Neuro ICU > CNS Infections

CNS Infections (Meningitis & Encephalitis)

Central nervous system (CNS) infections — including meningitis, encephalitis, and brain abscess — are life-threatening conditions requiring ICU-level care. They are characterized by infection and inflammation of the brain, spinal cord, and/or surrounding membranes, resulting in a range of neurological, cognitive, and functional impairments.

Meningitis refers to inflammation of the meninges (the membranes surrounding the brain and spinal cord). Encephalitis refers to inflammation of the brain parenchyma itself. These conditions can occur independently or together (meningoencephalitis).

Types of Infection

  • Most common causative organisms: Streptococcus pneumoniae, Neisseria meningitidis, Listeria monocytogenes (elderly/immunocompromised), and Group B Streptococcus (neonates).

    • Onset: rapid — hours to 1–2 days

    • Classic triad: fever, severe headache, neck stiffness (meningismus). Present in only ~44% of cases — absence does not rule out diagnosis.

    • Additional symptoms: photophobia, phonophobia, altered consciousness, nausea/vomiting, seizures, focal neurological deficits

    • Petechial/purpuric rash: suggests meningococcal meningitis — medical emergency

    • Mortality: 20–30% despite treatment; significant morbidity in survivors

    • Treatment: empiric IV antibiotics (ceftriaxone ± ampicillin) + dexamethasone started immediately, before or concurrent with LP; do not delay antibiotics for imaging

    • Isolation: droplet precautions until 24 hours of effective antibiotic therapy

  • Most commonly caused by enteroviruses. Generally self-limiting and less severe than bacterial meningitis. Rarely requires ICU admission except in immunocompromised patients or when encephalitis is concurrent.

    • Symptoms: similar to bacterial but typically less severe; fever, headache, neck stiffness, photophobia

    • Treatment: supportive; no specific antiviral therapy for most enteroviruses. Acyclovir if HSV is suspected.

  • Inflammation of the brain parenchyma — most commonly caused by Herpes Simplex Virus (HSV-1), which is the most common cause of sporadic fatal encephalitis.

    • Symptoms: fever, altered consciousness, behavioral and personality changes, seizures, focal neurological deficits (aphasia, hemiparesis), memory impairment

    • Temporal lobe involvement is characteristic of HSV encephalitis — memory impairment and aphasia are prominent features

    • Treatment: IV acyclovir — must be started immediately if HSV encephalitis is suspected, before confirmation

    • Prognosis: mortality ~5–15% with treatment; significant cognitive and behavioral sequelae are common in survivors

  • Increasingly recognized cause of encephalitis — the immune system attacks proteins in the brain rather than an infectious agent. Most common: Anti-NMDA receptor encephalitis.

    • Symptoms: psychiatric symptoms (anxiety, psychosis, behavioral changes), seizures, movement disorders, autonomic instability, decreased consciousness

    • Key feature: often presents with prominent psychiatric symptoms before neurological signs — may initially be admitted to psychiatry

    • Treatment: immunotherapy (steroids, IVIG, plasmapheresis); removal of underlying tumor if present (thymoma, ovarian teratoma)

    • Prognosis: good with early treatment — most patients improve significantly, though recovery can take months

  • A focal collection of pus within the brain parenchyma, typically from direct spread (sinusitis, otitis media, dental infection), hematogenous spread, or trauma/neurosurgery.

    • Symptoms: headache (most common), fever, focal neurological deficits depending on location, seizures, altered consciousness. Classic triad present in only ~20% of cases.

    • Treatment: IV antibiotics + surgical drainage (aspiration or excision) for most abscesses >2.5 cm; smaller abscesses may be managed with antibiotics alone

    • Therapy implications: focal deficits depend on abscess location — motor, cognitive, language, and visual deficits all possible

Diagnosis

  • Lumbar puncture (LP) with CSF analysis: gold standard. CSF profile differentiates bacterial (low glucose, high protein, high WBC with neutrophils), viral (normal glucose, mildly elevated protein, lymphocytes), and autoimmune encephalitis

  • MRI brain: preferred over CT; identifies parenchymal changes, temporal lobe involvement (HSV), abscesses, and cerebral edema

  • EEG: evaluates for subclinical seizure activity — common in encephalitis

  • Blood cultures before antibiotic administration

  • Autoimmune panel (CSF and serum): anti-NMDA, anti-LGI1, anti-CASPR2, and others if autoimmune encephalitis is suspected

Isolation Precautions — Know Before You Enter

  • Bacterial meningitis (N. meningitidis): Droplet precautions until 24 hours of effective antibiotic therapy — surgical mask required within 3 feet of patient
  • Bacterial meningitis (other organisms): Standard precautions only — not transmitted person-to-person
  • Viral meningitis/encephalitis: Standard precautions; contact precautions if enteroviral (fecal-oral transmission)
  • Autoimmune encephalitis / brain abscess: Standard precautions
  • Always: Check the patient's room signage and confirm precaution status with nursing before entering

Therapy Implications

  • Isolation precautions affect session setup — confirm precaution type before entry, don appropriate PPE, and plan equipment needed for the session before entering the room to minimize trips in and out.

  • Cognitive and behavioral changes are prominent in encephalitis — especially HSV and autoimmune subtypes. Memory impairment, confusion, personality changes, and psychosis can all be present. Assess cognition before assuming therapy can proceed as planned.

  • Seizure risk is high — many CNS infection patients are on AEDs and/or continuous EEG monitoring. Review seizure precaution status and EEG findings before each session. See the Status Epilepticus page for activity guidance during seizure recovery.

  • Hearing loss is a common complication of bacterial meningitis — refer to audiology and SLP early. Communication adaptations may be needed during therapy sessions.

  • Fatigue is marked — CNS infection and its treatment are physiologically demanding. Keep sessions short; monitor for fatigue-related decline in participation quality.

  • For autoimmune encephalitis, recovery can be prolonged and non-linear. Patients may appear to plateau and then improve weeks later — frame goals and family expectations accordingly.

  • For brain abscess, focal deficits parallel the location — treat similarly to stroke, with ADL, cognition, motor, and communication goals based on neurological presentation.

Activity Decision Framework — CNS Infections

Activity parameters depend on infection control status, fever, neurological stability, and seizure control. Always confirm isolation precautions and activity orders before initiating therapy.

Tier Clinical Status Guidance
GO Hemodynamically stable; afebrile or fever controlled; seizures controlled; neurologically stable; isolation precautions confirmed and PPE donned Proceed per activity orders; assess cognition at start of session; adapt session to neurological presentation
MODIFY Febrile but stable; significant fatigue or cognitive impairment limiting participation; high medication burden (AEDs, sedatives) affecting alertness Shorten session; reduce cognitive and physical demands; focus on highest-priority functional goals; reassess tolerance throughout
YIELD Isolation precaution status unknown; seizure control uncertain; activity order not yet placed; significant behavioral agitation Confirm precautions with nursing; review seizure status; obtain activity order; assess safety for session before proceeding
DEFER Acute phase of bacterial meningitis (first 24–48 hrs of antibiotics); high fever with hemodynamic instability; active SE; significantly elevated ICP Hold active therapy; passive positioning appropriate if cleared; reassess as infection is treated and patient stabilizes
STOP Seizure during session; acute neurological deterioration; patient becomes acutely unresponsive Stop immediately; protect patient; call for help; do not leave patient alone; notify team and document

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References

Hamby, J. R. (2024). The nervous system, part 2: Neurodegenerative diseases and other conditions. In H. Smith-Gabai & S. E. Holm (Eds.), Occupational Therapy in Acute Care (3rd ed., pp. 449–496). AOTA Press.

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Venkatesan, A., Tunkel, A. R., Bloch, K. C., Lauring, A. S., Sejvar, J., Bitnun, A., Glaser, C. A., Mailles, A., Rupprecht, C., Yoder, J. A., Bloch, E. M., Briese, T., Fowler, R. A., Lo, T. Q., Bleecker, M., Cohen, B. A., Day, G. S., Fung, C., … International Encephalitis Consortium. (2013). Case definitions, diagnostic algorithms, and priorities in encephalitis. Clinical Infectious Diseases, 57(8), 1114–1128. https://doi.org/10.1093/cid/cit458