Meningitis, Encephalitis, Brain Abscess Flashcards
What is meningitis
It is the inflammation of the protective membranes (meninges) surrounding the brain and the spinal cord and the CSF
The CSF is found in between which membranes
The pia and the arachnoid matter
Where does the spinal cord end
Between L1 and L2
Mention the protective membranes
Pia, dura and arachnoid mater
What are the types of meningitis
Viral meningitis
Bacterial meningitis
Parasitic meningitis
Fungal meningitis
Non-infective meningitis
What is the most common type of meningitis
Viral meningitis
In which seasons are viral meningitis common
Summer and fall
Which type of virus cause about 85% percent of meningitis cases
Enterovirus
Mention some viruses which can also cause meningitis
Coxsackievirus A and B
Echovirus
Mention some bacteria which cause meningitis
Streptococcus pneumoniae
Neiserria meningitidis
Haemophilus influenza
Listeria monocytogenes
Staphylococcus aureus
What is the second most common type of meningitis
Bacterial meningitis
Which type of meningitis is likely to affect people with a weakened immune system
Fungal meningitis
Mention some fungi which causes meningitis
Cryptococcus
Blastomyces
Histoplasma
Coccidiodes
Which type of meningitis is caused by other medical conditions or treatments
Non-infective meningitis
Examples of conditions which causes meningitis
Lupus
Cancer
Certain medications like NSAIDs for certain people
Which type of meningitis is rare
Parasitic meningitis
Which type of meningitis is not spread between people
Parasitic meningitis
Which type of meningitis could go away without treatment
Viral meningitis
Which type of meningitis could be chronic
Fungal meningitis
Meningitis can occurs when the meninges are covered by the infecting agent
True or false
True
What substance will increase in the CSF in meningitis
Proteins
What are some risk factors in meningitis
Respiratory tract infection
Otitis media
Mastoiditis
Head trauma
Splenectomy
Sickle cell disease
Immunosuppressive therapy
Immnunocompromised host
Alcoholic patients
Patients with hardware. Eg. Ventriculoperitoneal shunt
What are some early clinical features of meningitis
Headache
Leg pain
Cold hands and feet
Abnormal skin colour
Fever
Chills, nausea, vomiting
Which bacteria is there most common cause of petechial rash
Neisseria
What are some investigations to make with a patient suspected of meningitis
Lumbar puncture (measure open pressure, gram stain CSF for microscopy, culture, etc)
Blood culture (FBC , CXR, U &E, LFT, glucose, coagulation screen)
Stool sample for viruses
CT scan/MRI may show swelling or inflammation
CXR/CT SCAN of chest or sinuses
What is the main investigation for meningitis
Lumbar puncture
Where is the lumbar puncture done
The space between L3 and L4
What are some contraindications of lumbar puncture
Intra-cranial mass
Focal signs. Eg. Hemiparesis
Papilloedema
Head trauma
Middle ear pathology
Major coagulopathy
Infection at the site of lumbar puncture
CT scan (mass lesion or raised ICP)
What are some management approaches to patients with bacterial meningitis
Emergent CSF analysis and initiation of immediate antiadjunctive and adjunctive therapies
Empiric antimicrobial therapy should be instituted as soon as possible to eradicate the causative organism
Antimicrobial therapy should last at least 48 to 72 hours or until the diagnosis of bacterial meningitis can be ruled out
Continued therapy should be based on the assessment of clinical improvement, cultures, and susceptibility testing results.
In addition to antibiotics, dexamethasone is a commonly used therapy for the treatment of pediatric meningitis
Dexamethasone should be administered prior to the first antibiotic dose and not after antibiotics have already been started
Dexamethasone has shown to cause a significant improvement in CSF concentrations of pro-inflammatory cytokines, glucose, protein, and lactate as well as a significantly lower incidence of neurologic sequelae commonly associated with bacterial meningitis
The commonly used IV dexamethasone dose is 0.15 mg/kg every 6 hours for 2-4 days
If you’re treating a bacterial meningitis what drug should you start with before antibiotics
Dexamethasone
What antiviral drug do you give for a patient with viral meningitis
Acyclovir
What antibiotic drug do you give for a patient with a bacterial meningitis
3rd generation cephalosporins like ceftriazone
What is the first and second line preventative antibiotic for meningococcal meningitis
Ciprofloxaxin 500mg stat
Rifampicin 600mg bd x2
What is encephalitis
Inflammation of the brain parenchyma often due to infections viral or bacterial (mostly viral) or from an immune system disorder
What are some viruses which cause encephalitis
Herpes
Enteric
Paramyxo
Arbo
Influenza viruses, adenovirus, parvovirus, rubella virus, rabies (rare)
What is the most common cause of viral encephalitis in industrialized nations
HSV encephalitis
HSV-1 and HSV-2
Which causes about 90% cases of encephalitis
HSV-1
HSV-2 is more common in immuno-compromised patients and neonates
HSV-2 viral encephalitis is transmitted via
Genital mucosa
HSV-1 infects the human with encephalitis via
Oral mucosa
Virus then travels along the trigeminal nerve to ganglion
What is the typical clinical presentation of viral encephalitis
Acute flu-like prodrome
High fever
Severe headache
Altered consciousness (lethargy, drowsiness, confusion, coma)
Seizures
Focal neurological signs
What are some subtle presentations of viral encephalitis
Low grade fever
Speech disturbances (dysphagia, aphasia)
Behavioral change
Subacute and chronic presentations of viral encephalitis can be caused by which viruses
CMV
VZV
HSV
What are some investigations for viral encephalitis
CSF study
Blood study
Enhanced CT/MRI with contrast
Toxoplasma tests
MRI brain: right temporal lobe (high signal in a patient with herpes encephalitis)
What is the viral treatment for encephalitis
Acyclovir for 14-21 days
What is the bacterial treatment for encephalitis
Ceftriazone
Metronidazone
What are some poor prognostic factors of encephalitis
GCS < 7
Delay in starting acyclovir (especially > 2 days)
What is a cerebral abscess
It is a focal pyogenic infection of the brain
What are some effects of cerebral abscess
Direct involvement and destruction of the brain
Compression of the parenchyma
Elevation of intracranial pressure (interfering with blood and/or CSF flow)
What is the pathophysiology of an abscess
It begins as a localized cerebritis (1-2 weeks)
Evolves into a collection of pus surrounded by a well-vascularized capsule (3-4 weeks)
List the pathogenesis of cerebral abscess
Direct spread from contiguous foci
Hematogenous spread from remote foci
Penetrating trauma/surgery
Cryptogenic
Some contiguous foci include
Otitis media/mastoiditis
Sinusitis
Dental infection, typically molar infections
Meningitis rarely complicated by brain abscess
How does direct spread of encephalitis spread
Direct extension through infected bones and spread through emissary veins, diploic veins and local lymphatics
In which artery do brain abscesses spread (hematogenous spread)
Middle cerebral artery distribution
List some conditions which serve as middlemen for hematogenous spread of brain abscesses
Emphysema
Lung abscesses
Bronchiectasis
Endocarditis
Wound infections
Pelvic infections
Infra-abdominal source
Which bacteria normally causes brain abscesses
Streptococci and anaerobes
Staphylococcus aureus, anaerobic GNR common after trauma or surgery
Clinical manifestations of cerebral abscesses depends on the location of the lesion. What are the clinical features for lesions in the parietal lobe
Headache
Visual field defects
Endocrine disturbances
Clinical manifestations of cerebral abscesses depends on the location of the lesion. What are the clinical features for lesions in the cerebellum
Nystagmus
Ataxia
Vomiting
Dysmetria
Clinical manifestations of cerebral abscesses depends on the location of the lesion. What are the clinical features for lesions in the temporal lobe
Ipsilateral headache
Aphasia
Visual field defect
Clinical manifestations of cerebral abscesses depends on the location of the lesion. What are the clinical features for lesions in the frontal lobe
Headache
Drowsiness
Inattention hemiparesis
Motor speech disorder
Differential diagnosis for cerebral abscess
CVA
Hemorrhage
Aneurysm
Subdural emphysema/Epidural abscess
What is the difference in an MRI between an abscess and a tumor
An abscess has a hypo-dense center with surrounding smooth thin walled capsule and areas of peripheral enhancement
Tumors have diffuse enhancements and irregular borders
Not so a sensitive test but if air seen, consider possibility of brain abscess. What investigation test for cerebral abscess is this
Skull x-ray
What are imaging study investigations for cerebral abscess
Skull x-ray
MRI (more sensitive for early cerebritis, satellite lesions, necrosis, edema, especially posterior fossa)
CT scan (if ring enhancing lesion(s) are seen)
99m Tc brain scan (very sensitive, useful where CT or MRI not available)
What are some specific investigation tests for encephalitis
Aspirate
WBC (normal in 40%, only moderate in ~50%, and only 10% have WBC > 20,000)
CRP (almost invariably elevated)
ESR (usually moderately elevated)
Blood culture (often negative but should still be done)
Lumbar puncture
Why is lumbar picture contraindicated in patients with known or suspected brain abscesses
There is risk of herniation
When do you subject a cerebral abscess patient to medical treatment only
When he is a poor surgical candidate
When he has multiple abscesses in a dominant location
When his abscess size <2.5 cm with concomitant meningitis, ependymitis or early abscess (cerebritis?) which will improvement on antiboitics
Better vascularized cortical lesions are more likely to respond to antibiotics alone than subcortical/white-matter lesions that are poorly vascularized
(Serial imaging important to monitor response)
What are some poor prognostic markers of cerebral abscess
Delayed or missed diagnosis
Inappropriate antibiotics
Multiple, deep or multi-loculated abscesses
Ventricular rupture (80-100% mortality)
Fungal, resistant pathogens
Neurological compromise at presentation
Short duration with severe acute meningeal signs
Rapidly progressive neurological Impairment
Immunosuppressed host
Poor localization, especially in the posterior fossa (before CT)
