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 (japanese encephalitis)
- 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
- Taoxoplasmosis gondii (AIDS)
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?
- (Infectious prodome - fever, rash, lymphadenopathy, cold osres, conjunctivitis, meningeal signs)
- Bizarre encephalopathic behaviour or confusion
- Decreased GCS/Coma
- Fever
- Headache
- Focal neurological signs
- Seizures
- Meningitsm - fever, headache, drowsiness
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
How can rabies present?
Features of encephalitis, hydrophobia (water provoked muscle spasms), delusions, hallucinations and anxiety
Acending paralysis of the limbs
Parasthesia at site of lesion
Rabies pre-exposure prevntion
+
Rabies post-exposure treatment
Active immunisation
Wash wound, active rabies immunisation, human rabies immunoglobulin (passive immunisation)
What investigations would you consider doing in someone with features of encephalitis?
-
Bloods
- FBC - reduced WBC (immunopcompromsised)
- U+Es
- Clotting screen
- Septic screen + Blood cultures
- Blood cultures, Viral PCR, Malaria film, Toxoplasma IgM titre, HIV test, Mantoux test
- CXR - TB?
-
Contrast enhanced CT brain
- Focal bilateral temporal lobe involvement is suggesive of HSV encephalitis (areas of oedema)
-
LP
- Obvs CT first
- Send CSF for PCR for HSV (PCR is 95% specific for HSV1)
-
EEG
- Non specific slow wave activity
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
How would you manage someone with encephalitis?
- Start aciclovir within 30 mins arrival
-
Supportive therapy in HDU
- Oxygen, IV fluids, steroids, phenytoin (for seizures)
- Anticonvulsants for seizures
- Dexamethaose - if raised ICP
What is mortality rate in untreated encephalitis?
70%
What is the mortality rate in treated encephalitis?
10-30%
Whats the difference between a brain abscess and brain empyema?
Abscess - localised area of pus in brain
Brain empyema - thin layer of pus between dura and arachnoid membrains
What are causes of a cerebral abscess?
Direct spread =75%
Haematogenous spread =25%
- Ear/Sinus/dental/peridontal infection
- Skull fracture
- Congenital heart disease
- Endocarditis (blood borne)
- Bronchiectasis
What are the typical causative bacteria implicated in brain abscesses?
- Strep anginosss (sinus/teeth)
- Bacteriodes (sinus/teeth)
- Staphylococci (penetrating trauma)
What are symptoms of a brain abscess?
- Headache - worse on bending over/lying down
- Fever
- Generally unwell
- Seizures
- Signs of raised ICP
- Features of underlying source - dental, sinus, infection
What are signs seen in someone with a cerebral abscess?
- Decreased GCS/Coma
- Signs of sepsis elsewhere
- Fever
- Focal neruology
- Signs of increased ICP
- Meningism may be present
What investigations might you consider doing in someone with a cerebral abscess?
- CT/MRI
LP NOT PERFORMED DUE TO DANGER OF CONING - Bloods - FBC, ESR
- Biopsy (aspiration)