Infections of The Nervous System Flashcards
What is the definition of meningitis, encephalitis and myelitis?
- Meningitis = inflammation / infection of meninges
- Encephalitis = inflammation / infection of brain substance
- Myelitis = inflammation / infection of spinal cord
In reality the distinction is artificial and patients often have a
mixture
What are the clinical features of meningitis?
•Clinical Features
–“classical triad” – fever, neck stiffness and altered mental status
–Present with a short history of progressive headache associated with
- Fever (>38º) and
- Meningism (neck stiffness, photophobia, nausea and vomiting)
Neck stiffness is examined by passively bending the neck forward
–Cerebral dysfunction (confusion, delirium, declining conscious level) is common and GCS is <14 in 69%
–Cranial nerve palsy (30%), seizures (30%), focal neurological deficits (10-20%) may also occur
–Look for a petechial skin rash (Tumbler test)
•hallmark of meningococcal meningitis, but can also occur in viral meningitis
What are the differentials for meningitis?
Infective: bacterial, viral, fungal
Inflammatory: Sarcoidosis
Drug induced: NSAIDs, IVIG
Malignant: Metastatic, haemotological
What are the bacterial causes of meningitis?
Neisseria meningitidis (meningiococcus)
Streptococcus pneumoniae
What are the viral causes of meningitis?
Include enteroviruses
What are the clinical features of encephalitis?
–Flu-like prodrome (4-10days)
–Progressive Headache associated with fever
- +/- meningism
- Progressive cerebral dysfunction
–Confusion
–Abnormal behaviour
–Memory disturbance
–Depressed conscious level
- Seizures
- Focal symptoms / signs
How does viral encephalitis compare with bacterial meningitis?
Viral encephalitis is generally slower than bacterial meningitis and cerebral dysfunction is a more prominent feature
Cerebral dysfunction = Confusion, abnormal behaviour, memory disturbance, depressed conscious level
What are the differentials for encephalitis?
–Infective: Viral (most common is HSV)
–Inflammatory: Limbic encephalitis (Anti VGKC Anti NMDA receptor)
ADEM
–Metabolic: Hepatic, Uraemic, Hyperglycaemic
–Malignant: Metastatic, Paraneoplastic
–Migraine
- Post ictal - The postictal state is the altered state of consciousness after an epileptic seizure. It usually lasts between 5 and 30 minutes, but sometimes longer in the case of larger or more severe seizures, and is characterized by drowsiness, confusion, nausea, hypertension, headache or migraine, and other disorienting symptoms
What are the antibodies associated with autoimmune encephalitis?
Anti VGKC (voltage gated potassium channel)
Anti - NMDA
What are the feautres of Anti - VGKC?
Frequent seizures
Amnesia (not able to retain new memories)
Altered mental state
What are the features of NMDA receptor autoimmune encehpalitis?
Flue like prodrome
Prominent psychiatric features
Altered mental state and seizures (as seen in anti VGKC)
Progressing to a movement disorder and coma
What are the investigations for meingitis?
Blood cultures (searching for bacteraemia)
Lumbar punture (CSF culture/microscopy)
No need for imaging if there is no contraindications for LP
What are the investigations for encephalitis?
Blood cultures
Imaging (CT scan and MRI)
Lumbar puncture
EEG
What are contraindications to lumbar punture?
Indications for CT before a lumbar puncture:
- Focal neurological deficit, not including cranial nerve palsies (focal signs suggest a focal brain mass)
- New onset seizures
- Papiloedema - swelling of the optic disk caused by increase in intracranial pressure (very rarely unilateral)
- Abnormal level of consciousness, interfering with proper neurological examination (glasgow coma scale less than 10) - reduced conscious level suggests raised intracranial pressure
Severe immunocomprimised state
What are the CSF findings in meningitis for bacterial meningitis and viral meningitis and encephalitis?
