Infections of the CNS

Question 1

petechial/purpuric rash

Answer 1

doesnt go away when pushed with glass

Question 2

Complications - meningitis

Answer 2

May affect 20+% of survivors

Seizures
Hearing difficulties
Other cranial nerve problems Focal paralysis Hydrocephalus
Intellectual disability
Ataxia

Question 3

Complications - sepsis

Answer 3

Limb amputations
Arthritis and join pain
Skin necrosis and scarring
Organ dysfunction: liver, kidney, adrenal glands

Question 4

meningitis

Answer 4

inflammation of the meninges

Question 5

encephalitis

Answer 5

inflammation of brain parenchyma

Question 6

sepsis

Answer 6

life-threatening organ dysfunction caused by dysregulated host response to infection

Question 7

Blood-brain barrier (BBB)

Answer 7

– Tightly packed endothelial cells line the blood vessels in the brain mechanically supported by thin basement membrane.
– Breach by infectious agents causes encephalitis.

Question 8

Blood- cerebrospinal spinal fluid (CSF) barrier

Answer 8

– Similar barrier at arachnoid membrane and in ventricles.

– Breach by infectious agents causes meningitis.

Question 9

• Direct Spread to the CNS via

Answer 9

• Sinuses
• Otitis media
• Skull fracture

Question 10

how is the BBB breached

Answer 10

– Growing across & infecting cells comprising barrier
– Passive transfer in intracellular vacuoles
– Carriage across in infected white blood cells

Question 11

what are the three causes of meningitis

Answer 11

• infection
• auto-immune
• malignancy

Question 12

what are the dangers of neonatal meningitis - early onset

Answer 12

• Occurs <7 days
• Infected by heavily
colonised mother
• Premature rupture of membranes
• Pretermdelivery
• 60%fatalityrate

Question 13

what are the dangers of neonatal meningitis - late onset

Answer 13

• Occurs <3 months
• Lack of maternal
antibody
• Poor hygiene in nursery • 20%fatalityrate

Question 14

Neisseria meningitidis

Answer 14

Only infect humans
Normal microbiota in nasopharynx
Transmission by droplet spread or direct contact from carriers At least 12 serotypes - different in polysaccharide antigens
5 pathogenic serogroups strains – A, B, C, W135, Y

Question 15

Haemophilus influenzae

Answer 15

Six capsular serotypes (a-f) known to cause disease

Most virulent strain is H. influenzae type b (Hib)

Question 16

Streptococcus pneumoniae

Answer 16

• Normal microbiota in nasopharynx
• There are over 90 bacterial serotypes
• Common cause of meningitis in young children and adults with specific risk factors (e.g. older, diabetic, alcohol excess, asplenic*)
• Pneumococci also causes pneumonia, otitis media and bloodstream infections

Question 17

Babies /small children:

clinical features

Answer 17

– Tense or bulging soft spot on their head
– Refusing to feed
– Irritable when picked up, with a
high pitched or moaning cry
– A stiff body with jerky movements, or else floppy and lifeless

Question 18

• Blood test

Answer 18

– Biochemistry: U&E, CRP, lactate, glucose
– Haematology: FBC, clotting
– Microbiology: Blood culture, meningococcal & pneumococcal PCR, HIV test

Question 19

CSF test

Answer 19

– Biochemistry: Protein & Glucose – Microbiology:
• White cell count
• Gram stain & bacterial culture
• Meningococcal & pneumococcal PCR
• Viral PCR tests
• TB: microscopy, molecular tests & culture
• Cryptococcal: Indian Ink, CrAg, fungal culture

Question 20

what are things to remember when taking a lumbar puncture

Answer 20

Measure the opening pressure

Take matched blood and CSF glucose samples Collect enough fluid (and some to spare!)

Question 21

Are there situations when you should delay or omit doing a lumbar puncture?

Answer 21

• Risk of bleeding

* Focal neurology suggesting a mass lesion in the brain

Question 22

When do we need CNS imaging?

Answer 22

An important role of CT, in some patients, is to exclude mass lesions and/or oedema, which might make an LP dangerous.
In these patients a reduction of the CSF pressure below the lesion following an LP could precipitate herniation of the brainstem or cerebellar tonsils.
This may occur in patients with brain abscess, subdural empyema, tumour, or a necrotic swollen lobe in encephalitis.

Question 23

Routine vaccination now against:

Answer 23

• Haemophilus influenzae b
• Pneumococcus
• Meningococcus A,B,C, W, Y
Vaccines against other neurological infections: • Polio, tetanus

Question 24

Viral Meningitis

Answer 24

• Identify by PCR of CSF
• Usually regarded as ‘benign’ & self-limiting
• Long-term neuropsychiatric sequelae have been described – Anxiety, Depression, Neurocognitive dysfunction

Question 25

Encephalitis

Answer 25

Most common cause: Herpes Simplex Virus-1
Symptoms & signs: altered cerebration Confusion, abnormal behaviour, seizures, fever
Investigations: similar to meningitis
Typical findings on CSF, temporal lobe changes on MRI scan
Treatment: high dose IV aciclovir

Question 26

Brain abscess

Answer 26

Pre-disposing factors: otitis media, mastoiditis, sinusitis Causes: often oral nasopharyngeal microbiota
Aerobic (S. aureus, Strep. milleri)
Anaerobic (Bacteroides sp., Fusobacterium sp.) Pathophysiology:
Diffuse inflammation -> focal lesion and pia mater suppuration Symptoms & signs: headache, focal neurology, seizures Investigations: CT / MRI scan +/- invasive sampling
Treatment: Antibiotics (often ceftriaxone + metronidazole)

Question 27

Transmissible Spongiform Encephalopathies (TSEs)

Answer 27

Rare prion diseases
“Proteinacious infectious particles”
Cause vacuoles and plaques in nervous tissue
Highly resistant to heat, chemical agents and irradiation No treatment, no vaccine, fatal