Infection of the nervous system Flashcards
What is encephalitis?
Encephalitis means acute inflammation of brain parenchyma, usually viral
What is the most common cause of encephalitis?
Viral
What are viral causes of encephalitis?
- HSV 1 + 2
- Arbovirus
- CMV
- EBV
- VZV
- HIV
- Measles
- Mumps
- Rabies
- West nile virus
- Tick-borne encephalitis
What are non-viral causes of encephalitis?
- Any bacterial meningitis
- TB
- Malaria
- Listeria
- Lyme disease
- Legionella
- Leptospirosis
- Aspergillosis
- Crytococcus
- Schistosomiasis
- Typhus
What would be your differential diagnosis for someone with features of encephalitis?
If no infectious prodrome, think encephalopathy
- Hypoglycaemia
- Hepatic encephalopathy
- Diabetic ketoacidosis
- Drugs
- Hypoxic brain injury
- Uraemia
- SLE
- Wernicke’s encephalopathy
What are autoimmune causes of encephalitis?
Limbic encephalites
- Paraneoplastic limbic encephalitis
- Voltage gated potassium channel limbic encephalitis
- Anti-NMDA receptor antiobody panencephalitis
What are signs and symptoms of encephalitis?
- Bizarre encephalopathic behaviour or confusion
- Decreased GCS/Coma
- Fever
- Headache
- Focal neurological signs
- Seizures
When should you suspect encephalitis?
Whenever someone presents with odd behaviour, decreased consciousness focal neurology or seizure which was preceded by an infectious prodrome
What kind of infectious prodromes would you want to find out about in someone presenting with features of encephalitis?
- Pyrexia
- Rash
- Lymphadenopathy
- Cold sores
- Conjunctivitis
- Meningeal signs
What might cold sore indicate about the cause of a presentation of encephalitis?
Caused by Herpes Simplex virus
What might parotid gland swelling indicate as to the cause of encephalitis?
Caused by mumps
What might be the cause of someone presenting with features of encephalitis, hydrophobia, delusions, hallucinations and anxiety?
Rabies
What investigations would you consider doing in someone with features of encephalitis?
- Bloods - Blood cultures, Viral PCR, Malaria film, Toxoplasma IgM titre, HIV test, Mantoux test
- Contrast enhanced CT
- LP
- EEG
In someone with features of encephalitis, what would focal bilateral temproal lobe involvement on Contrast-enhanced CT indicate ?
HSV encephalitis
What would meningeal enhancement on contrast-enhanced CT suggest in someone with features of encephalitis?
Meningeal involvemnent
What should you do before doing an LP?
CT scan to rule out coning
What are features seen on LP in someone with encephalitis?
- Increased CSF protein
- Increased lymphocytes
- Decreased glucose
What is important to remember when interpreting LP CSF results for someone with suspected encephalitis?
Normal CSF does not exclude ecnephalitis