Infections of the nervous system Flashcards
What is meningitis?
Inflammation/infection of the meninges
What is encephalitis?
Inflammation/infection of the brain substance
What is myelitis?
Inflammation/infection of the spinal cord
What is the name given to the artificial distinction with a mixture of CNS infection?
encephalomyelitis
Classic triad of clinical features of meningitis
fever, neck stiffness and altered mental status
3 symptoms of meningism
neck stiffness
photophobia
nausea and vomiting
How do you test neck stiffness?
passively bend neck forward and lift head up and should fall down but it does not in meningitis
What kind of rash Is present in meningitis?
petechial non-blanching
What is the rash in meningitis a hallmark of?
meningococcal meningitis (can also occur in viral in meningitis)
Some symptoms of meningitis
cerebral dysfunction, cranial nerve palsy, focal neurological signs
Differential diagnosis for meningitis
infective = bacterial, viral, fungal
Inflammatory = sarcoidosis
Drug induced = NSAIDS, IVIG
malignant = metastatic, haematological
2 bacterial causes of meningitis
Neisseria meningitidis - meningococcus
streptococcus pneumoniae - pneumococcus
Viral cause of meningitis
Enterovirus
Give 2 differences between bacterial and viral encephalitis
viral onset is slower and the cerebral dysfunction is a more prominent feature
Differential diagnosis of encephalitis
Infective = viral (HSV)
Inflammatory = limbic encephalitis
metabolic eg hyperglycaemia
migraine
How many important antibodies are there in autoimmune encephalitis? What are they?
2
anti VGKC
Anti NMDA receptor
What is the priority with meningitis and encephalitis?
exclude and treat infection
Meningitis investigation
blood cultures and lumbar puncture
Encephalitis investigation
blood culture, lumbar puncture, imaging scans, EEG
2 contraindications of lumbar puncture
Focal symptoms or signs suggesting a focal brain mass
Reduced conscious level suggesting a raised ICP
Why is glucose in CSF with bacterial meningitis reduced?
bacteria use glucose as a food source
Compare CSF findings in bacterial and viral meningitis with white cell count
both increased
bacterial - neutrophils
viral - lymphocytes
How is HSV encephalitis diagnosed?
PCR of CSF for viral DNA
How is HSV encephalitis treated?
Aciclovir
What do type 1 and type 2 HSV cause?
type 1 - cold sores
Type 2 - genital herpes
Where is HSV latent in the CNS?
neurological ganglia
What type of HSV usually causes encephalitis except in neonates?
1
Do enterovirus cause gastroenteritis?
No
How are enteroviruses spread?
faecal-oral
Are enteroviruses a large family of DNA or RNA viruses?
RNA
How are arbovirus encephalitides transmitted?
by vector (tick,mosquito) from a non human source
What does arbo mean?
Arthropod borne
Why is arbovirus encephalitides relevant to travel?
Common in other parts of the world and can be immunised to prevent
What is a brain abscess?
Localised area of pus within the brain
What is a subdural empyema?
Thin layer of pus between the dura and arachnoid mater membranes over the surface of the brain
Clinical features of brain abscess/empyema
fever headache, focal signs eg seizure, dysphasia, hemiparesis
What are the signs of raised ICP?
papilloedema, depressed conscious level
What are common underlying sources of infection for a brain abscess/empyema?
sinusitis, dental, ear infection
Causes of brain abscess and empyema
penetrating head injury
spread of adjacent infection
blood borne infection eg bacterial endocarditis
Neurosurgical procedure
Diagnosis of brain abscess/empyema
CT/MRI
investigate source
blood cultures
biopsy and drainage of pus
What are the 2 main organisms present in the mixture of empyema?
streptococci
anaerobes
Management of brain abscess
1st line = surgical drainage
penicillin for streps
metronidazole for anaerobes
What is HIV encephalopathy?
HIV related dementia
Most common type of meningitis in HIV?
cryptococcal
Diagnostics of HIV related illnesses
india ink - cryptococcal antigen - CSF makes circles
HIV PCR
JCV PCR
toxoplasmosis serology (IgG)
3 spirochaetes in the CNS
lyme disease, syphilis, leptospirosis
Lyme disease - how is it transmitted?
vector borne - wooded areas
Systems lymes disease affects
skin, rheumatological, MSK, ophthalmological, cardiac, neurological
How many stages of lymes disease is there?
3
Stage 1 characteristic bite at site of tick bite
erythema migrans
How many organ systems are affected in stage 2 of lymes disease?
1 or more
usually neurological and MSK
When does stage 3 of lymes disease occur?
after a period of latency
Investigation of lymes disease
serological tests
PCR of CSF
EMG
CSF lymphocytosis
Treatment of lymes disease
prolonged antibiotic treatment for 3-4weeks
What are the 3 stages of Neurosyphilis/syphilis
primary, secondary and latent
What group of viruses are polioviruses and how many types are there?
enterovirus
1,2,3
In polio what has to be affected for there to be paralysis?
anterior horn cell of LMN
What is rabies?
Acute infectious diseases of CNS affecting almost all mammals
How is rabies transmitted to humans?
bite
salivary contamination of an open lesion
How is rabies neurotropic?
enters peripheral nerves and migrates to CNS
Symptoms of rabies
paraesthesia at sight of lesion
ascending paralysis and encephalitis
Diagnosis of rabies encephalitis
culture, detection, PCR or serology
Where is rabies encephalitis mainly found and what animals?
Africa/Asia
dogs and bats
Pre-exposure prevention method of rabies
active immunisation with killed vaccine
what 3 groups are given pre-exposure prevention of rabies?
bat handlers
regular handlers of imported animals
selected travellers to enzootic areas
What is meant by enzootic?
Regularly affecting animals in a particular area or at a particular season
Post exposure treatment of rabies
wash wound
give active rabies immunisation
give human rabies Ig if risk is high
Is human rabies immunoglobulins active or passive immunisation?
passive
What is the causative organism of tetanus?
clostridium tetani
What type of bacteria is clostridium tetani and clostridium botulinum?
anaerobic gram positive spore forming bacillus
What affects the NMJ in tetanus?
toxins produced by the bacteria
What do the toxins in tetanus do to the NMJ?
block it and prevent inhibition of motor neurons
Tetanus signs
rigidity and spasm
Prevention of tetanus
immunisation - toxoid
give combined with other antigens eg DPaT
penicillin and IG for high risk wounds and patients
Causative organism in botulism
clostridium botulinum
What does the neurotoxin in botulism do and how does it work?
binds irreversibly to presynaptic terminal and prevent Ach release
Where is clostridium botulinum naturally present?
soil, dust and aquatic environments
3 modes of infection of botulism
infancy - intestinal colonisation
food borne - outbreaks
wound - drug users
Incubation period of clostridium botulinum
4-14 days
Presentation of botulism
ANS dysfunction - dilated pupils
descending symmetrical paralysis, respiratory failure
How is botulism diagnosed?
nerve conduction studies
toxin in blood
culture from debrided wound
Treatment of botulism
Anti-toxin (A,B,E)
Penicillin/metronidazole
radical wound debridement
What is a prion?
transmissible protein particle
Aetiology of CJD
sporadic, new variant, familial, acquired eg blood transfusion
When should sporadic CJD be considered?
> 60
very rapidly progressive dementia
What is new variant CJD linked to?
bovine - infected material
genetic susceptibility
Investigation of CJD
MRI
EEG
CSF