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Flashcards in Infections of the CNS Deck (27)
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1
Q

petechial/purpuric rash

A

doesnt go away when pushed with glass

2
Q

Complications - meningitis

A

May affect 20+% of survivors

Seizures
Hearing difficulties
Other cranial nerve problems Focal paralysis Hydrocephalus
Intellectual disability
Ataxia
3
Q

Complications - sepsis

A

Limb amputations
Arthritis and join pain
Skin necrosis and scarring
Organ dysfunction: liver, kidney, adrenal glands

4
Q

meningitis

A

inflammation of the meninges

5
Q

encephalitis

A

inflammation of brain parenchyma

6
Q

sepsis

A

life-threatening organ dysfunction caused by dysregulated host response to infection

7
Q

Blood-brain barrier (BBB)

A

– Tightly packed endothelial cells line the blood vessels in the brain mechanically supported by thin basement membrane.
– Breach by infectious agents causes encephalitis.

8
Q

Blood- cerebrospinal spinal fluid (CSF) barrier

A

– Similar barrier at arachnoid membrane and in ventricles.

– Breach by infectious agents causes meningitis.

9
Q

• Direct Spread to the CNS via

A
  • Sinuses
  • Otitis media
  • Skull fracture
10
Q

how is the BBB breached

A

– Growing across & infecting cells comprising barrier
– Passive transfer in intracellular vacuoles
– Carriage across in infected white blood cells

11
Q

what are the three causes of meningitis

A
  • infection
  • auto-immune
  • malignancy
12
Q

what are the dangers of neonatal meningitis - early onset

A
• Occurs <7 days
• Infected by heavily
colonised mother
• Premature rupture of membranes
• Pretermdelivery
• 60%fatalityrate
13
Q

what are the dangers of neonatal meningitis - late onset

A

• Occurs <3 months
• Lack of maternal
antibody
• Poor hygiene in nursery • 20%fatalityrate

14
Q

Neisseria meningitidis

A

Only infect humans
Normal microbiota in nasopharynx
Transmission by droplet spread or direct contact from carriers At least 12 serotypes - different in polysaccharide antigens
5 pathogenic serogroups strains – A, B, C, W135, Y

15
Q

Haemophilus influenzae

A

Six capsular serotypes (a-f) known to cause disease

Most virulent strain is H. influenzae type b (Hib)

16
Q

Streptococcus pneumoniae

A
  • Normal microbiota in nasopharynx
  • There are over 90 bacterial serotypes
  • Common cause of meningitis in young children and adults with specific risk factors (e.g. older, diabetic, alcohol excess, asplenic*)
  • Pneumococci also causes pneumonia, otitis media and bloodstream infections
17
Q

Babies /small children:

clinical features

A

– 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

18
Q

• Blood test

A

– Biochemistry: U&E, CRP, lactate, glucose
– Haematology: FBC, clotting
– Microbiology: Blood culture, meningococcal & pneumococcal PCR, HIV test

19
Q

CSF test

A

– Biochemistry: Protein & Glucose – Microbiology:
• White cell count
• Gram stain & bacterial culture
• Meningococcal & pneumococcal PCR
• Viral PCR tests
• TB: microscopy, molecular tests & culture
• Cryptococcal: Indian Ink, CrAg, fungal culture

20
Q

what are things to remember when taking a lumbar puncture

A

Measure the opening pressure

Take matched blood and CSF glucose samples Collect enough fluid (and some to spare!)

21
Q

Are there situations when you should delay or omit doing a lumbar puncture?

A
  • Risk of bleeding

* Focal neurology suggesting a mass lesion in the brain

22
Q

When do we need CNS imaging?

A

An important role of CT, in some patients, is to exclude mass lesions and/or oedema, which might make an LP dangerous.
In these patients a reduction of the CSF pressure below the lesion following an LP could precipitate herniation of the brainstem or cerebellar tonsils.
This may occur in patients with brain abscess, subdural empyema, tumour, or a necrotic swollen lobe in encephalitis.

23
Q

Routine vaccination now against:

A

• Haemophilus influenzae b
• Pneumococcus
• Meningococcus A,B,C, W, Y
Vaccines against other neurological infections: • Polio, tetanus

24
Q

Viral Meningitis

A
  • Identify by PCR of CSF
  • Usually regarded as ‘benign’ & self-limiting
  • Long-term neuropsychiatric sequelae have been described – Anxiety, Depression, Neurocognitive dysfunction
25
Q

Encephalitis

A

Most common cause: Herpes Simplex Virus-1
Symptoms & signs: altered cerebration Confusion, abnormal behaviour, seizures, fever
Investigations: similar to meningitis
Typical findings on CSF, temporal lobe changes on MRI scan
Treatment: high dose IV aciclovir

26
Q

Brain abscess

A

Pre-disposing factors: otitis media, mastoiditis, sinusitis Causes: often oral nasopharyngeal microbiota
Aerobic (S. aureus, Strep. milleri)
Anaerobic (Bacteroides sp., Fusobacterium sp.) Pathophysiology:
Diffuse inflammation -> focal lesion and pia mater suppuration Symptoms & signs: headache, focal neurology, seizures Investigations: CT / MRI scan +/- invasive sampling
Treatment: Antibiotics (often ceftriaxone + metronidazole)

27
Q

Transmissible Spongiform Encephalopathies (TSEs)

A

Rare prion diseases
“Proteinacious infectious particles”
Cause vacuoles and plaques in nervous tissue
Highly resistant to heat, chemical agents and irradiation No treatment, no vaccine, fatal