Central Nervous System Infection
Michael Kaminski
Meningitis
Etiology
- Bacteria:
- Community: pneumococcus, meningococcus, H flu, GBS, Listeria
- Nosocomial: more GNRs; Unusual: Syphilis, Lyme, Leptospira, TB
- Viral: enteroviruses, HSV 1/2, VZV
- Fungal: crypto, histo, blasto, cocci
- Non-infectious: autoimmune (GPA, SLE, Sjogrens, CNS sarcoid), neoplastic (lymphoma, leukemia), drugs (NSAIDs, IVIg, ICIs)
Hx and Exam
- Fever, hypothermia, AMS, seizures, HA, meningismus, CN deficits
Evaluation
- BCxs, head CT (technically only if FNDs, AMS, papilledema, seizures, immunocompromised, hx of CNS structural disease [tumors, shunts]), LP
- LP studies: opening pressure, cell count/diff, glucose, protein, bacterial and fungal Cx, Biofire Meningoencephalitis Panel. Send an extra tube to be frozen for future tests (Order ‘Miscellaneous test’ and for test name put “Please freeze CSF in virology;” reference lab: VUMC, specimen type: CSF)
- Consider: Serum HIV, Crypto Ag; CSF: VDRL, Crypto Ag, fungal and AFB cultures, MTB PCR, WNV Ab, Histoplasma Ag
Management
- Empirically start: CTX 2g IV q12h + Vancomycin
- Cefepime 2g IV q8h instead of CTX if immunocompromised or nosocomial
- +ampicillin 2g IV q4h if c/f Listeria (immunocompromised, pregnant, age>50)
- +acyclovir 10 mg/kg IV q8h if c/f HSV or VZV meningitis/encephalitis
- +doxycycline 100mg BID if c/f tick-borne
- If c/f pneumococcus: dexamethasone 0.15 mg/kg q6h 20 minutes before abx
- ID consult for adjustments, duration
Encephalitis
Etiology & Pathogenesis
- Viral: (HSV1/2, VZV, enteroviruses, arboviruses [WNV, EEE, SLE, Powassan], Measles, Mumps, HIV, Rabies), Postinfectious: (ADEM)
Clinical Presentation
- AMS, behavioral changes, seizures, FNDs, +/- meningisumus
- HSV: Temporal lobe; VZV: dermatomal vesicles; WNV: flaccid paralysis + rash; Rabies: hydrophobia
Diagnostics & Workup
- MRI brain (HSV: temporal lobe; Arbovirus: thalamic/BG)
- LP: opening pressure, lymphocytic pleocytosis (<250 WBC), protein <150, normal glucose; Meningoencephalitis PCR panel, WNV serology
- EEG
Brain Abscess
Etiology & Pathogenesis
- Direct spread (25–50%): dental infection, frontal/ethmoid sinusitis (→ frontal lobe), otitis media/mastoiditis (→ temporal lobe/cerebellum)
- Oral/sinus/otogenic: Strep (especially S. anginosus group), anaerobes, Haemophilus
- Post-neurosurgery/trauma: S. aureus, CoNS, Enterobacterales, PsA
- Hematogenous spread (20–35%): Multiple abscesses at grey-white junction; endocarditis, cyanotic CHD, pulmonary AVMs, lung abscess
- Strep, S. aureus. Immunocompromised: Toxo, Nocardia, Aspergillus+Mucorales, Listeria
- Unknown (10–35%)
Clinical Presentation
- Headache, Fever, FNDs, Seizures, AMS, neck stiffness, papilledema
Diagnostics & Workup
- MRI with contrast (Ring-enhancing; DWI hyperintense)
- Blood cultures before abx; Toxo IgG, anticystericercal Abs if appropriate host/exposures + consistent imaging
- LP: Generally contraindicated due to herniation risk
Management
- Consult NSGY for needle aspiration (Gram stain, aerobic/anaerobic/fungal/AFB Cxs, histopath)
- Empiric Abx per source: Hematogenous spread (CTX+metro), Oral/sinus/otogenic extension (CTX+metro), Post NSGY (Vanc+Cefe), Penetrating trauma (Vanc+CTX). Duration: 6–8W IV
- Adjuncts: Dexamethasone for significant mass effect, AEDs if seizure
Epidural Abscess
Etiology
- Hematologic spread (endocarditis, bacteremia) vs direct extension (instrumentation)
Management
- Consult Spine surgery, STAT if c/f cord compression
- BCxs, HIV, Spine CT w contrast vs MRI, TTE if c/f endocarditis
- Empiric Vancomycin + CTX (Cefepime if c/f PsA)
