CNS infections Flashcards
What is encephalitis?
Inflammation of the brain
If a patient presents with odd behaviour, decreased consciousness, focal neurology or seizure preceded by an infectious prodrome, what should you suspect?
Encephalitis.
What is usually the cause of encephalitis?
Viral infection
What viral infections can cause encephalitis?
HSV 1&2 Arboviruses CMV EBZ VZV Measles, mumps, rabies, west nile virus, tick-borne encephalitis
What are some non-viral causes of encephalitis?
Any bacterial meningitis TB Malaria Listeria Lyme disease Legionella
Signs and symptoms of encephalitis?
Preceding flu-like illness Bizarre behaviour Confusion Reduced GCS Fever Headache Focal neurological signs Seizures History of travel or animal bite Meningism is usually absent.
What things can we do to diagnose encephalitis?
Contrast enhanced CT scan done before LP
Lumbar puncture - moderately increased CSF protein and lymphocytes and low glucose
EEG showing diffuse abnormalities can help confirm diagnosis
How do we manage encephalitis?
Aciclovir for HSV and ZVZ within 30m of patient arriving for 14 days
Ganciclovir for CMV
Repeat LP to ensure successful treatment
Phenytoin for seizures if needed
What is the mortality of untreated viral encephalitis?
70%
What are the signs of a cerebral abscess?
Seizures Fever Localised signs or symptoms of raised ICP Coma Signs of sepsis elsewhere
Investigations for cerebral abscess?
CT/MRI
Increased WCC, increased ESR
What is meningitis?
Inflammation of the meninges (lining of brain and spinal cord)
What is meningococcal septicaemia?
Refers to the meningococcus bacterial infection in the bloodstream. It is the cause of the classic ‘non-blanching rash’
Infective and non-infective causes of meningitis?
Infective
- Bacterial
- Viral
- Fungal
- Parasitic
Non-infective
- Paraneoplastic
- Drug side effects
- Autoimmune (SLE/vasculitis)
What are the 3 ways infection can enter the meninges?
- Direct contiguous spread - nasal carriage, otitis media, sinusitis
- Neurosurgical complications - post op or infected shunts, trauma
- Via blood stream - bacteraemic (most common)
Describe the pathophysiology of infective meningitis
- Brain is normally protected by the BBB and prevents immune system from attacking brain tissue
- In meningitis when pathogens have found their way into the brain, they can multiply and are evaded from the immune system
- Blood vessels become leaky allowing, WBCs and cytokines to enter the meninges and accounts for the changes we see in the CSF (increased WCC etc)
- Depending on the severity, infection might remain confined to the subarachnoid space but in severe forms, the brain parenchyma can become infected and cause permanent damage without treatment
Clinical presentation of meningitis?
Classic
- Fever
- Headache
- Neck stiffness
Others
- nausea and vomiting
- photophobia
- irritability
- confusion, sleepiness, coma in severe infection
Treatment of meningitis at first presentation?
- Bacterial meningitis is a medical emergency
- 5% mortality when treated & 20% permanent effects
- IM benzylpenicillin immediately and admit to hospital
Management of meningitis at hospital?
- Assess GCS
- Blood cultures
- Broad spectrum IV antibiotics - ceftriaxone or cefotaxime
- Special considerations - penicillin allergy, immunocompromised (listeria meningitis so add amoxicillin) and recent travel (penicillin resistance, add vancomycin)
- Steroids - dexamethasone to reduce morbidity, tissue inflammation and neuronal damage
- Lumbar puncture - definitive diagnosis for meningitis
- Inserted in L3-L4 intervertebral space
- CSF sent to microbiology to assess cell count
- biochemistry to check glucose and protein concentration
- microbiology for gram stain and culture
- viral PCR
- No absolute contraindication but some relative:
- abnormal clotting, anticoagulation treatment, petechial rash, raised intracranial pressure
When would we consider doing a CT head before a LP in meningitis?
Exclude a mass lesion or increased ICP as these can lead to brain herniation when removing CSF:
- Aged >60
- Immunocompromised state
- History of CNS disease, previous stroke.
- Seizures <1 week of presentation
- GCS <14
- Focal neurological signs
- Papilloedema
- Atypical history
What type of bacteria is Neisseria meningitidis?
What percentage of adult and teenage populations are carriers?
Gram neg cocci
- 5-11% adult carriers
- 25% teenage carriers
Describe how the infective organisms for meningitis differ depending on age (neonate, children, adult, elderly)
Neonate: listeria, group B strep, e coli
Children: N meningitidis, strep pneumoniae, Haemophilus influenzae type b
Adults: N meningitidis, strep pneumoniae
Elderly: N meningitidis, strep pneumoniae, Listeria
How to tell the difference between viral and bacterial depending on analysis of CSF (appearance of CSF, microscopy, protein, glucose)
Appearance, microscopy, staining, protein, glucose of CSF bacterial
- cloudy
- polymorphs (neutrophils) on microscopy
- staining: organisms can be seen on gram film
- protein: high
- glucose: low
Appearance, microscopy, staining, protein, glucose of CSF viral
- Clear
- lymphocytes on microscopy
- no organisms seen on staining
- protein high
- glucose normal
Appearance, microscopy, staining, protein, glucose of CSF TB
- fibrin web
- lymphocytes on microscopy
- protein high
- glucose low
Appearance, microscopy, staining, protein, glucose of CSF in cryptococcal
- appearance fibrin web
- microscopy lymphocytes
- protein high
- glucose low
what do we do for contacts of those with N meningitidis?
Identify close contacts and antibiotic prophylaxis (ciprofloxacin or rifampicin) to reduce the risk and prevent onward transmission
Where are clostridium tetani spores found globally?
In soil
Who is at higher risk of getting tetanus
- those who are not vaccinated and IVDU
What toxins are produced by tetanus
- tetanolysin (tissue destruction)
- tetanospasmin (clinical tetanus)
What is the difference between generalised tetanus and localised tetanus?
Generalised tetanus:
- Spread through lymphatics or blood to multiple nerve terminals
- Locked jaw → sardonic smile
- Opisthotonos - spasm of back muscles
- HTN, tachycardia, arrhythmia and fever if toxin affects the autonomic nervous system
Localised tetanus:
- Develops when only the nerve supplying the affected skin are involved causing painful contraction at the site of injury
Can rabies be treated? How is it managed
No, invariably fatal 99%
Managed with sedatives.