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Flashcards in Central Nervous System Infections Deck (24)
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Meningitis definition

Inflammation of the meninges
-> leptomeningitis-> inflammation centred on the subarachnoid space
-> pachymeningitis->inflammation centred on dura

1

Meningitis routes of infection

Blood Bourne
Parameningeal suppurations-> otitis media, sinusitis-> infections which are good at getting through meninges
Direct spread though Duran defect-> surgery, trauma
Direct spread though cribriform plate

2

CSF infection

Difficult to treat
Low protein-> no complement etc
Low IgG
No lymphatics
BBB-> drugs need to by lymphilic

3

Bacterial Meningitis inflammatory process

Endotoxins of gram negative bacteria and peptidoglycan components of gram positive cell walls-> potent inflammatory mediators-> TNF, IL-1,6,8, PAF, NO. Can resist phagocytosis-> bacteriaemia
-> migration of neutrophils to the CSF-> release of proteolytic products and O radicals
-> damage to vascular endothelium-> increased BBB permeability
-> alteration of CSF dynamics

4

Meningitis symptoms and signs

Global headache
Neck and back stiffness
Nausea and vomiting
Photophobia

Fever, can be absent in really bad infection
Petechial/purpuric rash
Kernigs signs positive due to hamstring spasm, neck stiffness-> can't put head on chest

5

Clinical features of meningitis

Fever 97%
Meningism 82%
Impaired conciousness
Rash
Seizures
Hypotension

6

Meningitis in infants

Typical signs are not always present <18/12
Flaccid later opisthotonos
Bulging fontanelle due to increased ICP
Fever and vomiting often the only sign
Strange cry
Convulsions

7

Lumbar puncture

Most rapid diagnostic test
Distinguish between bacterial and viral
Risk of herniation (coning)from increase intra cranial pressure
-> if longer history
-> focal neurology, drowsy
Only do it if not contraindicated
Treat first

8

CT scan

Benefits-> identifies SOL or other lesion, very rarely show meningeal flare
Disadvantages:
Delay
Doesn't help diagnosis of meningitis
Poor predictor of raised ICP
Poor distinction between com/non com hydrocephalus
Indicated when:
-> diagnosis is in doubt
-> focal abnormalities
-> com or seizures non urgent

9

CSF changes in meningitis

Normally < 5 lymphocytes
Blood glucose should be half that in blood
Viral-> 50-1000 WBC, predominately mononuclear neutrophilic
Bacterial-> 100-5000 WBC, predominately neutorphilic, low glucose
TB-> 50-300 WBC, mononuclear
Cryptococcal-> 20-500, mononuclear

10

Causes of lymphocytic CSF

TB
Partially treated bacterial infection
Leptospirosis
Lyme borreliosis
Viral meningo-encephalitis
Syphillis
Lymphocytic Leukaemias

11

Rapid diagnostic tests for meningitis

Gram stain on deposit 50% sensitivity
Agglutination tests look for antigen-> meningococcal! HiB, cryptococcal
PCR
-> meningococcal on EDTA blood and CSF
HSV/Enterovirus
Mtb

12

Causes of bacterial meningitis

Neisseria meningitis-> children/ young adults
Streptococcus pneumoniae-> children vaccine
Group B streptococci, eschrichia coli, listeria monocytogenes-> neonates

13

Pneumococcal meningitis

Predisposing factors-> alcohol, diabetes, hypospenism, myeloma, immunosuppression
Pneumonia and/or otitis media present in <50%
Impaired consciousness, neurological signs and seizures more common
Morality 30% with therapy

14

Listeriosis

Poo and contaminated fridge food
Meningo-encephalitis
Affects brain stem with ataxia and movement disorders, neck stiffness
Gram stain negative
Ampicillin +\- gentamicin
Morality 20%

15

Complications of meningitis

Death
Subdural collection
Cerebral vein thrombosis
Hydrocephalus
9-15% deafness convulsions
Visual/motor/ sensory deficit

16

Management of meningitis

Antibiotics
Adequate oxygenation
Prevention of hypoglycaemia and Hyponatraemia
Anticonvulsants
Decrease intracranial hypertension
Steroids-> give prior to antibiotics for beneficial effect

17

Causes of viral meningitis

Enteroviruses
Herpes viruses-> heroes simplex, varicella zoster
Mumps and measles
Flavaviruses

18

Encephalitis

Inflammation of the brain
Cerebral irritation/dysfunction:
-> irritability, altered personality, drowsiness
-> ataxia
-> excessively brisk tendon reflex
-> signs of cerebral/brain stem failure
-> signs of brain swelling
Myelopathy->motor and sensory signs
Encephalopathy-> reduced conciousness

19

Organisms that cause encephalitis

Viral-> herpes simplex, polio, rabies
Bacterial-> listeria! treponema, borrelia

20

Myelitis

Inflammation of the spinal chord
Can occur with or without encephalitis
Transverse-> acute transaction of spinal chord
-> vasculitis of anterior spinal artery
-> primary infection-> VZV , TB, syphlis, schistosomiasis
-> post infectious-> measles, mumps, rubella, upper resp
-> direct invasion of spinal chord-> VZV, borrelia, HTLV-1 throaric
Ascending-> ascending flaccid paralysis and sensory loss
Anterior horn cells eg polio flaccid paralysis muscle pain, no sensory or bladder dysfunction-> polio, Enterovirus 71, some arboviruses and rabies virus

21

Encephalomyelitis

Encephalitis and myelitis as over lapping causes
Primary or post infection
Direct invasion, vasculitis interrupting blood supply or immune response to infection

22

Entry to CNS for Encephalomyelitis

Blood most common
Some via peripheral nerves-> rabies and polio
Respiratory-> measles, mumps, VZV, c.neoformans
GI tract-> poliovirus, other enteroviruses, listeria
Subcutaneous-> arthropod Bourne viruses, ricketsii, trypanosomes
Mucosa-> herpes simplex, VZV

23

Herpes simplex encephalitis

Haemorrhagic necrosis especially in temporal lobes
CSF abnormal in 97%
RBCs in an atraumatic LP
Mild lymphocytosis
Characteristic MRI
Morality 60% if left untreated

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