CNS infections

Question 1

4 mechanisms of CNS infection

Answer 1

1. Haematogenous spread via epithelium (most common - e.g. Meningococcus via respiratory epithelium)
2. Direct spread (surgery or accident)
3. Local extension (ear infections)
4. PNS into CNS (rabies)

Question 2

Meningitis organisms

Answer 2

Fever, headache, stiff neck
Meningococcus (N meningiditis)
S pneumoniae
Hib
- Infants: Listeria, GBS, E coli

Question 3

Encephalitis organisms

Answer 3

Disturbed brain function
Rabies, arbovirus
Trypanosoma species
Prions
Amoeba

Question 4

Myelitis organisms

Answer 4

Disturbed nerve transmission

Poliovirus

Question 5

Neurotoxin organisms

Answer 5

Paralysis, rigid (tetanus) or flaccid (botulinum)
Clostridiom tetani
Clostridium botulinum

Question 6

1. Acute bacterial meningitis

Answer 6

Rapid deterioration
3 main organisms (N meningiditis, S pneumoniae, Hib + in infants Listeria, E coli, GBS)
N meningiditis - 50% meningitis, 10% septicaemia, 40% both
CSF: High neutrophils, high protein, low glucose, turbid

Question 7

2. Chronic bacterial meningitis

Answer 7

No rapid deterioration, gradually worsening headache
TB
Immunosuppressed patients
Granuloma formation
CSF: Very high protein, neutrophils / lymphocytes,

Question 8

3. Aseptic (viral) meningitis

Answer 8

Most common CNS infection
Coxsackie B and echoviruses in 80-90%; HSV2
Self-limiting, resolves in 1-2w
CSF: High lymphocytes

Question 9

Meningitis vs. encephalitis

Answer 9

Brain function disturbance more common in encephalitis

Question 10

Headaches, fever, speech disturbance

Loses consciousness

Answer 10

Encephalitis

Question 11

Meningitis with incomplete vaccinations

Gram negative coccibacilli

Answer 11

Hib

Question 12

HIV
High opening pressure on LP
India Ink stain of CSF = yeast cells with halos
Pigeon droppings

Answer 12

Cryptococcus neoformans

Question 13

Meningitis in baby

Gram positive rods

Answer 13

Listeria monocytogenes

Question 14

2wk worsening headache

Ziehl-Neelson stain

Answer 14

TB meningitis

Question 15

Forgetful + doesn’t make sense
Ataxia
Muscle spasms
EEG - periodic sharp waves

Answer 15

CJD

Question 16

Positive microscopic agglutination test
Farming project in Africa
Aerobic spirochaetes

Answer 16

Leptospirosis

(Characterised by initial non-specific leptospiraemic phase then meningitis, liver damage + renal failure when IgM forms

Question 17

Causes of encephalitis

Answer 17

Enteroviruses (Coxsackie A+B, echovirus, polio)

Herpes Simplex 1 + 2

Question 18

Mollaret’s

Answer 18

Recurrent meningitis

Question 19

Meningitis in baby

K1 antigen, lack of circulating IgM

Answer 19

E coli

Question 20

CSF: Colourless, raised lymphocytes

Answer 20

Viral meningitis

Question 21

CSF: Turbid, raised neutrophils, high protein, low glucose

Answer 21

Bacterial meningitis

Question 22

CSF: Turbid, raised neutrophils / lymphocytes, low glucose, high protein

Answer 22

TB meningitis

Question 23

Xanthochromia (straw coloured CSF)

Answer 23

SAH

Question 24

Tx meningitis

Answer 24

Ceftriaxone (+ Amoxicillin to cover listeria)

Question 25

Tx meningo-encephalitis

Answer 25

Acyclovir + Ceftriaxone (+Amoxicillin to cover listeria)

Question 26

HSV most likely to cause meningitis?

Answer 26

HSV2