Infections of the Nervous System Flashcards
what is Meningitis?
inflammation / infection of meninges
what is Encephalitis?
inflammation / infection of brain substance
what is Myelitis?
inflammation / infection of spinal cord
what are the symptoms of Meningitis
fever short history of progressive headache blotchy rash that doesn't fade when a glass is rolled over it stiff neck photophobia nausea or vomiting drowsiness or unresponsiveness seizures Cranial nerve palsy
what is the differential diagnosis of meningitis?
Infective: Bacterial, Viral, Fungal
Inflammatory: Sarcoidosis
Drug induced: NSAIDs, IVIG
Malignant: Metastatic Haematological e.g. Leukaemia
what are the bacterial causes of meningitis?
Neisseria meningitidis
Streptococcus pneumoniae: Gram positive cocci in chains
sensitive to penicillin
what are the viral causes of meningitis?
enteroviruses
what are the symptoms of Encephalitis?
Flu-like prodrome (4-10days) Progressive Headache associated with fever \+/- meningism Progressive cerebral dysfunction Confusion Abnormal behaviour Memory disturbance Depressed conscious level Seizures Focal symptoms / signs
what is the difference between viral encephalitis and bacterial meningitis?
viral encephalitis-generally slower and cerebral dysfunction is a more prominent feature
what is the differential diagnosis of encephalitis?
Infective: Viral (most common is HSV)
Inflammatory: Limbic encephalitis (Anti VGKC, Anti NMDA receptor), ADEM
Metabolic: Hepatic, Uraemic, Hyperglycaemic
Malignant: Metastatic, Paraneoplastic
what are the two important antibodies of Auto-immune Encephalitis?
Anti-VGKC (Voltage Gated Potassium Channel)
Anti-NMDA receptor
what are the investigations of meningitis?
Blood cultures (bacteraemia) Lumbar puncture (CSF culture/microscopy) No need for imaging if no contraindications to LP
what are the investigations of Encephalitis?
Blood cultures
Imaging (CT scan +/- MRI)
Lumbar puncture
EEG
what are the indications for CT before lumbar puncture?
Focal symptoms or signs suggest a focal brain mass
Reduced conscious level suggests raised intracranial pressure
what are the CSF findings in bacterial meningitis?
opening pressure: increased
cell count: high, mainly neutrophils
glucose: reduced
protein: high
what are the CSF findings in viral meningitis and encephalitis?
opening pressure: normal/increased
cell count: high, mainly lymphocytes
glucose: Normal (60% of blood glucose)
protein: slightly increased
describe Herpes simplex (HSV) encephalitis
commonest cause of encephalitis in Europe
Lab diagnosis by PCR of CSF for viral DNA
Treat with aciclovir on clinical suspicion
Over 70% mortality and high morbidity if untreated
what herpes simplex type cause Encephalitis?
other than neonates, nearly all caused by type 1
describe enteroviruses
Tendency to cause CNS infections (neurotropic)
Spread by the faecal-oral route
Many can cause non-paralytic meningitis
They do NOT cause gastroenteritis
Include polioviruses, coxsackieviruses and echoviruses
what is Arbovirus encephalitides?
Transmitted to man by vector (mosquito or tick) from non-human host e.g. : West Nile virus St Louis Encephalitis Western Equine Encephalitis Tick Borne Encephalitis Japanese B Encephalitis travel history important
what are the Clinical Features of brain abscess and empyema?
Fever, Headache
Focal symptoms / signs (Seizures, dysphasia, hemiparesis)
Signs of raised intracranial pressure (Papilloedema, false localizing signs, depressed conscious level)
Meningism may be present, particularly with empyema
Features of underlying source
e.g dental, sinus or ear infection
what are the causes of brain abscess and empyema?
Penetrating head injury
Spread from adjacent infection: Dental, Sinusitis, Otitis media Blood borne infection e.g. Bacterial endocarditis
Neurosurgical procedure
what are investigations of brain abscess and empyema?
Imaging: CT or MRI
investigate source
blood cultures
Biopsy (drainage of pus)
what are the organisms present in brain abscess?
Streptococci in 70% of cases, especially the penicillin-sensitive “Strep milleri” group
Anaerobes in 40 - 100% of cases- Bacteroides, Prevotella
what is the management of brain abscess?
Surgical drainage if possible
Penicillin or ceftriaxone to cover streps
Metronidazole for anaerobes
High doses required for penetration
Culture and sensitivity tests on aspirate provide useful guide
what are HIV indicator illnesses of the brain?
Cerebral toxoplasmosis Aseptic meningitis /encephalitis Primary cerebral lymphoma Cerebral abscess Cryptococcal meningitis Space occupying lesion of unknown cause Dementia Leucoencephalopathy
what are the diagnostics of Brain infections in HIV patients
india Ink, cryptococcal antigen Toxoplasmosis serology (IgG) JC virus PCR CMV PCR HIV PCR
what are the Spirochaetes in the CNS?
Lyme Disease (Borrelia burgorferi) Syphilis (Trepomena pallidum) Leptospirosis (Leptospira interrogans)
what is stage 1 of lyme disease?
Early localized infection (1-30d)
Characteristic expanding rash at the site of the tick bite: erythema migrans
50% flu like symptoms (days – 1 week)
Fatigue, myalgia, arthralgia, headache, fever, chills, neck stiffness
what is stage 2 of lyme disease?
Early disseminated infection (weeks – months after initial infection)
Haematologic or lymphatic spread
Musculoskeletal and neurologic involvement
Neurologic involvement (10-15%) untreated patients
PNS > CNS
Mononeuropathy
Mononeuritis multiplex
Painful radiculoneuropathy
Cranial neuropathy
what is stage 3 of lyme disease?
Chronic infection (months to years after period of latency)
Musculoskeletal and neurologic involvement most common
Neurologic involvement:
As described for stage 2
Subacute encephalopathy
Encephalomyelitis
Does NOT cause a chronic fatigue syndrome
what are the investigations of lyme disease?
Complex range of serological tests CSF lymphocytosis PCR of CSF MRI brain / spine (if CNS involvement) Nerve conduction studies / EMG (if PNS involvement)
what is the treatment of lyme disease?
Prolonged antibiotic treatment
intravenous ceftriaxone
oral doxycycline
describe the presentation of syphilis?
has a similar 3 stage presentation Tertiary disease (neurosyphilis) years/decades after primary disease - not common
what are the investigations of neurosyphilis?
Treponema specific and non-treponemal specific (VDRL) antibody tests
CSF lymphocytes increased, evidence of intrathecal antibody production, PCR
what is the treatment of neurosyphilis?
High dose penicillin
describe Poliomyelitis
Caused by poliovirus types 1, 2 or 3 - all enteroviruses
asymptomatic
Paralytic disease in ~1%
infects anterior horn cells of lower motor neurones
Asymmetric, flaccid paralysis, esp legs
No sensory features
Polio Immunisation
describe rabies
Acute infectious disease of CNS affecting almost all mammals
Transmitted to human by bite or salivary contamination of open lesion
Neurotropic - virus enters peripheral nerves and migrates to CNS
Paraesthesiae at site of original lesion
Ascending paralysis and encephalitis
what can prevent/treat rabies?
pre-exposure: Active immunisation with killed vaccine
post-exposure: Give active rabies immunisation
Give human rabies immunoglobulin (passive immunisation) if high risk
describe tetanus
infection with Clostridium tetani anaerobic Gram positive bacillus, spore forming wound may not be apparent toxin acts at neuro-muscular junction blocks inhibition of motor neurones rigidity and spasm
what can prevent tetanus?
immunisation (toxoid)
given combined with other antigens (DTaP}
penicillin and immunoglobulin for high risk wounds/patients
describe botulism
Clostridium botulinum
Anaerobic spore producing gram positive bacillus
Neurotoxin: Toxin binding blocks acetylcholine release
Naturally present in soil, dust and aquatic environments
what is the clinical presentation of botulism?
Incubation period 4-14 days Descending symmetrical flaccid paralysis Pure motor Respiratory failure Autonomic dysfunction Usually pupil dilation
what are the investigations of botulism?
Nerve conduction studies
Mouse neutralisation bioassay for toxin in blood
Culture from debrided wound
what is the treatment of botulism?
Anti-toxin (A,B,E)
Penicillin / Metronidazole (prolonged treatment)
Radical wound debridement
what are post infective inflammatory syndromes?
Preceding infection (viral, bacterial) or immunization
“Molecular mimicry”
Latent interval between the precipitating infection and onset of neurological symptoms
Autoimmune
describe Creutzfeldt-Jakob Disease (CJD)
Transmissible Proteinaceous particle – Prion
what is the aetiology of CJD?
Sporadic CJD New variant CJD Familial CJD (10-15%) Acquired CJD (<5%) ( eg blood transfusion)
what are the clinical features of Sporadic CJD?
Consider in any rapidly progressive dementia Insidious onset (usually older than 60) Early behavioural abnormalities Myoclonus Progressing to global neurological decline Motor abnormalities Cortical blindness Seizures may occur Death often within 6 months
what is the differential diagnosis of Sporadic CJD
Alzheimer’s disease with myoclonus - Usually more prolonged
Subacute sclerosing panencephalitis (SSPE) - Very rare, chronic infection with defective measles virus
CNS vasculitis
Inflammatory encephalopathies
describe new variant CJD
Younger onset <40
Linked to Bovine Spongiform Encephalopathy in Cattle
Early behavioural changes more prominent
Longer course (average 13 months)
what are the investigations of sporadic and variant CJD?
MRI: Pulvinar sign in variant CJD Often no specific changes in sporadic CJD EEG: Generalised periodic complexes typical Often normal in initial stages CSF: Normal or raised protein Immunoassay 14-3-3 brain protein (non-specific, but very helpful in correct clinical context)
