Week 2 CNS Flashcards
What are the common CNS infections?
- Bacterial meningitis
- Cryptococcus neoformans meningitis
- TB meningitis
- Viral meningitis
- Viral encephalitis
- Brain abscess
What are the 3 layers of the meninges and where is CSF found in them?
- Dura mater (most superficial)
- Arachnoid mater
- Pia mater (deepest)
- CSF flows between pia and arachnoid mater (in subarachnoid space)
How is the blood brain barrier formed?
- Endothelial cells forming the capillaries in the brain and spinal cord have tight junctions between them
- The tight junctions lead to limited permeability of the capillaries -> BBB
What are the pros and cons of the BBB?
Pro:
- Protects CNS from pathogens and toxic substances
Cons:
- Prevents entry of immunoglobulins, complement and antibiotics
- Some antibiotics may require 2x of the dosage to penetrate the BBB
- Once a pathogen penetrates the BBB, initial host defense mechanism is ineffective
Causes of bacterial meningitis? (IMPT)
Causes:
- Neisseria meningitidis
- Streptococcus pneumoniae
- Haemophilus influenzae
- Group B Strep (neonates)
- Escherichia coli (neonates)
- Listeria monocytogenes (neonates, pregnant women and immunocompromised)
S/s of bacterial meningitis? (IMPT)
s/s:
- Photophobia (inability to tolerate bright light)
- Non-blanching rash
- Generalised headache
- Neck stiffness
- Abnormal mental state/ conscious level
- Symptoms develop quickly, within hours
Management and prevention of bacterial meningitis? (IMPT)
Management (if there are no signs of ^ ICP) :
- Lumbar puncture to get CSF
- Blood culture
- Give steroids before antibiotics (if Abx given before CSF taken, might have fewer bacteria detected)
- Immediate processing by lab needed
- C&S of CSF to guide treatment
- PCR may be done if meningitis is strongly suspected but culture is negative
- Abx given must be IV route in order to penetrate the BBB
- Neisseria meningitidis shorter 5-7 days recovery w treament
- Haemophilus influenzae longer 10-14 days recovery as infx more serious
Prevention:
- Vaccination against the 3 common bacteria
- For close contacts, give chemoprophylaxis (faster) if infx caused by N. meningitidis or H. influenzae
Complications of bacterial meningitis?
- High mortality
- Brain damage
- Hearing loss
Causes and s/s of Cryptococcus neoformans meningitis? (IMPT)
Causes:
- By fungus found in soil contaminated by bird guano or in areas where that fungus can grow well in
- Inhalation can lead to entering bloodstream then brain
S/s:
- Headache
- Personality change and confusion
- Coma
- Symptoms may develop over days or weeks
How do you diagnose and treat Cryptococcus neoformans meningitis?
Diagnosis:
- Positive india ink stain on CSF
- Positive Cryptococcal antigen from CSF
- CSF culture
Treatment:
- Months of antifungal therapy
Tuberculosis meningitis cause, diagnosis and treatment?
- Mostly with miliary TB (Tb from lungs which spread to bloodstream and formed lesions in organs)
- Presentation similar to bacterial meningitis
- Fatal within 5-8 weeks if untreated
Diagnosis:
- AFB smear and culture
- PCR to detect TB from CSF
Treatment:
- Antimicrobial agents for treating pulmonary TB
Causes of viral meningitis?
- Enterovirus
- Coxsackie virus
- Mumps (if no vaccination)
- HSV
- VZV
- EBV, CMV
Presentation, diagnosis and treatment of viral meningitis?
s/s:
- Headache
- Photophobia
- Neck stiffness
- Rash
Diagnosis:
- PCR
Management:
- Supportive treatment (as VM is usually self-limiting)
(Viral) Meningitis vs encephalitis
Meningitis:
- Infx and inflammation of the meninges
Encephalitis:
- Infx and inflammation of the brain tissue itself
What are the 3 main categories of viral encephalitis?
- Mosquito borne (arbovirus)
- Animal to human (rabies)
- Human to human
