Infections of the Nervous System Flashcards
What is inflammation of the meninges called?
Meningitis
What is inflammatio of the brain substance called?
Encephalitis
What is inflammation of the spinal cord called?
Myelitis
Do patients normally present with inflammation of only one part of the nervous system?
No, they present with a mixture of meningitis, encephalitis and myelitis
What are the clinical features of meningitis?
- Classical triad
- Fever, neck stiffness and altered mental status
- Present with a short history of progressive headache associated with
- Fever (>38 degrees)
- And meningism (neck stiffness, photophobia, nausea and vomiting)
- Cerebral dysfunction
- Confusion, delirium, declining conscious level)
- GCS <14 in 69%
- Cranial nerve palsy (30%), seizures (30%), focal neurological deficits (10-20%)
- Petechial skin rash (look for with Tumbler test)
- Hallmark of meningococcal meningitis but can also occur in viral meningitis
What is the classical triad of clinical features for meningitis?
- Fever, neck stiffness and altered mental status
What is meningism?
Clinical syndrome of headache, neck stiffness, and photophobia, often with nausea and vomiting
What cerebral dysfunction can patients with meningitis present with?
Confusion
Delirium
Declining conscious leve
GSC < 14
What is the differential diagnosis for meningitis?
- Infective
- Bacterial, viral, fungal
- Inflammatory
- Sarcoidosis
- Drug induced
- NSAIDs
- IVIG
- Malignant
- Metastatic
- Haematological
- Such as leukaemia, lymphoma, myeloma
What are some bacterial causes of meningitis?
- Neisseria meningitidis (meningococcus)
- Streptococcus pneumoniae (pneumonococcus)
What is the most common viral cause of meningitis?
Enteroviruses
What are the clinical features of encephalitis?
- Flu like prodrome (4 to 10 days)
- Progressive headache associated with fever
- With or without meningism
- Progressive cerebral dysfunction
- Confusion
- Abnormal behaviour
- Memory disturbance
- Depressed conscious level
- Seizures
- Focal symptoms/signs
What progressive cerebral dysfunction can patients with encephalitis display?
- Confusion
- Abnormal behaviour
- Memory disturbance
- Depressed conscious level
Is the onset of viral encephalitis faster or slower than the onset of bacterial meningitis?
Slower
Is cerebral dyfunction worse with viral encephalitis or bacterial meningitis?
Viral encephalitis
What is the differential diagnosis 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 (after seizure)
What are 3 different kinds of encephalitis?
Viral encephalitis
Autoimmune encephalitis
What are 2 important antibodies associated with autoimmune encephalitis?
- Anti-VGKC (voltage gated potassium channel)
- Frequent seizures
- Amnesia (not able to retain new memories)
- Altered mental state
- Anti-NMDA receptor
- Flu like prodrome
- Prominent psychiatric features
- Altered mental state and seizures
- Progressing to a movement disorder and coma
How does the clinical presentation differ between autoimmune encephalitis associated with anti-VGKC and anti-NMDA?
- Anti-VGKC (voltage gated potassium channel)
- Frequent seizures
- Amnesia (not able to retain new memories)
- Altered mental state
- Anti-NMDA receptor
- Flu like prodrome
- Prominent psychiatric features
- Altered mental state and seizures
- Progressing to a movement disorder and coma
When dealing with someone who presents with meningitis/encephalitis like symptoms, what is the priority?
Exclude and treat infection
What investigations are done for meningitis?
- Blood cultures (bacteraemia)
- Lumbar puncture (CSF culture)
- No need for imaging if no contraindications to lumbar puncture
What investigations are done for encephalitis?
- Blood cultures
- Imaging
- CT scan with or without MRI
- Lumbar puncture
- EEG
What are indications for CT scan before lumbar puncture (contraindications to lumbar puncture)?
- Focal neurological deficit, not including cranial nerve palsies
- Suggests a focal brain mass
- New-onset seizures
- Papilloedema
- Abnormal level of consciousness, interfering with proper neurological examination (GCS < 10)
- Reduced conscious level suggests raised intracranial pressure
- Severe immunocompromised state
How does the CSF differ between bacterial meningitis and viral meningitis/encephalitis in terms of:
- opening pressure
- cell count
- glucose
- protein
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What is done to identify the bacteria responsible for bacterial meningitis?
What does HSV stand for?
Herpes simplex virus
What is required to diagnose HSV encephalitis?
- Lab diagnosis by PCR of CSF for viral DNA
What is HSV encephalitis treated with?
- Treat with aciclovir on clinical suspicion
What are the different herpes group of viruses?
VZV
EBV
CMV
What are the 2 different kinds of HSV?
Type 1
Type 2
What kind of sores are caused by HSV types 1 and 2?
- Cold sores (type 1 more than 2)
- Genital herpes (type 1 and 2)
Where does HSV remain latent after primary infection?
Virus remains latent in the trigeminal or sacral ganglion after primary infection:
- As with all herpes viruses, once infected, always infected
Does type 1 or type 2 HSV more commonly cause encephalitis as a complication?
Type 1
What are enteroviruses?
Are a large family of RNA viruses
Human infections with no animal reservoir
By what route are enteroviruses spread?
Spread by the faecal-oral route
What are examples of enteroviruses?
- Polioviruses
- Coxsackieviruses
- Echoviruses
What are some other, less common causes of encephalitis?
Arbovirus encephalitis
Brain abscess and empyema
How is arbovirus transmitted?
- Transmitted to man by vector (mosquito or tick) from non-human host
- Is arthropod borne
- Relevant to travel
- Travel history important
- Some preventable by immunisation
What is a brain abscess?
- Brain abscess is localised area of pus within the brain
What is subdural empyema?
- Subdural empyema is a thin layer of pus between the dura and arachnoid membranes over the surface of the brain
What are clinical features of brain abscess and empyema?
- Fever, headache
- Focal symptoms/signs
- Seizures dysphagia, hemiparesis
- Signs of raised intracranial pressure
- Papilloedema, false localising signs
- Depressed conscious level
- Meningism may be present, particularly with empyema
- Features of underlying source
- Such as dental, sinus or ear infection
What is the differential diagnosis for brain abscess and empyema?
- Any focal lesion, but most commonly tumour
- Subdural haematoma
What are some causes of brain abscess and empyema?
- Penetrating head injury
- Spread from adjacent infection
- Dental, sinusitis, otitis media
- Blood borne infection
- Bacterial endocarditis
Neurosurgical procedure