FunMed: PBL 8 (Meningitis)

Question 1

Define ‘photophobia’

Answer 1

Extremely sensitive to light

Question 2

Define ‘tachypnoea’

Answer 2

Abnormally rapid breathing

Question 3

What is dexamethasone?

Answer 3

Synthetic drug of corticosteroid type used as anti-inflammatory agent

Question 4

What are the two groups of causes of meningitis?

Answer 4

Bacterial and viral

Question 5

Which bacteria commonly cause meningitis?

Answer 5

Neisseria Meningitidis (most common), S. pneumoniae, Listeria monocytogenes, Haemophilis influenza type B

Question 6

What does rash in meningitis indicate?

Answer 6

Bacteria is systemic and not just in CNS (meningococcal septicaemia)

Question 7

What are the different types of meningococcal bacteria?

Answer 7

A, B, C, W, X, Y, Z

Question 8

What viruses cause meningitis?

Answer 8

Enteroviruses - usually cause mild stomach infection and are contagious
Herpes simplex virus - genital herpes and coldsores
E. Coli - more common in infants

Question 9

What are the symptoms of meningitis in infants?

Answer 9

High fever with cold hands/feet, vomit and refusal to feed, agitated and rapid breathing, unusual high-pitched cry, red rash which doesn’t fade when glass rolled over it

Question 10

What are the symptoms of meningitis in adults?

Answer 10

Drowsiness, difficulty walking, confusion, irritability and severe headache

Question 11

Why does pneumococcal bacteria tend to cause meningitis more often in infants?

Answer 11

Streptococcus pneumoniae more harmful because their immune systems haven’t built up immunity to these bacteria yet

Question 12

How is meningitis diagnosed?

Answer 12

Lumbar puncture (L3-L4) to analyse CSF

Question 13

In meningitis diagnoses what are they looking for in the CSF?

Answer 13

Neutropil dominant WBCs (bacterial) and lymphocyte dominant in viral meningitis, low glucose concentration,

Question 14

How is lumbar puncture conducted?

Answer 14

If intracranial pressure not dangerously high, lie patient in foetal position, draw line connecting iliac crests posteriorly and enter spindal needle into subarachnoid space at this point (below spinal cord)

Question 15

Why may CT scan be required prior to conducting lumbar puncture?

Answer 15

If the intracranial pressure is elevated, lumbar puncture could lead to brain herniation, so if there is any likelihood due to recent head trauma, or known immune system disorder, CT is done

Question 16

By which two routes may bacteria reach the meninges?

Answer 16

May be inhaled and invade the mucous membrane of the nasopharynx due to damage to mucous membrane or trauma (direct contact) –> will then cling to meninges using bacteria pili OR through blood stream (through BBB)

Question 17

Outline the layers of the meninges

Answer 17

Dura mater (periosteal and meningeal layer), arachnoid, pia mater

Question 18

Describe the dura mater

Answer 18

Outermost layer of meninges and has two layers (periosteal and meningeal)

Question 19

Describe the arachnoid mater

Answer 19

Middle layer of meninges (cobweb over surface of brain)

Question 20

Describe the pia mater

Answer 20

Inner most layer of meninges which is thin layer attached to surface of brain and is loosely connected to arachnoid

Question 21

Where does CSF circulate between arachnoid and pia?

Answer 21

Subarachnoid space

Question 22

How is CSF formed?

Answer 22

By choroid plexus in lateral ventricles and then spreads to the rest of the CNS

Question 23

Where does CSF enter the subarachnoid space from?

Answer 23

4th ventricle

Question 24

How would a supratentorial (uncal) brain herniation present?

Answer 24

Dilated pupil due to CN III (oculomotor) compression as temporal lobe presses on midbrain

Question 25

How would an infratentorial (tonsillar) brain herniation present?

Answer 25

Cardiorespiratory dysfunction due to compression of lower brainstem

Question 26

What is the prognosis for meningitis?

Answer 26

Untreated = nearly always fatal
Viral meningitis = resolves spontaneously
Bacterial meningitis = depends on age and underlying cause (33% of patients have neurological abnormalities at discharge and 11% 5 years later)

Question 27

How can you prevent meningitis contraction?

Answer 27

Prevent contact with someone infected, get vaccinated against A,C,W,Y, as well as childhood vaccination programmes as well as use of antibiotics if in exposure to someone with meningitis

Question 28

Describe the pathophysiology of meningitis

Answer 28

Bacteria colonise in mucus –> invade bloodstream –> survival and multiply –> cross BBB –> invade meninges and CNS –> increase permeability of BBB (and greater lymphocyte numbers in CSF) –> oedema follows –> increased intracranial pressure –> release of pro-inflammatory compounds –> pressure on brain –> neuronal injury

Question 29

What is meant by ‘empiric antibiotics’?

Answer 29

Antibiotics given without exact diagnosis

Question 30

Describe the treatment of meningitis

Answer 30

Empiric antibiotics should be given immediately, and use of corticosteroids such as dexamethasone to suppress overactive inflammation. May change antibiotic when results are back to make more effective.

Question 31

What are some of the difficulties with treating meningitis?

Answer 31

Many antibiotics cannot cross BBB to reach meninges

Question 32

Why may dexamethasone (NSAID) be started early in treatment of suspected meningitis?

Answer 32

Help to reduce swelling around brain –> reduce oedema to reduce neurological deficits. Dampen immune system so symptoms not as bad.