Micro 5 - CNS infections and meningitis

Question 1

Causative organisms in

acute
chronic
aseptic

meningitis

Answer 1

acute
bacteria

chronic
TB, cryptococcus, spirochetes, syphilis
(immunocompromised)

aseptic
viral

Question 2

Commonest causative agents of acute meningitis

Answer 2

NHS
Neisseria meningitides (gram -ve diplococci, non-haemolytic)
Haemophilus influenzae
Streptococcus pneumoniae (gram +ve diplococci, a haemolytic)

Others
Listeria monocytogenes (gram +ve rod)
E coli
GBS

Question 3

Key cause of meningoencephalitis

Answer 3

listeria monocytogenes

Question 4

Septicaemia - the clinical spectrum is produced by 4 processes

Answer 4

o Capillary leak – hypovolaemia – albumin + other plasma proteins
o Coagulopathy – bleeding + thrombosis – endothelial injury results in platelet release reactions, the protein C pathway + plasma anticoagulants area affected
o Metabolic derangement – acidosis
o Myocardial failure + multi-organ failure

Question 5

Chronic TB meningitis

Who does it affect
Which parts of the CNS does it affect
MRI
Complications

Answer 5

Immunocompromised

Meninges, spinal cord, dilation of ventricles, basal cisterns of brain

Leptomeningeal enhancement on MRI

Tuberculous granuloma
Tuberculous abscess
Cerebritis

Question 6

Which is the commonest infection of the CNS and how do you treat it

Answer 6

Aseptic meningitis

o Self-limiting disease that resolves in 1-2 weeks
o Supportive – analgesics, anti-emetics, antipyretics
o Do not give anti-virals!!

Question 7

RF for

o Neisseria meningitides
o Streptococcus pneumoniae

Answer 7

Both - complement deficiency, hyposplenism (susceptible to encapsulated organisms),

o Neisseria meningitides – hypogammaglobulinemia

o Streptococcus pneumoniae - immune defect (alcoholic), infection (pneumonia), entry through fracture, previous head trauma with CSF leak

Question 8

Transmission of

meningitis
encephalitis

Answer 8

Meningitis
 Person to person transmission from asymptomatic carriers

Encephalitis 
•	Transmission is commonly either person to person or through vectors
o	Mosquitos
o	Lice
o	Ticks

Question 9

Commonest cause of encephalitis

in the UK
Worldwide

Answer 9

UK HSV2

Worldwide arboviruses

Question 10

CNS infections clinical syndromes

Answer 10

Meningitis
Encephalitis
Myelitis (disturbance of nerve transmission e.g. polo)
neurotoxin
e.g. • Clostridium botulinum  botulism  Canned/vacuum packed foods, honey, –> descending paralysis (flaccid)
• Clostridium tetani  tetanus  cut on metal –> spastic paralysis (rigid)

Question 11

How can a brain abscess develop?

Answer 11

o Direct extension (e.g. otitis media, mastoiditis, para-nasal sinuses)
o Occasionally spread haematogenously (e.g. endocarditis)

• Causative organisms (Strep >Staph > gram -ve > other)

Question 12

CSF

Polymorphs vs

Mononuclear cells

Answer 12

Polymorphs = neutrophils = bacterial infection

Mononuclear = lymphocytes = viral/TB

Question 13

Bacterial, viral, TB meningitis from low to high

WCC

Protein

Glucose

Answer 13

WCC
viral –> TB –> bacterial

Protein
Viral –> bacterial –> TB

Glucose
TB + bacterial same –> viral

Question 14

look at qs on ppt

Answer 14

x

Question 15

Cryptococcus buzzwords

Answer 15

Fungal
India ink stain
High opening pressure on LP - pathognomic of cryptococcus
Immunocompromised people e.g. HIV, MSM

Question 16

TB meningitis buzzwords

Answer 16

gram stain shows nothing
chronic headache (causes chronic meningitis)
leptomeningeal enhancement on MRI

Immunocompromised

Meninges, spinal cord, dilation of ventricles, basal cisterns of brain

Tuberculous granuloma
Tuberculous abscess
Cerebritis

can be seen under a microscope (If you can see it under a microscope, it is not a virus (viruses are too small to be seen on a microscope))

(causes chronic meningitis)