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.
Cranial Epidural abscess
More indolent course (as opposed to subdural abscess)
Initial focus usually sinuses, ear, mastoid infections but can occur after
trauma or surgical procedures.
Signs and symptoms include headache, fever, seizures, focal
neurologic signs, altered mental status but may be overshadowed by
symptoms/signs from primary source of infection.
Fever and headache
are most common complaint and patient may
feel well until progresses to subdural empyema, meningitis, or brain
abscess.
MRI diagnostic procedure of choice-can cross midline unlike subdural
Combined medical and surgical treatment.
Spinal Epidural Abscess
May develop within hours to days (after hematogenous seeding) or
may be more chronic (weeks to months, usually with vertebral osteo or contigous focus), TB also more gradual
Pain most consistent symptom
Fever in 60-70% patients
Neurologic signs depend on level affected
Neurologic manifestations can be reversible before complete
paralysis occurs so need to do imaging and intervention emergently
if considering diagnosis.
Usually occurs secondary to hematogenous spread
IV drug users, infective endocarditis
Blood cultures frequently positive-bacteremia
Contigous foci (1/3 of cases)
Often occurs with vertebral osteomyelitis
Unidentified source (20-40% cases)
Diabetes present in up to 50% patients.
Almost all source is Staphylococci and Streptococci
MRI is diagnostic procedure of choice.
Empiric antibiotics should include coverage for S. aureus
and gram negative bacilli
Surgical therapy is imperative if signs of neurologic
dysfunction (paralysis less than 24-36 hours)
Nonsurgical therapy if no neurologic deficits or too high risk
but requires frequent monitoring.
What are the stages of spinal epidural abscess 4 stages
back pain and tenderness at level of infection
radicular pain and paresthesias
impaired spinal cord function; motor paresis and sensory deficits
complete paralysis
Encephalitis
Inflammatory process involving brain parenchyma with
clinical or laboratory evidence of neurologic dysfunction.
Viruses, bacteria, and auotimmune form majority of known
cases.
Differs from meningitis:
there is a Region of inflammation
Altered mental status (hallmark of encephalitis)
CSF exam similar in both
-viruses are also the more common cause
HSV-1
Herpes Simplex Encephalitis
Among most severe of all human viral infections of brain
>70% mortality with no or ineffective therapy
Accounts for10-20% of encephalitis viral infections
Occurs throughout the year and in patients of all ages
Majority caused by HSV-1
Clinical features: Fever, **personality change, dysphasia, autonomic dysfunction: altered mental status
Requires high index of clinical suspicion
Cerebrospinal fluid (CSF) findings
Lymphocytic meningitis (mean of 100 cells/mm3)
Presence of red blood cells
Elevated protein
Normal in 5-10% of patients on first evaluation
CSF Polymerase Chain Reaction
Sensitivity 98%
Specificity 94%
Positive predictive value 95%
Negative predictive value 98%
If negative, may need new CSF sample in 3-7 days
Treatment of HSV-1 and 2
Acyclovir
West Nile Virus
Most people:
No clinical illness or symptoms (~80%)
Some develop West Nile Fever (~20%)
Severe WNV Disease (1 in 150)
Meningitis
Encephalitis/Meningoencephalitis
Poliomyelitis-like flaccid paralysis
Diagnosis Serum IgM antibody (8-14 days of illness onset) CSF reveals lymphocytic pleocytosis and elevated protein; glucose is normal CSF IgM (positive in >90%) CSF PCR (<60% sensitivity) Neuroimaging Treatment is usually supportive
St Louis encephalitis virus
Japanese encephalitis virus
EEE virus
St. Louis encephalitis virus
Mosquito vector; bird reservoir
Endemic in western US; periodic outbreaks in eastern US
Urinary symptoms early; SIADH (one-third of cases)
Serology; CSF IgM
Japanese encephalitis virus
Most common cause of mosquito-borne encephalitis worldwide
Mainly children; rice fields where vectors breed
Seizures and parkinsonian features; poliomyelitis-like flaccid paralysis
Serology; CSF IgM
Eastern equine encephalitis
Mosquito vector; bird reservoir in North America
Primarily Atlantic and Gulf coast states
Abrupt onset with fulminant course; seizures common
High case-fatality rate (50-70%)
Serologic testing
High CSF WBC count (>1000 cells/mm3)
Powassan virus
Powassan virus
Tick vector (Ixodes scapularis in NE); rodent reservoir
Prevalence among animal hosts and vectors increasing
New England states
Serology; CSF IgM
Rhabdovirus
Encephalitic (furious) form (80%) Agitation alternating with lucidity Hypersalivation Hydrophobia Bizarre behavior Disorientation, stupor, coma, death
Paralytic (dumb) form
Ascending paralysis; early muscle weakness
Later cerebral involvement
Diagnosis
Culture and RT-PCR of saliva
Immunofluorescent detection of viral antigens and RT-PCR in nuchal
biopsy
CSF antibodies and RT-PCR
Brain biopsy (antigen detection/Negri bodies)
Therapy
Supportive
Post-exposure prophylaxis (rabies immune globulin at bite site and vaccine)
