Encephalitis Flashcards
define encephalitis?
Encephalitis is defined as inflammation of the brain parenchyma
what are the differences between meningitis and encephalitis?
outline the aetiology of encephaltis?
causative agents identified in 50% of cases
most commonly due to VIRAL INFECTION
what is the most common viral cause of encephalitis?
HERPES SIMPLEX VIRUS- most common in UK-> usually affects temporal lobes
what is the most common cause of encephalitis in immunocompromised patients?
Toxoplasmosis – causes ring-enhancing lesions on MRI – common in HIV pts
what are the different causes of encephalitis?
Viral Causes
- Herpes Simplex Virus - MOST COMMON in the UK - usually affected temporal lobes
- VZV
- Mumps
- Adenovirus
- Coxsackie
- EBV
- HIV
- Japanese encephalitis
Non-Viral (RARE)
- Neisseria meningitides (main cause of meningoencephalitis)
- Syphilis
- TB
- Mycoplasma
- Typhoid fever
- Brucellosis
- Leptospirosis
- Group C beta-haemolytic streptococci
In immunocompromised patients
- CMV
- Toxoplasmosis – causes ring-enhancing lesions on MRI – common in HIV pts
- Listeria
- West Nile Virus
Autoimmune or Paraneoplastic
- Associated with certain antibodies (e.g. anti-NMDA, anti-VGKC, anti-GABA-R
what are the risk factors for encephalitis?
Less than 1yr or 65yrs+
Immunodeficiency
Viral infections
Immunocompromised (e.g. organ transplantation)
Bites (animals + insects)
summarise the epidemiology of encephalitis?
UK incidence: 7.4/100,000
what are the presenting symptoms of encephalitis?
In most cases, encephalitis is self-limiting and mild
Subacute onset (hours to days)
Headache
Fever
Rash depending on causative agent
Vomiting
Behavioural changes - odd behaviour (apathy, akinetic mutism, psychotic behavior, personality changes + hallucinations) and confusion
History of seizures
Cough and GI infection may also be seen depeding on causative agent
Focal neurological symptoms (e.g. dysphagia, hemiplegia, babinski sign, cranial N deficits, ataxia)
Usually preceded by an infectious prodrome – fever, rash, lymphadenopathy, cold sores, conjunctivitis – before neurological signs
Obtain a detailed TRAVEL HISTORY
what are the signs of encephalitis on physical examination?
Reduce consciousness
Bizarre encephalopathic behaviour
Deteriorating GCS
Seizures
Pyrexia
Signs of Meningism:
- Neck stiffness
- Photophobia
- Kernig’s test positive
Signs of raised ICP:
- Cushing’s Response: hypertension + bradycardia + irregular breathing
- Papilloedema
Focal neurological signs
MMSE may reveal cognitive/psychiatric disturbance
what are the appropriate investigations for encephalitis?
bloods
Throat swab
Nasopharyngeal aspirate
Sputum culture
CT/MRI
EEG
what bloods do you need to as an investigation for encephalitis?
FBC - high lymphocytes (indicates viral cause)
Peripheral blood smear (preferably @ time of fever spike – imp for malaria)
Blood cultures
U&Es – SIADH (hyponatraemia) may occur as a result of encephalitis
LFTs – may be elevated with Coxiella burnetii, Rickettsia, tick-borne disease, CMV, EBV.
Viral serology
Toxoplasma IgM titre
Malaria film
what is the chest x ray needed for in encephalitis?
detect cause
May detect Mycoplasma,Legionella, influenza, parainfluenza, tuberculosis, Coccidioides, Histoplasma, blastomycosis, Coxiella burnetii, or sarcoidosis.
may detect a non-infectious or infectious cause (e.g., tuberculosis, sarcoidosis)
what can be seen on the MRI, CT, EEG in encephalitis?
CT Brain – norm @ start but may show hypodensities later on
MRI - depends on aetiology; often hyperintense lesions, and increased diffusions indicating oedema
EEG – often shows background slowing but non-specific
Meningeal enhancement suggests meningoencephalitis
- High lymphocytes
- High monocytes
- High protein
- Glucose is usually normal or low
- CSF PCR – 95% specific for HSV-1
- CSF culture
- CSF serology
