• bacterial
  • S pneumoa, N. meninbgits, H. influ
  • others: L monocytogenes, S agalactiae and gram negative infections
  • in setting of trauma/post surgery: staph and gram negatives
• spirochetes: Treponoma pallidum, Borrelia burgdorferia
• protozoa- amoebae (N. fowleri, Acanthamoeba)
• helmniths: angiostrongylus

• viral: major cause of aseptic meningitis
  • enterovirus (major cause of viral meningitis)
    • epidemiology- children in summer/fall
  • arboviruses: usually St. Louis encephalitis virus
    • epidemiology- arthopod transmission
  • mumps virus (in nonimmunized)
  • herpes virus: HSV, EBV, CMV, VZV
  • HIV

• virulence factors
  • fimbrae (H influ, N. mening)- mediate adhearance to nasopharyngeal epithelial cells
  • surface encapsulation (H flu, S pneumo, N mening) inhibit phagocytosis
• host factors
  • alternative complement pathway activated by capsular polysaccharides
  • BBB has increased permeability due to cytokine release (IL-1, TNF)
• subarachnoid space inflammation
  • once bacteria enters subarachnoid space, host defenses are inadequate (low level of complement, Ig in CSF)
  • inflammation due to cell wall induced cytokine release
• increase BBB permeability and release of toxic factors from neutrophils and bacteria leads to cerebral edema causing increases in intracranial pressure 

• group B strep (S. agalact.)
• E coli
• Listeria monocytogenes
• gram negative

• group B strep (S. agalact.)
• E coli
• Listeria monocytogenes
• Haemophilis influenza
• Strept. pneumo
• N. meningitis

• H. influenza
• N. meningitis
• Strep pneumo

• strept pneumo
• N. meningitis

• S. pneumo
• N. meningitis
• gram negative
• Listeria monocytogenes

• S aureus
• S epidermicus
• gram negative

• most common etiological agent in US
• associated with suppurative foci of infection
  • pneumonia (second most)
  • otitis/mastoiditis (MAJOR)
  • sinusitis
  • endocarditis
  • head trauma with CSF leak

• usually capsular type b strains
• associated with pharyngitis or otitis in most cases
• use to be common in children under six, but incidence decreased due to vaccination
• older pts associated with:
  • splenectomy
  • sickle cell
  • DM
  • immune deficiency
  • alcoholism

• mostly in children and young adults
• epidemics involve serogropus A and C
• nasopharyngeal acquisition of infection
• chemopx needed

• common in neonates
• outbreaks associated with:
  • consumption of contaminated coleslaw, raw veggies, milk, cheese
• in adults, assoc. with:
  • elderly
  • alcoholism
  • malignancy
  • DM
  • immune suppression
  • hepatic/renal disease

• occur in neonates
  • septicemia associated with premature, premature rupture of membranes, low birth weight
• onset of meningitis > seven days after birth
• adults:
  • DM
  • alcoholism
  • cardiac/hepatic/renal disease
  • malignancy

• etiology
  • E coli
  • Klebsiella
  • Pseudomonas
  • Salmonella
  • Serratia
• epidemiology
  • neonates
  • elderly
  • immunocompromises
  • follows head trauma and neurosurgery
  • may be associated with gram negative sepsis

• fever, headache, meningismus, signs of cerebral dysfunction (confusion, delirum)
• cranial N. palsies as result of increase ICP (III, IV, VI, VII)
• seizures and focal neurological findings due to cortical ischemia resulting from inflammation and thrombosis of bv's

• increase protein
• decrease glucose
• increase neutrophils
• increase ICP
• most of time, gram stain and culture are positive

• antiinflammatory agents
  • dexamethasone for children with H flu or can be used in adults with S pneumo
  • benefits pts with cerebral edma, raised ICP, alteration of consciousness
  • administration prior to or concomitant with antibioitics is optimal for reducing subarachnoid space inflammation

• immunopx
  • no suitable vaccine against serogroup B (causes half of cases)
  • vaccine against A, C, Y serogroups for:
    • complement component def.
    • asplenics
    • travelers to areas of epidemics
    • military recruits
    • now a routine childhood immunization
• chemopx
  • household members
  • daycare center contacts
  • medical personnel directly exposed to oral secretions
  • px with rifampin/cipro/ceftriaxone

• H influenza
  • immunopx
  • rifampin for all close contacts (household members, daycare contacts)
  • in households of kids less than 2 yrs old to eliminate nasopharyngeal colonization
• S. agalactiae
  • administration of ampicillin during labor to mothers colonized and with risk factors
  • ex: prolonged rupture of membranes

• host barriers
  • mucocilliary apparatus
  • alveolar macrophages
  • IgA associated with Gi and respiratory mucosa
• CNS invasion may occur directly across capillary endothelial cells (BBB) via choroid plexus epithelium, along olfactory bulb, etc
• CNS infection lead to inflammatory response and release of cytokines

• fever, headache, nuccal rigidity, photophobia, nausea, vomitting, myalgias
• enteroviral meningitis may be associated with exanthems, myopericarditis, conjunctivitis, herpangina, pleurodynia
• HSV2 meningitis may be associated with urinary retention, paresthesias, motor weakness

• ICP can be normal or increased (increase less than in bacterial)
• increase lymphocytes
• normal protein and glucose levels

• definition- signs and symptoms, CSF abnormalities waxing and waning for at least 4 weeks
• etiology
  • fungal- Cryptococcus, Histoplasma, Coccoidimycosis, Sporitrichosis
  • mycobact- TB
  • spirochetes: syphillis, Lyme disease

• fever
• meningismus
• headache
• behavioral change
• CN palsy
• PPD positive

• most have positive culture and negative acid fast bacteria smear
• increase in lymphocytes

• dx- TB CSF PCR
• therapy
  • long term therapy
  • begin at least 4 drugs anti-TB therapy

• fever
• MS changes
• meningeal signs
• photophobia
• seizures (rare)
• headache

Most AIDS pts are missing a lot of these symptoms, except headache and fever

• very few have WBC elevation (remember, their WBC's are dying)
• positive CSF crypto Ag
• positive serum

• high dose amphotericin, azole (fluconazole)
• consider flucytosine as well

• infectin of parenchyma of brain
• usually accompany meningial inflammation
• characterized by alterations in consciousness
• commonly accompanied by focal neurological signs and seizures

• in US, usually caused by HSV [cause both meningitis (HSV2) and encephalitis (HSV1)]
• worldwide
  • rabies (India, Mexico)
  • measles (Africa)
  • Japanese B encephalitis (China)
• can be caused by arthopod born viruses
  • Eastern/Western Equine Encephalitis
  • St Louis Encephalitis

• epidemiology- biphasic age distribution
• symptoms/signs
  • focal neurological signs
  • behavioral changes
  • alterations in consciousness common
    • may complain in strange oders, reflects temporal lobe involvements
• dx- elevation of RBC in CSF, PCR, MRI, EEG
• tx- acyclovir
• high mortality and morbidity

• contiguous focus of infection
  • otitis
  • mastoiditis
  • sinusitis
  • dental infection
  • skull osteo
  • face/scalp infection
  • head injury
  • post neuro surgery
• hematogenous spread- lung abscess, endocarditis

• dx
  • MRI is procedure of choice
  • biopsy, aspiration is needed for microbio dx
• tx- emperic therapy
  • medical and surgical approach
  • corticosteroids for cerebral edema

• intracellular protozoan parasites
• cats are definitive hosts
• prevalance of tissue cysts in meats is high, however other foods can be contaminated
• maternal fetal transmission occurs
• high incidence of CNS infection in immunocompromised host

• when CD4 below 100
• may be due to reactivated viruses or newly acquired infections
• most frequent cause of focal CNS in AIDS
• may present with:
  • CN palsies
  • motor/sensory deficits
  • change in mental status
  • meningitis

• CT scan with multiple bilateral ring enhancing lesions
• serum toxoplasma IgG levels usually positive
• CNS lesions will decrease in size with therapy

• Pyrimethamine combined with Sulf
• pts who deteriorate despite therapy may need brain biopsy