CNS Infections Flashcards
What are the different CNS infections?
Meningitis
Encephalitis
What is meningitis?
Inflammation of the brain meninges
What is the pathology of acute bacterial meningitis?
Pia-arachnoid congested with neutrophils
Layer of pus forms
May organise to form adhesions, causing cranial nerve palsies and hydrocephalus
What is the pathology of chronic meningitis?
Brain is covered in exudate with numerous meningeal tubercles (small abscesses)
Adhesions form
Cerebral oedema occurs
What is the pathology of viral meningitis?
Predominantly lymphocytic
No pus formation, neutrophils or adhesions, little to no cerebral oedema
What is an example of a cause of chronic meningitis?
TB
What is the most common cause of meningitis?
Viral
When in the year does viral meningitis occur more often?
Late summer, early autumn
What are the most common causative organisms of viral meningitis?
Enteroviruses - coxsackie or echo viruses
Herpes simplex
How does the onset of viral meningitis differ from bacterial?
Viral has more insidious onset
What are the three ways that bacteria can spread into the CNS?
Spread from nasopharynx
Direct extension due to skull fractures or para-meningeal foci in the mastoid or air sinuses
Spread from remote foci due to sepsis
What are the most common causative bacteria in meningitis?
Strep pneumoniae Neisseria meningitis Haemophilus influenzae Listeria monocytogenes TB
Who are more likely to get strep pneumoniae meningitis?
Hospitalised patients CSF skull fractures Diabetics Alcoholics Young children
Who are more likely to get neisseria meningitis?
Young children
How can neisseria meningitis be differentiated?
Rash doesn’t blanch
What is the name for meningitis caused by neisseria meningitis?
Meningococcal meningitis
Who are more likely to get haemophilia influenzae meningitis?
<40 year olds
What is the most common cause of meningitis in children under 4?
Haemophilus type B
Who are more likely to get listeria monocytogenes meningitis?
Over 55 year olds, or neonates
Soft cheese consumption
Immunocompromised
What is important about listeria monocytogenes meningitis?
Resistant to ceftriaxone - ampicillin/amoxicillin used instead (co-trimoxazole if pen allergic)
Who are more likely to get fungal meningitis?
Severely immunosuppressed (e.g. active HIV)
How can fungal meningitis be differentiated?
More subtle presentation
What are infective and non-infective causes of aseptic meningitis?
Infective: HIV, cryptococcal, TB
Non-infective: vasculitis, dural sinus thrombosis, drug-induced (NSAIDs, co-trimoxazole)
What are the more likely causative organisms in neonates?
Listeria
Group B strep
E coli
What are the more likely causative organisms in children <10?
Haemophilus influenza
What are the more likely causative organisms in people aged 10-21?
Meningococcal
Pneumococcal
What are the more likely causative organisms in people aged >21?
Pneumoccal
Neisseria meningitides
What are the more likely causative organisms in the elderly?
Pneumococcal
Listeria
What are the more likely causative organisms in immunocompromised patients?
All the conventional organisms
TB
Cryptococcal
What are the more likely causative organisms in patients with skull fractures?
Pneumococcal
What are the more likely causative organisms in patients who have had surgery or open head wound?
Staph aureus
What are the more likely causative organisms in patients with a CSF shunt?
Staph epidermidis
What is the main triad of symptoms in meningitis?
Fever
Headache
Neck stiffness
What are the visual symptoms of meningitis?
Photophobia
What are the dermatological symptoms of meningitis?
Non-blanching purpuric rash (meningococcal)
What are the neurological symptoms of meningitis?
Confusion
Agitation
Altered level of consciousness
Seizures
What is Kernig’s sign?
Pain and resistance on passive extension of the knee with a flexed hip
What is the clinical presentation of meningitis?
Fever, headache, neck stiffness
Visual (photophobia)
Dermatological (Non-blanching purpuric rash - meningococcal septicaemia)
Neurological (Confusion, agitation, altered level of consciousness, seizures)
Kernig’s sign
Vomiting, riggers, malaise
What are the patterns of onset in meningitis?
Develops within hours or minutes in acute bacterial meningitis
More insidious in viral or encephalitis
What investigations should be done in meningitis?
Bloods Throat swab CXR (if TB suspected) Lumbar puncture CT brain before LP if needed
What is the diagnostic investigation for meningitis?
Lumbar puncture
What bloods should be done in meningitis?
FBC U&Es Coagulation screen Glucose Cultures
What are the contraindications to a lumbar puncture?
Immunosuppressed Papilloedema Focal neurological signs Altered level of consciousness History of CNS disease
Why does a CT brain need to be done if any contraindications to LP are present?
To rule out raised ICP
What results from a LP would suggest viral meningitis?
Cell - lymphocytes Gram stain - negative Bacterial antigen - negative Protein - normal Glucose - normal
What results from a LP would suggest bacterial meningitis?
Cell - neutrophils Gram stain - positive Bacterial antigen - positive Protein - high Glucose - low <70% plasma
What results from a LP would suggest TB meningitis?
Cell - lymphocytes Gram stain - positive or negative Bacterial antigen - negative Protein - high or very high Glucose - low <60% plasma
What results from a LP would suggest aseptic meningitis?
Cell - low WCC Gram stain - negative Bacterial antigen - negative Protein - minimally increased Glucose - normal
What is the management for bacterial meningitis?
1st line - ceftriaxone
Penicillin allergy - chloramphenicol + vancomycin
>60 or immunosuppressed (listeria) - add amoxicillin (co-trimoxazole if penicillin allergy)
Give dexamethasone with or just before first dose of antibiotics - if pneumococcal confirmed continue for 4 days, if ruled out stop dex
When should you not give dexamethosone with antibiotics?
Post-surgical meningitis
Severe immunocompromise
Meningococcal or septic shock
Patient hypersensitive to steroids
What is the management for viral meningitis?
Treat as bacterial until viral confirmed
Then stop antibiotics and care switched to supportive
What contact tracing needs to be done in meningitis?
Notify public health
Contact prophylaxis - ciprofloxacin single dose
How many who survive meningitis are affected by after-effects?
25%
What are examples of after-effects that can occur in meningitis?
Lim loss Deafness Blindness Cerebral palsy Quadriplegia Severe mental impairment
What are complications of meningitis?
Purulence - exudate compressing cranial nerves (III and IV most vulnerable)
Invasion causing abscesses
Cerebral oedema
Hydrocephalus
What is encephalitis?
Inflammation of the brain parenchyma (substance of the brain)
How is encephalitis different from encephalopathy?
Encephalopathy is not always an infection, but can be any condition that alters brain function or structure
What are the microbiological causes of encephalitis?
herpes simplex
Varicella zoster
CMV/HIV
What is the presentation of encephalitis?
Similar to meningitis
Seizures
How is encephalitis differentiated from meningitis?
Presence of: Psychosis Odd behaviours Speech and memory problems Confusion
What investigations are done for encephalitis?
Lumbar puncture
EEG
MRI
How can HSV encephalitis be determined?
Bilateral focal temporal lobe enhancement on MRI
What is the treatment of encephalitis?
Acyclovir
What is meningoencephalitis?
Headache, fever and neck stiffness PLUS features of encephalitis
What are the causes of a brain abscess?
Skull fractures
Endocarditis
Ear, sinus or dental infection
What is the presentation of a brain abscess?
Raised ICP (headache, drowsiness)
Focal neurological signs
Fever
Epilepsy
What investigations are done for brain abscesses, and what do they show?
CT/MRI - shows ring-enhancing mass, usually with surrounding oedema
Don’t do LP - because of raised ICP
What is the management of brain abscess?
Neurosurgical referral for urgent drainage
High dose antibiotics
Mortality is high
What is progressive multifocal leukoencephalopathy?
Caused by infection with JC virus within multiple areas of infection
Causes demyelinaion
What are the risk factors for progressive multifocal leukoencephalopathy?
Immunosuppression
Autoimmune disease
Use of MS drugs (tysabri)
How is progressive multifocal leukoencephalopathy diagnosed?
Symptoms of demyelination (similar to MS)
LP - JC virus DNA
MRI - enhancing lesions
What is the treatment for progressive multifocal leukoencephalopathy?
No effective treatment - treat underlying cause
