Meningitis and Encephalitis Flashcards
Bacterial meningitis epidemiology? Etiology? Pathophysiology ?
Incidence —> 5-10 cases/100.000 person/year. They are most common in extreme age categories, in elderly and newborns. The most frequent etiology of bacterial meningitis is S. pneumoniae (49%), and the second most common cause is N. meningitidis (34%).
Pathophysiology —> Microorganisms penetrate the subarachnoid space through : Hematogenous spread -> most frequent route of diffusion, direct penetration (e.g. in presence of a wound), extension of nearby or contiguous infectious foci (e.g. infections in the nose or nasal sinuses), lymphatic peri-venous spread (less frequent). Regardless of the mechanism of entry, there will be bacterial replication in subarachnoid space and subarachnoid inflammation.
Signs and symptoms of bacterial meningitis?
They depend on the patients age.
Infants —> symptoms include irritability, poor feeding, vomiting, respiratory systems, apnea. Signs include fever, lethargy, stupor, coma, seizures, petechial or purpuric rash.
Children and adults —> symptoms include headache, neck stiffness, unconsciousness, photophobia, respiratory problems. Signs include fever, lethargy, coma, focal neurological deficits, seizures, cranial nerve palsies, petechial or purpuric rash.
Neisseria meningitidis in meningitis?
It is a gram negative diplococci, often found intracellularly which causes acute cloudy/prurulent CSF meningitis. It is the second most common cause of meningitis and commonly affects young children especially those who go to school, clubs or gym.
Risk factors include complement deficiency which predisposes to infection.
It is transmitted via inter human spread through salivary particles.
Serotypes B and C are most virulent and only B accounts for 50% of sporadic cases. A and C are more frequent during outbreaks.
Clinical features include meningitis symptoms, meningococcal septicemia suspicions like purpuric rash, DIC and Waterhouse friderichsen syndrome.
Complications include CN deficits, brain infractions, cognitive disabilities and hydrocephalus, these all occur in 10-20% of cases.
Lethality related to sepsis is 30% and 6-12% related to late recognition.
Chemoprophylaxis for close contact must be given within 24h and it include : ciprofloxacin 500mg single dose, ceftriaxone 250mg single dose, rifampicin 600mg every 12h for 2 days.
