CNS infection

Question 1

Meningitis

Answer 1

Inflammation of the meninges

Question 2

Routes of meningitis

Answer 2

• blood-borne
• parameningeal suppuration (pus; from ear/sinus infection)
• direct spread through dura (surgery/trauma)
• rare – direct spread through cribriform plate

Question 3

Age groups:

Answer 3

• N. meningitidis (meningococcus): Main one inchildren/young adults
• Strep pneumoniae (Pneumococcus) Elderly/children < 2
• Hib: Cildren <5
• E. coli: Neonates
• Listeria monocytogenes: Neonates/immunocompromised

Question 4

Meningititis pathogenciticy

Answer 4

Bacteria in nasopharynx → bacteraemia → subarachnoid space → immune/inflammatory response → cerebral capillary endothelium

Question 5

Signs and Symptoms Meningitis

Answer 5

Meningism – global headache, neck/back stiffness, N+V, photophobia

Kernig’s sign; neck stiffness; Brudzinskis sign (if flex pts neck, pts hips and knees also flex)

These symptoms could also occur in: UTI, dysentery, malignancy

Question 6

Lumbar puncture

Answer 6

Most rapid Dx test, can normally distinguish between bacterial/viral

Risk of herniation – if long Hx, focal neurology, drowsy → indicating ↑ICP – LP could ↑ risk herniation

Question 7

CSF changes

Answer 7

• Bact: 90/10 polymorphs/lymphocytes; decreased glucose
• Viral: 10/90 polymorphs/lymphocytes
• TB: More lymphocytes than polymorphs, protein increased, low glucose

Question 8

Meningitis management

Answer 8

• bactericidal AB.
• O2
• prevent hypoglycaemia + hyponatraemia
• Anticonvulsants
• Decrease ICP

Question 9

3 groups of drugs

Answer 9

Penetrate CSF normally – e.g. chloramphenicol
Penetrate inflamed meninges/at high doses – e.g. benzylpenicillin + 3rd gen cephalosporins Poor CSF penetration – gentamycin, 1st gen cephalosporins

Question 10

1st line treatment

Answer 10

Cefotaxime/Ceftriaxone

• HIb and unknown over 2y/o

1st line treatment – active against causative organisms (incl some resistant strains) Well tolerated + good penetration into inflamed CSF
Cefotax 6hrly; Ceftriax 12hrly

Question 11

Benzylpenicillin

Answer 11

Most active agent against Pneumococcus (but resistance increasing), adequate penetration of inflamed CSF Dose every 4 hours

Use if know organism sensitive e.g. Meningococcus

Question 12

Causes of brain abscess

Answer 12

• direct spread via vvs (from ear/sinus infections)
• haematogenous spread (from lung abcesses/endocarditis – tend to get multiple abcesses)
• direct implantation – trauma/surgery
  
  • Stre. milleri, anaerobes, polymicrobial

Question 13

Brain abscess treatment

Answer 13

Surgical: drain, excise

MEdical: ABs