7. Infections of the CNS Flashcards
Glass test, non blanching is….
A rash that does not fade under pressure is a sign of meningococcal septicaemia
Clinical features of meningitis?
Headache, sore throat, drowsiness
Intravascular coagulation, endotoxaemia, shock, multi-organ failure, raised intracranial pressure
Rapid onset fever, photophobia, neck stiffness (typically viral)
Level of consciousness falls (typically viral)
Petechial or purpuric rash (typically viral)
Symptoms of meningitis mainly seen in babies?
Tense/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
Which features of meningitis are more specific a viral origin?
Rapid onset fever, photophobia, neck stiffness (typically viral)
Level of consciousness falls (typically viral)
Petechial or purpuric rash (typically viral)
Encephalitis is…
Inflammation of the brain
Sepsis is…
Whole body inflammation when your body goes into a system inflammatory response syndrome (SIRS)
3 methods of invasion into the CNS by micro organised?
BBB
B- CSF BARRIER
Direct spread
Mechanism of invasion to CNS by micro-organisms via the BBB?
Breach results in….
– Created by tightly packed endothelial cells lining the blood
vessels in the brain.
– Endothelial cells mechanically supported by thin basement membrane.
– Breach by infectious agents causes ENCEPHALITIS.
Mechanism of invasion to CNS by micro-organisms via B-CSF barrier?
Breach results in….
– Similar barrier at arachnoid membrane and in ventricles. – Breach by infectious agents causes meningitis.
Mechanism of invasion to CNS by micro-organisms via direct spread?
From sinuses, otitis media and skull fractures
What laboratory investigations should be done to confirm a diagnosis for infections of the CNS?
Blood test, such as:
- Culture
- NAAT
- Glucose
- FBC
- U&E
- Clotting
CSF test, such as:
- White cell count
- Gram stain
- Ziehl-neelsen stain (
- India ink
- NAAT
Which diseases does the ziehl neelsen stain and the india ink stain identify?
Ziehl-neelsen= Tb
India ink= India ink staining of cerebrospinal fluid is a sensitive test for the presence of cryptococcus neoformans.
When should a lumbar puncture not be done?
Supratentorial and infratentoral pressure difference
Infeciton of the skin overlying the needle entry site
Name 4 bacterial infections causing meningitis?
Neisseria meningitidis
Haemophilus influenzae
Streptococcus pneumoniae
Mycobacterium tuberculosis
Name 5 viral infections causing meningitis?
3 x enteroviruses
1 x herpes
1 x paramyxovirus
Enteroviruses:
• Echovirus
• Coxsackie viruses A & B
• poliovirus
Herpes viruses:
• Herpes simplex 1& 2
Paramyxovirus:
• Complication of mumps
Fungal infections causing meningitis
Cryptococcus neoformans
** India ink stain**
3 protozoa infections causing meningitis?
Amoebae
Naegleria
Acanthamoeba
Characteristics of Neisseria meningitidis as a meningococcal disease: Gram.... Infects only.... where does it lie.... Transmission... Strains...
- Gram negative. Intracellular diplococus
- Only infects humans. Exists as normal microbiota in nasopharynx
- Transmission by droplet spread or direct contact from carriers
- 5 strains – A, B, C, W135, Y
Characteristics of Haemophilus influenze as a meningococcal disease: Gram.. Structure... Serotypes... Most virulent strain is?
- Gram-negative
- Coccobacilli (spherical)
- Six capsular serotypes (a-f) known to cause disease
- Most virulent strain is H. influenzae type b (Hib)
Characteristics of streptococcus pneumoniae as a meningococcal disease: Type of disease? Shape? Gram? Where found?
- Pneumococcal disease
- Chains of cocci
- Gram positive
- Exists as normal microbiota in nasopharynx
- Also causes pneumonia, otitis media
Virulence factors of bacterial meningitis?
- Anti-phagocytic polysaccharide capsule
- Endotoxin (released when disintegrates)
- IgA protease
- Outer membrane proteins (OMPs)
- Pili (fimbriae)
Cloudy CSF indicates
Bacterial meningitis infection
What is the significance of age in predicting a diagnosis of meningitis?
Ages most at risk are:
2 months -4 years
65yrs-79yrs
Which bacterial meningeal pathogens are responsible for meningitis in neonates?
Escherichia coli
Group B Streptococcus Listeria monocytogenes
Which bacterial meningeal pathogens are responsible for meningitis in <5 yrs old?
Neisseria meningitidis Haemophilus influenzae
Which bacterial meningeal pathogens are responsible for meningitis in young adults?
Neisseria meningitidis
Which bacterial meningeal pathogens are responsible for meningitis in older?
Streptococcus pneumoniae Listeria monocytogenes
Which bacterial meningeal pathogens are responsible for meningitis in immunosuppressed?
Mycobacterium tuberculosis Cryptococcus neoformans
Early onset of neonatal meningitis:
When?
Due to?
Risks associated?
• Occurs <7 days
• Infected by heavily
colonised mother
Risks:
• Premature rupture of membranes
• Pretermdelivery
• 60% fatality rate
Late onset of neonatal meningitis:
When?
Due to?
Risks associated?
• Occurs <3 months
Cause:
• Lack of maternal
antibody
• Poor hygiene in nursery
• 20% fatality rate
Complications of bacterial meningitis?
- Sepsis
- Intellectual deficit
- Deafness
- Arthritis
- Skin necrosis
When treating suspected bacterial meningitis, what is given?
IV broad spectrum antibiotics e.g. ceftiaxone, cefotaxime, ceftriaxone, amoxicillin and gentamicin
What is the main method for prevention of meningitis spread?
VACCINES e.g. • MenC (meningococcal group C) • Hib (Haemophilus influenzae type B) • BCG (Mycobacterium tuberculosis) • Strep. Pneumoniae (pneumonococcal) • MenB (meningococcal group B) • Men ACWY (quadrivalent)
Notification, Prevention and Control strategy for meningitis?
Meningococcal disease is a notifiable disease under the Public Health etc. (Scotland) Act 2008.
Reference Laboratories:
• Scottish Haemophilus, Legionella, Meningococcus and Pneumococcus Reference Laboratory (SHLMPRL)
Public Health Action:
• Public Health will identify the close contacts and arrange antibiotics. Vaccination may also be required.
• If the patient is a child at school information letters and MRF info leaflets for all school parents are arranged.
Public Awareness:
• The public should be aware of the key signs and symptoms and to seek urgent medical advice if concerned.
Viral meningitis: Common? Diagnostic tool? Treatment? Vaccine available?
- Milder disease than bacterial but more common
- NAAT is a valuable diagnostic tool. Identify in faeces, urine, CSF, serology
- No specific treatment
- Aciclovir (herpes)
• Use of vaccination (polio)
Tuberculous meningitis: Associated with which disease? Cause? Diagnosis? Treatment? Vaccine?
- Frequently associated with miliary TB
- Usually develops when Rich focus discharges contents in sub-arachnoid space
- Acid-fast bacilli in CSF smear. NAAT and culture from CSF
- Treated with rifampicin, isonazid, pyrazinamide, ethambutol
- Vaccination with BCG
Encephalitis (infection to CNS):
Origin?
Primary vs secondary?
• Usually viral in origin. Viruses gain access to CNS via blood or neurons
• 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
Signs of cerebral dysfunction in encephalitis>
– Abnormal behaviour – Seizures – Altered consciousness – Nausea – Vomiting – Fever
How does a brain abscess form?
Beings as diffuse inflammation of brain matter progressing to a focal lesion.
Arise from pia mater suppuration
(Can be visualised by MRI or CT)
Diagnosis of brain abscess?
Culture from aspiration pus
Brain Abscess - Causes and predisposing factors?
• Predisposing factors
– Otitis media (ear inflammation)
– Mastoiditis
– Sinusitis
Cause:
• Oral-nasopharyngeal microbiota
– Aerobic (S. aureus, Strep. milleri)
– Anaerobic (Bacteroides sp., Fusobacterium sp.)
• Immunocompromised (eg. HIV, transplantation)
– Protozoa (Toxoplasma gondii)
– Fungi (Candida sp., Nocardia sp., Aspergillus sp.)
What is a TSE?
Transmissible spongiform encephalopathies
Prion disease i.e. cause of brain disease, have no nucleus, not visible under microscope
TSE that affect humans
• Affects humans…
– Creutzfeldt-Jakob disease (CJD)
– New variant Creutzfeldt-Jakob disease (nvCJD)
Direct damage to nerve cells in…
poliomyelitis
• Release of neurotoxins released at a distant site by bacteria, name 2 diseases this occurs in
(eg. botulism, tetanus)
