Infections of the Nervous System Flashcards
What are the main three important nervous system infections?
Meningitis - inflammation of meninges
Encephalitis - inflammation of brain substance
Myelitis - inflammation of spinal cord
What can cause meningitis? Including specific pathogens
Infective - bacterial, viral, fungal
Inflammatory - sarcoidosis
Drug induced - NSAIDs, IVIG
Malignancy - metastatic, haematological
Bacterial - neisseria meningitidis (meningococcus), streptococcus pneumoniae (pneumococcus)
Viral causes include enteroviruses
What are the symptoms/signs of meningitis?
Triad - fever, neck stiffness, altered mental state
Short history of progressive headache associated with fever >38deg and meningism (neck stiffness, photophobia, nausea/vomiting)
Cerebral dysfunction common, decreased GCS in most
Cranial nerve palsy, seizures, focal neurological deficits may also occur
Petechial skin rash - hallmark of meningococcal but can also occur in viral
What investigations may be done in suspected meningitis?
Blood cultures (bacteraemia)
LP (CSF culture/microscopy)
No need for imaging if no contraindications to LP
When may an LP be contraindicated?
Focal symptoms or signs suggesting focal brain mass
Reduced conscious level suggesting raised ICP
New onset seizures
Severe immunocompromised state
What might the LP findings be in bacterial vs viral meningitis?
Neutrophils high in bacterial
Lymphocytes high in viral
Reduced glucose in bacterial
Relatively normal in viral
High protein in bacterial
Slightly increased in viral
What are the different causes of encephalitis?
Infective - viral (commonly HSV)
Inflammatory - limbic encephalitis, acute disseminated encephalomyelitis
Metabolic - hepatic, uraemic, hyperglycaemic
Malignant - metastatic, paraneoplastic
Migraine
Post ictal
Autoimmune - anti VGKC, anti NMDAR
- seizures, altered mental state
- amnesia in VGKC
- movement disorder/coma in NMDAR
Symptoms/signs of encephalitis?
Flu-like prodrome (4-10 days)
Progressive headache associated with fever +/- meningism
Progressive cerebral dysfunction - altered mental state, GSC
Seizures
Focal symptoms/signs
Onset of viral generally slower, cerebral dysfunction more prominent
What investigations may be done in suspected encephalitis?
Blood cultures
Imaging (CT +/- MRI)
LP
EEG
Viruses than cause encephalitis?
HSV
- lab diagnosis by CSF PCR
- aciclovir on clinical suspicion
- 70% mortality if untreated
Enteroviruses
- faecal oral
- polio, coxsackie, echoviruses
Arbovirus encephalitides
- vector
- relevant to travel
What are the risk factors for brain abscess/empyema causing encephalitis
Penetrating head injury
Spread from adjacent infection
Blood-borne infection e.g. bacterial endocarditis
Neurosurgical procedure
What are the symptoms/signs of abscess/empyema causing encephalitis?
Fever, headache
Focal symptoms/signs (seizures, dysphasia, hemiparesis)
Signs of raised ICP (papilloedema, false localising signs, depressed GCS)
Meningism may be present, particularly with empyema
Features of underlying source e.g. dental, sinus, ear infection
Consider subdural haematoma
What investigations may be done in suspected abscess/empyema causing encephalitis?
Imaging (CT/MRI)
Investigate source
Blood cultures
Biopsy (pus drainage)
Often mixtures of organisms involved
- streptococci in 70% of cases
How is abscess/empyema causing encephalitis treated?
Surgical drainage if possible Penicillin/ceftriaxone to cover streps Metronidazole for anaerobes High doses required Culture and sensitivity tests on aspirate provide useful guide
What are some indicator illnesses for HIV?
Cerebral toxoplasmosi Aseptic meningitis/encephalitis Primary cerebral lymphoma Cerebral abscess Cryptococcal meningitis SOL of unknown cause Dementia Leucoencephalopathy
What brain infections are common in HIV patients with low CD4 counts?
Cryptococcus neoformans
Toxoplasma gondii
Progressive multifocal leukencephalopathy
Cytomegalovirus
HIV-encephalopathy (HIV-associated dementia)
PCR often used
Toxoplasmosis serology
Cryptococcal antigen
What spirochaetes can affect the CNS?
Lyme disease (borrelia burgdorferi) Syphilis (trepomena pallidum) Leptospirosis (leptospira interrogans)
How is Lyme spread and what are its signs/symptoms?
Tick (wooded areas) (borrelia burgdorferi)
- rash at bite area
- 50% flu-like symptoms
- can disseminate over weeks/months, become multi-system and chronic
- does not cause CFS
- can cause encephalomyelitis, subacute encephalopathy
How might you investigate/treat Lyme disease?
Complex range of serological tests CSF lymphocytosis PCR of CSF MRI brain/spine (if CNS involvement) Nerve conduction studies
Prolonged antibiotic treatment
- IV ceftriaxone
- oral doxycycline
How does neurosyphilis present/progress? What investigations are done and how is it treated?
3 stage progression
Primary > secondary > latent
Tertiary disease can occur years after primary but not common
Treponema specific and non-Treponema specific antibody tests
CSF lymphocytes increased, evidence of intrathecal antibody production
PCR
High dose penicillin
What are some important vaccines against nervous system infections?
Poliomyelitis
- 99% asymptomatic
- can be paralytic
- injected vaccination (against all 3 types of virus)
Rabies
- virus enters peripheral, migrates to CNS
- rabies encephalitis - no useful tests before disease apparent
- diagnosis with culture, serology
- post exposure - wash, give active rabies immunisation, give human rabies Ig if high risk
Tetanus
- clostridium tetani
- anaerobic gram+ bacilli, spore forming
- toxin at NMJ, blocks motor neuron inhibition
- toxoid immunisation with others (DTaP)
- penicillin and Ig for high risk wounds/patients
Botulism
- anaerobic gram+ spore forming
- blocks ACh release
- treatment with anti-toxin, metronidazole/penicillin, radical wound debridement
What are post-infective inflammatory syndromes?
Latent interval between precipitating infection and onset of neurological symptoms
- autoimmune
Examples
- acute disseminated encephalomyelitis (CNS)
- Guillain Barre (PNS)
What is an example of a prion disease?
Creutzfeldt-Jakob Disease Transmissible proteinaceous particle Consider in any rapidly progressive dementia Global neurological decline - motor abnormalities Death often <6 months
Don’t mistake for Alzheimer’s with myoclonus
What is new variant Creutzfeldt-Jakob disease and how is it investigated?
Younger onset (<40) Linked to bovine spongiform encephalopathy in cattle Early behavioural changes more prominent
MRI - pulvinar sign - usually not seen in sporadic CJD so suggests new variant
EEG - generalised periodic complexes typical
CSF - normal or raised protein
