CNS Infections Flashcards
Discuss the features and symptoms of meningitis
- Infection of subarachnoid space and inflammation of leptomeninges
- Features- headache , neck stiffness, photophobia, fever, lethargy/ irritability, vomiting, purpuric rash (meningococcal disease), luging fontanelle, high pitched cry
What are the CSF findings associated with the various types of meningitis
- Pyogenic (bacterial) - very high neutrophils, very low glucose , gram positive and high in protein
- TB- high lymphocytes, low glucose, very high protein, Ziehl nelson positive
- Viral- High lymphocytes, normal glucose, slightly high protein
Discuss the pathophysiology of Meningitis
- Nasopharyngeal colonisation with bacteria leads to
1. Bactraemia in blood stream
2. Local invasion that will progress to either intracellular neiserria meningitides or intercellular haemophilia influenzae
-Both organisms have polysaccharide capsules that can overcome the complement cascade which is the immune systems first line of defence
In the CNS there are no immunoglobulins so there is no complement cascade so infection can invade via the choroid plexus and grow due to complement deficiency
The host response is what causes meningitis
Discuss the breakdown of the blood brain barrier in Meningitis
- Bacterial replication in CSF causes interleukin release (IL1, IL6 and TNF)
- Polymorphs become attached to the site of infection and cause activated polymorphs chemotaxis
- This causes endothelial disruption and albumin leak causing increased cerebral blood flow and cerebral oedema
What are the various ages that meningitis can occur
- Infant- most likely group B strep, E Coli, Listeria (acquired infection maternal vagina)
- Toddler- N Meningitidis, S pneumonia, H Influenzae (stopped due to vaccine)
- Over 4s and adult- N Meningitidis, S pneumonia
What are the 3 main organisms responsible for causing meningitis
- S pneumonia- gram positive, found on blood agar- green zone of haemolytic around them, sometimes penicillin resistant, person to person spread is rare
- Haemophilus influenzae- gram negative rods -Need X and V factors to grow Grow best on chocolate agar, Beta lactamase positive (so resistant to penicillins)
- Neisseria Meningitidis- Gram negative diplococci, oxidase positive, sugar fermentation- maltose and glucose- always penicillin sensitive and 2nd and 3rd gem cephalosporins too
What are the treatments given at each age group for Meningitis
Baby= Ampicillin and Cefotaxime
Toddler= Ceftriaxone
Over 4s/ Adult= Ceftriaxone
Immunotherapy
-Dexamethasone can be given before B lactate antibiotics to decrease cerebral oedema
What vaccine is available for meningitis
- Hib Vaccine
- PRP polyribosylribitrol phosphate
- T cell independent
- New conjugated meningococcal group C vaccine- Children and 15-17 yr olds
- Primary immunisation for children - pneumococcal 7 talent conjugate vaccine and 23 valent polysaccharide vaccine
What are the prophylactic measures given for meningitis
- Hib propylaxi- household contacts with unimmunised children under 4 given Rifampicin
- N men. for household and kissing contacts - 10 days pf Rifampicin or ciprofloxacin
- Meningococcal disease- Vaccine if A or C and notification- contact tracing
What are the main causative agents of viral meningitis and discuss the features
- Most common= enteroviruses
- HSV 2 (and HSV 1), VZV, CMV -Mumps, adenovirus, HIV
- Enteroviral meningitis= good prognosis
- Coxsachieviruses, echoviruses, enteroviruses
- Symptoms: URTI, conjunctivitis , pharyngitis, pneumonia, myopericarditis, gastroenteritis, mild meningeal irritation
Treatment: Supportive, some are preventable by vaccine eg mumps and measles
What are the causes of aseptic meningitis
- Fungi
- TB
- Syphillus
- Brucella
- Mycoplasma
- Paraminigeal infection
- Protozoa
Describe the features of TB meningitidis
- Insidious onset age less than 6
- 3-6 months post initial infection or exposure to TB
- Miliary TB will occur in 50%
- GRADUAL ONSET - MAKES IT DIFFERENT
- Personality change, irritability, fever, drowsiness, neck stiffness, cranial nerve palsy , depressed conciousness
Treatment- 4 drugs
-2 Months of isoniazid pyrazinamide and an amino glycoside or ethambutol once a day for 7-10 months
THEN
-Isonizid and rifamicipin after 2 months for up to a year
-Total therapy= 9-12 months
What are the most likely causes of meningitis in immunocompromised patients
What are the most likely causes of meningitis in immunocompromised patients
- Listeria monocytogenes - raw milk and soft cheese
- Cyptococcus (yeast)
What are the viral and non viral causes of encephalitis
Viral -HSV 1 and HSV 2 -Arboviruses -Rabies -Enteroviruses -Influenza -VZV
Non-viral- -N. Meningitidis -Listeria monocytogenes -Leptospirosis -Malaria -TB -Borrelia
