Infections of the CNS Flashcards
What is meningitis?
Inflammation of the meninges
Does not have to be infectious but usually is
What is encephalitis?
Inflammation of the brain
Does not have to be infectious but usually is
What is meningoencephalitis?
Inflammation of the brain and the meninges
What is myelitis?
Inflammation of the spinal cord
Can be infectious (but not always)
What is a cerebral abscess?
Collection of pus in the brain
What is an epidural/ subdural abscess?
Pus in the epidural or subdural space
Which bacteria commonly cause meningitis?
Neisseria meningitidis (Meningococcus) Haemophilus influenzae type B (HiB) Streptococcus pneumoniae (Pneumococcus) Group B Streptococci Listeria monocytogenes Mycobacterium tuberculosis
What viruses can cause meningitis?
Enterovirus Varicella Zoster virus (VZV) HIV Mumps Measles
What fungi can cause meningitis?
Cryptococcus neoformans
What viruses can cause encephalitis?
Herpes Simplex virus (HSV) Varicella Zoster virus (VZV) HIV Arboviruses Rabies
What can cause cerebritis?
Bacteria associated with immunodeficiency or abscesses
What bacteria usually causes abscesses?
Streptococci
What parasite can cause cysts?
Toxoplasmosis
What viruses can cause myelitis?
Poliomyelitis
Rabies
What is the most common form on meningitis in the UK?
MenB
What are the common clinical features of all CNS infections?
Fever Headache Neck stiffness Photophobia Rash Reduced GCS Confusion Seizures
What are the clinical features of meningococcal infections?
Acute Sepsis Purpuric rash Peripheral gangrene Often seen in children and young adults with possible outbreaks
What are the clinical features of pneumococcal infections?
Less acute
No rash
High mortality/ morbidity
What form of CNS infection is generally associated with respiratory tract infections, trauma and immunocompromised patients?
Pneumococcal
What form of bacteria is more commonly picked up in neonates during birth?
Group B Strep
Low mortality but risk of CN damage
Who is most at risk of Listeriosis?
Neonates
Elderly
Immunocompromised
Pregnant women
What are the clinical features of bacterial meningitis caused by tuberculous?
Gradual onset of fever
Confusion
Coma
High CSF protein
What type of infection are brain abscesses commonly associated with?
Chronic URTIs (e.g. sinusitis or otitis media)
What investigations should be carried out to diagnosis a CNS infection?
Bloods (FBC + CRP, U+Es, coagulation tests - APTT/ PT)
Blood cultures
HIV test (possibly)
Lumbar puncture
Head CT (if risk of raised ICP/ brain lesions)
What is tested for in CSF for patients with suspected meningitis?
RCC/ WCC Organisms PCR test Protein Glucose (compare with blood glucose)
What are the contraindications for LP?
Raised ICP Infection at LP site Coagulation abnormality Septic shock/ convulsions Obvious/ extensive purpura
What features indicate a raised ICP?
GCS <12 (or >2 falls) Focal neurology Seizures Bradycardia / Hypertension Papilloedema
What can happen in a patient with raised ICP if a lumbar puncture is performed?
Coning (herniation of brain through the foramen magnum)
What should normal CSF look like?
Clear and colourless
Where is a lumbar puncture generally taken from?
Between L3 and L4 (although can be between L1 and L5)
[L5/S1 in children]
Why can a purpuric rash be misleading?
Only occurs in meningococcal meningitis
Why is it important to take 2 sets of blood cultures?
Risk of contamination
Not reliable once antibiotics started
What are the indicators of a bacterial infection in CSF?
High WCC (esp. neutrophils) High protein Low glucose (compared to serum glucose levels)
What are the indicators of a viral infection in CSF?
Slightly high WCC (esp. lymphocytes)
Slightly high protein
Normal glucose (compared to serum glucose levels)
What are the indicators of a tuberculous infection in CSF?
High WCC (esp. lymphocytes) Very high proteins Low glucose (compared to serum glucose levels)
What are the priorities for immediate intervention when treating meningitis?
Early recognition
ABC (then secure airway, high flow O2, IV access, fluid resuscitation)
Urine output
Mental state
Neurology (focal neurological signs; persistent seizures; papilloedema)
What are the treatment guidelines for meningitis?
Assessment prior to LP
Critical care (and postpone LP) if signs of raised ICP, shock or respiratory failure
Monitor and stabilise circulation
What medication should be administered for suspected bacterial meningitis?
IV 2g Cefotaxime/ Ceftriaxone
IV 0.15mg/kg Dexamethasone
What medication should be administered for suspected listeriosis?
IV 2g amoxicillin
What medication should be administered for suspected viral encephalitis?
IV 10mg/kg aciclovir
What is used to prevent development of meningitis in those potentially exposed?
Chemoprophylaxis (500mg ciprofloxacin single dose or 600mg rifampicin for 2 days)
What viruses commonly cause peripheral nerve infections?
Herpes simplex (oral HSV1, genitals HSV2) Varicella Zoster (chickenpox/ shingles)
How does shingles track?
Along dermatome
