Infections of the CNS Flashcards
Define: meningitis:
inflammation of the meninges - can have inflammation of all 3 layers
- normally just the subarachnoid and pia mater
Define: encephalitis:
inflammation of the brain parenchyma
Define: myelitis:
inflammation of the spinal cord
Define: radiculitis:
inflammation of the nerve roots
Define: abscess:
local suppuration leading on to collection or abscess
What are the characteristics of acute meningitis?
Inflammatory cells in the CSF
Pleocytosis (the presence of an abnormally large number of lymphocytes in the cerebrospinal fluid) is the hallmark of meningitis but some fungi and immunocompromised patient can have meningitis without having cells in CSF
What can cause meningitis?
viruses, bacteria (most common ones), fungi, parasites, drugs (aspirin, ibuprofen), autoimmune, malignancy and aseptic meningitis
What are the clinical presentations of meningitis?
fever
headache - cough and sneeze can cause it to worsen due to increased ICP
photophobia
neck stiffness
focal weakness
With or without altered consciousness
signs of meningeal irritation- Kernig’s sign and brudzinski’s sign
What is Kernig’s sign?
thigh is flexed at the hip and knee at 90 degree angles and subsequent extension in the knee is painful
What is Brudzinski’s sign?
forced flexion of the neck elicits a reflex flexion of the hips
- unable to press head to chest
What are some key questions to ask in a pt history if you are querying CNS infection?
Travel RF for HIV Immuno-compromised Exposure to insects - Lymes disease Exposure to sick animals Ingestion of contaminated food, water Illness of community e.g. measles / mumps
What are some key examinations if you are querying CNS infection?
Lymphadenopathy Rash Oral examination - candida/leukoplakia IV drug sites Head injuries Other sites for infection
What is the incidence of bacterial meningitis and what are the most common causes in adults?
annual incidence in western countries = 06-4/100,000 - THIS can be up to 10x higher in less developed
Streptococcus pneumoniae Neisseria meningitides (both @80%)
What the most common causes of bacterial meningitis in children?
Haemophilus influenza type B
Meningococcus
Pneumococcus
What are common infections in vulnerable pt groups?
aerobic gram -ve = e.coli, klebsiella, pesudomonas, salmonella
Staphylococcus aureus - esp in immunocompromised/or pt has a central line
What are the initial investigations and management for meningitis?
Examine CSF - lumbar puncture
Raised ICP and cerebral herniation are well recognised complications of severe bacterial meningitis therefore a decision needs to be made as to wether or not to do a LP
- CSF sent for gram stain, C&S, sugar and protein measurement and PCR
initiate anti-bacterial and anti-viral therapies with steroids
What is the normal opening pressure of CSF and how does it vary in different types of meningitis??
12-20 cm CSF
- bacterial = raised
- viral = normal/mildly raised
- TB = raised
- Fungal = raised
How does the appearance of CSF change in different types of meningitis?
Bacterial = turbid, cloudy, purulent Viral = clear - looks normal TB = clear or cloudy Fungal = clear or cloudy
How does the CSF WCC change in different types of meningitis?
normal = <5 bacterial = raised >100 viral = raised 5-1000 TB = raised 5-500 Fungal = 5-500
How does the CSF white cell type vary in different types of meningitis?
bacterial = neutrophils viral = lymphocytes TB = lymphocytes fungal = lymphocytes
How does the CSF protein level vary in different types of meningitis?
Normal <0.4 g/L bacterial = raised viral = mildly raised TB = markedly raised fungal = raised
How does the CSF glucose level vary in different types of meningitis?
Normal 2.6-4.5 mmol bacterial = very low viral = normal/slightly low TB = very low fungal = low
What are the treatments for meningitis?
3rd gen cephalosporin (cefotaxime / ceftriaxone) = initial
If penicillin resistant strep suspected = use vancomycin with or without rifampicin is added
steroid given shortly before abx - improves the outcome of pneumococcal meningitis in adults and haemophilus in children
What are the complications of meningitis?
reduced consciousness - due to raised ICP
cerebral oedema
raised ICP - can cause papilloedema - if this has occurred advised not to do lumbar puncture
seizures
infarctions
venous sinus thrombosis
subdural effusion/emphysema
Is meningitis a notifiable disease?
yes - public health authorities should be contacted
What does strep pneumoniae look like?
Small 0.8 micron, non-spore forming, non-motile gram +ve cocci
diplococci
coated in a capsule of complex polysaccharide
Meningitis often follow a recent nasopharnygeal colonization of virulent strain
What are the risk factors for contracting pneumococcal meningitis?
Co-existing pneumonia - 25% acute sinusitis acute otitis media - 30% HIV Immuno-compromised state More severe than other forms - 11-19% comatose, 7-21% seizures, aphasia, cranial palsies, hemiparesis
what is the prognosis for pneumococcal meningitis?
75% Intracerebral complications
40% systemic complications
sequela - hearing loss, other cranial palsies, hemiparesis Prescribe antibiotics/steroids
What does neisseria meningitidis look like?
Non-spore forming, non-motile, gram -ve dilococcus
appears as kidney shaped
13 serogroups
B,C,Y europe and america
What are key clinical presentations of meningococcal meningitis?
Rash (non-blanching petechial purpuric rash) - as soon as its noticed give abx to prevent sepsis occurring
Urticarial and maculopapular rash may also occur
Septicaemia and meningitis
Shock/DIC (disseminated intravascular coagulation) can lead to coma and death
What is the treatment for meningococcal meningitis?
penicillin G and ampicillin are the drugs of choice
3rd gen cephalosporin
What is the incidence of TB meningitis?
increasing even in developed countries due to increased travel, increased incidence of HIV and increasing multi drug resistance
UK 6000 cases of TB annually - 5-10% thought to have CNS TB
its only natural reservoir is humans - infect through inhalation - replicate in alveoli and then spread
In CNS foci they are subependymal
What are the duration of symptoms like in TB meningitis?
vary from days to months
release of tubercle leads to vasculitis, adhesions and inflammation
What are the diagnostic tests for TB meningitis?
direct microscopy for AFB - ZN stain
CSF cultures - more likely to be +ve but several weeks to become +ve
PCR- only sensitive in 50%
Immunological test of the ability of T lymphocytes to produce gamma interferon in response to TB antigen
What is the treatment for TB meningitis?
4 drugs for 2 months
followed by 2 drugs for 9-12 months
Drugs: rifampicin, isoniazid, pyrazinamide, ethambutol
Adjunctive steroids reduce mortality, continue for 4-8 weeks and tapered gently
what are some other examples of bacterial meningitis?
syphilitic meningitis lyme neuroborreliosis nocardia listeria brucella leptospirosis
What are some examples of viral meningitis?
enterovirus - most common coxssackie HSV 1 / 2 CMV/ EBV HIV MMR
What are some examples of fungal meningitis?
rare but devastating incidence has increased due to immune suppression They can also space occupy - cryptococcus neoforms - commonest form -more common in HIV - histoplasma capsulatum - blastomyces dermatidis - coccidioides - candida and aspergillus
What are some of the key characteristics of cryptococcus neofromans?
dimorphic (yeast/filamentous phase)
Brain MRI shows cryptococcomas
low grade fever
Indian ink staining of CSF is positive in 80%
cryptococcal antigen can be tested - can have significantly raised ICP
What is the treatment for cryptococcus neofromans?
amphotericin B
flucytosine
fluconazole
What are the main facts about encephalitis?
inflammation affecting brain parenchyma viruses are the most common causes toxoplasma, amoebae and bacteria can cause it too paraneoplastic process autoimmune limbic encephalitis metabolic conditions
What does encephalitis present as?
severe headache reduced consciousness seizures focal neurological signs altered behaviour hallucinations fever
What are the investigations for encephalitis?
lumbar puncture imaging if required CSF for PCR antibody testing (IgM and IgG) serum for atypical pathogens
What is the acute management for encephalitis?
antivirals control immediate complications prevent late complications intravenous acliclovir ampicillin and getamicin for listeria ganciclovir/foscarnet/cidofovir for CMV and HHV6
What does HSV1 cause?
viral encephalitis
1 = 90% and 2=10% - access brain via nasal mucosa
primary infection occurs via oral mucosa and then spread along the trigeminal nerve to the trigeminal ganglion
What are the key clinical presentations induced by HSV encephalitis?
flu like prodrome 93% were febrile in one study disorientation in 76% speech disturbance in 59% behavioural change in 41% seizure in 33% lethargy, drowsiness, confusion and coma
What is the treatment for HSV induced encephalitis?
aciclovir reduces the risk of fatal outcome from 70% to less than 20%
given for 14-21 days
mortality is reduced the morbidity remains high
2/3s of survivors have significant neuropsychiatric sequela
What are the complications of treatment for hsv encephalitis?
impaired memory
behavioural changes
dysphasia
epilepsy
What are brain abscess?
space occupying lesions because of inflammation of the parenchyma leading to suppuration and surrounded by well vascularised capsule
- incidence= 1/10000
spread: blood, contiguous focus, direct inoculation
What are the causes of brain abscesses?
otogenic infection paranasal sinusitis blood borne infection peridontal infection trauma or neurosurgery bacterial meningitis
Present very similarly to encephalitis
What is the clinical presentation of brain abscess?
fever, headache, focal neurological signs, reduced consicous levels, raised ICP and papilloedema
What investigations are carried out for brain abscesses?
FBC/ inflammatory markers
blood cultures
CT/MRI
What are the treatments for brain abscesses?
abx
seizure control
pressure monitoring for raised ICP
surgical aspiration
