Infections in the CNS Flashcards
1
Q
What is meningitis?
What is encephalitis?
What is meningoencephalitis?
A
- Meningitis –> inflammation of the meninges
- Encephalitis –> inflammation of the brain (usually viral)
- Meningoencephalitis –> inflammation of the brain and meninges
2
Q
What is myelitis?
What is a brain abcess?
What is a subdural/ epidural abscess?
A
- Myelitis is inflammation of the spinal cord
- Cerebral abscess is a collection of pus within the brain
- Subdural/ epidural abscess is a collection of pus within the subdural/ epidural space.
3
Q
Describe the aetiology of meningitis?
What organisms can cause it?
A
- Meningitis can be caused by bacteria, viruses and fungal infections
-
Bacterial:
- Most common is meningococcus bacteria –> Neisseria meningitidis
- Next common is pneumococcus bacteria –> Streptococcus pneumonaie
-
Group B streptocci
- remember streptococci bacteria are oval shaped, round bacteria that arrange themselves into strips/ form chains
- Haemophilis Influenza type B (HiB)
- Listeria monoctyogenes –> tends to affect older/ younger/ pregnant, caused by ingestion of food with listeria monocytogenes bacterium
- Mycobacterium Tuberculosis (TB) –> insidious as builds up slowly
-
Viral:
- Enterovirus
- HIV
- VZV - varicella zoster virus
- mumps
- measles
-
Fungal:
- Cryptococcus neoformans (commonly found in bird excrement, can infect patients already infected with HIV).
4
Q
What is the aetiology of encephalitis?
what organisms can cause it?
A
- Encephalitis is mostly viral:
- Herpes simplex virus (HSV)
- HIV
- VZV (varicella zoster virus)
- arboviruses –> viruses transmitted by tick
- Rabies
5
Q
What is the aetiology of myelitis?
what organisms can cause it?
A
- Myelitis is virally caused:
- rabies
- poliomyelitis (poliovirus)
6
Q
What is cerebritis?
What causes it?
What causes brain abscesses?
What causes brain cysts?
A
- Cerebritis is infection in the brain that normally leads to the formation of an abscess within the brain itself and is associated with autoimmunity
- Brain abscesses mostly caused by bacteria –> commonly streptococci
- Cysts –> mostly parasitic in cause
7
Q
Describe the epidemiology of meningococcal disease
A
- There are 5 types of meningococcal bacterium –> A, B, C, W, & Y.
- Meningococcal group B (Men B) bacteria are the most common cause of bacterial meningitis un the UK
- Meningococcal group C used to be a common cause of meningitis prior to the introduction of the Men C vaccine in 1999.
- Meningococcal group W used to be rare in the UK, but cases have increased since 2009, Men ACWY vaccine replaced Men C vaccine, given to over 14 yrs - 25 yrs.
8
Q
What age groups does meningitis tend to affect?
A
- Meningitis tends to affects the very young (babies 0-12 months)
- Then tails off until around late teens - early 20’s
- Often attendance at university correlates with later presentation
- Meningococcus bacteria is carried in the backs of many people throats and does not cause them a problem, but can transfer to others and induce infection and immune reaction.
9
Q
Why might it be of interest if a patient has travelling to africa or taken part in the Hajj when considering meningitis?
(Hajj is annual pilgrammage to mecca).
A
- Of interest as there have been a number of outbreaks of meningitis on the Hajj.
- N. meningitidis is found worldwide, but the highest incidence occurs in the “meningitis belt” of sub-Saharan Africa.
- Meningococcal disease is hyperendemic in this region, and periodic epidemics during the dry season (December– June) reach up to 1,000 cases per 100,000 population.
- By contrast, rates of disease in the United States, Europe, Australia, and South America range from 0.15 to 3 cases per 100,000 population per year.
10
Q
What are the clinical features of meningitis and encephalitis?
A
- The symptoms of meningitis and encephalitis have some overlap
- Early meningitis –> sudden fever, headache, leg pain, cold hands and abnormal skin colour
- Later presentation –> meningism:
- Stiff neck
- Photophobia
- drowsiness
- Nausea and vomiting
- Non blanching Rash (purpuric rash) - rash does not disappear when pressed under glass, can present with purpuric rash only, without any other symptoms –> meningococcyeal septicaemia
- Seizures
- Decreased conciousness GCS
- Encephalitis:
- sudden fever
- sudden headache
- odd behaviour/ changes in behaviour
- confusion/ disorientation
- focal CNS signs –> affecting brainstem
- Seizures (more common in encephalitis)
- decreased conciousness on GCS
11
Q
What is the GCS scale?
A
- GCS scale most commonly used scale to monitor levels of conciousness
- Split into best eye, verbal and motor response
- Best Eye response:
- Spontaneously opens (E4)
- To verbal (E3)
- To pain (E2)
- No response (E1)
- Best verbal response:
- Normal speech, fully orientated (V5)
- Confused speech (V4)
- Inappropriate speech (words only) (V3)
- Incomprehensible sounds (V2)
- No response (V1)
- Best motor response:
- Obeys commands - M6
- Localises to pain - M5
- Withdraws from pain - M4
- flexion towards pain - M3
- extension towards pain -M2
- No response -M1
12
Q
How can meningococcal infections overlap with other conditions?
A
- Meningitis can present by itself, where the infection remains only within the CNS
- More often than not it overlaps with septicaemia, where the infection induces systemic inflammatory response
13
Q
What are the specific clinical features associated with meningococcal infections?
A
- Affects children and young adults, often associated with outbreaks
- Acute
- Sepsis
- Purpuric rash
- peripheral gangrene
14
Q
What are the specific clinical features associated with pneumococcal infections?
A
- Associated with RTI’s, trauma and immunocompromised
- Less acute, no rash
- high morbidity and mortality (as effects elderly and those with comorbidities).
15
Q
What are the specific clinical features of Group B streptoccocal infections?
A
- Neonates acquire the bacteria during birth
- Low mortality but risk of CNS damage
16
Q
What are the clinical features of listeriosis?
A
- Listeriosis is associated with:
- neonates/ elderly/ pregnant/ immunocompromised
- meningoencephalitis
- rhomboencephalitis (inflammation of hindbrain - brainstem and cerebellum).
- Positive blood culture –> hence importance of taking blood culture as well as LP.
17
Q
What are the clinical features of Tuberculosis infection?
A
- Tuberculosis infection associated with:
- insidious onset of fever
- coma and confusion
- high CSF protein
- only 8ml required for culture
18
Q
What are the clinical features of Brain absess?
A
- Brain abscess is associated with:
- chronic URTI’s such as sinusitis and otitis media
- insidious onset
- or seizures
19
Q
Explain the management steps that you would take if a patient was presenting with suspected meningitis?
Comment on diagnostic tests/ treatment steps
A
- First identify whether it is pure meningitis or septicaemia:
- Purely meningitis –> photophobia and stiff neck, no shock
- Septicaemia –> purpuric rash, shock, cold peripheries and low BP –> in this case refer to ICU, will take blood cultures, give empirical antibiotics IV, airway support, fluid resuscitation, vasopressors/ +ve inotrope, delay Lumbar puncture until stable
- Meningitis –> Are there any signs of raised ICP? (looking for papilloedema, seizures, focal CNS signs)
- If yes –> get ICU help, delay LP until patient is stable due to risk of coning/ brain herniation via foramen magnum. ICU will take blood culture/ give IV antibiotics / airway support / fluid resusc, monitor until stable.
- If no –> Take blood cultures:
- FBC, Glucose, U & E’s (kidney function), coagulation time (looking for complication of disseminated intravascular coagulation) (APPT- activated partial prothromboplastin time/ PT- prothrombin time)
- Take 2 x blood cultures
- Blood sent for PCR test to identify pathogen
- Consider additional tests for HIV/ TB
- Perform Lumbar puncture within 1 hr:
- Take 3 x samples , 1 and 3 sent for microbiology and microscopy
- Look for RBC (perfect sample has none, decreases with sample number)
- Look for WBC –> help identify organism
- Colour and opening pressure
- Organism for culture
- Protein –> raised due to damage to BBB
- Glucose –> should be low due to use by pathogen/ immune cells
- Give empiral IV antibiotic (ceftriaxone) (do this before LP if waiting longer than 1 hr).
- Give IV dexamethasone
- Monitor, alter antibiotic once results back based on pathogen and sensitivity.
- Patient isolated for 24 hrs
- Inform public health england and local health authority.
- Prophylaxis for immediate contacts of patient
20
Q
What are the factors looked for in a CSF sample from Lumbar puncture?
A
- RBC’s –> perfect sample has no RBC’s , should decrease with consecutive samples (1- 3)
- WBC’s –> identify specific organism
- Colour/ appearance
- opening pressure
- Protein (raised due to BBB damage)
- Glucose (reduced due to metbaolism by immune cells/ infecting agent) (compare to blood glucose).
21
Q
What is abnormal about this CT?
A
- Loss of ventricles and sulci due to raised ICP caused by major inflammation
22
Q
What pathology is shown here?
A
- Large brain abscess in the frontal lobe –> patient presented with personality changes
23
Q
What spinal level is a lumbar puncture done at?
A
- LP done between L3/L4 to avoid the spinal cord which finishes at L1/L2.
- potential risk of damage to spinal nerves coming off cauda equina
24
Q
What is turbid CSF?
A
- Turbid CSF is CSF that is white in appearance due to high WBC count
25
Q
What specific indicators of CSF allow us to make a diagnosis of the cause of meningitis?
A
- 1) opening pressure - anything above 18 cm of water is abnormal = raised ICP
- 2) Appearance –> either cloudy or microoganisms seen –> bacterial
- 3) RCC > 1 per mm3 –> traumatic LP or subarachnoid haemorrhage –> compare sample 1 and 3
- 4) WCC > 5 per mm3 –> abnormal:
- Mostly neutrophils –> bacterial
- mostly lymphocytes –> TB or viral meningitis (or abscess).
- 5) protein > 1g/L = bacterial or TB meningitis
- 6) Glucose –> if less than 50% blood glucose then bacterial or TB
26
Q
Fill the blanks
A
27
Q
Outline the two main pharmacological treatments given for meningitis?
What are their mechanisms of action?
A
- IV empirical antibiotic –> ceftriaxone —> inhibits synthesis of bacterial wall
- Given for 1 week alongside
- Dexamethasone —> agonist at glucocorticoid receptor, antiinflammatory, given to prevent compression injuries in the CNS.
28
Q
Describe how the prognosis can change depending on the type of meningitis infection
A
- Meningococcal meningitis:
- mortality - 10%
- cranial nerve palsies including deafness
- post infective immunological complication –> arthritis and pericarditis
- Meningococcal septicaemia (without meningitis):
- Septicaemia caused by meningococcal bacterium even without meningits has mortality of 40%
- purpuric gangrene and loss of peripheries
- post infective immunological complications –> arthritis and pericarditis
- Pneumococcal meningitis:
- mortality 25%
- Cranial nerve palsies
- Relapse and metastatic infections
29
Q
Explain the prevention procedure for meningitis - both acute and long term prevention
A
- Chemoprophylaxis:
- For household and kissing contacts –> ciprofloxacin 500 mg single dose and rifampacin 600 mg 2/ day for 2 days
- Immunoprophylaxis: Vaccines exist against
- meningococcus A/C/ W135/ Y/ B
- Pneumococcus (7 serotypes)
- Haemophilus influenza type B (HiB)
- some causes of viral meningitis
