Infections of the Nervous System Flashcards
What is meningitis?
Inflammation/infection of the meninges
What is encephalitis?
Inflammation/infection of brain substance
What is myelitis?
Inflammation/infection of the spinal cord
What is the classic triad of meningitis?
Fever
Neck Stiffness
Headache
What are the classic signs of meningitis?
Fever Neck stiffness Photophobia Nausea Vomiting Headache
How is neck stiffness examined?
By passively bending the neck forward
Describe GCS in meningitis patients
Often a little lower than normal
<14 in 69%
What type of rash is seen in meningitis?
Petechial rash
What test should be done on a petechial skin rash in suspected meningitis?
Tumbler test
What is non-blanching petechial skin rash a hallmark sign of?
Meningococcal meningitis
What are the common bacterial causes of meningitis?
- Neisseria meningititis (meningococcus)
- Streptococcus pneumoniae (pneumococcus)
What do viral causes of meningitis include?
Enterioviruses
What are the clinical features of encephalitis?
Flu like prodrome Progressive headaches with fever \+/- meningism Cerebral dysfunction Altered brain function - confusion, abnormal behaviour, memory disturbance, depressed conscious level Seizures Focal symptoms
What is a distinguishing feature between encephalitis and meningitis?
Onset of encephalitis is generally slower than for bacterial meningitis and cerebral dysfunction is a more prominent feauture
What investigations should be carried out for meningitis?
Blood cultures
Lumbar puncture
No need for imaging if no contraindications to LP
What investigations should be carried out for encephalitis?
Blood cultures
Imaging (CT scan+/- MRI)
LP
EEG
What are the contraindications for a lumbar puncture?
Focal symptoms or signs that suggest a focal brain mass
Reduced conscious levels suggesting raised ICP
GCS <10
Severely immunocompromised state
New onset seizures
What is opening pressure?
The pressure of CSF that is detected just after a needle is placed into the spinal canal
Describe opening pressure in meningitis and encephalitis
Meningitis - increased
Encephalitis - normal/increased
Describe cell count in meningitis and encephalitis
Meningitis - high, mainly neutrophils
Encephalitis - high, mainly lymphocytes
Describe glucose in meningitis and encephalitis
Meningitis - reduced
Encephalitis - normal
Why is glucose reduced in meningitis?
Because the bacteria consume the glucose 1
What do you have to do when testing glucose in encephalitis and meningitis?
Have to take a 3rd blood sample to compare to the red of the body cannot compare to a ‘normal’ figure
What is the first line of treatment in suspected meningitis?
IV ceftriaxone
What should you do if the patient is presenting clinically septic or pyrexial?
Do a LP
But do not do a blood culture
What is the commonest cause of encephalitis in europe?
Herpex simplex encephalitis
What investigation should you do for HSV encephalitis?
LP
What is the lab diagnosis for HSV encephalitis?
PCR of CSF for viral DNA
What is the Rx for HSV encephalitis?
AciclovirIV
When should aciclovir be given in HSV encephalitis?
On clinical suspicion - don’t wait for lab confirmation
What general things does herpes simplex cause?
Cold sores
Genital herpes
Where does herpes simplex virus lay dormant?
Dorsal route ganglion
What type of HSV causes encephalitis?
Nearly all caused by type 1 other than in neonates
What common virus can encephalitis be a rare complication of?
HSV
What is meant by neurotropic?
a virus, toxin, or chemical) tending to attack or affect the nervous system preferentially.
What do enteroviruses tend to attack?
Nervous system
How are enteroviruses spread?
Faecal-oral route
What are examples of enteroviruses?
Polioviruses, coxsackieviruses, echoviruses
What is a brain abscess?
Localised area of pus within the brain
What is a subdural empyema?
Thin layer of pus between the dura and arachnoid membranes over the surface of the brain
How does subdural empyema present?
With a high pressure headachw
What can be the features of an underlying source of subdural empyema?
Dental, sinus or ear infection
What are the differential diagnosis for brain abscess?
An focal lesion
More commonly a tumour
Subdural haeatoma
What are the causes for brain abscess and empyema?
Penetrating head injury
Spread from adjacent infection (dental, sinusitis, otitis media)
Blood borne infection
Neurosurgical procedure
How is diagnosis for brain abscess and empyema made?
CT or MRI
Investigating source
Blood cultures
Biopsy
What is the most common organisms present in a brain abscess?
Often a mixture of organisms present
Streptococci in 70% of cases
What is the management of brain abscess?
Surgical drainage if possible
Penicillin of ceftriaxone AB
Why are HIV positive patients susceptible to infection?
Because their immune system is compromised
What is the suspicion when a patient presents with cerebral toxoplasmosis?
That they have HIV
What is the most common cause of brain abscess in patients with HIV?
Cerebral toxoplasmosis
What is the diagnosis for HIV brain infection?
LP
What does toxoplasmosis serology IgG suggest?
Past infection
What does toxoplasmosis serology IgE suggest?
Acute infection
What does borrelia burgoferi cause?
Lyme disease
Which organisms causes syphilis?
Trepomena pallidum
What is the vector for lyme disease?
Tick
What are the 3 spirochaetes in the CNS?
Lyme Disease (Borrelia burgorferi)
Syphilis (Trepomena pallidum)
Leptospirosis (Leptospira interrogans)
Describe stage 1 of lyme disease?
Early localised infection Characteristic rash at the site of the tick bite 50% flu like symptoms fatigue myalgia Arthralgia Headache Fever Chills Neck stiffness
Describe stage 2 of lyme disease infection
Early disseminated infection (weeks – months)
One or more organ systems become involved
Haematologic or lymphatic spread
Musculoskeletal and neurologic involvement most common
Describe stage 3 lyme disease
Chronic infection Occurring after a period of latency Musculoskeletal and neurological involvement most common Subacute encephalopathy Encephalomyelitis
Does lyme disease cause chronic fatigue syndrome?
No
What s the investigation for lyme disease?
Complex range of serology tests CSF lymphocytosis PCR of CSF MRI brain/spine Nerve conduction studies EMG if there is PNS involvement
What is the treatment for lyme disease?
Prolonged AB treatment
IV ceftriaxone
Oral doxycycline
What are the 3 stages of neurosyphilis?
Primary
Secondary
Latent
In which stage of neurosyphilis is there neuro involvement?
Tertiary
How is neurosyphilis diagnosed?
Serology
Which antibody tests should be carried out for neurosyphilis?
Treponema - specific
Non specific treponemal
What is the treatment for neurosyphilis?
High dose penicillin
What type of virus are poliovirus?
Enterovirus
What are the 3 types of poliovirus?
Types 1,2,3
Where does poliovirus infect in poliomyelitis?
Anterior horn cells of lower motor neurons
What are the motor features of poliomyelitis?
Asymmetric, flaccid paralysis esp in the legs
What % of polio viruses are asymptomatic?
99%
What are the sensory features of poliomyelitis?
No sensory features
What does the polio vaccination contain?
All 3 types of polio
What is rabies?
Acute infectious disease of CNS affecting almost all mammals
How is rabies transmitted?
By bite or salivary contamination of open lesions
What type of virus is rabies?
Neurotropic
How does the rabies virus progress?
Enters PNS and migrates to CNS
What are the symptoms of rabies?
Paraesthesiae at the site of origin
Ascending paralysis and encephalitis
Who is at risk of rabies in the UK?
Bat handlers
How is rabies diagnosed?
Culture
Detection
Serology
What are important sources of human infection of rabies?
Dogs in africa/asia
What is pre-exposure prevention of rabies?
Active immunisation with killed vaccine
What is the post-exposure treatment for rabies?
Wash wound
Give active rabies immunisation
Give human rabies immunoglobulin if high risk
What is tetanus infection with?
Clostridium tetanis
Where do toxins in tetanus act?
The the neuromuscular junction
How do toxins in tetanus affect the neuro-muscular junction?
Blocks the inhibition of motor neurons
Keep firing
What is the signs of tetanus
Rigidity and spasms
How is tetanus prevented?
Immunisation
Which organisms causes botulism?
Clostridium botulinum
How does botulism act as a neurotoxin?
Binds irreversibly to the presynaptic membranes of peripheral neuromuscular and autonomic nerve junctions
Toxin binding blocks Ach release
How is there recovery from botulism?
Sprouting new axons
What is the clinical presentation of botulism?
Incubation period of 4-14 days
Descending symmetrical flaccid paralysis
Pure motor
Respiratory failure
Autonomic dysfunction (usually pupil dilation)
What is the diagnosis for botulism?
Nerve conduction studies
Culture from debrided wound
What is the treatment for botulism?
anti-toxin (A,B,E)
Penicillin
Radical wound debridement
What is CJD?
rare, degenerative, invariably fatal brain disorder.
Forms of CJD
Sporadic
New variant
Familial CJD
Acquired
Who should sporadic CJD be considered in?
Rapidly progressing dementia
What are the clinical features of sporadic CJD?
Insidious onset
Early behavioural abnormalities
Rapidly progressing dementia
Myoclonus
What signs suggest global neurological decline in CJD?
Motor abnormalities Cerebellar ataxia Extrapyramidal: tremor, rigidity, bradykinesis, dystoinia Pyramidal: weakness, spaciticity Cortical blindness Seizures may occur
What is the progression for sporadic CJD?
Rapid progression
Death often within 6 months
What is the onset age for new variant CJD?
<40
Younger onset
What are the investigations for new variant CJD?
MRI
EEG
CSF
What can be seen in MRI in new onset CJD?
Pulvinar sign
What can be seen on MRI in sporadic CJD?
Often no specific changes are seen
What is seen on CSF in new variant CJD?
normal or raised protein
What is the most common form of CJD?
Sporadic
What protein can be detected in CJD that is not specific but is very helpful in correct clinical context of CJD?
Immunoassay 14-3-3 brain protein
What is the treatment for CJD?
There is no treatment that can control or cure CJD
What is there an infiltration of in CJD?
Prions
