Encephalitis Flashcards
What is encephalitis?
Inflammation of the brain parenchyma associated with neurological dysfunction
How does encephalitis differ from meningitis?
Inflammation of the brain tissue vs inflammation of the meninges
In what percentage of cases of encephalitis is an aetiological agent identified?
~50%
What is the most common type of causative organism of encephalitis?
Viruses
Other than viruses, what else can cause encephalitis?
- Other organisms
- Toxins
- Autoimmune disorders
What are the two types of viral encephalitis?
- Acute viral encephalitis
- Post-infectious encephalitis
What is acute viral encephalitis?
Direct viral infection of the brain
What is post-infectious encephalitis?
An autoimmune process that occurs following infection elsewhere in the body
What is the most common viral cause of encephalitis?
HSV
What other viruses can cause encephalitis?
- CMV
- Adenovirus
- Influenza virus
- Rabies
What are the bacterial causes of encephalitis?
- TB
- Mycoplasma
- Listeria
- Lyme disease
- All causes of bacterial meningitis
What fungi can cause encephalitis?
- Histoplasmosis
- Candidiasis
What parasites can cause encephalitis?
- Toxoplasmosis
- Schistosomiasis
What are the risk factors for encephalitis?
- Age <1
- Age >65
- Immunodeficiency
- Travel to endemic locations
What is the clinical hallmark of acute encephalitis?
Triad of:
- Fever
- Headache
- Altered mental status
What do most patients with viral encephalitis initially present with?
Symptoms of meningitis
What are the symptoms of meningitis?
- Fever
- Headache
- Neck stiffness
- Vomiting
What symptoms often follow the symptoms of meningitis in cases of viral encephalitis?
- Altered consciousness
- Convulsions
- Focal neurological signs
- Signs of raised ICP
- Psychiatric symptoms
What are the signs of raised ICP?
- Severe headache
- Vertigo
- Nausea
- Convulsions
- Mental confusion
At what point should patients be diagnosed with encephalitis?
When there is altered consciousness, lethargy or personality change for >24 hours with no other explainable cause
What investigations can be used to help identify encephalitis?
- MRI brain scan
- EEG
- LP
- Urinalysis
- Bloods
Why is an MRI useful in diagnosing encephalitis?
Can determine inflammation and differentiate other possible causes
Why can EEG be used in diagnosing encephalitis?
Produces background slowing as an early sign of cerebral involvement
Why is an EEG not very useful in diagnosing encephalitis?
Not very specific
What test should be performed on LP?
PCR of CSF to detect viral DNA
What are the potential differentials for encephalitis?
- Aseptic meningitis
- Toxic/metabolic encephalopathy
- Malignant hypertension
- Intracranial tumours and cysts
- SLE
- Intracranial bleed
- Traumatic brain injury
- Ischaemic strokes
- Bacterial meningitis
What should the initial management of encephalitis consist of?
Antiviral therapy and supportive management
What antiviral should be given an immunocompetent host?
IV aciclovir 10mg/kg every 8 hours for 10-21 days
On what assumption is the administration of IV aciclovir in encephalitis made?
That the causative agent is HSV
Why is it assumed the causative agent of the encephalitis is HSV?
Most cases are
What antiviral therapy should be given to immunocompromised patients in encephalitis?
Combination therapy of ganciclovir, forscarnet and aciclovir
What supportive care may be given in encephalitis?
- Endotracheal intubation
- Mechanical ventilation
- Circulatory support
- Prevention and management of secondary bacterial infection
- DVT prophylaxis
- GI prophylaxis
What medical management should be considered for patients with raised ICP due to encephalitis?
Corticosteroids and mannitol
What surgical interventions can be considered if medical management of raised ICP in encephalitis fails?
Shunting or surgical decompression by craniotomy
When specifically may surgical intervention be required in raised ICP due to encephalitis?
Impending uncal herniation
Why do IV fluids need to be managed carefully in encephalitis?
So as not to aggravate cerebral oedema
What additional treatments can be given in encephalitis?
Anti-convulsants and sedatives if needed
What should be given instead of anti-virals if the cause of encephalitis is bacterial?
Antibiotics
What should be given if the cause of encephalitis is post-infectious?
Immune modulators
What are the potential complications of encephalitis?
- Inappropriate ADH secretion
- DIC
- Cardiac and respiratory arrest
- Epilepsy
- Neuropsychiatric impairment
- Physical problems
What neuropsychiatric impairment might occur as a result of encephalitis?
- Changes in personality
- Cognitive, behavioural or emotional impairment
- Severe amnestic syndrome
What physical problems may occur as a result of encephalitis?
- Balance, coordination and dexterity problems
- Speech and swallowing problems
- Total dependency
