Meningitis (Malhotra) Flashcards
What is meningitis?
How do pathogens enter CSF (3)?
- Inflammation of the meninges
- Infection of the subarachnoid space
- Exudate over spinal cord and brain
- CSF w/ inflammatory changes (pleocytosis - abnormal cells in CSF indicating inflammation)
Pathogens enter CSF via
- Paracellular passage
- Transcellular transport (during active or passive transcytosis)
- Invasion within WBCs during diapedesis
Understand the epidemiology (incidence and predisposing factors) and pathogenesis of meningitis
Incidence of bacterial meningitis: Overall - 1.4/100,000
Predisposing factors:
- Altered immune status (malnutrition, steroids, complement deficiency, HIV)
- Functional or congenital asplenia (sickle cell disease)
- Chronic disease (diabetes, alcoholism, HIV, liver disease)
- Head trauma (CSF leak)
- Bacteremia
Pathogenesis:
1. Organism enter nasopharynx and colonize upper respiratory tract
2. Organism breeches host defenses (i.e. phagocytosis, opsonization)
3. Organism replicates in sub epithelial tissue
4. Hematogenous spread to CNS (bacteremia)
Seeding of meninges by blood-borne organisms via choroid plexus
5. Penetration of BBB
6. Development of inflammatory response leads to brain edema, inc. intracranial pressure, brain ischemia
Common organisms responsible for bacterial meningitis
Acute bacterial meningitis - most common organisms:
- Streptococcus pneumoniae (SP) - winter - highest mortality (30%)
- 25%-35% penicillin resistant
- Primary agent in adults and young children - Neisseria meningitidis (NM) - year round - mortality - 3%
- Most common in children/adolescents/young adults (most colleges require students to get vaccine for type B) - Group B beta-hemolytic Streptococcus
- Most common cause in neonates (common colonizer of female vaginal area so as babies are born, they get colonized by this)
Understand the clinical presentation associated with bacterial meningitis.
Bacterial
- Life threatening (acute and severe)
- Common findings: fever, neck stiffness, abnormal state of consciousness
- Inflamed meninges (flex neck, flex hip and knee)
- Photophobia
- Lethargy
- Increased intracranial pressure (infants: bulging fontanelle, adults: headache)
- NM meningitis** associated with petechiae and/or purpura
- SP meningitis** associated with respiratory infections (ear or sinus)
Understand the significant laboratory values associated with bacterial meningitis.
Bacterial
- # cells: > 1000 [>500 WBC]
- CSF glucose: low
- CSF protein: high
- water: high
- stain: gram +
- culture: +
Recognize the common acute complications of bacterial meningitis.
Death Shock Seizures SIADH Subdural effusions Cerebral hemorrhage Extrameningeal infection (access) Deafness Ataxia Paralysis/Cerebral palsy
Identify the preventative measures employed in decreasing the incidence of both bacterial and aseptic meningitis.
Bacterial:
Hib - active immunization (YES), post exposure prophylaxis (YES - rifampin)
NM - active immunization (YES), post exposure prophylaxis (YES - rifampin, or ciprofloxacin, or ceftriaxone)
SP - active immunization (YES), post exposure prophylaxis - NO
Gram-negative bacilli - active immunization (NO), post exposure prophylaxis - NO
Viral:
Mumps: MMR (2 dose series starting at 24 mo)
Common cause for aseptic meningitis
Viral
- Enterovirus (echovirus, coxsackie b)
- Herpes viruses (HSV2 > HSV1, varicella zoster, epstein-barr)
- Arbovirus (eastern, western equine, st. louis)
- Mumps
- HIV
Understand the clinical presentation associated with aseptic meningitis.
Fever, headache, stiff neck
Mild (enterovirus)
Severe fatal (HSV)
Changes in mental status (seizures) suggest concurrent encephalitis
What is the onset of acute meningitis and how long does it typically last?
Onset: within hours to days
Duration:
Understand the significant laboratory values associated with aseptic meningitis.
WBC:
