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Medical Sciences B > Infection and inflammation > Flashcards

Infection and inflammation Flashcards

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USMLE® Step 1 flashcards
1
Q

What are the infections and inflammations of the CNS?

A
  • meningitis
  • encephalitis
  • meningoencephalitis
  • brain abscess
  • spinal spscess
  • myelitis
  • meningomyelitis
  • sub-dural empyema
  • intracranial or intraspinal phlebitis
  • encephalopathies from infectious agent (prions, viruses)
  • poliomyelitis
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2
Q

What are the infections and inflammations of the PNS?

A

Polyneuropathies (eg. Guillain-Barre syndrome)

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3
Q

What is the definition of meningitis?

A

inflammation of brain meninges and or spinal cord

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4
Q

What are the infective causes of meningitis?

A
  • viral
  • bacterial
  • fungal
  • parasitic
  • opportunistic infections
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5
Q

What is an opportunistic infection?

A
  • infection that would not usually harm a healthy individual

* affects someone that is in an immunocompromised state

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6
Q

What are the non-infective causes of meningitis?

A
  • chemicals (eg. steroid therapy)
  • drugs
  • trauma (penetrating head wound)
  • neurosurgery
  • chronic renal failure
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7
Q

What are the most common types of meningitis?

A
  • acute bacterial meningitis

* aseptic meningitis

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8
Q

What is the aetiology of Acute bacterial meningitis?

A

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
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9
Q

What is the pathophysiology of Acute bacterial meningitis?

A

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
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10
Q

What are the clinical features of Acute bacterial meningitis?

A
  • 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
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11
Q

What is the pathophysiology of headache in acute bacterial meningitis?

A
  • distended blood vessels (increases ICP)
  • menial irritation
  • pus collects in occipital area by gravity
  • the meninges are pain sensitive
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12
Q

What is Waterhouse-Friderischsen syndrome?

A

When in Acute bacterial meningitis,
• dehydration and vascular collapse -> shock
• especially in meningococcal septicemia

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13
Q

What is Brudzinski’s sign?

A

Abrupt neck flexion in the supine patient results in involuntary flexion of the hips and knees

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14
Q

What is Kernigs sign?

A

Attempts to extend the knee from the flexed thigh position are met with strong passive resistance

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15
Q

What is the pathophysiology of Brudzinski’s and Kernigs sign?

A

Due to irritation of nerve roots passing through inflammed meninges as they are brought under tension

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16
Q

What are the aetiologies of Aseptic meningitis?

A

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
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17
Q

What are the clinical features and investigation findings of Aseptic meningitis?

A

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
18
Q

What is the definition of subacute and chronic meningitis?

A

Meningeal inflammation without antibiotic use lasting >2 weeks (subacute) or >1 month (chronic)

19
Q

What is the aetiology of Subacute and Chronic meningitis?

A
  • fungal, TB, sarcoid, Lyme disease, AIDS, syphilis, neoplasms (leukaemia, lymphomas, melanomas, carcinomas, gliomas)
  • immunosuppressive therapy
  • AIDS
  • acute lymphoblastic leukaemia
20
Q

What are the clinical features of Subacute and Chronic meningitis?

A

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
21
Q

What is encephalitis?

A

• 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

22
Q

What is a brain abscess?

A
  • 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
23
Q

What is a subdural empyema?

A
  • 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
24
Q

What is poliomyelitis?

A
  • 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
25
Q

What is the incubation, transmission and period of communicability of poliomyelitis?

A
  • 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
26
Q

What are the clinical features of poliomyelitis? how is it diagnosed?

A
  • 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
27
Q

How is poliomyelitis prevented? susceptibility and reliance?

A
  • 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
28
Q

What is the DDx of poliomyelitis?

A
  • tick bite paralysis (but stops with tick removal)
  • Guillain Barre syndrome
  • Postencephalitic syndrome
  • cerebral palsy
  • trauma
  • some drugs
29
Q

What is Guillain-Barre syndrome?

A
  • 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
30
Q

Myelitis

A
  • inflammation of spinal cord
  • fever, back pain localized in affected area
  • tenderness maybe
  • neurological deficits below lesion often
31
Q

Meningomyelitis

A

inflammation of meninges of spinal cord and spinal cord

32
Q

Meningoencephalitis

A

inflammation of meninges and brain

33
Q

Prion diseases

A
  • 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)
34
Q

Compare bacterial meningitis, viral meningitis and encephalitis (viral): site

A

Bacterial men.: pia, arcahnoid, CSF, ventricles

Viral men.: meninges

Encephalitis: meninges, white & grey matter

35
Q

Compare bacterial meningitis, viral meningitis and encephalitis (viral): infectious route

A

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

36
Q

Compare bacterial meningitis, viral meningitis and encephalitis (viral): lesion

A

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

37
Q

Compare bacterial meningitis, viral meningitis and encephalitis (viral): manifestations

A

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

38
Q

Compare bacterial meningitis, viral meningitis and encephalitis (viral): CSF

A

Bacterial men.: + pressure, bacteria, + protein levels, - glucose, neutrophils, monocytes

Viral men.: + pressure, normal glucose, lymphocytes

Encephalitis: same as for viral meningitis

39
Q

Compare bacterial meningitis, viral meningitis and encephalitis (viral): treatment

A

Bacterial men.: antibiotics

Viral men.: antiviral agents and steroids

Encephalitis: herpes infections, antiviral agents, control of intracranial pressure

40
Q

Explain the progression of meningitis to the point where the patient may become unconscious

A

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)
41
Q

What is the pathophysiology of photophobia in meningitis?

A
  • trigeminal nerve receives pain from meninges (being overstimulated)
  • additional stimulus from light on cornea irritates it

Medical Sciences B (23 decks)

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