and fungal testing and cultures.^{1, 2}
• CSF lactate is promising for diagnosis.
• Any elevation of WBC in the CSF is diagnostic for meningitis, but one must determine whether the cause is bacterial, viral, fungal, or due to other etiology.¹

Treatment

• Administration of antimicrobial therapy should be started promptly and should not be delayed if an LP cannot be obtained in a timely manner.
• In patients who require a CT head, empiric antimicrobials should be started prior to CT to avoid delays in therapy.⁹
• Empiric IV antibiotics given 2 hours (or less) before an LP will not affect the CSF analysis.⁶

Antibiotic therapy

• Empiric therapy should be based on patient risk factors and age.⁹

• In patients with severe beta-lactam allergies (eg, anaphylaxis, SJS/TEN, DRESS) with normal renal function consider:

• In immunocompromised patients, aztreonam should be added for pseudomonas coverage as long as the patient is not allergic to aztreonam itself or IgE-mediated allergy to ceftazidime as aztreonam and ceftazidime share an R1 group.⁹
• Empiric therapy for healthcare-associated meningitis must cover for both gram-positive and gram-negative organism and includes:

• In patients with severe beta-lactam allergies (e.g., anaphylaxis, SJS/TEN, DRESS) and for whom meropenem is contraindicated, consider aztreonam (2 g IV every 6 to 8 hours) or ciprofloxacin (400 mg IV every 8 to 12 hours).⁹

Steroids

• Decrease the inflammatory response and may be effective in decreasing cerebral edema, reducing the risk of hearing loss and neurologic sequelae.¹
• Steroids should be started before or along with the first dose of antibiotics; administration after antibiotics may result in harm.^{1, 3, 10, 11}
• The Infectious Disease Society of America includes dexamethasone in its algorithm for adults.⁶
  • Dexamethasone (0.15 mg/kg) in adults with suspected or proven pneumococcal meningitis.⁶

Increased ICP

• Consider increased ICP in those with confusion, isolated cranial nerve palsy with severe symptoms such as obtundation, a nonreactive pupil, and bradycardia with hypertension.
• US of the optic nerve can be helpful.
• Provide analgesia, raise head of the bed, and administer hypertonic to lower ICP.
• Increase the MAP to ensure cerebral perfusion pressure.

Close-contact prophylaxis

• Close contacts (same household members, daycare, or those in direct contact with the patient’s oral secretions) of those diagnosed with meningitis due to meningitidis should be treated with rifampin or a fluoroquinolone.^{2, 3}

Disposition

• Admit for IV antibiotics.
• Patients with severe disease will likely require an admission to the ICU.
• Droplet precautions are required if there is any suspicion of meningococcal meningitis.^1-3

Pearls and Pitfalls

• The classic triad of fever, nuchal rigidity and altered mental status is seen in less than 50% of adult cases of bacterial meningitis.
• Do not rely on Kernig or Brudzinski signs, as these have poor sensitivity.
• Use broad spectrum antibiotics while performing your evaluation.
• Delaying antibiotic therapy until the LP is completed is the most common error in ED management of meningitis. IV antibiotics given 2 hours or less before the LP will not affect the CSF results.
• Steroids should only be given before or accompanied with the first dose of antibiotics; giving them after may result in harm.
• Provide chemoprophylaxis to close contacts of those diagnosed with meningococcemia.

• Meningitis: Why do we miss it?
• Sick Meningitis Patient
• Meningitis Pearls and Pitfalls

References:

1. Fitch, Michael T. “Meningitis & Encephalitis.” Edited by Al’ai Alvarez. Society for Academic Emergency Medicine.https://www.saem.org/about-saem/academies-interest-groups-affiliates2/cdem/for-students/online-education/m4-curriculum/group-m4-neurology/meningitis-encephalitis. Last updated 2019. Accessed August 15, 2022.
2. Walls, Ron M., et al. “Central Nervous System Infections.” Rosen’s Emergency Medicine Concepts and Clinical Practice, 9th ed., vol. 1, Elsevier, Philadelphia, PA, 2018, pp. 1328–1340.
3. Toy, Eugene C., et al. “Infectious: Bacterial Meningitis.” Case Files: Emergency Medicine, 4e., McGraw-Hill Education, New York, NY, 2017. UT Southwestern Medical Center Library, Accessed 15 Aug. 2022.
4. Hasbun R., Tunkel Allen, Mitty Jennifer. Clinical features and diagnosis of acute bacterial meningitis in adults. 2022. UpToDate. Accessed August 15, 2022 from: https://www.uptodate.com/contents/clinical-features-and-diagnosis-of-acute-bacterial-meningitis-in-adults/print
5. Sato R, Kuriyama A, Luthe SK. Can We Rule Out Meningitis from Negative Jolt Accentuation? A Retrospective Cohort Study [published correction appears in Headache. 2018 Apr;58(4):631]. Headache. 2017;57(4):586-592. doi:10.1111/head.13022
6. Markovchick Vincent J., Pons, Peter T., Bakes, Katherine M. Emergency Medicine Secrets. Elsevier, St. Louis, MO, 2011, pp. 163-168.
7. Hasbun R, Abrahams J, Jekel J, Quagliarello VJ. Computed tomography of the head before lumbar puncture in adults with suspected meningitis. N Engl J Med. 2001; 345(24):1727-1733. doi:10.1056/NEJMoa010399
8. Lucrecia Salazar, Rodrigo Hasbun. Cranial Imaging Before Lumbar Puncture in Adults with Community-Acquired Meningitis: Clinical Utility and Adherence to the Infectious Diseases Society of America Guidelines. Clinical Infectious Diseases. 2017. Volume 64 (Issue 12): Pages 1657–1662, https://doi.org/10.1093/cid/cix240. Accessed August 15, 2022.
9. Hasbun R., Tunkel Allen, Mitty Jennifer. Initial therapy and prognosis of bacterial meningitis in adults. 2021. UpToDate. Accessed August 15, 2022 from: https://www.uptodate.com/contents/initial-therapy-and-prognosis-of-bacterial-meningitis-in-adults/print
10. van de Beek D, Brouwer MC, Thwaites GE, Tunkel AR. Advances in treatment of bacterial meningitis. Lancet. 2012;380(9854):1693-1702. doi:10.1016/S0140-6736(12)61186-6
11. Chaudhuri A. Adjunctive dexamethasone treatment in acute bacterial meningitis. Lancet Neurol. 2004;3(1):54-62. doi:10.1016/s1474-4422(03)00623-9