Meningitis Flashcards
What are the 3 most common organisms that cause acute bacterial meningitis?
somepeople BS nomeningitis
Streptococcus pneumoniae (SP)
Primary agent in adults and young children
In US, leading causing of bacterial meningitis post Hib
~60% decline in rates of meningitis due to S. pneumo since introduction of Prevnar vaccine in children(NM)
Neisseria meningitidis
Most common in children/adolescents/ young adults
Group B beta-hemolytic Streptococcus
Most common cause in neonates
What all all common causes of Bacterial meningitis
some people bs no meningits have generic sad and bad lies
S. pneumo
Group B strep
Neisseria meningitis
Haemophilus influenzae type b (Hib)
Less common secondary to vaccine
Gram-negative enterics
E. coli
and others are important pathogens in neonates
Uncommon in adults and children
Listeria monocytogenes
Elderly, neonates, immunocompromised
Staphylococcus aureus
Uncommon meningeal pathogen
Bacillus anthracis
What is the mechanism for NM infection?
Transiently colonizing bacteria of upper respiratory tract are common etiologic agents
Nasopharyngeal mucosal epithelium provides local immunity; also is attachment site for bacteria
pili
ie, N. meningitidis
Organism breeches host defenses
N. meningitidis produce IgA protease and escape
phagocytosis by capsular polysaccharide
Encapsulated organisms inhibit neutrophil phagocytosis and complement-mediated killing
Seeding of meninges by blood-borne organisms via choroid plexus Penetration of blood-brain barrier Development of inflammatory response Brain edema and increased intracranial pressure Brain ischemia
What are the 3 edemas ,
vasogenic
cytotoxic
interstitial
Vasogenic edema
Disruption of BBB and leakage of capillary vessels
Cytotoxic edema
Increased intracellular fluid 2° cell injury, endothelial cells themselves are swollen
Interstitial edema
-edema between cells,
Purulent exudate in arachnoid space interferes with
reabsorption of CSF and obstruction of flow
Movement of fluid from ventricular system to
parenchyma
What are the clinical characteristics of meningitis
Bacterial Meningitis
Increased intracranial pressure
Infants: bulging fontanelle
Adults: headache
Cerebral edema and ischemia, thrombosis of cerebral vessels, cortical necrosis
> Coma, ataxia, seizures, focal neurological signs, cranial nerve palsies (deafness, ocular muscle weakness)
Papilledema is unusual
Special features/clues
NM meningitis associated with petechiae (1mm non-blanching, red, flat skin lesions) and/or purpura
SP meningitis may be associated with respiratory infections (ear or sinus infection)
Neonates Non-specific findings: Poor feeding, increased sleeping, decreased urine output, irritability, vomiting and diarrhea
What are CSF findings in bacterial meningitis
normal
# cells: 0-5/mm^3
Protein: 15-45 mg/dL
Glucose: 50-75 mg/dL
> 1000 cells
opening pressure HIGH
*polymorphonuclear cells
high protein >150
Low glucose 20-40
What are CSF findings for tuberculosis and fungal
normal
# cells: 0-5/mm^3
Protein: 15-45 mg/dL
Glucose: 50-75 mg/dL
<5000 cells
opening pressure HIGH
- lymphocytes ** distinguishes from bacterial
- increased protein >150
- low glucose (20-40)
What are the findings for viral meningitis in CSF?
normal
# cells: 0-5/mm^3
Protein: 15-45 mg/dL
Glucose: 50-75 mg/dL
<1000 cells
- normal or high opening pressure
- increased lymphocytes
- normal or high protein
- *glucose NORMAL
What are aseptic causes of meningitis
Enter hermes abode less have meningitis
Enterovirus* (echovirus, coxsackie b)
Leading cause of aseptic cases
Seasonal presentation: most cases in summer, early fall
Herpes viruses (HSV2*>HSV1, Varicella zoster, Cytomegalovirus, Epstein-Barr virus)
Arbovirus (eastern, western equine, St. Louis)- Insect vector
Mumps -unimmunized
HIV
LCV - rare cause
*Mycobacterium tuberculosis is also aseptic because it doesn’t grow on regular medium
What are the pathophysiology of brain abscesses
-Contigous (middle ear, mastoid, sinuses): you get a head and neck infection usually in middle ear, extension of infection up into skull, thru the brain, this is the most common cause of brain abscesses
Hematogenous dissemination - lung abscess, empyema, congenital heart disease, bronchiectasis, infective endocarditis
Trauma (cranial fracture, neurosurgery, foreign
body injury
Cryptogenic
Most common locations of brain abscesses
Sinusitis
Frontal lobe most common, temporal lobe or sella turcica in sphenoid sinusitis
Otitis media>temporal lobe or cerebellum
Dental infections>usually frontal lobe
Multiple locations implies hematogenous seeding
What are differences between brain abscesses and meningitis
- Nuccal rigidity is uncommon
- Systemic features (fever) are usually absent
- Lumbar puncture is contraindicated, you have increased pressure, you are at risk of herniation.
Toxoplasmosis and brain abscesses
Toxoplasma gondii most common protozoal cause of brain abscess.
Transmission mainly by ingestion of tissue cysts in contaminated meat or food or oocysts in food/water
contaminated from cat feces.
Various clinical presentations but most common is
intracerebral mass lesions or encephalitis in immuncompromised hosts (HIV, transplant, malignancy)
Can have focal or nonfocal neurological symptoms
(weakness, HA, altered mental status, lethargy) initially with
most developing focal symptoms, some rapidly fatal
encephalitis
Prediliction for basal ganglia and brainstem
MRI brain is test of choice. CT can also be used.
Rounded isodense or hypodense lesions with ring
enhancment-usually multiple lesions
Can have mass effect and edema.
Serology (serum IgG titers)
CSF PCR
AIDS pts-consistent CT or MRI findings with positive
serology empiric treatment with repeat imaging in 10-14
days (should show imprvement)
Cranial Subdural Empyema
microbio is same as brain abscesses, staphylococci, streptococci.
Neurologic emergency: progress rapidly and spread to different areas
Most common predisposing condition is ear and sinus infections
Polymicrobial infections common.
Signs and symptoms secondary to increased intracranial pressure,
meningeal irritation, or focal cortical inflammation
Fever is present in most cases
Headache predominant complaint, Vomiting is common as ICP
increases.
Altered mental status
Focal neurologic signs (hemiparesis, hemiplegia, ocular palsies, dilated pupils, \ hemaniopsia, cerebellar signs
Spinal Subdural Empyema
Rare condition usually occurs secondary to metastatic infection from another site.
Most frequently caused by Staphylococcus aureus *** also in FA
Coagulase negative Staph, gram negatives, and strep less
frequent.
Clinical presentation: radicular pain and symptoms of
cord compression (can occur at multiple levels)
Can be difficult to distinguish from epidural abscess and
can occur simultaneously.
MRI is diagnostic procedure of choice.
Empiric antibiotics until culture results and surgical
decompression.
