Encephalitis (N) Flashcards
Define encephalitis.
Inflammation of the brain parenchyma associated with neurological dysfunction, such as altered state of consciousness, seizures, personality changes, cranial nerve palsies, speech problems, and motor and sensory deficits
What are the causes of encephalitis? (4)
- most commonly viral infection (HSV-1 most common)
- non-viral infections: bacterial, fungal, parasitic (syphilis, S. aureus)
- also in immunocompromised patients (CMV, toxoplasmosis, Listeria)
- also in those with autoimmune/paraneoplastic syndromes (associated with certain antibodies: anti-NMDA, anti-VGKC)
What is the most common cause of viral encephalitis?
HSV-1
What are some other causes of viral encephalitis? (8)
- HSV-1
- VZV
- mumps
- adenovirus
- Coxsackie
- EBV
- HIV
- Japanese encephalitis
What demographics is encephalitis most common in?
Bimodal distribution:
- age <1y
- age >65y
Describe the onset and severity of encephalitis.
- subacute onset (hours to days)
- self-limiting and mild (in most cases)
What are the clinical features of encephalitis? (8)
- initial flu-like symptoms with pyrexia and headache that persist
- altered mental state
- fever + malaise
- rash
- headache
- focal neurological deficits - depending on which area of brain is inflamed
- seizures
- meningismus - headache, photophobia, neck stiffness
What are some focal neurological deficits you might see in encephalitis? (4)
- changes in personality or behaviour
- difficulty speaking, dysphagia
- weakness or loss of movement / hemiplegia
- loss of consciousness
What are some signs of meningism you might find in encephalitis? (3)
- headache
- photophobia
- neck stiffness
What might you see on examination in encephalitis? (9)
- altered mental state + reduced consciousness
- bizarre encephalopathic behaviour
- deteriorating GCS
- acute flaccid paralysis
- seizures
- pyrexia
- meningism - headache, photophobia, neck stiffness, Kernig’s test +ve
- signs of raised ICP (Cushing’s triad, papilloedema)
- focal neurological signs
What might MMSE reveal in encephalitis?
Cognitive/psychiatric disturbance
What issue may arise secondary to encephalitis, and what are the features of this?
Raised ICP:
- Cushing’s triad:
- widened pulse pressure (hypertension)
- bradycardia
- irregular breathing
- papilloedema
What key clinical features distinguish encephalitis from meningitis? (2)
- altered mental state (and personality change)
- seizures
What do we need to remember to ask about in encephalitis?
Travel history
What are some risk factors for encephalitis? (9)
- age <1 or >65
- immunosuppression
- post-infection / viral infection
- bodily fluid exposure
- organ transplantation
- animal/insect bites
- travel
- season
- nasal/sinus irrigation
What are the first-line investigations for encephalitis? (5)
- lumbar puncture for CSF analysis
- FBC
- peripheral blood smear - detection of Plasmodium falciparum and Ehrlichia
- serum electrolytes - SIADH (hyponatraemia)
- LFTs - elevated
What does FBC show in encephalitis? (3)
- high lymphocytes - viral
- neutrophilia - bacterial
- eosinophilia - parasitic
What is the main investigation that we do in encephalitis and what would it show?
CSF analysis via lumbar puncture:
- high lymphocytes
- high protein
- normal glucose
What cell types would predominate in viral vs bacterial encephalitis in CSF analysis?
- virus - lymphocytes
- bacteria - neutrophils
What do we need to do before lumbar puncture in encephalitis?
Do CT before to exclude significantly raised ICP
What investigation will confirm the presence of HSV in encephalitis?
CSF - viral PCR (95% specific for HSV-1)
What other investigations are there for encephalitis? (4)
- bloods - hyponatraemia, raised WCC, elevated LFTs
- blood culture - to detect bacterial infections
- throat swab - to detect viruses
- MRI/CT brain - exclude any mass lesions
What might MRI/CT head show in encephalitis? (2)
- MRI will show swelling and increased brains signals
- CT head may also show temporal lobe changes of HSV
What might EEG show in encephalitis?
Often shows background slowing
