Infections of the nervous system Flashcards
What is meningitis?
Inflammation of the meninges.
What are the symptoms and signs of meningitis?
Symptoms:
- photophobia
- N/V
Signs –> classical triad:
- fever
- neck stiffness
- altered mental status
(Also petechial skin rash - hallmark of meningococcal meningitis)
What are the main organisms that cause meningitis?
Bacterial:
- Neisseria meningitidis (meningococcus)
- Strep pneumoniae (pneumococcus)
Viral:
- enterovirus
Which investigations would you do for suspected meningitis?
- blood cultures looking for bacteraemia
- lumbar puncture: culture CSF and do microscopy looking for bacteria
Don’t need to use imaging unless there are CI’s to LP.
What are CI’s to LP?
- presence of focal signs/symptoms suggest a focal brain mass
- reduced consciousness level suggests a raised ICP
–> in both cases, CT before LP
How can meningococcal meningitis be treated?
IV ceftriaxone.
What is encephalitis?
Inflammation of the brain.
What are the signs and symptoms of encephalitis?
Signs:
- fever
- meningism
- progressive cerebral dysfunction
- focal signs
Symptoms:
- flu-like prodrome
- progressive headache
What is the most common type of encephalitis in Europe?
HSV encephalitis - mostly type 1 HSV, but in neonates type 2.
How is HSV encephalitis diagnosed?
Lab diagnosis by PCR of CSF for viral DNA.
How is HSV encephalitis treated?
Aciclovir - over 70% mortality and high morbidity if untreated.
Where does HSV remain latent?
Trigeminal or sacral ganglion after primary infection.
Which family viruses can cause non-paralytic meningitis?
Enteroviruses: faecal-oral soread. Includes polioviruses.
Which organisms are the main cause of encephalitis in other parts of the world?
Arboviruses - mosquito or tick-borne. Importance of travel history.
What is a brain abscess?
Localised area of pus within the brain.
What is a subdural empyema?
A thin layer of pus between the dura and arachnoid membranes over the surface of the brain.
What are the symptoms and signs of brain abscess/empyema?
Symptoms:
- headache that is worse in the morning
- coughing
- sleeping
Signs:
- raised ICP (papilloedema, depressed conscious level)
- fever
- meningism
What causes a brain abscess/empyema?
- penetrating head injury
- spread from adjacent infection (dental, otitis media)
- blood-borne infection eg bacterial endocarditis
How are brain abscess/empyema investigated?
- Imaging: CT/MRI
- Blood cultures
- Drainage of pus
Which organisms cause brain abscess?
Streptococci in 70% of cases, especially the Strep milleri group (Strep anginosis, Strep intermedius and Strep constellatus). Usually anaerobic organisms - bacteriodes, Prevotella etc.
How are brain abscesses managed?
- Surgical drainage if possible
- Penicillin/ceftriaxone for Strep
- Metronidazole for anaerobes
–> need high doses to penetrate the BBB
Which illnesses indicate HIV?
- cerebral toxoplasmosis
- aseptic meningitis/encephalitis
- primary cerebral lymphoma
- cerebral abscess
- Cryptococcal meningitis
HIV encephalopathy –> HIV-associated dementia
How is HIV diagnosed?
HIV PCR. Can also do CMV PCR, JC virus PCR, toxo serology (IgG) etc.
Describe Cryptococcal meningitis.
Mostly caused by C.neoformans. Most clinical cases present with meningoencephalitis - common in people with AIDS or on high doses of immunosuppression.
Name 3 spirochaetes that can affect the CNS.
Borrelia burgorferm (Lyme), Treponema pallidum (Syphilis) and Leptospira interrogans (Leptospirosis).
Name the rash that occurs in Lyme disease.
Erythema migrans - occurs at the site of the tick bite.
Describe the 3 stages of Lyme disease.
1) Early localised infection (1-30 days): flu-like symptoms and erythema migrans rash.
2) Early disseminated infection (weeks-months): haematologic or lymphatic spread; 1 or more organs becomes involved; neurological involvement (PNS).
3) Chronic (months - years): MSK and neuro symptoms; subacute encephalopathy and encephalomyelitis.
What are the investigations for Lyme?
- serology
- PCR of CSF
- MRI (if brain/spine involvement)
How is Lyme disease treated?
IV ceftriaxone and oral doxycycline.
Describe neurosyphilis.
- Uncommon tertiary form of syphilis
- VDRL antibody test, PCR, look for CSF lymphocyte increase etc
- Treat with high dose penicillin
Which cells are affected by paralytic poliomyeitis?
Anterior horn cells of LMN. Causes asymmetric, flaccid paralysis mainly of the legs with no sensory features.
Describe the polio vaccine.
- contains serotypes 1, 2 and 3
- injected (as oral caused a higher incidence of polio than there is in the UK)
What is rabies?
- Neurotropic virus that causes ascending paralysis and encephalitis
- Diagnosis is by culture, detection and serology
- Dogs and bats are important reservoirs of human infection
- Immunisation available (killed)
- If exposed give rabies Ig
What is tetanus?
- caused by Clostridium tetani (spore-forming, anaerobic gram positive bacillus)
- toxin acts at NMJ
- causes rigidity and spasm
- DTaP vaccine (toxoid)
- penicillin and Ig for high risk patients
What is botulism?
- Clostridium botulinum (anaerobic, spore-forming, gram positive bacillus)
- neurotoxic - blocks ACh release at the NMJ and autonomic junction
- IDU, food-borne or infantile infection
- purely motor; descending symmetrical flaccid paralysis
- treat with anti-toxin (ABE), penicillin and metronidazole
Name 2 post-infective inflammatory syndromes.
- CNS: acute disseminated encephalomyelitis (ADEM)
- PNS: Guillain-Barre syndrome (GBS)
What causes post-infective inflammatory syndromes?
A preceding infection or immunisation. Usually due to molecular mimicry - cause autoimmune destruction.
What is CJD?
Prion disease - sporadic, new variant etc. Very rare.
When should sporadic CJD be considered?
- in any case of rapidly progressive dementia
- over 60’s
- motor decline: ataxia, extrapyramidal and pyramidal
- seizures, cortical blindness
- rapid progression and death within 6 months
What are the differentials for sporadic CJD?
- Alzheimer’s disease with myoclonus
- Subacute sclerosing panencephalitis
- CNS vasculitis
- Inflammatory encephalopathies
What is new variant CJD?
- younger onset (<40)
- linked to BSE in cattle: eating infected material
- longer course of infection (13 months)
How would you investigate suspected CJD?
- MRI
- EEG
- CSF
