CNS infections

Acute infections of the CNS

  • Acute bacterial meningtis

    • Neonatal: group B streptococci, E. coli, Listeria. monocytogenes.

    • Children >6 months: H. influenza, S. pneumonia

    • Adolescents, adults: S. pneumonia, N. meningitis.

    • Elderly: S. pneumonia, L. monocytogens, GBB

    • Post-operative shunts: S. aureus, gram negative rods.

  • Viral meningitis

  • Encephalitis

  • Brain abscess

  • Subdural empyema

  • Infectious thrombophlebitis

Meningitis

  • Meningitis is the inflammation of the meninges around the brain and/or spinal cord. Caused by bacterial or viral inf, or by non-inf causes such as medications.

  • Pt. with fever and stiff neck or neurologic sx, especially if another concurrent inf or head trauma is present.

  • Aseptic meningitis is usually milder than bacterial meningitis and may be preceded by URI or pharyngitis. Viruses are common causes, as is drug-induced inflammation: NSAID, TMP/SMX. Distinction between bacterial, viral, and noninfectious etiology cannot be made clinically.

  • Bacterial meningitis is a medical emergency. Therapy should not be delayed for Dxtic measures because prognosis depends on rapid initiation of antimicrobial treatment.

Dx:

  • LP: measure OP, examination of CSF protein, glucose, cell count with differential, and Gram stain with culture. BC should always be obtained.

  • Typical CSF findings in bacterial menigitis include neutrophilic pleocytosis, markedly elevated CSF protein, and decreased glucose level.

  • In aseptic meningitis, lymphocytic CSF pleocytosis is common (although neutrophils may predominate very early in the disease course), and CSF PCR can detect enteroviruses, herpes simplex virus (HSV), and HIV.

  • Depending on the clinical scenario, other potentially useful CSF studies include plasma reagin (RPR), acid-fast stain, latex agglutination antigen detection, cryptococcal antigen, arbovirus antibodies, and PCR for HSV and enteroviruses.

  • A head CT scan before LP is controversial but is generally not required for nonelderly, immunocompetent patients who present without focal neurologic abnormalities, seizures, or diminished level of consciousness.

Tx:

  • Supportive and antimicrobial therapy.

  • Whenever acute bacterial meningitis is suspected, high-dose parenteral antimicrobial therapy should be started as soon as possible. Until etiology of the meningitis is known, an empiric regimen should be based on the CSF GS and patient risk factors:

    • If no organisms are seen, high dose 3G cephalosporins (ceftriaxone, 2 g IV q12h) and vancomycin, 1 g IV q8h-12h, are recommended while culture results are pending.

    • Ampicillin 2 g IV q4h, should be added for immunocompromised and older (>50 years of age) patients for coverage of Listeria.

    • In the postneurosurgical setting, or after head or spinal trauma, broad-spectrum coverage with high-dose vancomycin and ceftazidime or cefepime, 2 g IV q8h, is indicated. Empiric regimens should be altered once culture and sensitivity data are known.

    • Dexamethasone, 10 mg IV q6h, started just before or during initial ABx and given for 4 days, reduces the risk of a poor neurologic outcome in patients with meningitis caused by Streptococcus. pneumoniae. Steroids have not proven to be of benefit for bacterial meningitis caused by other organisms, and thus should be discontinued if a different pathogen is isolated.

  • Therapy for specific infections

    • S. pneumoniae, IV PCN G, 4 million units q4h, x 14 days, is appropriate when the isolate is fully susceptible to PCN. High-dose ceftriaxone or cefotaxime is used for susceptible or intermediate PCN isolates, and vancomycin is added if there is ceftriaxone resistance or high-level PCN resistance. Options for severely PCN-allergic Pts are vancomycin + rifampin, 300 mg PO tid; or chloramphenicol, 1 g IV q6h. Vancomycin should not be used alone. Dexamethasone is a useful adjunct early in treatment.

    • N. meningitidis, high-dose ceftriaxone or cefotaxime is continued for at least 5 days after the patient has become afebrile, usually a 7-day total course. Chloramphenicol is an option for PCN allergic Pt. Respiratory isolation is required for at least the first 24 hours of treatment. Close contacts (e.g., persons living in the same household and health care providers) having close contact with secretions, e.g., intubation) should receive prophylaxis with either ciprofloxacin, 500 mg PO x 1; rifampin, 600 mg PO bid x 2 days; or ceftriaxone, 250 mg IM. Terminal component complement deficiency (C5-C9) should be ruled out in patients with recurrent meningococcal infections.

    • Listeria monocytogenes meningitis is seen in immunocompromised adults and the elderly. Tx is with ampicillin, 2 g IV q4h, in combination with a systemically administered aminoglycoside, for at least 3-4 weeks. TMP/SMX, TMP, 5 mg/kg IV q6h) is an alternative for PCN allergic patient.

    • Gram-negative bacillary meningitis is usually a complication of head trauma or NS procedures. High-dose ceftazidime or cefepime, 2 g IV q8h, is used for most pathogens, includingPseudomonas aeruginosa. High-dose ceftriaxone or cefotaxime may be used for susceptible pathogens. Alternatives including meropenem and ciprofloxacin.

    • S. aureus meningitis is usually a result of high-grade bacteremia, direct extension from a parameningeal focus, or NS procedures. Oxacillin and naficillin, 2 g IV q4h, are the drugs of choice. 1G cephalosporins do not reliably penetrate into the CSF. Vancomycin should be used for PCN-allergic patients, and when methicillin resistance is likely or confirmed. RIF may also be necessary.

    • Enteroviral meningitis, Tx is supportive care. Acyclovir, 10 mg/kg IV q8h, is used for moderate to sever HSV meningitis

Ventriculitis and Ventriculoperitoneal Shunt Infections

  • Typically seen in NS patients

  • Caused by coagulase-negative staphylococci, S. aureus, and Propionibacter species.

  • Tx with Vancomycin IV +/- rifampin or intraventricular vancomycin. Removal of an infected shunt is often necessary for cure.

Encephalitis

  • Inflammation of the brain parenchyma, usually associated with viral infections.

Etiology:

HSV-1 is the most common cause of sporadic infection.

Dengue and other arboviral meningoencephalitides such as West Nile Virus (WNV).

Dx: Fever, neurologic abnormalities, particularly with personality change or seizures, and usually without meningeal signs.

Dxtic testing: Check for HSV-1 in CSF by PCR; however, a negative PCR does not rule out HSV encephalitis.

MRI brain with temporal lobe enhancement

Tx: Acyclovir, 10 mg/kg IV q8h infused x 1 hour with adequate hydration, which should be initiated at first suspicion and continue with 14 - 21 days, unless diagnosis is ruled out. Delayed initiation of therapy greatly increases the risk of poor neurologic outcomes.

Brain Abscess

Etiology: In a immunocompetent host brain abscess is usually of bacterial origin, most likely as a result of spread from a contiguous focus or from septic emboli from endocarditis. Infection is often mixed, with oral streptococci, S. aureus, and anaerobes being the most common pathogens.

Dx: Radiographic dx with presence of ring-enhanced lesions seen on CT with contrast or MRI. A microbiologic etiology must be determined by aspiration, Bx, or at the time of surgery.

Tx: Empiric therapy should be chosen to cover the most likely pathogens based on the primary infection site.

Medications: When there is no h/o preceding inf, give 3G cephalosporin combined with metronidazole and vancomycin until cultures come back

Surgical Management: Often is surgical with addition of systemic antimicrobials.

Neurocysticercosis

Etiology: Disease is caused by cyst forms of Taenia solium in the brain. Infections is acquired from eating undercooked pork that contains eggs of T. solium, which is endemic in Mexico and Central America.

Dx: Suspected when a patient with new-onset seizures of unknown etiology and exposure to endemic areas. Brain imaging reveals characteristic multiple unilocular cysts that may or may not enhance. Serologic tests are available at the CDC.

Pt. can have sz, hydrocephalus, and neurological abnormalities.

Tx: may need surgery and/high-dose albendazole or praziquantel, depending on the location of cysts and severity. Anticonvulsants, ICP monitoring, and steroids can be needed to control symptoms.