Bacterial meningitis
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Bacterial meningitis
Definition
- Bacterial infection of meninges
Etiology
- Adults
- Streptococcus pneumoniae
- Neisseria meningitidis
- Listeria monocytogenes in immunocompromised, elderly, alcoholics, adn diabetes
- Haemophilus influenzae
- Infants:
- Group B Streptococcus
- Escherichia coli
- Haemophilus influenza
- Listeria monocytogenes
- Head trauma or neurosurgery
- Staphylococcus aureus
- Gram-negatives
Risk factors
- Immunosuppression
- Diabetes
- Splenic dysfunction or splenectomy (e.g. sickle cell)
- Alcoholism
- Recent neurosurgery
- CSF leak
- Shunt infections
- Head trauma
- Chronic otitis media
Presentation
- Typically, an acute onset of headache with fever and vomiting after viral prodrome
- Bacterial vs. aseptic/viral meningitis
- Headache or neck pain (70-80%)
- Fever (75%)
- Altered level of consciousness (70%)
- Clinical signs
- Brudzinski's sign (unhelpful)
- Kernig's sign (may be specific)
- Jolt test (very sensitive)
- Seizures or focal neurological deficits (rare, poor prognosis)
- Rash (purpuric with Neisseria)
- Ask about recent travel and sick contacts
Investigations
- Lab
- CBC with differential
- Electrolytes
- Liver enzymes
- Blood cultures
- Imaging
- CT head to rule out abscess or increased ICP
- MRI head if suspicion for herpes encephalitis
- Temporal lobe enhancement (usually unilateral)
- Other
- Lumbar puncture after CT head
CSF Interpretation
- Gram stain positive
- Glucose <1.0
- CSF:blood glucose <0.23
- Protein >2.2
- WBC >2000
- PMNs >1180
Management
- Blood cultures before antibiotics
- Start empiric antibiotics and dexamethasone
- Infants
- Children
- Adults
- Ceftriaxone 2g bid
- vancomycin 1g q12h
- +/- ampicillin 2g 14h if >50
- Dexamethasone 10mg q6h x72h
- +/- acyclovir
- >65 years old
- Treat like immunocompromised
- CT head if reduced or altered level of consciousness
- Lumbar puncture
- Adjust antibiotics based on Gram stain and cultures
Complications
- Cerebral edema with raised ICP
- Hydrocephalus
- Seizures
- Arterial ischemia or infarction
- SIADH
- Subdural effusion or subdural empyema
- Venous sinus thrombosis
- Cranial nerve palsies, especially deafness
References
- a b c Michael C. Thigpen, Cynthia G. Whitney, Nancy E. Messonnier, Elizabeth R. Zell, Ruth Lynfield, James L. Hadler, Lee H. Harrison, Monica M. Farley, Arthur Reingold, Nancy M. Bennett, Allen S. Craig, William Schaffner, Ann Thomas, Melissa M. Lewis, Elaine Scallan, Anne Schuchat. Bacterial Meningitis in the United States, 1998–2007. New England Journal of Medicine. 2011;364(21):2016-2025. doi:10.1056/nejmoa1005384.
