6. Viruses of the CNS Flashcards
What is the difference between meningitis and encephalitis?
Meninges vs parenchyma inflamed
Encephalitis affects normal brain function and seizures predominate
What are the viral causes of meningitis?
Enteroviruses
Mumps
Herpes: HHV6, VZV, HSV
Arboviruses
What are the viral causes of encephalitis?
Herpes viruses
West Nile virus
Japanese encephalitis
Rabies
What are the viral causes of post infectious encephalitis?
Measles
VZV
What are the viral causes of neonatal brain infections?
Rubella
CMV
Zika virus
How do viruses enter the CNS to cause meningitis?
Enteroviruses via bloodstream
Rabies and HSV along nerve pathways
Through olfactory mucosa
What are the findings in CSF in a viral meningitis?
High protein, normal glucose
High lymphocytes
PCR only
Apart from viruses, what can cause a raised lymphocyte count in CSF?
Spirochaetes, fungi, TB
Malignancy in the meninges
Connective tissue disease
Partial antibiotic treatment
What is the treatment for viral meningitis?
Mild and self limiting:
rest, hydration and anti-pyretics
Seizures management
Consider antivirals in neonates
How can viral meningitis be prevented?
MMR vaccine
Which herpes virus most commonly causes encephalitis in neonates vs adults and children?
HSV 2 in neonates
HSV 1 in adults
What part of the brain is affected in HSV encephalitis in neonates vs in adults?
Neonates: global, infection is disseminated beyond CNS
Adults: Temporal lobe, confined to CNS
What are the clinical features of HSV encephalitis?
Acute neurological syndrome: behavioural disturbance, hemiparesis, aphasia, focal seizures
How is HSV encephalitis diagnosed?
Temporal lobe changes on MRI
EEG
HSV PCR on CSF
What is the treatment for HSV encephalitis?
IV aciclovir
How is west nile virus transmitted?
Mosquito bites
Birds are also hosts: suspect a rise in cases if ‘bird falls’
What are the clinical features of west nile virus?
80% no symptoms
Some mild flu-like illness
1% develop encephalitis or meningoencephalitis
How is west nile virus diagnosed?
IgM on blood or CSF
PCR not useful as v short viraemic period
What is the management of west nile virus?
Usually self limiting
Hospital support if severe
What does the incubation period of rabies depend on?
Where the bite is eg. foot could take 12 weeks, face could take 3
What are the clinical features of rabies?
Prodrome: fever, transient pain at bite, salivation
Restlessness, irritability, aggression, seizures
How is rabies diagnosed?
History of a bite, travel
PCR on CSF or saliva
Biopsy from nape of neck for immunofluorescence
Serology only if never had vaccine or PEP
What is the treatment for rabies?
Wash would ASAP
PEP within 10 days: Ig around bite and IM, rabies vaccine
How is Japanese encephalitis acquired?
Infected mosquito
Mostly children infected or non-natives as adults acquire immunity
What are the clinical features of Japanese encephalitis?
<1% get the disease
acute encephalitis or meningitis with acute flaccid paralysis
How is japanese encephalitis diagnosed?
Clinical with a history of travel
IgM of blood and CSF
How is japanese encephalitis prevented?
Avoid exposure to mosquitos
Immunisation
What is spinal paralytic polio?
Asymmetric paralysis, usually in legs
-muscles supplied by efferent nerves from infected anterior horn cells
What is bulbar polio?
Weakness of tongue and pharyngeal muscles
What is post polio syndrome?
30-40 years after paralytic polio patient gets increased weakness and muscle pain
Due to loss of initially affected neurons
What is the treatment of paralytic polio?
Supportive
Ventilation, monitor BP etc if bulbar involvement
What diseases are caused by the Zika virus?
Congenital zika syndrome
Guillan-Barre syndrome
What is Congenital zika syndrome?
Microcephaly
Partially collapsed skull, reduced brain tissue and brain damage
What is the predominant feature of Guillan Barre syndrome?
Ascending paralysis
What is SSPE?
Persistant measles in CNS years after infection causes behavioural and intellectual deterioration and seizures
What is TSE?
Transmissable Spongiform Encephalopathy
Fatal degenerative brain disease caused by protein accumulations
What are the types of TSE?
Sporadic/familial: inherited protein, older onset, rapid
Variant: ingestion of BSE containing products
Iatrogenic
What are the clinical features of sporadic TSE?
Memory impairment, cognition and cerebellar ataxia
Late: dementia and ataxia
What are the clinical features of variant TSE?
Behavioural or psych changes
Ataxia and involuntary movements
How is TSE diagnosed?
MRI
CSF for 14-3-3 protein
Diagnosis can only be confirmed at autopsy
What is seen at autopsy in TSE?
Spongiform changes
Amyloid plaques
Prion proteins
How is TSE prevented?
Protect blood and food supply
Surgical equipment used on brain, spinal cord and posterior eye on a patient with CJD should not be reused
Low risk surgeries can be reused if autoclave used to decontaminate
