Week 7 . Central Nervous System Infections Flashcards Preview

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Flashcards in Week 7 . Central Nervous System Infections Deck (168)
1

What is Meningitis?

Inflammation of the meninges

2

What is encephalitis?

Inflammation of the brain tissue

3

What is meningo-encephalitis?

It is inflammation of the meninges and brain tissue

4

What defines Aseptic meningitis?

White cell count >5x106/L (5/mm3) in cerebrospinal fluid (CSF) --> higher CSF count for children

Negative bacterial culture of the CSF

5

What is the main cause of aseptic meningitis?

Viruses are the most common cause

6

What are less common cause of aseptic meningitis?

Partially treated bacterial meningitis
Listeria
TB
Syphilis
Malignancy
Autoimmune conditions
Drugs

7

General virus structure?

Nucleic acid

Capsid
protein coat
made up of capsomeres (subunits)

Some have lipid envelope (derived from host cell membrane)

Some contain other proteins/enzymes

8

What is the mode of action of viral enzymes?

for replicating genetic material, influencing transcription, protein modification

9

What types of nucelic acid can you have in a virus?

DNA or RNA

Single stranded, double stranded

Linear or circular (e.g. Hepatitis B - DNA)

10

What is the action of viral proteins?

Form capsid/membrane projections

11

Who most commonly gets viral meningitis?

In children --> aged around 5

Neonates

12

What is the common causes of viral meningitis?

Enteroviruses --> leading cause
Herpes viruses
Mumps Virus
HIV

13

Give examples of enteroviruses that can cause viral meningitis? (5)

Echoviruses
Coxsackie viruses
Parecho viruses
Enteroviruses 70 and 71
Poliovirus

14

What are the different types of herpes viruses that can cause viral meningits?

Herpes Simplex Virus 2 (HSV 2) >> HSV 1
Varicella Zoster Virus (VZV)
Cytomegalovirus (CMV), Epstein Barr Virus (EBV)
HHV6, HHV7

15

Is HSV 2 or HSV 1 common cause of viral meningitis?

HSV 2

16

What viruses can cause viral meningitis and the mosiquito is the vector?

Arboviruses-->
Japanese Encephalitis virus, yellow fever

17

What are 7 less common causes of viral meningitis?

Adenovirus

Measles

Influenza

Parainfluenza type 3

Lymphocytic choriomeningitis virus (LCMV)

18

What should be taken during a history of a person with suspected meningitis?

It’s very important to take a travel history, sexual history and check if the patient is immunocompromised

19

What is pathogenesis of viral meningitis?

Colonisation of mucosal surfaces
Invasion of epithelial surface
Replication in cells
Dissemination and CNS invasion

20

How is CNS invasion occur in viral meningitis?

Via cerebral microvascular endothelial cells --> haematogenous spread e.g enteroviruses

Via choroid plexus epithelium

Spread along the olfactory nerve --> neurotropic e.g. HSV and VZV

21

What is the symptoms of viral meningitis due to?

Symptoms mainly due to inflammatory response in the CNS

It is usually not the virus causing the inflammation but the bodies response to the body

22

What are the general clinical presentations of viral meningitis?

Fever

‘Meningism’
Headache
Neck stiffness
Photophobia

Sometimes ‘viral’ prodrome (e.g. lethargy, myalgias, arthralgias, sore throat, D&V, rash)

23

Is it easy to distinguish between viral and bacterial meningitis?

No it is difficult

24

What is the initial treatment of viral meningitis?

You treat with antibiotics until LP is done. Preventing process to it being a bacterial cause

25

What are the clinical presenation of viral meningitis in children?

Are lot more suttle

Look for nuchal rigidity (neck stiffness) and bulging anterior fontanelle

26

What are the different examinations that can be done to assess viral meningitis?

Kernig’s sign: With hip and knee flexed to 90o, the knee cannot be extended due to pain/stiffness in the hamstrings

B) Brudzinski’s sign
Flexing the neck causes the hips and knees to flex

Nuchal rigidity =
Resistance to flexion of the neck --> in very severe cases of meningitis

27

What are the different investigations that can be done for viral meningitis?

Blood test

Ct scan

Lumbar puncture

28

What are you testing for in a blood test for diagnosing viral meningitis?

FBC, U&E, CRP, clotting
Blood culture

29

Why is a Ct scan done of a person with possible viral meningitis?

To look for any raised ICP.
To see if there is any alternative diagnosis, such as mass lesion, subarachnoid haemorrhage.

30

What are you testing for once you have done a lumbar puncture in a person with potential viral meningitis?

Microscopy, Culture, Sensitivity (MC&S)

Protein

Glucose (must check blood glucose at same time)

Viral PCR: enteroviruses, HSV, VZV

31

Why do you check glucose blood levels against CSF glucose levels?

It is not the absolute glucose levels in the CSF that is important but the ratio with blood glucose levels

32

What are the CSF findings in viral meningitis?

White cell count (Pleocytosis = white cells in CSF)
Lymphocytic, usually

33

What is the gold standard test for viral meningitis?

Viral PCR

34

When should you do a CT scan before lumbar puncture?

If there are:
Focal neurological signs, Presence of papilloedema, Continuous or uncontrolled Seizures or GCS ≤12
Clotting

35

What samples are needed to do a enterovirus PCR?

Throat swab/ stool sample

36

What are you testing for if you do a serology test?

Mumps
Epstein Barr Virus /Cytomegalovirus
HIV
Other viruses as indicated, e.g. travel-related

37

What is the general treatment of viral meningitis?

Start appropiate Iv antibiotics ( cefotaxime) if any risk of bacterial meningitis.

No specific treatment in viral meningitis, might treat HSV and VZV with aciclovir

Mainly supportive therapy --> analgesia and antipyretics

38

What is the outcome of viral mengitis?

Generally good prognosis but some evidence that long term patients can have headaches and cognitive dysfunction.

It is notifiable

39

What are the symtpoms and treatment of enteroviral mkenigitis?

Fever, vomiting, anorexia, rash, upper respiratory tract symptoms are common
No specific treatment
Full recovery normal

40

When is enteroviral meningitis usually present?

Most common cause

Classically late summer/autumn epidemics

41

What does HSV1 and 2 cause?

HSV1 – causes cold sores and viral encephalitis

HSV2 – causes genital herpes and meningitis --> 2nd most common cause

42

When does HSV2 cause viral meningitis?

Can follow primary infection (3-12/7 after genital lesions) or occur during/between relapses

43

Does aciclovir have a profound effect in preventing viral meninigitis?

No evidence that aciclovir is effective

44

What is Mollaret's meningitis?

Repeated aseptic meningitis and commonest cause is HSV2

45

What does varcieela zoster virus usually cause?

Primary = chickenpox (varicella)

Secondary = shingles (zoster)

46

When does VZV cause viral meningitis?

Meningitis unusual but can occur during chickenpox, shingles (so look for a rash), on its own, or after vaccination

47

What cases of mumps causes viral meningitis?

10-30% of cases

48

What is the onset of mumps causing viral meningitis?

CNS symptoms 5 days after onset of parotitis

Other features:
Abdominal pain
Orchitis

49

What are the assoicated features of a HIV patient with viral meningitis?

Fever
Lymphadenopathy
Pharyngitis
Rash

50

What is the main cause of viral Encephalitis?

Herpes Simplex Virus (1 & 2)
(90% are HSV 1)

51

What are other causes of encephalitis?

VZV, EBV, CMV
Measles
Mumps
Enteroviruses (including polio)

Bacteria (e.g. Strep pneumoniae, Neisseria meningitidis, TB)

Acute disseminated encephalomyopathy (ADEM

52

What are the clinical features of encephalitis?

Altered mental state (confusion/bizarre behaviour -> coma)
Fever
Headache
Meningism (may be absent)

+/- Focal neurology:
Seizures - Cranial nerve palsy
Weakness - Ataxia
Dysphasia/aphasia

53

What investigations are done for encephalitis?

Blood tests:

CT – likely to be necessary before LP

MRI – may see changes typical of HSV encephalitis
Lumbar puncture: Same test as meningitis
EEG:
In HSV encephalitis 75% will show abnormal temporal lobe activity

54

What part of the brain does HSV1 attack?

Temporal lobe

55

What are the findings of encephalitis?

Same as viral meningitis

56

What is the treatment of encephalitis?

High dose IV aciclovir
10mg/kg tds
14-21 days

Start on clinical suspicion (do not wait for CSF results – it is a medical emergency)

Oral switch not recommended
Insufficient evidence to recommend steroids

57

Herpes Simplex Encephalitis has a high incidence in what group of people?

Under 20's and over 50's.

Equal distribution beteen Males and Females

58

What is the primary cause of Herpes Simplex Encephalitis ?

Direct transmission of the virus along the neural/olfactory pathway

59

What is the reactivation cause of Herpes Simplex Encephalitis?

So reactivation at the trigeminal ganglia

60

What is the pathogenisis of Herpes Simplex Encephalitis ?

Acute focal necrotising encephalitis
Inflammation / swelling of brain tissue

61

What is the outcome of Herpes simplex Encephalitis?

Mortality if untreated: 70%

Mortality if treated remains high:
28% at 18 months
If GCS

62

What are the possible complications with HSE?

Paralysis

Speech loss

Personality change

63

What is Acute disseminated encephalomyelopathy (ADEM)?

Immune-mediated CNS demyelination

64

Cause of Acute disseminated encephalomyelopathy (ADEM)?

Can follow viral illness or vaccination (e.g. influenza)

65

What are the clinical features of ute disseminated encephalomyelopathy (ADEM)?

Clinical features same as encephalitis
CSF findings = viral meningitis.
MRI helpful.

66

What is the treatment and outcome of ADEM?

Treatment is immunosupressants and steroids.

Recovery is variable

67

What is the symptoms of brain abscess?

Insidious onset of fever, headache, +/- neck stiffness
+/- Altered conscious level, seizures, focal neurological signs

Usually bacterial, may be parasitic

68

What is the action of the skulll and verterbral column in terms of protection?

They protect the brain and spinal cord from mechanical pressure and spread of infection

69

Invasion by microrganism can occur via 2 ways , what are they?

Blood-borne invasion
Blood-brain barrier
Blood CSF barrier

Ascend up via the Peripheral nerves

70

What is the normal cell count in a healthy person?

less than 5

71

What is the normal glucose and protein levels in a normal healthy person?

Glucose 2.5-4 mmol/L

Protein 0.15-0.4g/L

72

What is the cell count and cell type of a person with bacterial meningitis?

greater than 200 and polymorphs cell type

73

What is the glucose and protein level of a bacterial meningitis comapred to normal?

Glucose

74

What is the cell count and cell type of viral meningitis?

20-200 and Lymphocytes

75

What is the glucose and protein level of viral meningitis compared to normal?

Glucose --> normal or reduced
Protein--> Normal or increased

76

What is the cell count and cell type of TB and Cryptococcus meningitis?

20-200 cell count

Cell type: lymphocytes

77

What is the glucose and protein levels of TB meningitis compared to normal?

Reduced glucose levels

Increased Protein levels

78

What is the glucose and protein levels of Crypotococcus meningitis compared to normal?

Normal or reduced Glucose levels

Increased Protein levels

79

How many capsular types of Neisseria meningitides is there? What are the 5 most common types?

13 capsular types: A, B, C, W135, Y most common

80

Where is the natural habitat of the Neisseria meningitidis?

Natural habitat in nasopharynx
5-20% carriers (increased in smokers)
Half carried strains non-capsulate

81

What type of bacteria is Neisseria meningitidis?

Gram negative diplococci
Require blood for growth

82

How many capsular types of Neisseria meningitidis is there?What are the 5 most common types?

13 capsular types: A, B, C, W135, Y most common

83

How can Neisseria meningitis be detected?

Can also be detected by nucleic acid amplification (PCR)

84

How does Neisseria meningitis survive in the blood stream?

Presence of a capsule - protects against complement-mediated bacteriolysis and phagocytosis
Ability to modify host cell inflammatory processes ie. host cell cytokine production

85

What is the mode of action of Neisseria meningitis?

Able to cross the BBB and multiple in the subarachnoid space

86

What are the 4 common infections caused by Neisseria meningitidis?

Fulminant (suddenly and quickly) septicaemia
Septicaemia with purpuric rash

Septicaemia with meningitis

Pyogenic (purulent) meningitis with no rash

87

What are less common infections caused by neisseria meningitidis?

Chronic meningococcal bacteraemia with arthralgia (pain in joint)

Focal sepsis

Conjunctivitis = is a common condition that causes redness and inflammation of the thin layer of tissue that covers the front of the eye

Endophthalmitis= is an inflammation of the internal coats of the eye

88

What is the treatment against neisseria meningitidis?

Ceftriaxone, cefotaxime--> first line
Penicillin = If the strain is sensitive to it will use penicillin




89

When do you give chemoprophylaxis to treat Neisseria meningitidis?

When there is contact of invasie disease so close or kissing contacts.

Give rifampicin and ciprofloxacin

90

What vaccinations are there aginst neisseria meningitis?

Active gainst group A, C and W135

Not active against group B

91

Is the prevelance of Neisseria meningitidis constant throughout the year?

No fluctuates over time, winter peaks, variable serogroup predominance

92

What are local outbreaks of Neisseria meningitidis dependent on?

Population of susceptible individuals

High transmission rate

Virulent, capsulate strain

93

What is the carriage of Haemophilis influenza?

Restricted to humans
Only 5-10% carry capsulate strains

Blood loving” : Unable to grow in the absence of blood or certain constituents of blood

94

How does Haemophilis influenza enter the blood stream?

Present in the throat carriage.
It invades the submucosa
Then invades the blood stream

95

What type of bacteria is Haemophilus influenza?

Small, pleopmorphic Gram negative cocco-bacilli or bacilli

96

What can Haemophlis influenza cause and in who?

Meningitis
Infants > 2months – 2 years

97

How many strains of Haemophlis influenzae is there and which caues the most invasive disease?

Six antigenic types a-f
Type b causes the most invasive disease

Some strains produce polysaccharide capsule

98

What is the structure of Type B capsule?

Fimbriae. IgA proteases, Outer membrane proteins/lipolysaccahride

99

Does Haemophilis influenza cause influenza?

NO

100

What is the treatment of Haemophils influenzae?

Ceftriaxone, cefotaxime
Ampicillin
β-lactamase producing strains common

101

What Chemoprohylaxis is given for invasive contact?

Rifampicin

102

What has been the effect of H.infleunza Type B conjugate vaccine?

Massive reduction in the incidence of invasive disease

103

What type of bacteria is Streptococcus pneumoniae?

Gram positive cocci, with cells in pairs

104

What does Strep. pneumoniae require to grow?

Requires blood or serum for growth. α-haemolytic activity on blood

105

What colour does agar look when Strept. pneumoniae has been cultured?

Green colour

106

How many types of polysaccahride capusle does Strept. penumoniae have?

95 cpsular types

107

Where is the normal habitiat of Strept. pneumoniae?

Human respiratory tract

108

How is Strept. pneumonia transmitted?

Transmission is via droplet spread

109

What is Optochin?

It is a chemical used in cell culture technizues for the presumptive identification of Steptococcus pneumoniae

110

What age is Pneumococcal meningitis seen in?

Seen in all ages

111

Who is at more risk of getting infected by pneumococcal meningitis?

More common and more severe in elderly.

Also more common in immunocompromised patients

112

What is the treatment for Pneumococcal meningitis?

Cefriaxone and cefotaxime

113

Do you give chemoprophlaxis of close contact in treatment for Pneumococcal meningitis?

No

114

When should steroids be given for adults with meninigitis?

Must be given shortly before or with first dose of antibiotics.

Be given if S.penumoniae is suspected but no benefit in meniningcoccal meningitis?

115

What antibiotic should be given and for how long for treating a adult with meningitis?

Dexamethasone 0.15 mg/kg IV every 6 hours x 2-4 days

116

What causes Pneumococcal meningitis?

Streptococcus pneumoniae

117

What infections causes neonatal meningitis?

Group B beta-haemolytic Streptococci
Escherichia coli
Listeria monocytogenes

118

What are the different onset times of neonatal meningitis?

Early ( 5 days). Usually meningitis

119

What is the treatment of Neonatal meningitis?

Cefotaxime

Ampicillin and gentamicin:
Ampicillin covers all streptococci
Gentamicin covers all E.coli

120

What is the complications with meningitis?

Death

Overwhelming sepsis
Raised intracranial pressure

Longer term problems

Deafness
Delayed development
Seizures
Stroke
Hydrocephalus

121

What are the causes of lymphocytic meningitis?

Viral meningitis --> most common

Spirochete bacteria ( e.g.treponemal and borelia)

Polio virus can cause meningitis that may lead to paralysis

TB

122

What is the diagnosis difficult of Tb meningitis?

Acid fast bacilli often not seen on microscopy
Delay in diagnosis leads to a worse prognosis

123

What is the treatment for Tb meningitis?

12 months standard TB treatment
Steroids beneficial

124

What staining do you do for direct detection of TB? Why don't you do alcohol and acid fast?

Don't do alcohol and acid fast as the stain does not wash off.

Use Ziehl Neelsen stain
Or
Flourescent antibody stain

125

What is the cause of brai abscess?

Usually bacterial

Spread of organisms from adjacent structures
e.g. middle ear, sinuses: Streptococci anaerobes

Blood stream spread e.g Staphylococcus aureus

126

What is the diagnosis and treatment of brain abcess?

Need brain imaging to confirm the diagnosis
Prolonged course of antibiotic therapy

127

How does a patient become in contact with Toxomplasma gondii encephalitis and how do you get toxoplasmosis?

Exposed to under cooked food or cat faeces

Sits in the brain asymptomatically and is activated when the immune system is weakend.

128

What is the cause of Crypotococcal meningitis?

Cryptococcus is a yeast

129

What stain can you see cryptococcal meningitis?

Indian ink stain

130

In what patients is cryptoccocal meningitis a common problem in? What is the onset rate?

Common problem in patients with late stage HIV

Insidious onset

131

How is crpytococcal meningitis treated?

Prolonged course of treatment with amphotericin, flucytosine or fluconazole.

132

At what age is encephalitis caused by Japanese encephalitis virus common?

Most commonly affects children

133

What is the prognosis of encephalitis caused by Japanese encephalitis virus?

One third die in the acute illness
One third left with severe long term neurological disability
One third recover

134

How is rabies encephalitis and Japanese encephalitis virus prevented?

By vaccine

135

What type of bacteria is Clostridum tetani?

Gram positive spore forming bacillus

Terminal round spore (drumstick)

Strict anaerobe

136

How does clostridium tetani spread?

Organism widespread in the soil

Implantation of contaminated soil into a wound

Wound may be major or minor

137

What organism caues tetanus?

Clostridium tetani

138

How does Clostridium tetani cause tetanus?

It is not invasive but produces tetanospasmin a neurotoxin

139

How does the tetanospasmin work and spread?

Toxin genes plasmid encoded

Toxin spreads via bloodstream and retrograde transport

Binds to ganglioside receptors and blocks release of inhibitory interneurones

Convulsive contraction of voluntary muscles

140

What is the most common entry site of clostridium tetani?

Through the foot

141

What is the symptoms of Tetanus?

Tonic muscle spasms
Trismus
Opisthotonus

Respiratory difficulties

Cardiovascular instability
(sympathetic nervous system)

142

What is the treatment and prevention for tetani?

Treatment:
Antitoxin (horse or human)
Penicillin or metronidazole

Drugs for spasms
Muscle relaxants
Respiratory support

Prevention--> Toxoid

143

What infections have 1st line treatment of Ceftriaxone, cefotaxime?

Haemophilus influenzae

Neisseria meningitidis

Streptococcus pneumoniae

144

What is brain abscess?

A brain abscess is a focal suppurative process within the brain parenchyma (pus in the substance of the brain)

145

Is the cause of brain abscess due to one or multiple organisms?

Usually polymicrobial (mixed).

146

What is the most common cause of brain abscess?

Streptococci (60-70%) e.g. Streptococcus “milleri” --> pus forming

147

How does S. Aureus cause Brain abscess?

10-15%) most common after trauma/surgery

148

What are the Gram negavtive enteric bacteria that cause brain abscess?

E.coli, Pseudomonas spp

149

What other organisms can cause brain abscess?

Fungi, Mycobacterium tuberculosis, Toxoplasma gondii, Nocardia, Actinomyces

150

What are the 4 clinical setting in which brain abscess can develop in?

Direct spread from “contiguous” suppurative focus (e.g. from ear, sinuses, teeth)

Haematogenous spread from a distant focus e.g. endocarditis, bronchiectasis (often multiple abscesses)

Trauma (e.g., open cranial fracture, post-neurosurgery) --> S.aureus

Cryptogenic --> common in immunocompromised people

151

What is the clinical presentation of brain abscess?

Headache --> most common
Focal neurological deficit
Confusion
Fever ( use funduscope and if seen then not good

152

What is the management of brain abscess?

Drainage is treatment of choice (N.B small abscesses can be treated with antibiotics alone)

153

What is the aim draining brain abscess?


To urgently reduce intracranial pressure

Due to trauma or severe : to confirm diagnosis

Could be something else: like a lesion

To obtain pus for microbiological investigation

To enhance efficacy of antibiotics --> some treatment cannot penetrate through pus

To avoid spread of infection
into the ventricle

154

What is the difficulty in giving antibiotic treatment for brain abscess?

The physiological properties of the blood-brain barrier and the blood-CSF barrier are distinct
Penetration of drugs into the CSF and brain tissue differ
Can make it hard to achieve therapeutic concentrations in intracranial pus

155

What antibiotics achieve therapeutic concentrations in intracranial pus?

Ampicillin, penicillin, cefuroxime, cefotaxime, ceftazidime, and metronidazole

156

What is the empirical treatment regime for Sinugenic/odontogenic abscess?

iv cefotaxime 2g 6-hourly +
iv metronidazole 500mg 8-hourly

157

What is the empirical treatment regime for Otogenic abscess

iv benzyl penicillin 2.4g 6-hourly +
iv ceftazidime 2g 8-hourly +
iv metronidazole 500mg 8-hourly

Drained abscess: treat for 4-6 weeks, “oral switch” can be an option

158

What are the complications of brain abcess?

Raised intracranial pressure, mass effect, coning

Rupture (usually into ventricles) causing ventriculitis

159

What is subdural empyema?

Infection between dura and arachnoid mata

160

What are the causes of subdural empyema?

Causes: (often polymicrobial) anaerobes,
Streptococci
Aerobic Gram negative bacilli,
Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus

161

How does infection spread to cause subdural empyema?

Spread of infection from sinuses (50-80%), middle ear and mastoid (10-20%) or distant site (5%, haematogenous) and following surgery or trauma

162

What is the clinical presentation of subdural empyema?

Headache, fever, focal neurological deficit, confusion, seizure, coma

163

What is the management of sudural empyema?

There should be urgent surgical drainage of pus, antimicrobial agents

Culture of pus should guide antibiotic therapy

164

When is Ventriculoperitoneal (VP) shunt and external ventricular drain (EVD) used?

Inserted into there ventricle to monitor intracranial pressure or drain CSF in patients with hydrocephalus

165

What is the problem with Ventriculoperitoneal (VP) shunt and external ventricular drain (EVD)?

It can cause infection on the VP shunt and EVD as it can become colonised with orgnaisms that can lead to vasculitis

166

How do you diagnose Ventriculoperitoneal (VP) shunt and external ventricular drain (EVD) infection?

By CSF microscopy and culture

167

What is the most common cause of Ventriculoperitoneal (VP) shunt and external ventricular drain (EVD) infection?

Coagulase-negative staphylococci.

It is normal skin flora that is introduce to the device at time of indroduction.

It can either block the device or the bugs spill into the ventricle and other structures

168

What is the treatment for entriculoperitoneal (VP) shunt and external ventricular drain (EVD) infection?

Treatment: device removal, intraventricular antibiotics