Infections of the Nervous System Flashcards
What is the definition of meningitis?
inflammation/infection of the meninges
What is the definition of encephalitis?
inflammation/infection of brain substance
What is the definition of myelitis?
inflammation/infection of the spinal cord
What is the classic triad of features of meningitis?
fever, neck stiffness and altered mental status
What is the common histroy of meningitis like?
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
What part of the brain may be dysfunctioning in 69% of >14?
Cerebral dysfunction (confusion, delirium, declining conscious level)
What other less common things may be a result of meningitis?
Cranial nerve palsy (30%)
seizures (30%)
focal neurological deficits (10-20%)
Look skin rash using a tmbler test in cases of meningitis, what is this a sign of?
hallmark of meningococcal meningitis, but can also occur in viral meningitis
What are some differential diagnosis of meningitis?
Infective: Bacterial, Viral, Fungal
Inflammatory: Sarcoidosis
Drug induced: NSAIDs, IVIG
Malignant: Metastatic and Haematological
e.g. Leukaemia, Lymphoma, Myeloma
What are some bacterial causes of meningitis?
Neisseria meningitidis (meningococcus)
Streptococcus pneumoniae (pneumococcus)
What is the commenest viral cause of meningitis?
enteroviruses
What are the 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
How is viral encephalitis different from bacterial meningitis?
Onset of a viral encephalitis is generally slower than for bacterial meningitis and cerebral dysfunction is a more prominent feature
What are some 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)
Is auto-immune encephalitis as common as viral encephalitis?
May be as common as viral encephalitis
What are 2 important antibodies in auto-immune encephalitis?
Anti-VGKC (Voltage Gated Potassium Channel)
Anti-NMDA receptor
What Investigations of Meningitis?
Priority is to exclude (and treat) infection
Blood cultures (bacteraemia)
Lumbar puncture (CSF culture/microscopy)
No need for imaging if no contraindications to LP
What Investigations for Encephalitis?
Priority is to exclude (and treat) infection
Blood cultures
Imaging (CT scan +/- MRI)
Lumbar puncture
EEG
What do focal symptoms or signs suggest
What does reduced conscious level suggest
Focal symptoms or signs suggest a focal brain mass
Reduced conscious level suggests raised intracranial pressure
What are some contra-indicatiosn for a lumbar puncture?
focal neurological deficit, not including cranial nerve palsies
new-onset sezuires
papllioedema
abnormal level of consciousness, interfering with proper neurological examination
severe immunocomprimised state
Describe the CSF finding differences in bacterial meningitis and viral meningitis/encephalitis:
opening pressure
cell count
glucose
protein
Bacteria use glucose so lower in bacterial
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Herpes simplex (HSV) encephalitis - is it rare or common?
Relatively rare, but commonest cause of encephalitis in Europe
What is the diagnosis of Herpes simplex (HSV) encephalitis?
Lab diagnosis by PCR of CSF for viral DNA
(opposed to growing bacteria as this is viral)
What is the treatment of herpes simplex (HSV) encephalitis?
Treat with aciclovir on clinical suspicion
What is the prognosis of herpes simplex (HSV) encephalitis if left untreated?
Over 70% mortality and high morbidity if untreated
Herpes simplex is one of what groups?
One of the herpes group of viruses
What are the different types of HSV and what do they cause
HSV types 1 & 2 cause:
cold sores (type 1 >> 2)
genital herpes (type 1 & 2 (more so in type 2))
How does HSV present?
Virus remains latent in the trigeminal or sacral ganglion after primary infection
(as with all herpesviruses, once infected, always infected)
Virus never leaves the body – causes acute infection then the virus disappears in the ganglia and lies dormant and if the patient goes under any stress, physical or emotional and then the virus gets reactivated and another re-infection happens and the symptoms come
How does HSV cause encephalitis?
Encephalitis is a rare complication of HSV
other than neonates, nearly all caused by type 1
What do enteroviruses (large family of RNA viruses) cause?
viral meningitis
What do enteroviruses have a tendency to cause?
CNS infection
Who do enteroviruses effect?
humans only
no animal reservoir
How are enteroviruses spread?
faecal oral route
Enterovirus are _____ virus which is different form herpes which is _____ virus
Enterovirus are RNA virus which is different form herpes which is DNA virus
What is an arbovirus and can it cause encephalitis
yes it causes arbovirus encephalitides
Inflammation of the brain (encephalitis) caused by infection with an arbovirus, a virus transmitted by a mosquito, tick or another arthropod
How is arbovirus encephalitides transmitted?
Transmitted to man by vector (mosquito or tick) from non-human host
WHat is important to do when someone present that may have a arbovirus encephalitides
Relevant to travel so a travel history important and some preventable by immunisation
What is a brain abscess?
localized area of pus within the brain
What is subdural empyema?
thin layer of pus between the dura and arachnoid membranes over the surface of the brain
What are the clinical features of a 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
Features of underlying source - e.g dental, sinus or ear infection
What are some 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 is the diagnosis of brain abscess and empyema
Imaging: CT or MRI
investigate source
blood cultures
Biopsy (drainage of pus)
What organisms tend to be present in a brain abscess?
Often mixtures of organisms present (polymicrobial) - depend on predisposing condition
Streptococci in 70% of cases - Strep anginosus, Strep intermedius, Strep constellatus
Anaerobes (any organism that does not require oxygen for growth) in 40 - 100% of cases
What is the management of a 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 conditions seen in patients would make you suspect HIV
- Cerebral toxoplasmosis
- Aseptic meningitis/encephalitis
- Primary cerebral lymphoma
- Cerebral abscess
- Cryptococcal meningitis
- Space occupying lesion of unknown cause
- Dementia
- Leucoencephalopathy
Spirochaetes in the CNS may cause what diseases?
- Lyme Disease (Borrelia burgdorferi)
- Syphilis (Trepomena pallidum)
- Leptospirosis (Leptospira interrogans)
How is lyme disease transmitted?
Vector borne: Tick (wooded areas)
Spirochaete: Borrelia burgdorferi
How many stages of lyme disease is there?
3
Where does lyme disease affect in the body?
it is multi-system
Skin, rheumatological, neurological/neuropsychiatric, cardiac and ophthalmological involvement
Untreated 80% will develop multi-system disseminated disease
What symptoms is there in stage 1 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 seen in stage 2 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
PNS > CNS
What is seen in stage 3 lyme disease?
similar to stage 2 but further down the line
Chronic infection - months to years
occuring after a period of latency
Musculoskeletal and neurologic involvement most common
Neurologic involvement
Does NOT cause a chronic fatigue syndrome
What is the investigtion of lyme disease?
Complex range of serological tests
CSF lymphocytosis - higher-than-normal amount of lymphocytes
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
How does neurosyphilis present?
syphilis has a similar 3 stage presentation
primary - secondary - latent
tertiary disease (neurosyphilis) years/decades after primary disease - not common
How do you investiage syphilis?
antibody tests
CSF lymphocytes increased
What is the trestment of neurosyphilis?
high dose penicillin
moving onto important vaccines
What causes Poliomyelitis?
Caused by poliovirus types 1, 2 or 3
all enteroviruses
What does polimyelitis cause?
- 99% of infections are asymptomatic
- Paralytic disease in ~1%
infects anterior horn cells of lower motor neurones
Asymmetric, flaccid paralysis, esp legs
No sensory features
What is the polio immunisation?
In UK, both contain all three poliovirus types
UK 2004 changed from oral to injected vaccine
What is rabies?
Acute infectious disease of CNS affecting almost all mammals
How is rabies transmitted?
Transmitted to human by bite or salivary contamination of open lesion
Rabies is neurotropic, what does this mean?
virus enters peripheral nerves and migrates to CNS
WHat are the symptoms of rabies?
- Paraesthesiae (an abnormal sensation, typically tingling or pricking (‘pins and needles’)) at site of original lesion
- Ascending paralysis and encephalitis
What is the diagnosis of rabies encephalitis?
No useful diagnostic tests before clinical disease apparent
Diagnosis: PCR and Serology
WHat is the pre-exposure prevention of rabies?
active immunisation with killed vaccine
What is the post-exposure treatment of rabies?
Wash wound
Give active rabies immunisation
Give human rabies immunoglobulin (passive immunisation) if high risk
What is tetanus an infection of?
infection with Clostridium tetani
anaerobic Gram positive bacillus, spore forming
How does tetanus cause infection?
wound may not be apparent
toxin acts at neuro-muscular junction
blocks inhibition of motor neurones
What does tetanus cause?
rigidity and spasm (risus sardonicus)
How is tetanus prevented?
Immunisation (toxoid)
given combined with other antigens (DTaP)
Penicillin and immunoglobulin for high risk wounds/patients
What is botulism?
a serious illness caused by the botulinum toxin. The toxin causes paralysis
Anaerobic spore producing gram positive bacillus
Binds irreversibly to the presynaptic membranes of peripheral neuromuscular and autonomic nerve junctions
Toxin binding blocks acetylcholine release
Recovery is by sprouting new axons
Naturally present in soil, dust and aquatic environments
What are the modes of botulism infection?
Infantile (intestinal colonization)
Food-borne (outbreaks)
Wound: Almost exclusively injecting or “popping” drug users
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 is the diagnosis 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
Creutzfeldt-Jakob Disease (CJD) is what type of disease?
Prion
prion is a type of protein that can trigger normal proteins in the brain to fold abnormally
What is the aetiology of CJD?
Sporadic CJD
New variant CJD
Familial CJD (10-15%)
Acquired CJD (<5%)
• Cadeveric Growth Hormone
• Dura matter grafts
• Blood transfusion
How common is CJD?
Very rare: sporadic 1 per million per year (incidence)
When would you consider sporadic CJD in a patient?
Consider in any rapidly progressive dementia
What are the clinical 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 is the prognosis of sporadic CJD?
rapid progession
death often within 6 months
What age does new varient CJD present at?
Younger onset <40
What is more prominent in new varient CJD?
Early behavioural changes more prominent
What investigations can be used for CJD?
MRI - Often no specific changes in sporadic CJD
EEG
CSF - Normal or raised protein