Encephalitis Flashcards
Define encephalitis
Infection and inflammation of the brain parenchyma. Broad term with various causative agents.
What is the epidemiology and risk factors for encephalitis?
- Around 2500 cases in England per year
- Extremes of age - particularly HSV-1 which is usually more severe
- Immunocompromisation
What causes encephalitis the most?
Viruses
Which virus causes encephalitis in 95% of cases?
HSV-1
What are other viruses that cause encephalitis?
VZV, EBV, CMV, HIV, measles, mumps, arboviruses (West Nile)
What is a non-viral cause of encephalitis?
Toxoplasmosis (close contact with cats, parasitic infection)
Describe the pathophysiology of encephalitis
- An intracranial infection provokes an inflammatory response causing inflammation of the cortex, white matter, basal ganglia and brain stem depending on the causative organism
- This results in neurological signs and systemic signs of infection
- The frontal and temporal lobes are mostly affected
What are the symptoms of encephalitis?
Classic triad of:
- Fever
- Headache
- Encephalopathy/altered mental status/focal neurological signs (Insidious onset, can also be abrupt)
Describe other symptoms that may be present
- Features of a viral infection to begin with - fever, malaise, nausea, headaches
- Behavioural change - common early sign
- Decreased consciousness, confusion
- Focal neuro signs - cranial nerve palsies, hemiparesis, cerebellar ataxia, dysphagia, dysarthria
- Seizures
- Signs of raised ICP may lead to coma
What is a sign that shows the temporal lobe is affected?
Aphasia
What might it suggest if the symptoms are like in meningism?
Meningo-encephalitis
What are some differential diagnosis for encephalitis?
Anything that causes behavioural change
eg.
- DKA
- Hypoglycaemia
- Stroke
etc
What do you do for investigations for encephalitis?
- MRI head
- Lumbar puncture
- EEG (electroencephalogram)
What is seen on MRI for encephalitis?
- Shows swelling and inflammation (HSV typically affects temporal lobes), may show signs of raised ICP
- Unilateral usually temporal encephalitis
What is seen on EEG for encephalitis?
- May indicate encephalitis (periodic sharp followed by slow waves)
- Non specific firing of 2H2 periodically
What is seen on lumbar puncture for encephalitis?
- Shows elevated lymphocytes
- normal glucose
- typically a raised protein
What is the treatment of encephalitis?
- Suspected encephalitis - empirically start IV Acyclovir until results
- HSV or VZV - Immediate IV Acyclovir (Ganciclovir can be used in VZV)
What is the treatment of encephalitis in immunocompromised patients?
use combination antiviral therapy
What would you use to treat seizures in encephalitis?
anticonvulsants e.g., Primidone
