CNS infections Flashcards
What are the 2 main infections of the CNS?
Meningitis
Encephalitis
What is meningitis?
Serious infection of the meninges, the outer membranes covering the brain and spinal cord
What are some of the classifications of meningitis?
Acute pyogenic (Bacterial)
Acute aseptic
Acute focal suppurative
Chronic bacterial
Main bacteria in neonatal bacterial meningitis?
Listeria monocytogenes
Group B Streptococci
E. coli
Main bacteria in bacterial meningitis of infants
H. influenza
Main bacteria in bacterial meningitis of those 10-21
Neisseria meningitidis (Meningococcal)
Streptococcus pneumoniae (Pneumococcal)
Main bacteria in bacterial meningitis of those 21-65
Streptococcus pneumoniae
Neisseria meningitidis
Main bacteria in bacterial meningitis in those over 65
Streptococcus pneumoniae
Listeria monocytogenes
Main bacteria in bacterial meningitis in immunosuppressed patients
Listeria monocytogenes
Main bacteria in bacterial meningitis in those who have undergone neurosurgery or head trauma
Staphylococcus
Gram negative bacilli (Klebsiella pneumoniae, E.coli, Pseudomonas aeruginosa)
Main bacteria in bacterial meningitis in those who have had a fracture of the cribriform plate?
Streptococcus pneumoniae
What is the most common form of meningitis?
Viral meningitis
What are the most common viruses in meningitis?
Enteroviruses (echovirus, Coxsackievirus)
Mumps
HSV
Herpes zoster virus
HIV
Measles
Influenza
Arboviruses
What is meant by aseptic meningitis?
Meningitis in which the CSF contains cells but no bacteria
What are some causes of aseptic meningitis?
Viral infection
Fungal infection
Parasitic infection
Atypical TB
Lyme disease
Kawasaki disease
How does meningitis occur
Microorganisms reach the meninges either by direct extension from the ears, nasopharynx, cranial injury or congenital meningeal defect, or by bloodstream spread
Describe the pathology of acute bacterial meningitis
- The pia-arachnoid is congested with polymorphs
- A layer of pus forms
- This may organize to form adhesions, causing cranial nerve palsies and hydrocephalus
- Cerebral oedema occurs in any bacterial meningitis
Give the characteristics of meningococcal meningitis (Neusseria meningitidis)
- Found in the throats of healthy carriers
- Symptoms are caused by endotoxins
- Occurs mostly in young children
- Can cause local disease or septicaemia
- 12 capsular groups of meningococcus
Give the characteristics of H.influenza meningitis?
- Part of the normal throat microbiota
- Requires blood factor for growth
- 6 sub-types (b is most common and is vaccinated against)
Give the characteristics of pneumococcal meningitis (Streptococcus pneumonia)
- Commonly found in the nasopharynx
- Most common in hospitalised patients, CSF fractures, diabetics, alcoholics and children
- Rare but high mortality
Give the characteristics of listeria monocytogenes meningitis
- Gram +ve bacilli
- Commonly bacteraemic
- More common in neonates and immunosuppressed patients
What is the antibiotic of choice against listeria monocytogenes meningitis?
IV ampicillin/amoxicillin
Give the characteristics of tuberculous meningitis
- Usually caused by a reactivation of TB in the elderly
- Poor yield in CSF
- High morbidity
- Treated with RIPE
Give the characteristics of cryptococcal meningitis
- Fungal
- Mainly seen in HIV
- Subtle neurological presentation
How is cryptococcal meningitis managed?
IV amphoteracinB
Fluconazole
Give the pathology of chronic meningitis
- The brain is covered in a viscous grey–green exudate with numerous meningeal tubercles
- Adhesions are invariable
- Cerebral oedema occurs in any bacterial meningitis
Give the pathology of viral meningitis
- In viral meningitis there is a predominantly lymphocytic inflammatory cerebrospinal fluid (CSF) reaction without pus formation, polymorphs or adhesions
- There is little or no cerebral oedema unless encephalitis develops
How does meningitis present
Triad:
- Headache
- Neck stiffness
- fever
Also:
- Photophobia
- Vomiting
What are some special features of acute bacterial meningitis?
Sudden onset of symptoms with rigours and high fever
Also non-blanching rash
What is meningoencephalitis?
Meningitis with encephalitis
What is the main test used in meningitis?
Lumbar puncture
What tests are performed on lumbar puncture in meningitis?
- Tube 1 - Haematology - Cell count, differential
- Tube 2 - Microbiology - Gram stain, cultures
- Tube 3 - Chemistry - Glucose, protein
- Tube 4 - Haematology - Cell count, differential
White blood cell count and differential, Gram stain, glucose, protein, lactate, culture, and meningococcal and pneumococcal polymerase chain reaction (PCR)
What are some of the markers which are highly predictive of meningitis?
What is the management of viral meningitis?
Treatment is generally supportive - self-limiting condition lasting 4–10 days
Treatment of bacterial meningitis in adults
IV Ceftrioxone 2g BD
+
IV Dexamethasone 10mg QDS (with 1st Cef dose for 4 days)
Treatment of bacterial encephalomeningitis in adults?
IV Ceftrioxone 2g BD
+
IV Dexamethasone 10mg QDS (with 1st Cef dose for 4 days)
+
IV Aciclovir 10mg/kg TDS
Treatment of bacterial meningitis in those over 60 or those who are immunocompromised
IV Ceftrioxone 2g BD
+
IV Dexamethasone 10mg QDS (with 1st Cef dose for 4 days)
+
IV Amoxicillin 2g every 4 hours
Who should not be given steroids in bacterial meningitis?
Post-surgical meningitis
Severe immunocompromise
Meningococcal or septic shock
Those hypersensitive to steroids
Treatment of bacterial meningitis in children <3 months
Cefotaxime + Amoxicillin
Treatment of bacterial meningitis in children >3 months
- > 3 months 1st dose Cefotaxime followed 6 hours later with once daily Ceftriaxone
- +/- Dexamethasone IV starting before or with first dose of antibiotic
What are some possible complications of meningitis?
Purulence (At brain base or around nerves)
Invasion (Erosion of pia)
Cerebral oedema
Ventriculitis
Hydrocephalus
Limb loss
Deafness
Blindness
Cerebral palsy
Quadriplegia
What is encephalitis?
Acute inflammation of the brain parenchyma
What are the most common bugs of encephalitis?
Usually viral - usually HSV, VZV and other herpes group viruses, HHV-6, 7, enteroviruses and adenovirus
What is limbic encephalitis?
A form of antibody-mediated encephalitis which may be associated with underlying malignancy or autoimmune disorder
How does encephalitis present?
- Fever (90%)
- Meningism
- Personality and behavioural change, which progresses to a reduced level of consciousness and even coma
- Seizures (focal and generalised)
- Focal neurological deficits, such as speech disturbance
What investigations are required in encephalitis?
- MRI - bilateral medial temporal lobe involvement
- EEG
- CSF
- Viral - elevated lymphocytes, viral detection by CSF PCR
- Limbic - antibodies may be identifiable
How is suspected HSV and VZV encephalitis managed?
Immediate IV Acyclovir
How may limbic encephalitis be managed?
Treat tumour
Immunsuppression
What are the options for contact prophylaxis for meningitis?
- Rifampicin PO
- Ciprofloxacin PO
- Ceftrioxone IM
