Infections of the Nervous System Flashcards
What is meningitis?
Inflammation/infection of the meninges
What is encephalitis?
Inflammation/infection of the brain tissue
What is myelitis?
Inflammation/infection of the spinal cord
What is the classical triad of symptoms in meningitis?
Fever
Neck stiffness
Altered mental status
What rash should be looked for in suspected meningitis?
Petechial skin rash (tumbler test)
Hallmark test for meningococcal meningitis but can also occur in viral form
How is neck stiffness in meningitis tested?
Passively bending the neck forward
What is an inflammatory Ddx for meningitis?
Sarcoidosis
What are some malignant DDx for meningitis?
Metastatic malignancy
Haematological malignancy
What are some drug caused DDx for meningitis?
NSAID use
IVIG use
What are the two main causative bacterial agents of meningitis?
Neisseria meningitides (meningococcus) Streptococcus pneumonia (pneumococcus)
What are a key group of viral agents that can cause viral meningitis?
Enteroviruses
What are the clinical features of encephalitis?
Flu-like symptoms for 4-10 days Progressive headache associated with fever Meningism may or may not be present Cerebral dysfunction Seizures
Is the onset of viral meningitis slower or faster than that of bacterial meningitis?
Generally slower
Give some inflammatory DDx for encephalitis
Limbic encephalitis - anti VGCK/ anti NMDA receptor
What is the most common cause of encephalitis?
Viral - HSV most common
What should be considered if a patient has several seizures with little or no recovery period afterwards?
Viral encephalitis
What are the two forms of auto-immune encephalitis?
Anti-VGKC (voltage gated potassium channel)
Anti-NMDA receptor - more common
What are the features of auto-immune encephalitis causes by anti-VGKC type?
Frequent seizures
Amnesia (unable to retain new memories)
Altered mental state
What are the features of auto-immune encephalitis caused by the anti-NMDA receptor type?
Flu-like prodrome
Prominent psychiatric features
Altered mental state and seizures
Progressing to movement disorder and coma
What are the priorities when investigating and treating suspected meningitis and encephalitis?
Priority is to exclude infection and treat
What are the Ix for meningitis?
Blood cultures
LP (CSF culture/microscopy
No need for imaging if no contraindications to LP
What are the Ix for encephalitis?
Blood cultures
Imaging - CT +/- MRI
LP
EEG
What are the contraindications to LP?
Focal neurological deficit, not including cranial nerve palsies
New-onset seizures
Papilloedema
Abnormal level of consciousness, interfering with proper neurological exam (GCS)
Sever immunocompromised state
What does observing the contraindications to LP aim to prevent?
If there is raised ICP, one of the compensatory mechanisms is the shunt CSF from the brain into the spinal cord. This creates a high pressure in the cord of fluid that it essentially exerting an upwards force on the brain. In this situation if an LP is done, the pressure in the cord will decrease, allowing the brain to move towards the are a of lower pressure at which point herniation, coning and resultant death are likely to follow
Describe the opening CSF pressure in bacterial meningitis
Increased
Describe the opening CSF pressure in viral meningitis and encephalitis
Normal, may be increased
Describe the CSF white cell count in bacterial meningitis
High, mainly neutrophils
Describe the CSF white cell count in viral meningitis and encephalitis
High, mainly lymphocytes
Describe the CSF glucose content in bacterial meningitis
Reduced
Describe the CSF glucose content in viral meningitis and encephalitis
Normal (60% of blood glucose level)
Describe the CSF protein content in bacterial meningitis
High
Describe the CSF protein content in viral meningitis and encephalitis
Slightly increased
What is a cardinal sign of bacterial meningitis upon visualisation of the CSF
CSF is cloudy
What is the normal white cell count in CSF?
0-5
What are the two causative agents of bacterial meningitis and which is sensitive to penicillin?
Streptococcus pneumoniae - sensitive to penicillin
Nisseria meningitides
What is the commonest cause of encephalitis i Europe?
HSV
What is the test for HSV in encephalitis?
PCR of CSF for viral DNA
What is the treatment for HSV induced encephalitis UPON CLINICAL SUSPICION?
Treat with aclovir
What is the mortality for encephalitis caused by HSV if untreated?
70%
Where does the HSV remain after primary infection?
Trigeminal or sacral ganglion
What form of HSV causes encephalitis in all but neonates?
Type 1
Describe the enterovirus cause of encephalitis
Enteroviruses are a large family of RNA viruses
They tend to cause CNS infections
Spread by the faecal-oral route
Many can cause non-paralytic meningitis
They DO NOT cause gastroenteritis
Include polioviruses, coxsackiviruses and echoviruses
What is a brain abscess?
Localised area of pus within the brain
What is a subdural empyema?
A thin layer of pus between the dura and arachnoid membranes over the surface of the brain
What are the clinical features of brain abscess and empyema?
Fever Headache Focal symptoms and signs Signs of raised ICP Meningism may be present Features of underlying source e.g. dental, sinus or ear infection
Give some causes of brain abscess and empyema
Penetrating head injury
Spread form adjacent infection
Blood borne infection e.g. bacterial endocarditis
Neurosurgical procedure
What is required for a diagnosis of brain abscess and or empyema?
CT/MRI
Investigate source
Blood cultures
Biopsy (drainage of pus)
What bacterial organism is present in 70% of brain abscess cases, and what what group own particular? What is clinically significant about this group?
Streptococci, ‘strep millenni’ group
They are sensitive to penicillin
Outline the management for brain abscess
Surgical drainage
Penicillin or ceftriaxone to cover streps
Metronidazole for anaerobes
High doses required for penetration
High mortality without appropriate treatment
Give eight brain illnesses that may indicate HIV
Cerebral toxoplasmosis Aseptic meningitis/encephalitis Primary cerebral lymphoma Cerebral abscess Cryptococcal meningitis Space occupying lesion of unknown cause Dementia Leucoencephalopathy
