Infections of the Nervous System Flashcards
How does meningitis tend to present clinically?
- Short history of progressive headache
- Fever (>38 degrees)
- Neck stiffness
- Altered mental status
- Photophobia / nausea / vomiting
- GCS < 14 in 69%, cranial nerve palsy, seizures and focal neurological deficits may present
- Petechial skin rash (Tumbler test)
What does a petechial skin rash associated with meningitis symptoms indicate?
- Hallmark of meningococcal meningitis
Can also occur in viral meningitis
Differential diagnosis for meningitis?
- Infective: Bacterial, viral, fungal
- Inflammatory: Sarcoidosis
- Drug induced: NSAIDS / IV Immunoglobulin
- Malignant: Metastatic / Haematological
Bacterial causes of meningitis? Viral?
Bacterial:
- Neisseria meningitidis (meningococcus)
- Streptococcus pneumoniae (pneumococcus)
- Myobacterium Tuberculosis
Viral: enteroviruses
How does encephalitis tend to present clinically?
- Flu-like prodrome (4-10 days)
- Progressive headache
- Fever
- Cerebral dysfunction (confusion, abnormal behaviour, memory disturbance, depressed conscious level)
- Seizures
- Stiff neck / photophobia / nausea / vomiting
Differences in how encephalitis and meningitis tend to present?
- Onset of viral encephalitis slower than bacterial meningitis
- Cerebral dysfunction more prominent in encephalitis
Causes of encephalitis?
- Infective: viral, most common is HSV
- Autoimmune
- Inflammatory: Limbic encephalitis, ADEM
- Metabolic: Hepatic, uraemic, hyperglycaemic
- Malignancy
- Migraine
What are the two important antibodies for autoimmune encephalitis?
- Anti-VGKC (voltage gated potassium channel)
- Anti-NMDA receptor
How do the types of autoimmune encephalitis tend to present?
Anti-VGKC:
- Frequent seizures, amnesia, altered mental state
Anti-NMDA:
- Flu prodrome, psychiatric features, altered mental state and seizures, progresses to movement disorder and coma
Investigations for meningitis?
- Blood cultures
- Lumbar puncture (CSF culture / microscopy)
No need for imaging if no contraindications to LP
Investigations for Encephalitis?
- Blood cultures
- Imaging (CT +/- MRI)
- Lumbar puncture
- EEG
What are the contraindications to Lumbar Puncture? (indications for CT brain before LP)
- Focal neurological deficits (suggest focal brain mass)
- Abnormal consciousness level (suggests raised ICP)
- New onset seizures
- Papilloedema
What CSF findings after lumbar puncture help differentiate between bacterial meningitis and viral meningitis + encephalitis?
- Cell count high in both, mainly neutrophils in bac meningitis, mainly lymphocytes in viral men. + encephalitis
- Glucose reduced in bacterial men., normal in viral men. + encephalitis
- Protein high in bacterial meningitis, only slightly increased in viral men. + encephalitis
How is herpes simplex (HSV) encephalitis diagnosed? How is it treated?
- Diagnosed via PCR of CSF for viral DNA
- Treat with aciclovir if clinical suspicion
over 70% mortality if untreated
What are some signs of HSV infection?
- Cold sores
- Genital herpes
Once infected virus remains latent in trigeminal or sacral gnaglion, encephalitis is a rare complication of HSV
What does infection with enteroviruses tend to cause? How do they spread?
- Tend to cause CNS infections (non-paralytic meningitis), DO NOT cause gastroenteritis
- Spread faecal-oral route
- Include polioviruses, coxsackieviruses, echoviruses
What is an arbovirus and what does infection with them tend to cause?
- Athropod borne virus (mosquito / ticks)
- Cause encephalitis, travel history important
- Examples: West Nile virus, St Louis Encephalitis, Tick Borne encephalitis (place names are where first described not based on geographical distribution)
What is a brain abscess? What is a subdural empyema?
- Brain abscess: localized area of pus within the brain
- Subdural empyema: thin layer of pus between dura and arachnoid membranes
What is meningism?
- Neck stiffness
- Photophobia
- Nausea
- Vomiting
Clinical features of brain abscesses and empyema?
- Fever
- Headache
- Signs of raised ICP (papilloedema, depressed conscious level)
- +/- Meningism
- Underlying infection features (sinus / ear / dental)
What causes brain abscesses and empyema?
- Penetrating head injuries
- Spread from adjacent infection (dental/sinus/ear)
- Blood borne infection (bacterial endocarditis)
- Neurosurgical procedures
Investigations for suspected brain abscess / empyema?
- Imaging (CT or MRI)
- Blood cultures
- Biopsy (drainage of pus)
- Investigate source (associated infection)
Management of brain abscesses?
- Surgical drainage if possible
Antibiotics, culture can provide useful guide:
- Penicillin / Ceftriaxone to cover strep. bacteria
- Metronidazole for anaerobe bacteria
Who is at increased risk of CNS infection?
- Immunocompromised individuals
- HIV infections / AIDS patients
- Individuals taking immunosuppressants
