Central Nervous System Infections

Question 0

Meningitis routes of infection

Answer 0

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

Question 1

Meningitis definition

Answer 1

Inflammation of the meninges

• > leptomeningitis-> inflammation centred on the subarachnoid space
• > pachymeningitis->inflammation centred on dura

Question 2

CSF infection

Answer 2

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

Question 3

Bacterial Meningitis inflammatory process

Answer 3

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

Question 4

Meningitis symptoms and signs

Answer 4

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

Question 5

Clinical features of meningitis

Answer 5

Fever 97% 
Meningism 82%
Impaired conciousness 
Rash
Seizures 
Hypotension

Question 6

Meningitis in infants

Answer 6

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

Question 7

Lumbar puncture

Answer 7

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

Question 8

CT scan

Answer 8

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

Question 9

CSF changes in meningitis

Answer 9

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

Question 10

Causes of lymphocytic CSF

Answer 10

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

Question 11

Rapid diagnostic tests for meningitis

Answer 11

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

Question 12

Causes of bacterial meningitis

Answer 12

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

Question 13

Pneumococcal meningitis

Answer 13

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

Question 14

Listeriosis

Answer 14

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

Question 15

Complications of meningitis

Answer 15

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

Question 16

Management of meningitis

Answer 16

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

Question 17

Causes of viral meningitis

Answer 17

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

Question 18

Encephalitis

Answer 18

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

Question 19

Organisms that cause encephalitis

Answer 19

Viral-> herpes simplex, polio, rabies

Bacterial-> listeria! treponema, borrelia

Question 20

Myelitis

Answer 20

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

Question 21

Encephalomyelitis

Answer 21

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

Question 22

Entry to CNS for Encephalomyelitis

Answer 22

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

Question 23

Herpes simplex encephalitis

Answer 23

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