What starts with ‘E’, ends in ‘S’, and makes you lose your mind?
Exams. Coming soon 😥
Well, encephalitis too.
Definition: inflammation of the brain parenchyma
-Cause is usually viral and often never identified
-May have history of travel or animal bite
Viral: HSV-1 & 2 (most common in UK), CMV (immunocompromised), EBV, VZV, HIV, measles, mumps, rabies (Asia), tick-borne encephalitis, adenovirus, coxsackie, echovirus, enteroviruses, arboviruses transmitted by mosquitoes e.g. Japanese B encephalitis, St. Louis Encephalitis and West Nile Virus (USA)
Non-viral: any bacterial meningitis, syphilis, S.aureus, TB, malaria, listeria(immunocompromised), Lyme disease, legionella, leptospirosis, aspergillosis, Cryptococcus, schistosomiasis, typhus, toxoplasmosis (immunocompromised).
-Autoimmune or paraneoplastic
Epidemiology: annual UK incidence = 7.4 in 100,000
Symptoms: in many cases encephalitis is a mild self-limiting disease with a sub-acute onset (hours to days)
-acute, severe headache, felt over most of head
-neck stiffness, photophobia (meningism)
-rash, lymphadenopathy, cold sores, conjunctivitis
-Meningism: neck stiffness, Kernig’s sign (pain and resistance on passive knee extension with hip fully flexed)
After infectious prodrome:
-odd behaviour, confusion
-drowsiness/decreased consciousness (↓GCS)
-focal neurological signs e.g. hemiplegia, dysphasia
Signs of raised intracranial pressure: hypertension, bradycardia, papilloedema (on fundoscopy)
Consider encephalopathy if there is no infectious prodrome (e.g. hypoglycaemia, hepatic encephalopathy, DKA, drugs, hypoxic brain damage, uraemia, SLE, beri-beri)
–Bloods: FBC (↑lymphocytes), U&Es (SIADH may occur), blood cultures, ABG, viral serology-serum for viral PCR, toxoplasma IgM titre, malaria film
–Throat swab, MSU (mid-stream urine)
-Urgent CT head (MRI if allergic to contrast)
-Exclude mass lesion
-Focal bilateral temporal lobe involvement (oedema on MRI) suggests HSV encephalitis
MRI- Herpes Simplex Encephalitis
-Meningeal enhancement suggests meningoencephalitis
-Lumbar puncture- if no raised intracranial pressure (risk of brain herniation with LP). Look for signs of infection in the cerebrospinal fluid (CSF). Send CSF for viral PCR, including HSV.
= Moderately elevated CSF protein and lymphocytes, and decreased glucose
–Electroencephalogram (EEG)- urgent EEG showing diffuse abnormalities may help confirm encephalitis but does not indicate cause. May show epileptiform activity e.g. spiking activity in temporal lobes.
-Often wise to treat before exact cause known
–ACICLOVIR within 30 minutes (10mg/kg/8h IV over 1h), adjusting dose to eGFR (estimated glomerular filtration rate)
-Specific therapies for CMV and toxoplasmosis
-Toxoplasmosis: Pyrimethamine + sulfadiazine
-CMV: Ganciclovir IV or oral valganciclovir, foscarnet, cidofovir
-Supportive therapy, in HDU or ICU, if needed
-Mechanical ventilation if respiratory failure, monitor vital signs closely
-Manage fluid balance, resuscitate if needed, risk of cerebral oedema (consider dexamethasone)
-Symptomatic treatment e.g. PHENYTOIN for seizures, antipyretics, antiemetics, analgesia for headache
-post-encephalitic neurological sequalae, particularly epilepsy and cognitive impairment in 10-30% with variation according to viral aetiology.
-Mortality in untreated encephalitis is approx. 70%.
-Treated mortality is 20%.
-Survivors may have epilepsy or cognitive impairment. (More risk if > 30 years old, GCS < 6 on initiation of treatment).
References: Cheese & Onion, Rapid Medicine