Infections of the CNS Flashcards
What is more seroius meningitis or sepsis?
Sepsis
What are the clinical features of meningitis?
- Headache, sore throat, drowsiness
- Rapid onset fever, photophobia, neck stiffness
- Level of consciousness progressively falls
- Petechial or purpuric rash
- Intravascular coagulation, endotoxaemia, shock, multi-organ fever, raised intracranial pressure
- Life-threatening emergency
What is a petechial rash?
- Red/brown/purple pinpoint spots on the skin that are a result of bleeding
- Do not lose colour when touched
- Clinical sign of meningitis
How do you check whether an individual has meningococcal meningitis?
Glass test - skin does not blanch
What is purpura fulminans?
Blood spots, bruising and discolouration of the skin resulting from coagulation in small blood vessels within the skin and rapidly leads to skin necrosis and disseminated intravascular coagulation
- Sign of acute meningitis
What are some clinical signs of meningitis in babies?
- Tense or bulging soft spot on their head
- Refusing to feed
- Irritable when picked up, with a high pitched or moaning cry
- A stiff body with jerky movements, or else floppy and lifeless
What are some clinical signs that are more specific to meningitis than septicaemia?
- Severe headache
- Stiff neck (viral)
- Dislike of bright lights (viral)
- Seizures (viral)
What is sepsis?
Whole body inflammation
How can infectious agents reach the CNS?
- Breach by infectious agents of BBB at arachnoid membrane in ventricles -> meningitis
- Breach of blood brain barrier (tight junctions) -> encephalitis
- Direct spread;
Sinuses
Otitis media
Skull fracture
What laboratory tests should be carried out if patient is suspected of meningitis?
Blood - FBC - Coagulation screen - Blood culture - PCR or NAAT - Blood glucose - UandEs CSF - White cell count - Gram stain - Ziehl-Neelsen stain (TB) - India ink (negative stain - shows whether microbe has capsule) - NAAT
What stain/test is used to find out whether a microbe has a capsule?
India ink
When would a lumbar puncture not be performed?
- GCS <9
- Intracranial pressure
What are the 4 most common bacterial causes of meningitis?
- Neisseria meningitidis
- Haemophilus influenzae
- Streptococcus pneumoniae
- Mycobacterium tuberculosis
What are the most common viral causes of meningitis?
Enteroviruses - Echovirus - Coxsackie viruses AandB Hepres simplex 1 and 2 Paramyxovirus
What is paramyxovirus a compliacation of?
Mumps
What fungi can cause meningitis?
Cryptococcus neoformans (HIV+)
What are the protozoa which cause meningitis?
Sub-saharan Africa
- Amoebea
- Naegleria
- Acanthamoeba
What are the features of neisseria meningitidis?
- Meningicoccal
- Gram negative
- Intracellular diplococus
- Only infects humans
- Exists as normal microbiota in nasopharynx
How is neisseria meningitidis spread?
Droplet spread or direct contact from carriers
What are the 5 strains of neisseria meningitidis?
A, B, C W135, Y
What are the features of Haemophilus influenzae?
- Gram negative
- Cocobacilli
What are the different serotypes of haemophilus influenzae able to cause disease?
A-F
- Most virulent strain is type B (Hib)
What are the features of streptococcus pneumoniae?
- Pneumococcal disease
- Chains of cocci
- Gram positive
- Exists as normal microbiota in nasopharynx
- Also causes pneumonia, otitis media
What are some virulence factors bacteria can have in bacterial meningitis?
- ANti-phagocytic polysaccharide capsule
- Endotoxin
- IgA protease
- Outer membrane proteins (OMPs)
- Pili (fimbriae)
All play an important role in pathogenesis
What will CSF look like in bacterial meningitis vs viral and TB?
Bacterial = Turbid Viral = Clear TB = Clear (may cobweb)
What cells will be present in bacterial meningitis vs viral and TB?
- Polymorphs in bacterial and TB
- Lymphocytes in viral
How much protein will be in CSF in bacterial vs viral vs TB meningitis?
- Increased in all but more in bacterial and especially TB
What will the glucose levels be in CSF in bacterial vs viral vs TB meningitis?
- Reduced (0-5) in bacterial and TB
- Normal in viral
What gram stain will be performed in bacterial vs viral vs TB meningitis?
- Bacterial - gram negative usually
- Viral not applicable
- TB - do Ziehl-Neelson stain
What will the white cell count be in bacterial vs viral vs TB meningitis?
- Bacterial = Neutrophilia
- Viral and TB = Normal
Cobweb CSF present in what type of meningitis?
TB
When is pneumococcal meningitis most common?
< 1 year old
What are the most common causes of bacterial meningitis in neonates?
- Escherichia coli
- Group B streptococcus
- Listeria monocytogenes
What is the most common form of meningitis in young adults?
neisseria meningitidis
What are the features of early onset neonatal meningitis?
- Occurs <7 days
- Infected by heavily colonised mother
- Premature rupture of membranes
- Preterm delivery
- 60% fatality rate
What are the features of late onset neonatal meningitis?
- Occurs < 3 months
- Lack of maternal antibody
- Poor hygiene in nursery
- 20% fatality rate
What are the complications of bacterial meningitis?
- Sepsis
- Intellectual defecit
- Deafness
- Arthritis
- Skin necrosis
What treatment should be administered in a suspected meningococcal infection?
- IV/IM penicillin (Pre-admission)
- IV Ceftriaxone (on admission)
What treatment should be administered in a suspected meningococcal infection < 3 months old?
IV Cefotaxime + amoxicillin
Are meningococal diseases notifiable?
Yes
What is the main prevention for meningitis?
Vaccines
What is the most common type of meningitis?
Viral
What is a valuable diagnostic tool in meningitis?
NAAT
Is encephalitis usually viral or bacterial in origin?
Viral
How can viruses gain access to the CNS?
Via blood or neurons
How can encephalitis be classified?
Primary encephalitis
- First exposure to virus results in virus directly affecting brain / spinal cord
Secondary encephalitis
- Virus first infects another part of body, then affects CNS when reactivated
What are signs of cerebral dysfunction/encephalitis?
- Seizures
- Nausea and Vomiting
- Fever
- Altered consciousness
- Abnormal behaviour
What are brain abscesses?
- Begin as diffuse inflammation of brain matter progressing to focal lesion
- Arise from pia mater suppuration
- Visualised by MRI or CT scans
- Diagnosed by culture from aspirated pus
What are the predisposing factors to brain abcesses?
- Ottis media
- Mastoiditis
- Sinusitis
What are the oral-nasopharyngeal microbiota which can cause brain abscesses?
- Aerobic (S. aureus, strep milleri)
- Anaerobic (BActeroides sp., Fusobacterium sp.)
What are the immunocompromised diseases which can cause brain abcesses?
- Protozoa (toxoplasma gondii)
- Fungi (Candida sp, Nocardia sp, Aspergillus sp.)
What are transmiffible spongiform Encephalopathies (TSEs) caused by?
Prions
What are some prions that can affect humans?
- Creutzfeldt-Jakob disease (CJD)
- New variant Creutzfeldt-Jakob disease (nvCJD)
Animlas (Bovine Spongiform Encephalopathy)
