viral infections Flashcards
Difference between meningitis and encephalitis
Meningitis is the inflam of meninges
Encephalitis is the inflam of brain parenchyma
Present differently
Meningitis presentation :
fever, vomiting, headache, photophobia, neck stiffness, rash , irritability, confusion/reduced consciousness(partially awake and aware) , seizures
Encephalitis presentation (Affects functioning of brain)
- motor or sensory deficits
- behavior/personality changes
- altered mental state
- speech or movement disorders
- seizures
Viral causes of meningitis and encephalitis
Meningitis (self limiting causing viruses)
Mumps
Enteroviruses eg cox sackie B, echovirus– most common
Herpes simplex
Encephalitis Japanese encephalitis Rabies Enteroviruses Herpes Simplex WNV Varicella Zoster
Paralysis
enteroviruses esp polio , JE, Zika, WNV - flaccid paralysis (lower motor neurone with or w/o meninigitis)
Post infectious encephalitis
VZV, measles - present w acute illness and neuro symptoms
What are the characteristics of viral CNS infections ?
- Can be part of a generalised infection (e.g.
polio) - May solely affect the CNS
- May present some time after the initial
presenting infection (e.g. measles - SSPE)
Explain route of infection of virus
Multiplies in primary site then spreads to CNS via
1) blood - most common
2) nerves- HSV, rabies
3) olfactory mucosa
Causes damage to CNS via
multiplication and resulting damage and or host immune response (Cellular immune mediated and cytokine)
How does viral meningitis present?
• Classic symptoms – Fever – Headache – Neck stiffness – Vomiting – Photophobia • Not usually as sick as patients with bacterial meningitis • Symptoms usually evolve more slowly than bacterial meningitis (several days) • But may be indistinguishable from bacterial meningitis
Diagnosis of viral meningitis
CSF findings : • CSF typically clear and colourless
• CSF white cell count elevated (lymphocytes) and
protein elevated but glucose normal
• Sometimes called “aseptic” meningitis
• PCR: Enterovirus RNA/ HSV DNA/ VZV DNA
Differential diagnosis: A similar CSF picture is seen in
a number of other conditions e.g.
– Other infection: Leptospirosis, Syphilis, Lyme,
Cryptococcosis, Toxoplasmosis, occasionally TB
– Malignant infiltration of the meninges
– Connective tissue diseases
Treatment and prevention of viral meningitis
VIRAL MENINGITIS: TREATMENT
• Excluding the neonatal period, usually mild, selflimiting
• Supportive: Rest, hydration, anti-pyretics
• Seizure management
• Unclear whether aciclovir is of benefit in HSV
meningitis (N.B. differentiate from HSV encephalitis,
which must be treated with aciclovir)
VIRAL MENINGITIS: PREVENTION
• Mumps meningitis is preventable by vaccination
(MMR)
Causes of Viral encephalitis
HSV, rabies, JE and West Nile
Herpes simplex; HSV 1>2 in adults and >3months ; most common cause in NE countries
For adults: HSV1
- usually confined to CNS
- primary infection/reactivation
- temporal lobe mainly affected
- mortality at 70% w/o treatment
For neonates- HSV2
- usually involves dissemination
- acquire infection at birth
- global brain involvement ; brain is almost liquefied
- mortality 100% if untreated
Route of infection for HSV
The virus spreads from sites of primary infection,
or from latent infection in cranial nerve trigeminal ganglia or olfactory nerve, to
the frontal or temporal lobes of the brain
causes haemorragic necrosis and inflam infiltrates
Which is more benign and self limiting -viral encephalitis / meningitis?
viral meningitis
Clinical features of HSV encephalitis
Acute neurological syndrome
- hemiparesis
- aphasia
- behavioral changes
- focal seizures
Diagnosis of HSV encephalitis
MRI- temporal lobe change
EEG
CSF - HSV PCR
Tx of HSV encephalitis
If suspected- treat w IV aciclovir (even in neonatal encepha)
Characteristics of West Nile Virus
• Belongs to a group of viruses known as 'arboviruses’ (= “arthropod-borne” viruses; viruses transmitted by insects, ticks etc.) • Birds = usual host • Transmitted by the bite of an infected mosquito • Can infect humans, birds, horses and some other mammals • Temperate countries (e.g., Northern North America) – Late summer or early autumn • Tropical climates (temperatures are higher and mosquitoes active throughout the year) – Can be transmitted year-round
How does WNV present?
• No Symptoms: (80%)
• Mild Symptoms: mild influenza-like illness, with
fever, headache and generalised aches and pains –
usually make full recovery
• Severe Symptoms: (less than 1%)
– Encephalitis
– Meningoencephalitis
Risk increases with age + immunosuppression
