Infection and inflammation Flashcards
What are the infections and inflammations of the CNS?
- meningitis
- encephalitis
- meningoencephalitis
- brain abscess
- spinal spscess
- myelitis
- meningomyelitis
- sub-dural empyema
- intracranial or intraspinal phlebitis
- encephalopathies from infectious agent (prions, viruses)
- poliomyelitis
What are the infections and inflammations of the PNS?
Polyneuropathies (eg. Guillain-Barre syndrome)
What is the definition of meningitis?
inflammation of brain meninges and or spinal cord
What are the infective causes of meningitis?
- viral
- bacterial
- fungal
- parasitic
- opportunistic infections
What is an opportunistic infection?
- infection that would not usually harm a healthy individual
* affects someone that is in an immunocompromised state
What are the non-infective causes of meningitis?
- chemicals (eg. steroid therapy)
- drugs
- trauma (penetrating head wound)
- neurosurgery
- chronic renal failure
What are the most common types of meningitis?
- acute bacterial meningitis
* aseptic meningitis
What is the aetiology of Acute bacterial meningitis?
80% of cases are from:
• Neisseria meningitis (meningococcus) -kids and adults
• Hemophilus influenza b - kids epidemics
• Streptococcus pneumonia (pneumococcus) - adults
- spread by resp. droplets in close contact, hematogenous, or lesion
- often kids <2yrs
What is the pathophysiology of Acute bacterial meningitis?
Bacteria from sinusitis, epidural abscess OR contact of CSF with exterior (myelomeningocele, penetrating trauma, surgery)
- > meninges -> infection flourish in CSF
- > neutrophils drawn into CSF
- > exudate damages CNs, CSF pathway -> hydrocephalus or vascularities/thrombophlebitis -> ischaemia
- > arachidonic acid metabolites and cytokines from damage -> disrupt BBB -> oedema -> not enough ADH
- >
- ICP & septic shock -> death
What are the clinical features of Acute bacterial meningitis?
- Hx of resp illness or sore throat
- fever, headache, stiff neck (meningism)
- mechanical stimuli increases pain (by irritating meninges)
- nausea, vomiting, photophobia
- symptoms of infection source
- increases ICP (and associated symptoms) -> herniation
- seizures, cranial neuropathies
- dehydration, vascular collapse -> shock
- adhesions -> hydrocephalus -> compress brain and CNs
- Brudzinski’s, Kernigs sign
- CSF mononuclear leukocytosis
- low glucose
- slight protein elevation
- bacteria on culture
What is the pathophysiology of headache in acute bacterial meningitis?
- distended blood vessels (increases ICP)
- menial irritation
- pus collects in occipital area by gravity
- the meninges are pain sensitive
What is Waterhouse-Friderischsen syndrome?
When in Acute bacterial meningitis,
• dehydration and vascular collapse -> shock
• especially in meningococcal septicemia
What is Brudzinski’s sign?
Abrupt neck flexion in the supine patient results in involuntary flexion of the hips and knees
What is Kernigs sign?
Attempts to extend the knee from the flexed thigh position are met with strong passive resistance
What is the pathophysiology of Brudzinski’s and Kernigs sign?
Due to irritation of nerve roots passing through inflammed meninges as they are brought under tension
What are the aetiologies of Aseptic meningitis?
Infectious:
• viral: mumps, echovirus, poliovirus, coxsackievirus, herpes simplex, varicella zoster, infectious hepatitis, infectious mononucleosis, HIV
• post-infectious: measles, rubella, varicella
Non-infectious: • parameningeal disease: brain tumour, stroke, multiple sclerosis • reaction to intrathecal injections • vaccine reactions (rabies, pertussis) • drugs
What are the clinical features and investigation findings of Aseptic meningitis?
Same as acute bacterial meningitis:
• fever, headache, stiff neck, Brudzinski’s, Kernigs
• nausea, vomiting, seizures, cranial neuropathies, photophobia
• increased ICP (and associated symptoms) -> herniation
• dehydration, vascular collapse -> shock
• adhesions -> hydrocephalus -> compress brain and CNs
- CSF mononuclear leukocytosis
- normal glucose
- slight protein elevation
- NO bacteria
What is the definition of subacute and chronic meningitis?
Meningeal inflammation without antibiotic use lasting >2 weeks (subacute) or >1 month (chronic)
What is the aetiology of Subacute and Chronic meningitis?
- fungal, TB, sarcoid, Lyme disease, AIDS, syphilis, neoplasms (leukaemia, lymphomas, melanomas, carcinomas, gliomas)
- immunosuppressive therapy
- AIDS
- acute lymphoblastic leukaemia
What are the clinical features of Subacute and Chronic meningitis?
Same as acute meningitis BUT SLOWER:
• headache, stiff neck, Brudzinski’s, Kernigs
• nausea, vomiting, seizures, cranial neuropathies, photophobia
• increased ICP (and associated symptoms) -> herniation
• dehydration, vascular collapse -> shock
• adhesions -> hydrocephalus -> compress brain and CNs
- minimal fever
- if neoplastic: dementia, CN and peripheral palsies
- chronic hydrocephalus
- fatal in weeks of months
What is encephalitis?
• acute inflammatory disease of brain from direct viral invasion or to hypersensitivity initiated by virus or foreign protein
- Primary: viral -echovirus, coxsackie, arbovirus, herpes simplex, varicella zoster, mumps
- Secondary: immunological reaction to viral infection (measles, rubella, chicken pox)
Features:
• malaise, fever, signs of meningitis
• cerebral dysfunction: consciousness alterations, personality change, seizures, paresis, CN abnormalities
What is a brain abscess?
- intracerebral encapsulated collection of pus
- result of direct extension of area of infection (in or outside skull) or hematogenous spread
- s&s of + ICP
- focal neurological deficits
- s&s of infection
- CT or MRI
- lumbar puncture contraindicated (pressure too high)
- if unruptured, no CSF findings
What is a subdural empyema?
- collection of pus in subdural space
- FROM: result of meningitis, direct extension of other infection, surgery or bacteria
- headache, lethargy, focal neurological defects, seizures, coma, death
- CT, MRI
What is poliomyelitis?
- poliovirus type 1,2, 3 (rare)
- human reservoir (often kids), long term carrying is rare)
- worldwide occurrence, mostly developing countries
- before mass immunization -> highest incidence in temperate zones & developed countries
- more in summer
What is the incubation, transmission and period of communicability of poliomyelitis?
- incubation 7-14/7 for paralytic
- incubation range 3-35/7
- direct contact
- poor sanitation -faecal-oral route
- multiplies in alimentary tract
- most infectious during first few days of symptoms
What are the clinical features of poliomyelitis? how is it diagnosed?
- range of symptoms
- fever, malaise, headache, nausea, vomiting
- excruciating muscle pain, spasms, stiffness of back, flaccid paralysis
- resp muscles risk (2-10% fatality)
- asymmetrical paralysis
- most often minor (not paralytic)
- diagnosed by isolating virus from CSF, faeces, oropharyngeal secretions
How is poliomyelitis prevented? susceptibility and reliance?
- live attenuated trivalent oral vaccine (#1) or inactive
- 2, 4, 6 months and school entry
- booster prior to leaving school
- paralytic cases are rare
- susceptibility increases with age at time of infection
- different virus types (can have second attack)
- infants to resistant mother have passive immunity
What is the DDx of poliomyelitis?
- tick bite paralysis (but stops with tick removal)
- Guillain Barre syndrome
- Postencephalitic syndrome
- cerebral palsy
- trauma
- some drugs
What is Guillain-Barre syndrome?
- body attacking its own nerves
- polyneuritis developing 1-2wks after infection or immunization
- FROM: post-infectious (eg. mild resp infection or gastroenteritis)
Features: • upper and lower extremity weakness • facial weakness, dysphagia, dysarthria • weakness of muscles maybe severe • resp muscle weakness (need respirator) • most patients recover spontaneously within a few weeks
Myelitis
- inflammation of spinal cord
- fever, back pain localized in affected area
- tenderness maybe
- neurological deficits below lesion often
Meningomyelitis
inflammation of meninges of spinal cord and spinal cord
Meningoencephalitis
inflammation of meninges and brain
Prion diseases
- prions are abnormally folded proteins, which convert normal proteins into abnormal proteins
- increase in quantity during incubation
- resist UV, ionizing radiation, formaldehyde, heat, proteases, nucleases
- cause spongiform encephalopathies (eg. Creutzfeld-jakob disease, kuru)
Compare bacterial meningitis, viral meningitis and encephalitis (viral): site
Bacterial men.: pia, arcahnoid, CSF, ventricles
Viral men.: meninges
Encephalitis: meninges, white & grey matter
Compare bacterial meningitis, viral meningitis and encephalitis (viral): infectious route
Bacterial men.: nasopharynx following URT infection -> bloodstream
Viral men.: lining of resp. or GIT -> lymph -> blood
Encephalitis: herpes simplex, varicella zoster, enters CNS by blood or CNs
Compare bacterial meningitis, viral meningitis and encephalitis (viral): lesion
Bacterial men.: meningeal vessels become hyperaemic and permeable AND exudate pools by gravity to occiput
Viral men.: as for bacterial meningitis but less severe exudate
Encephalitis: nerve cell (gray matter) degeneration
Compare bacterial meningitis, viral meningitis and encephalitis (viral): manifestations
Bacterial men.: throbbing headache, legs and thigh flexion, stiff neck, vomiting, photophobia, confusion, rash
Viral men.: same but milder than bacterial
Encephalitis: fever, delirium, confusion, coma, seizure, paresis, paralysis
Compare bacterial meningitis, viral meningitis and encephalitis (viral): CSF
Bacterial men.: + pressure, bacteria, + protein levels, - glucose, neutrophils, monocytes
Viral men.: + pressure, normal glucose, lymphocytes
Encephalitis: same as for viral meningitis
Compare bacterial meningitis, viral meningitis and encephalitis (viral): treatment
Bacterial men.: antibiotics
Viral men.: antiviral agents and steroids
Encephalitis: herpes infections, antiviral agents, control of intracranial pressure
Explain the progression of meningitis to the point where the patient may become unconscious
URT infection (flu-like symptoms, malaise, fever, runny nose)
- > nasal or sinus mucosa
- > blood stream -> BBB
- > CSF and meninges (stiff neck, headaches, photophobia)
- > increase neutrophils fighting infection
- > thickening of CSF by exudate (interstitial oedema) and damages meninges/BBB (vasogenic oedema)
- > increase ICP (altered consciousness, increase BP, lower HR, low light reflex)
What is the pathophysiology of photophobia in meningitis?
- trigeminal nerve receives pain from meninges (being overstimulated)
- additional stimulus from light on cornea irritates it
