Intro to CNS Infections

Question 1

Common Symptoms in CNS infections

Answer 1

i. Big 3: fever, headache, altered mental state
ii. Encephalitis: acute inflammation of the brain. clinical features…fever, headache, seizures, neurologic signs,
iii. Encephalopathy: refers to diffuse cerebral dysfunction w/o inflammation usually due to toxin or metabolic dysfunction.

i. Big 3: fever, headache, altered mental state
ii. Encephalitis: acute inflammation of the brain. clinical features…fever, headache, seizures, neurologic signs,
iii. Encephalopathy: refers to diffuse cerebral dysfunction w/o inflammation usually due to toxin or metabolic dysfunction.

Question 2

Meningitis

Answer 2

occurs in subarachnoid space

1. 95% have 2 of these symptoms: headache, fever, nuchal rigidity (stiff neck), altered mentality (not as common)
2. Viral is most common (enterovirus)
3. Bacterial is life threatening…vaccine for these
4. Fungi, protozoa common in immunocompromised
5. Pathogens effect diff age groups
6. Virulence factor
   a. Capsule- allows evasion of immune system

Question 3

Encephalitis

Answer 3

diffuse parenchyma

1. Big 3 symptoms
2. Motor and sensory deficits not seen in meningitis
3. Progression to seizures, speech disturbances, lethary and coma
4. Etiology often unknown
5. Viral caused by enterovirus, arbovirus, herpes virus, or rabies
6. Nonviral: rickettsia, mycoplasma, acute disseminated encephalomyelitis
7. Empiric Treatment w/ acyclovir until HSV ruled out

Question 4

Abscess

Answer 4

focal infection of parenchyma

1. Symptoms: Big 3 and seizure
2. Can be caused by pre-existing ischemia, necrosis begins as cerebritis, and then becomes encapsulated
3. Bacteria
   a. Streptococci (most common)
   b. Pseudomonas, haemophilus, staph, bacteroides
4. Mycobacterium, fungi, or parasites in immunocompromised
5. Causes:
   a. Otitis media»temporal lobe/cerebellum abscess
   b. Dental/sinus infection»frontal lobe
   c. Hematogenous»multiple areas-territory of middle cerebral artery
   d. Trauma
6. Diagnosed…
   a. CT and MRI scans and needle aspiration to culture
   b. No lumbar puncture- not beneficial and risk of herniation
7. Treatment:
   a. Ceftriaxone + Metronidazole (parasites) and may require surgery if Staph (vancomycin) and pseudomonas (ceftazidime-4th gen ceph)
8. Rupture can cause meningitis

Question 5

Myelitis

Answer 5

infection of spinal cord

Question 6

Noninfectious causes

Answer 6

i. Subarachnoid hemorrhage, inflammatory disease (lupus), neoplasia, metabolic, drug

Question 7

Microbial invasion of brain

Answer 7

i. Hematogenous dissemination
ii. Contiguous spread from sinusitis, otitis media, mastoiditis
iii. Trauma or congenital lesions
iv. Retrograde axonal transport (i.e. rabies)

Question 8

TORCH Infections (perinatal)

Answer 8

i. Mild maternal morbidity, but have serious fetal consequences
ii. Meningitis: group B streo, E.coli, Listeria
iii. TORCH includes Toxoplasmosis, Other (syphilis, VZV, parvovirus B19), Rubella, Cytomegalovirus (CMV), and Herpes infections (HSV-2)
iv. Need to aggressively manage
1. Empiric antibiotics if suspect bacterial meningitis covering most likely agents
2. Take blood culture first
3. Bactericidal-10 fold greater than minimum inhibitory concentration
4. BBB effects penetration and characteristics of the drug
5. Antibiotic susceptibility testing

Question 9

CNS infection diagnosis

Answer 9

i. History and physical
ii. Blood culture and empiric treatment
iii. Neuroimaging (to get a sense of swelling in brain and detect lesion)
iv. Lumbar puncture/biopsy
v. Indentify organism (gram stain/PCR/RT-PCR
vi. Antibiotic susceptibility testing
vii. Switch to definitive treatment and or supportive therapy

Question 10

History and physical

Answer 10

1. Season: i.e. enterovirus is most common cause of viral meningitis and encephalitis and occurs primarily in late summer to fall
2. Geography: i.e. tick exposure, west nile virus

Question 11

Blood culture and empiric treatment

Answer 11

1. Empiric treatment include 3rd gen cephalosporins
   a. Bactericidal, small, lipophilic, low affinity for plasma binding proteins, and not a ligand of the efflux pumps at the blood brain barrier
   b. Newborns and individuals with CNS inflammation have increased penetration and can give steroid to make drugs more effective

Question 12

Neuroimaging (to get a sense of swelling in brain and detect lesion)

Answer 12

1. View mass lesions but not helpful for meningitis
2. Risk factors: trauma, immunocompromised, focal neurologic findings, or decreased consciousness
3. If focal mass lesions, then lumbar puncture should not be done to avoid risk of brain herniation due to the very high intracranial pressure

Question 13

Lumbar puncture/biopsy

Answer 13

1. Routine tests
   a. WBC count w/ differential
   b. RBC
   c. Glucose concentration
   d. Protein concentration
   e. Gram stain, bacterial culture
2. Interpretation
3. Bacterial meningitis findings compared to viral…higher pressure, polymorphonuclear leukocytes (eosinophil, neutrophil, basophil), low glucose (bacteria using it), higher protein, positive gram stain
4. Viral…more lymphocytes

Question 14

Aminoglycosides side effects

Answer 14

can cause ototoxicity and lead to activation of NMDA receptors

Question 15

Beta lactams side effects

Answer 15

can cause encephalopathy. Inhibit GABAa release, increased glutamate and can cause seizures. Renal failure inc risk

Question 16

Macrolides side effects

Answer 16

can cause ototoxicity and damage cochlea