Infections of the Nervous System Flashcards
What may untreated infection cause?
Brain herniation and death
Cord compression and necrosis with subsequent permanent paralysis
What are the common infections of the CNS?
Encephalitis, meningitis, meningoencephalitis, encephalomyelitis, epidural abscesses, neuritis, sepsis syndrome
What are the types of meningitis?
Acute pyogenic = bacterial
Acute aseptic = viral
Acute focal suppurative infection = brain abscess, subdural/epidural empyema
Chronic bacterial infection = TB
What is acute encephalitis?
Infection of the brain parenchyma
What would indicate a diagnosis of pyogenic meningitis?
Thick layer of suppurative exudate that covers leptomeninges over surface of brain = exudate in basal and convexity surface
How does pyogenic meningitis appear microscopically?
Neutrophils in subarachnoid space
How is pyogenic meningitis treated?
Ceftriaxone and dexamethosone
Amoxicillin if Listeria suspected
What are some features of viral meningitis?
Common = late summer/autumn Usually enteroviruses (e.g ECHO virus) Treated supportively as self limiting
How is viral meningitis diagnosed?
Viral stool culture
Throat and CSF swab
How is encephalitis treated?
Aciclovir = if delay predicted in getting test results then give preemptively
What are the features of encephalitis?
Stupor, coma, seizures, partial paralysis, confusion, psychosis, speech and memory symptoms, meningismus = insidious onset but may be sudden
What investigations are done for encephalitis?
Lumbar puncture, EEG and MRI
What are the symptoms of bacterial meningitis?
Fever, cold extremities, vomiting, drowsy, confusion, severe muscle pain, non-blanching rash, headache, stiff neck, photophobia
What organisms cause bacterial meningitis in children?
Neonates = listeria, group B strep, ecoli
Children = h, influenzae
Age 10-21 = neisseria meningitidis
What organisms cause bacterial meningitis in adults?
Age >21 = strep pneumoniae
Age >65 = strep pneumoniae
What are some risk factors for bacterial meningitis?
Decreased cell mediated immunity = listeria
Neurosurgery/head trauma = staph, gram negative rods
Cribrifrom plate fracture = strep pneumoniae
How common are complications from bacterial meningitis?
Very common = 25% of people who survive meningitis and septicaemia will life with life altering complications
What are some complications of bacterial meningitis?
Purulence, invasion, cerebral oedema, ventriculitis and hydrocephalus
What are some features of the purulence that arises from bacterial meningitis?
Clusters at base of brain
Convexities of rolandic and sylvian sulci
Exudate around nerves = especially CN III and VI
How can bacterial meningitis arise?
Nasopharyngeal colonisation
Direct extension of bacteria
Spread from remote foci of infection elsewhere
What organisms cause bacterial meningitis in immunocompromised patients?
Strep pneumoniae, staph aureus, listeria monocytogenes, m. tuberculosis, nocardia asteroides, cryptococcus neoformans
What causes meningococcal meningitis?
Neisseria meningitis = found in throats of healthy carriers
How does neisseria meningitis gain access to the meninges?
Probably via the bloodstream = bacteria may be found in leukocytes in CSF
What are some features of meningococcal meningitis?
Symptoms are caused by endotoxin
Most often occurs in children
Where can neisseria meningitis infection occur from?
Local disease, meningitis with septicaemia or fulminant septicaemia
What does haemophilus influenzae require for growth?
Blood factors
How many types of haemophilus influenzae are there?
Six types based on capsule differences = type b is most common cause of meningitis in children <4
What kind of vaccine is available for haemophilus influenzae meningitis?
Conjugated vaccine directed against the capsular polysaccharide antigen
Where is strep pneumoniae commonly found?
The nasophaynx = causes pneumococcal meningitis
What patients tend to get strep pneumoniae meningitis?
Hospitalised patients, patients with CSF skull fracture, diabetics, alcoholics and young children
May be related to CNS devices like cochlear implants
Is there a vaccine for pneumococcal meningitis?
Yes = new conjugate vaccine has been developed
What are some features of listeria monocytogenes?
Gram positive bacilli
Sporadic cases but on the rise
Mainly causes bacteraemia illness
What patients get listeria meningitis?
Neonates, patients >55 and those who are immunosuppressed (especially malignancy)
What is the antibiotic of choice for listeria?
IV ampicillin or amoxicillin
How does tuberculous meningitis occur?
Due to reactivation of latent infection or in elderly patients
What are some features of tuberculous meningitis?
Often non-specific ill health
Previous TB on CXR or poor yield from CSF
High morbidity if not treated
What is the treatment for tuberous meningitis?
Isoniazid and rifampicin
May add pyrazinamide and ethambutol
What are some features of cryptococcal meningitis?
Fungal = mainly seen in HIV when CD4 < 100
Disseminated infection
Subtle neurological presentation and aseptic picture on CSF
Serum and CSF cryptococcal antigen
How is cryptococcal meningitis treated?
IV amphotericin b/flucytosine and fluconazole
What are the signs of bacterial meningitis?
Fever, stiff neck, alteration in consciousness
When should you be cautious about performing a lumbar puncture?
If increased ICP is possible and in the setting of delerium
What are some features of a lumbar puncture?
Utilise sitting position if necessary
Measure opening pressure if flow is fast
Give antibiotics before doing the procedure
How is the CSF obtained from a lumbar puncture sent for interpretation?
Tube 1 = haematology
Tube 2 = microbiology
Tube 3 = chemistry
Tube 4 = haematology
What is PCR used for?
To differentiate between causes of meningitis
Can bacterial meningitis be culture negative?
Yes
What does aseptic meningitis refer to?
Non-pyogenic bacterial meningitis
What is the spinal fluid like in aseptic meningitis?
Low number of WBC, minimally elevated protein and normal glucose
What are the infectious causes of aseptic meningitis?
HSV 1 and 2, syphilis, listeria, TB, cryptococcus, leptospirosis, cerebral malaria, Lyme disease
What are the non-infectious causes of aseptic meningitis?
Carcinomatous, sarcoidosis, vasculitis, dural venous sinus thrombosis, migraine
What patients should go for a CT before having a lumbar puncture done?
Immunocompromised, history of CNS disease, new onset seizure, papilloedema, abnormal level of consciousness, focal neurological deficit
What are the red flags in meningitis?
GCS < 12 or fall in GCS >2
Focal neurology, seizure or shock
Bradycardia and hypertension
Papilloedema
When are steroids indicated?
In all patients with bacterial meningitis (don’t gove for viral)
When do steroids have the biggest benefit?
Treating pneumococcal meningitis
What are the contraindications for using steroids to treat meningitis?
Post surgical meningitis, severely immunocompromised, meningcoccal/septic shock, steroid hypersensitivity
Do Public health need to be notified of meningitis cases?
Yes
What are close contacts of meningitis cases given as prophylaxis?
Ciprofloxacin
