Infections of the nervous system Flashcards
What is Encephalitis?
inflammation/infection of the brain substance
What is myelitis?
inflammation/infection of the spinal cord
What is the ‘classical triad’ of symptoms for Meningitis?
Fever
Neck stiffness
Altered mental status
What are meningisms?
collective term for neck stiffness, photophobia, nausea and vomiting
What sorts of cerebral dysfunction appear in Meningitis patients?
confusion
delirium
declining conscious level - GCS <14 in 69%
What is the hallmark sign of meningococcal meningitis?
petechial skin rash - do tumbler test - if you can still see the rash through the glass then this is likely meningitis
What 4 types of meningitis can you get?
Infective - bacterial, viral or fungal
Inflammatory - sarcoidosis
Drug induced - NSAIDs, IVIG
Malignant - metastatic, haematological (leukemia, lymphoma, myeloma)
Name 2 common bacterium that cause bacterial meningitis
Neisseria meningitidis (meningococcus)
Streptococcus pneumoniae (pneumococcus)
Cause of viral meningitis?
enteroviruses
viral meningitis is much milder than bacterial
Clinical features of Encephalitis? (5)
Flu-like early symptoms (4-10days)
Progressive Headache associated with fever
+/- meningism
Progressive cerebral dysfunction
Seizures
Focal symptoms / signs
How is viral encephalitis different to the bacterial form?
viral encephalitis has a generally slower onset and cerebral dysfunction is a more prominent feature
Types of Encephalitis/ differential diagnosis? (6)
Infective - viral most common is HSV
Inflammatory - limbic encephalitis, ADEM
Metabolic - hepatic, uraemic, hyperglycaemic
Malignant - metastatic
Migraine
Post ictal (after repeated seizures - don’t fully recover)
What are the 2 important antibodies associated with auto-immune Encephalitis?
Anti-VGKC - (Voltage Gated Potassium Channel) causes frequent seizures, amnesia and altered mental state
Anti-NMDA receptor - causes prominent psychiatric features, altered mental state and seizures progressing to a movement disorder and coma
Person with auto-immune Encephalitis mistakenly attacks healthy brain cells
Investigations for Meningitis (3)
Blood cultures (bacteraemia)
Lumbar puncture (CSF culture/microscopy)
No need for imaging if no contraindications to LP
Investigations for Encephalitis?
Blood cultures
Imaging (CT scan +/- MRI)
Lumbar puncture
EEG - electroencephalogram
What are contraindications to Lumbar puncture? In these cases you should do a CT scan first.
If patient has:-
focal symptoms or signs suggest a focal brain mass
If they have reduced conscious level which suggests raised intracranial pressure
If you take CSF away from LP then you may cause focal mass to herniate if you alter the fluid balance
What are the CSF findings for Bacterial Meningitis. Mention:- cell count
glucose level
protein level
Cell count - high, mainly neutrophils
Glucose - reduced (bacteria use it up)
Protein - high
What are the CSF findings for Viral Meningitis and Encephalitis. Mention:- cell count
glucose level
protein level
Cell count - High, mainly lymphocytes
Glucose - Normal (60% of blood glucose - must compare CSF with blood sample)
Protein - slightly increased
Herpes simplex (HSV) encephalitis
rare but commonest type of encephalitis in europe
Lab diagnosis by PCR of CSF for viral DNA
treat with aciclovir
over 70% mortality and high morbidity if untreated
What do types 1 and 2 Herpes simplex cause?
cold sores - 1>2
Genital herpes - both
How does the Herpes virus act in the body?
Virus remains latent in the trigeminal or sacral dorsal root ganglion after primary infection
can become reactivated due to stress
(as with all herpes viruses, once infected, always infected)
Enteroviruses
Tendency to cause CNS infections (neurotropic) Human infections, no animal reservoir
Spread by the faecal-oral route
Many can cause non-paralytic meningitis
They do not cause gastroenteritis
Arbovirus encephalitis
Variety of virus groups
Geographical distribution. Vector – not present all over the world - need to take travel history.
transmitted to man by vector (mosquito or tick)
Called Arbo as ARthropod BOrne
What is a brain abscess
localised area of pus within the brain
Fever if abscess bursts and get meningitis
What is Empyema of the brain?
A collection of fluid around the brain – sub dural or extra dural
Clinical features of brain abscess or empyema?
Fever, Headache
Focal symptoms / signs - Seizures, dysphasia, hemiparesis, etc
Signs of raised intracranial pressure - papilloedema (optic disc swelling), depressed conscious level
Meningism may be present, particularly with empyema
Features of underlying source
e.g dental, sinus or ear infection or endocarditis
Causes of brain abscess and empyema?
Any focal lesion, but most commonly tumour
Subdural haematoma
Penetrating head injury
Spread from adjacent infection - sinusitis, dental, otitis media
Blood borne infection
e.g. Bacterial endocarditis
Neurosurgical procedure
How do you diagnose a brain abscess or empyema? What tests/imaging are done? (4)
Imaging: CT or MRI
investigate source
blood cultures
Biopsy (drainage of pus) – sample of abscess itself - this depends on where the problem is - if in brainstem then may not be able to take sample
Causative organisms for brain abscess?
Often mixtures of organisms present due to closed space (polymicrobial) - depends on predisposing condition
Streptococci in 70% of cases
Anaerobes in 40 - 100% of cases
Management of brain abscess? (4)
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 does a low CD4 count mean?
Patient’s HIV is not well managed
Diagnostic tests for HIV?
Cryptococcal antigen
Toxoplasmosis serology
CMV PCR - cytomegalovirus
HIV PCR
Spirochates: cause which diseases affecting the CNS (3)
Lyme Disease
Syphilis
Leptospirosis
Describe Lyme disease: including the 3 stages
spirochaete - Borrelia burgdorferi
multi-system - skin, rheumatological, neurological, cardiac and ophthalmological involvement
stage 1 - target rash, 505 flu like symptoms
stage 2 - one or more organ systems become involved (blood or lymphatic spread)
stage 3 - chronic infection, can take months to years
Which 2 systems are most commonly involved first in Lyme’s disease ?
Musculoskeletal
neurological
Neurological involvement in Lyme disease: examples
Subacute encephalopathy
Encephalomyelitis
Mononeuropathy - one nerve
Mononeuritis multiplex - multiple nerves
Painful radiculoneuropathy
Cranial neuropathy
Myelitis
Meningo-encephalitis
Investigations for Lyme disease (4)
Complex range of serological tests
CSF lymphocytosis - bacteria produce a more viral picture so lymphocytes are raised which you wouldn’t expect
MRI brain / spine (if CNS involvement)
Nerve conduction studies / EMG (if PNS involvement)
Treatment for Lyme disease
Prolonged antibiotic treatment – 3-4 weeks at least
intravenous ceftriaxone
oral doxycycline
Neurosyphilis
Syphilis (Treponema pallidum) has a similar 3 stage presentation - primary, secondary, latent
Test CSF for antibodies:- Treponema specific and non-treponemal specific antibody tests
Expect to see CSF lymphocytes raised
treat with high dose penicillin
Poliomyelitis
99% of infections are asymptomatic
caused by poliovirus types 1, 2 or 3
Asymmetric, flaccid paralysis, esp legs
No sensory features
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
Ascending paralysis and encephalitis
Rabies encephalitis
No useful diagnostic tests before clinical disease apparent - Once this disease is in place, it is very difficult to treat
Diagnosis: PCR and Serology
Important sources of human infection:
Dogs in Africa/Asia
Bats in the developed world.
Who is the rabies vaccine given to in UK
bat handlers
regular handlers of
imported animals
selected travelers to enzootic areas
Post-exposure treatment for rabies?
Wash wound
Give active rabies immunisation
Give human rabies immunoglobulin (passive immunisation) if high risk
If you just give the active vaccine then the body takes weeks to develop an antibody. Need to give active and passive for rabies immunoglobulin
Tetanus
Infection with c tetani
anaerobic Gram positive bacillus, spore forming
toxin acts at neuro-muscular junction
blocks inhibition of motor neurones
rigidity and spasm (risus sardonicus) – makes you very stiff
Prevention of tetanus?
Immunisation (toxoid)
given combined with other antigens (DTaP)
Penicillin and immunoglobulin for high risk wounds/patients
Botulism (clostridium botulinum) 3 modes of infection
Infantile (intestinal colonization) –
Immature gut
Food-borne (outbreaks) – canned food
Wound: Almost exclusively injecting or “popping” drug users
Presentation of botulsim
Incubation period 4-14 days
Descending symmetrical flaccid paralysis
Pure motor
Respiratory failure
Autonomic dysfunction
Usually pupil dilation
Diagnosis of botulism
Nerve conduction studies
Mouse neutralisation bioassay for toxin in blood – ethical? Need to be sure of diagnosis before testing on mouse
Culture from debrided wound
Treatment for botulism
Anti-toxin (A,B,E)
Penicillin / Metronidazole (prolonged treatment)
Radical wound debridement
Creutzfeldt-Jakob Disease (CJD)
a rare and fatal condition caused by an abnormal infectious protein in the brain called a prion.
It can be sporadic, new variant, familial or acquired (blood transfusion etc)
No treatment
When should you consider sporadic CJD as the diagnosis?
Consider in any rapidly progressive dementia
Clinical features:- Insidious onset (usually older than 60)
Early behavioural abnormalities
Rapidly progressive dementia
Myoclonus - quick, involuntary muscle jerk
What diagnoses are you thinking for sporadic CJD? (4)
Alzheimer’s disease with myoclonus
Subacute sclerosing panencephalitis (SSPE)
Very rare, chronic infection with defective measles virus
CNS vasculitis
Inflammatory
encephalopathies
Prognosis of sporadic CJD
death often within 6 months
New variant CJD
Younger onset <40
Linked to Bovine Spongiform Encephalopathy in Cattle
ie eating infected material
