Flashcards in FunMed: PBL 8 (Meningitis) Deck (32):
Extremely sensitive to light
Abnormally rapid breathing
What is dexamethasone?
Synthetic drug of corticosteroid type used as anti-inflammatory agent
What are the two groups of causes of meningitis?
Bacterial and viral
Which bacteria commonly cause meningitis?
Neisseria Meningitidis (most common), S. pneumoniae, Listeria monocytogenes, Haemophilis influenza type B
What does rash in meningitis indicate?
Bacteria is systemic and not just in CNS (meningococcal septicaemia)
What are the different types of meningococcal bacteria?
A, B, C, W, X, Y, Z
What viruses cause meningitis?
Enteroviruses - usually cause mild stomach infection and are contagious
Herpes simplex virus - genital herpes and coldsores
E. Coli - more common in infants
What are the symptoms of meningitis in infants?
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
What are the symptoms of meningitis in adults?
Drowsiness, difficulty walking, confusion, irritability and severe headache
Why does pneumococcal bacteria tend to cause meningitis more often in infants?
Streptococcus pneumoniae more harmful because their immune systems haven't built up immunity to these bacteria yet
How is meningitis diagnosed?
Lumbar puncture (L3-L4) to analyse CSF
In meningitis diagnoses what are they looking for in the CSF?
Neutropil dominant WBCs (bacterial) and lymphocyte dominant in viral meningitis, low glucose concentration,
How is lumbar puncture conducted?
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)
Why may CT scan be required prior to conducting lumbar puncture?
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
By which two routes may bacteria reach the meninges?
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)
Outline the layers of the meninges
Dura mater (periosteal and meningeal layer), arachnoid, pia mater
Describe the dura mater
Outermost layer of meninges and has two layers (periosteal and meningeal)
Describe the arachnoid mater
Middle layer of meninges (cobweb over surface of brain)
Describe the pia mater
Inner most layer of meninges which is thin layer attached to surface of brain and is loosely connected to arachnoid
Where does CSF circulate between arachnoid and pia?
How is CSF formed?
By choroid plexus in lateral ventricles and then spreads to the rest of the CNS
Where does CSF enter the subarachnoid space from?
How would a supratentorial (uncal) brain herniation present?
Dilated pupil due to CN III (oculomotor) compression as temporal lobe presses on midbrain
How would an infratentorial (tonsillar) brain herniation present?
Cardiorespiratory dysfunction due to compression of lower brainstem
What is the prognosis for meningitis?
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)
How can you prevent meningitis contraction?
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
Describe the pathophysiology of meningitis
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
What is meant by 'empiric antibiotics'?
Antibiotics given without exact diagnosis
Describe the treatment of meningitis
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.
What are some of the difficulties with treating meningitis?
Many antibiotics cannot cross BBB to reach meninges