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Neuro > CNS INFECTION > Flashcards

CNS INFECTION Flashcards

1
Q

Define meningitis

A

inflammation of the leptomeninges (the arachnoid and pia mater) and usually occurs due to a bacterial, viral, or fungal infection.

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2
Q

Most common cause of bacterial meningitis in the UK

A

N meningitidis and S pneumoniea - most common in adults is S. pneumoniae

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3
Q

Most commomn cause of viral meningitid

A

enterovirus
coxsackievirus

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4
Q

Common bacterial causes of MG?

A
  • Group B strep,
  • e coli
  • s pneumoniea
  • m tuberculosis
  • Neisseria mengitidis
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5
Q

common fungal causes of mg

A

cryptococcus neoformans
candida albicans

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6
Q

Rf for mg

A
  • Immunocompromised: numerous causes includingextremes of age(children and the elderly),infection(such as HIV) andmedication(such as chemotherapy)
  • Non-immunised: at risk ofH. influenza, pneumococcal and meningococcal meningitis
  • Crowded environment: students living in halls of residence are a commonly affected demographic
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7
Q

two methods of transmission for MG

A

Direct spread
Haematogenous

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8
Q

How does direct spread occur

A
  • pathogen gets inside the skull or spinal column, and then penetrates the meninges ending up in the CSF
  • sometimes the pathogen will come on open skin or through nose
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9
Q

how does haematogenous spread occur

A

Pathogen enters the bloodstream and moves through the endothelial cells in the blood vessels making up the blood-brain barrier and gets into the CSF.

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10
Q

What happens once a pathogen enters the CSF

A
  • begins to multiply
  • wbc release cytokines to recruit additional immune cells
  • more than 5microlitres will suggest meningitid
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11
Q

what happens to glucose and protein levels in the csf

A
  • glucose in csf falls to below 2/3 of the blood
  • protein increases
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12
Q

Signs of meningitis

A
  • Kernig’s sign: when the hip is flexed and the knee is at 90°, extension of the knee results in pain
  • Brudzinski sign: severe neck stiffness causes the hips and knees to flex when the neck is flexed
  • Petechial or purpuric non-blanching rash: associated with meningococcal disease (N. meningitidis)
  • Pyrexia
  • Reduced GCS
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13
Q

Symptoms of meningitis

A
  • meningism - headache, photophobia, neck stiffness
  • fever
  • nausea and vomitting
  • seizures
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14
Q

Investigations for MG

A
  • fbc- leukocytosis
  • CRP - raised inflammatory markers
  • coagulation and blood glucose required for comparison
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15
Q

Lumbar puncture and CSF analysis

A
  • CSF gram stain:S. pneumoniae(gram-positive cocci in chains);N. meningitidis(gram-negative diplococci)
  • CSF culture
  • CSF PCR:useful for viruses such as HSV and VZV
  • CSF interpretation
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16
Q

primary care management of MG

A

IV or IM benzylpenicillin STAT

17
Q

Bacterial management of MG

A
  • Steroids; dexamethasone - to reduce long term neurological symptoms -
  • Antibiotics
    3-50yrs = IV cefotaxime
    Over 50 = Iv cefotaxime and amoxicillin
18
Q

Viral management of MG

A
  • Aciclovir
  • conservative management
19
Q

Complications of MG

A
  • Abscess
  • Cerebral oedema
  • Hydrocephalus and brain herniation
  • Seizures
  • Sensorineural hearing loss
  • Waterhouse- Friderichsen syndrome
20
Q

What is encephalitis

A
  • inflammation of the brain paarenchyma, mostly affects frontal and temporal lobes
21
Q

Most common cause of encephalitis

A

Herpes simplex virus

22
Q

Other causes of encephalitis

A
  • Enteroviruses
  • Flaviviruses
  • Retroviruses
  • TB
  • Syphilis
23
Q

Rf for EC

A
  • Immunocompromise
  • Blood/fluid exposure:HIV and West Nile virus
  • Mosquito bite: West Nile virus
  • Transfusion and transplantation: CMV, EBV, HIV
  • Close contact with cats: toxoplasmosis
24
Q

Pathophsyiology of EC

A
  • Encephalitis is an immune response to the invasion of a pathogen, causing inflammation of the brain parenchyma.
25
Q

Describe what happens in EC

A

HSV gets into the sensory ganglia by travelling retrograde from skin and recurrent infection happens when it travels anterograde back to the skin. If it travels to the CNS, it leads to encephalitis. This is usually along olfactory or trigeminal nerves.

26
Q

SIGNS OF EC

A
  • Pyrexia
  • Reduced GCS
  • Focal neurological deficit, such as:
    • Aphasia
    • Hemiparesis
    • Cerebellar signs
  • May also have signs of meningitis: meningo-encephalitis
27
Q

Symptoms of EC

A
  • Fever
  • Headache
  • Fatigue
  • Confusion
  • Seizures
  • Behavioural changes:
    • Memory disturbance
    • Psychotic behaviour
    • Withdrawal or change in personality
28
Q

Primary investigations of EC

A
  • Blood tests:FBC, CRP, U&Es and blood culture
  • Throat swab:culture for viral organisms
  • HIV serology: now routinely tested in the emergency department
  • CT or MRI head:MRI is preferred and will show evidence of inflammation in the medial temporal and inferior frontal lobes in HSV encephalitis;CTis normal in ⅓ of cases
29
Q

Lumbar puncture analysis for EC

A
  • Analysis:lymphocytosis with raised protein in the case of viral aetiology
  • PCR:assays for common viral infections including HSV should be carried out
  • Culture:useful for bacterial causes
  • Serology:antibodies against specific viral antigens
30
Q

DD for ec

A
  • Meningitis
  • Encephalopathy
  • Status epilepticus
  • CNS vasculitis
31
Q

Management of EC

A

Antiviral med- aciclovir
Ganciclovir

32
Q

Encephalitis MRI

A

Bilateral medial temporal lobe involvement very supportive of encephalitis

Neuro (19 decks)

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