Infections of the Nervous System Flashcards
definition of meningitis
inflammation / infection of meninges
definition of encephalitis
inflammation / infection of brain substance
definition of myelitis
inflammation / infection of spinal cord
clinical features of meningitis
“classical triad” – fever, neck stiffness and altered mental status
Present with a short history of progressive headache associated with
Fever (>38º) and
Meningism (neck stiffness, photophobia, nausea and vomiting)
Neck stiffness is examined by passively bending the neck forward
Cerebral dysfunction (confusion, delirium, declining conscious level) is common and GCS is <14 in 69%
Cranial nerve palsy (30%), seizures (30%), focal neurological deficits (10-20%) may also occur
Look for a petechial skin rash (Tumbler test)
hallmark of meningococcal meningitis, but can also occur in viral meningitis
what are differential diagnosis of meningitis?
Infective: Bacterial, Viral, Fungal
Inflammatory: Sarcoidosis
Drug induced: NSAIDs, IVIG
Malignant: Metastatic
Haematological
e.g. Leukaemia, Lymphoma, Myeloma
what are the bacterial causes of meningitis?
Neisseria meningitidis (meningococcus) Streptococcus pneumoniae (pneumococcus)
what are the viral causes of meningitis?
enteroviruses
what are clinical features 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 are 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
Migraine
Post ictal (after seizure)
what are the two antibodies involved in auto-immune encephalitis?
Anti-VGKC (Voltage Gated Potassium Channel)
Frequent seizures
amnesia (not able to retain new memories)
Altered mental state
Anti-NMDA receptor Flue like prodrome Prominent psychiatric features Altered mental state and seizures Progressing to a movement disorder and coma
what are the investigations for meningitis?
Blood cultures (bacteraemia) Lumbar puncture (CSF culture/microscopy) No need for imaging if no contraindications to LP
what are the investigations for encephalitis?
Blood cultures
Imaging (CT scan +/- MRI)
Lumbar puncture
EEG
what are the indications for CT brain scanning before lumbar puncture?
focal neurological deficit, not including cranial nerve palsies
new onset seizures
papilloedema
abnormal level of consciousness, interfering with proper neurological examination
severe immunnocomprimised state
what do focal symptoms or signs suggest on a CT?
focal brain mass
what does reduced conscious level suggest on a CT?
raised intracranial pressure
what is the cell count in bacterial meningitis?
high, mainly neutrophils
what is the cell count in viral meningitis or encephalitis?
high, mainly lymphocytes
what is the levels of glucose in bacterial meningitis?
reduced
what are the glucose levels in viral meningitis and encephalitis?
normal 60% of blood glucose
what are the protein levels in bacterial meningitis?
high
what are the protein levels in viral meningitis and encephalitis
slightly increased
what would the result of a blood culture gram stain be?
gram positive cocci in chains- looks like streptococci
what is the commonest cause of encephalitis in europe?
herpes simplex (HSV) encephalitis
how would you treat HSV encephalitis?
aciclovir
what are the results of HSV type 1 and 2?
cold sores and genital herpes
how are enteroviruses spread?
faecal-oral route
what can enteroviruses cause?
non-paralytic meningitis
do enteroviruses cause gastroenteritis?
no
how is arbovirus encephalitis transmitted?
to man by vector form non-human host
what part of a history is related to arbovirus encephalitedes?
travel history- can be prevented by immunisation
what is a subdural empyema?
thin layer of pus between the dura and arachnoid membranes over the surface of the brain
what are clinical features of brain abscess and empyema?
Fever, Headache
Focal symptoms / signs
Seizures, dysphasia, hemiparesis, etc
Signs of raised intracranial pressure
Papilloedema, false localizing signs,
depressed conscious level
Meningism may be present, particularly with empyema
differential diagnosis of brain abscess and empyema
Any focal lesion, but most commonly tumour
Subdural haematoma
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
how would you diagnose brain abscess and empyema?
Imaging: CT or MRI
investigate source
blood cultures
Biopsy (drainage of pus)
how do you manage 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
High mortality without appropriate treatment
what are HIV indicators (brain)
Cerebral toxoplasmosis Aseptic meningitis /encephalitis Primary cerebral lymphoma Cerebral abscess Cryptococcal meningitis Space occupying lesion of unknown cause Dementia Leucoencephalopathy
diagnostics of brain infections in HIV
Cryptococcal antigen
Toxoplasmosis serology
CMV PCR
HIV PCR
what are the spirochaetes in the CNS?
Lyme Disease (Borrelia burgdorferi) Syphilis (Trepomena pallidum) Leptospirosis (Leptospira interrogans)
what is the vector invoolved in lyme disease?
tick
what are the stage 1 signs 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 are the stage 2 signs of lyme disease?
Early disseminated infection (weeks – months)
One or more organ systems become involved
Haematologic or lymphatic spread
Musculoskeletal and neurologic involvement most common
Neurologic involvement (10-15%) untreated patients
what are the stage 3 signs of lyme disease?
Chronic infection
months to years
occuring after a period of latency
Musculoskeletal and neurologic involvement most common
Neurologic involvement
As described for stage 2
Subacute encephalopathy
Encephalomyelitis
what are the investigations for lyme disease?
Complex range of serological tests
CSF lymphocytosis
MRI brain / spine (if CNS involvement)
Nerve conduction studies / EMG (if PNS involvement)
Prolonged antibiotic treatment
intravenous ceftriaxone
oral doxycycline
what are the three stages of syphillis?
primary, secondary, latent
what are the antibody tests involved in syphillis?
Treponema specific and non-treponemal specific antibody tests
what causes poliomyelitis?
poliovirus types 1, 2 or 3
how is rabies transmitted to a human?
by bite or salivary contamination of open lesion
how would you diagnosoe rabies encephalitis?
PCR and Serology
what is the tetanus infection?
Clostridium tetani
what type of bacillus is tetanus?
anaerobic Gram positive bacillus, spore forming
what does tetanus do?
blocks inhibition of motor neurones
rigidity and spasm (risus sardonicus)
how is tetanus preventable?
immunisation
what are the three modes of infection of botulism?
Infantile (intestinal colonization)
Food-borne (outbreaks)
Wound: Almost exclusively
injecting or “popping” drug users
what is the botulism infection?
Clostridium botulinum
how does botulism (Neurotoxin) work?
Binds irreversibly to the presynaptic membranes of peripheral neuromuscular and autonomic nerve junctions
Toxin binding blocks acetylcholine release
Recovery is by sprouting new axons
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
how would you diagnose 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 some post infective inflammatory syndromes?
“Molecular mimicry”Acute disseminated encephalomyelitis (ADEM)
Guillain Barre Syndrome (GBS)
what is the aetiology of creutzfeldt-jakob disease?
Sporadic CJD New variant CJD Familial CJD (10-15%) Acquired CJD (<5%) Cadeveric Growth Hormone Dura matter grafts Blood transfusion
clinicl features of sporadic CJD?
Insidious onset (usually older than 60)
Early behavioural abnormalities
Rapidly progressive dementia
Myoclonus
Progressing to global neurological decline
Motor abnormalities
Cerebellar ataxia
Extrapyramidal: tremor, rigidity, bradykinesis, dystonia
Pyramidal: weakness, spacticity, hyper-refexia
Cortical blindness
Seizures may occur
what are 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
what is the prognosis of sporadic CJD?
Rapid progression
Death often within 6 months
investigations of CJD?
MRI
EEG
CSF
