CNS infections Flashcards
What can an untreated CNS infection lead to?
Brain herniation and death
Cord compression and necrosis with subsequent permanent paralysis
What are the different types of CNS infections?
Encephalitis Meningitis Meningoencephalitis Encephalomyelitis Epidural abscess Neuritis Sepsis syndrome
What is meningitis?
Inflammation of the meninges
What is encephalitis?
Inflammation of brain parenchyma
What are the different types of meningitis?
Acute pyogenic
Acute aseptic (viral)
Acute focal suppurative (brain abscess, subdural and extradural empyema)
TB
What will pyogenic meningitis show?
Thick layer of suppurative exudate covering the leptomeninges over the surface of the brain
Exudate in the basal and convexity surface
What will meningitis show microscopically?
Neutrophils in the subarachnoid space
Are neutrophils present in viral meningitis?
NO - it is aseptic
What is the basic treatment for bacterial meningitis
Ceftriaxone IV 2g bd
AND
Dexamethasone IV 10mg qds (3ml of 3.3mg/ml base injection)
What are the risk factors for listeria infection?
Over 60 years
Immunocompromised including alcohol dependency and diabetes
What should be added to the empirical antibiotics if there are risk factors for listeria?
Amoxicillin IV 2g hourly
What is used instead of ceftriaxone in penicillin allergy?
Chloramphenicol IV 25mg/kg qds
What is used instead of amoxicillin cover for listeria in penicillin allergy?
Co-trimoxazole IV 120mg/kg divided into 4 doses/day
What should be added to empirical antibiotic therapy if there has been recent travel to a country with high rates of penicillin resistant pneumococci?
Vancomycin IV aiming for a pre dose level of 15-20mg/L OR rifampicin IV/PO 600mg bd
What are countries with high rates of pneumococcal resistance?
Canada China Croatia Pakistan Poland Spain Mexico Italy USA Greece Turkey
Should you continue dexamethasone in the case of a confirmed meningitis that is not pneumococcus?
No - stop
How long should dexamethasone be given?
4 days
What virus commonly causes meningitis?
Enteroviruses Coxsackie HSV VZV Paromyxovirus
How is viral meningitis diagnosed?
Viral stool culture
Throat swab
CSF PCR
What is encephalitis?
Diffusely inflamed cerebral cortex
What are the common signs of encephalitis?
Mental status changes
Confusion
Coma
INSIDIOUS ONSET
What investigations are performed for encephalitis?
LP
EEG
MRI
What is the treatment for encephalitis?
IV aciclovir 10mg/kg 8hrly
What is the treatment for viral meningitis?
Early management for bacterial meningitis then when viral confirmed STOP antibiotics, antivirals and steroids if enteroviral or mumps - supportive management
If HSV or VZV then antivirals continued
What are CT findings that are contraindications to an LP?
Significant brain shift/ swelling
Tight basal cisterns
What are the CSF findings for a bacterial infection?
Opening pressure: high Colour: cloudy Cells: high/v high (100-50,000) Differential: neutrophils CSF/plasma glucose: low <40% Protein (g/l): High >1
What are the normal CSF findings?
Opening pressure: 10-20 cm Colour: clear Cells: <5 Differential: lymphocytes CSF/plasma glucose: 50-66% Protein (g/l): <0.45
What are the CSF findings for a viral infection?
Opening pressure: normal/high Colour: "gin" clear Cells: Slightly increased (5-1000) Differential: lymphocytes CSF/plasma glucose: normal Protein: normal-high (0.5-1.0)
What are the CSF findings for TB meningitis?
Opening pressure: high Colour: cloudy/yellow Cells: slightly increased (<500) Differential: lymphocytes CSF/plasma glucose: low-very low (<30%) Protein (g/l): High-very high (1.0-5.0)
What are signs and symptoms of meningitis?
Headache Vomiting Pyrexia Neck stiffness Photophobia Lethargy Confusion Rash
What is the epidemiology of community acquired bacterial meningitis?
Neonates: listeria, group B strep, e.coli
Children: Hib
Ages 10-21: neisseria meningitidis
Age >21: streptococcus pneumoniae, neisseria meningitidis
>65: streptococcus pneumoniae, listeria
Immunocompromised: listeria
Neurosurg: staphylococcus aureus, gram neg bacillus
# cribriform plate: streptococcus pneumoniae
What are complications of meningitis?
Purulence at base of brain and convexities of rolandic and sylvian sulcus Exudate around CN 3 and 6 Invasion of pia = abscess Cerebral oedema Ventriculitis Hydrocephalus
What is the pathogenesis of bacterial meningitis?
- Nasopharyngeal colonization
- direct extension of bacteria (sinusitis, mastoiditis, brain abscess) or across skull defects/#
- remote foci of infection (endocarditis, pneumonia, UTI)
What should be looked at in the CSF?
Haematology: cell count, differential
Microbiology: gram stain, cultures
Chemistry: glucose, protein
PCR
Where can neisseria meningitidis (meningococcal) be found to colonize?
Throats and nasopharynx
What are the symptoms of neisseria meningitis due to?
Endotoxin release
Where can strep pneumoniae be found?
Nasopharynx
Who is most susceptible to pneumococcal meningitis?
Hospitalized patients Patients with CSF skull fracture Diabetics Alcoholics Asplenic Young children
Which meningitis are people with a HIV count below 100 likely to get?
Cryptococcus
How is cryptococcus diagnosed?
India ink
Subtle neurological presentaion
Asepti picture on CSF
V high opening pressure
What type of bacteria is listeria?
Gram positive bacillus
What is the treatment for TB meningitis?
Isoniazid + rifampicin (add pyrazinamide and ethambutol)
Who gets TB meningitis?
Re-activation
Elderly
Previous TB on CXR
Poor yield from CSF
What is the treatment for cryptococcal meningitis?
IV amphotericin B and fluconazole
What percentage of bacterial meningitis are culture-neg?
10-15%
Pre-LP use of oral antibiotics will lower culture positivity by 30%
What is aseptic meningitis?
Spinal fluid that has:
Low number of WBC
Minimally elevated proteins
Normal glucose
What are the common causes of aseptic meningitis/encephalitis?
HSV 1 and 2 Syphilis Listeria (occasionally) TB Cryptococcus Leptospirosis Cerebral malaria African tick typhus Lyme disease Carcinomatous Sarcoid Vasculitis Dural venous sinus thrombosis Migraine Drug: co-trimoxazole, IVIG, NSAID
What will HSV encephalitis look like on MRI?
Affects temporal lobes
What are the clinical signs of bacterial meningitis?
Fever
Stiff neck
Alteration in consciousness
Non-blanching purpuric/petichial rash
What is the contact prophylaxis regime?
600mg rifampicin orally 12-hourly for 4 doses or 10mg/kg orally 12 hourly for 4 doses (aged 3-11 mnths)
OR
500mg ciprofloxacin orally as a single dose for adults and children over 12
What vaccine are available for meningitis?
Neisseria meningitidis - men ACWY given to all school leavers
Hib
Streptococcus pneumoniae
What are CI to LP?
Immunocompromised state
History of CNS disease (mass lesion, stroke, focal infection)
New onset seizure
Papilloedema
Abnormal level of consciousness
Focal neurological deficit (blown pupils, ocular motility, abnormal visual fields, gaze palsy, arm or leg drift)
What are warning signs in meningitis?
Marked depressive conscious level (GCS <12) or a fluctuating conscious level (fall in GCS >2)
Focal neurology
Seizure before or at presentation
Shock
Bradycardia and hypertension (cushings response)
Papilloedema
