Infections, tumours and ICP control

Question 1

How do pathogens gain entry to CNS

Answer 1

Direct - otitis media, base of skull fracture
Blood borne - sepsis, infective endocarditis
Iatrogenic - VP shunt, surgery, LP

Question 2

What is inflamed in meningitis

Answer 2

Leptomeninges (pia and arachnoid)

Question 3

Causative organisms of meningitis in each age group

Answer 3

Neonates: Ecoli, listeria monocytogenes
2-5: haemophilus influenzae B
5-30: Neisseria meningitidis
>30: strep pneumoniae

Question 4

Complications of meningitis

Answer 4

Raised intracranial pressure 
Cerebral infarction 
Cerebral abscess 
Subdural empyema
Epilepsy

Question 5

Causative organism in chronic meningitis and complication of this type of infection

Answer 5

Mycobacterium tuberculosis

Can cause fibrosis of leptomeninges around brainstem leading to focal CN lesions

Question 6

What is encephalitis

Answer 6

Inflammation of brain parenchyma causing neurone death

Question 7

Causative organisms of encephalitis for different parts of brain

Answer 7

Temporal lobe: herpes virus
Spinal cord motor neurones: polio
Brainstem: rabies

Question 8

What commonly causes encephalitis in elderly/immunocompromised

Answer 8

Herpes zoster

Can be mild to severe

Question 9

What are prions

Answer 9

Normal soluble proteins found in neuronal synapses

Question 10

How do prions become mutated

Answer 10

Sporadically
Familial
Ingesting mutated prions

Question 11

Why are prions not pathogens

Answer 11

Only fulfil 1 of Koch’s postulates (found in all organisms suffering from disease)

Question 12

What do mutated prions cause and how

Answer 12

Spongiform encephalopathies
Mutated prions interact with normal prions causing a post translational conformational change leading to a mutated prion aggregate.
Thee aggregates cause neuronal death and lead to holes in the grey matter.

Question 13

Examples of spongiform encephalopathies

Answer 13

BSE
Scrapie
Variant Creutzfeldt-Jacob disease

Question 14

Definition of dementia

Answer 14

Acquired global impairment of intellect, reason and personality without impairment of consciousness

Question 15

What damages cholinergic neurones in AD

Answer 15

Neurofibrillary tangles - twisted filaments of Tau protein formed by hyperphosphorylation

Senile plaques - abnormal BV due to amyloid deposition in centre of plaque. Foci contain synaptic terminals, dendrites and enlarged axons

Question 16

Why does early onset AD have a higher prevalence in trisomy 21

Answer 16

3 genes are mutated:

Amyloid precursor protein
Presenilin 1 + 2 (make secretase to break down amyloid)

Question 17

Normal ICP

Answer 17

5-15 mmHg

Question 18

When is an above normal ICP pathological

Answer 18

Raised for at least several minutes

Question 19

Up to what ICP can compensatory mechanism work to maintain cerebral blood flow

Answer 19

60 mmHg

Question 20

How does the brain maintain blood flow in high ICP

Answer 20

Decreased blood volume
Decreased CSF volume
Brain atrophy (in chronic)

Question 21

What is a space occupying lesion of the brain

Answer 21

Deform or destroy brain around lesion leading to loss of symmetry and eventual herniation

Question 22

3 types of brain herniation

Answer 22

Subfalcine
Tentorial
Tonsilar

Question 23

Describe a subfalcine herniation

Answer 23

Ipsilateral cingulate gyrus is pushed under free edge of falx cerebri
Anterior cerebral artery occlusion so ischaemia of frontal, parietal and corpus collosum

Question 24

Describe a tentorial herniation

Answer 24

Uncus herniates through tentorial notch

Damages ipsilateral CNVIII and occludes posterior cerebral and superior cerebellar arteries

Question 25

What is a duret haemorrhage

Answer 25

Haemorrhage into brainstem (fatal)

Can be secondary to tentorial herniation

Question 26

Describe a tonsilar herniation

Answer 26

Cerebellar tonsils pushed into foramen magnum which compresses brainstem (rapidly fatal)

Question 27

Features of primary brain tumours

Answer 27

Very rare as cells don’t divide

Never metastasise

Question 28

Examples of benign brain tumours

Answer 28

Meningioma

Neurofibroma

Question 29

Example of malignant brain tumour

Answer 29

Astrocytoma

Question 30

Where do astrocytomas spread to

Answer 30

Along nerve tracts

Sub arachnoid space

Question 31

Percentage occurrence of types of stroke

Answer 31

85% infarction

15% haemorrhage (10% intracerebral and 5% subarachnoid)

Question 32

Describe causes of intracerebral haemorrhage

Answer 32

Hypertensive vessel damage
Charcot-Bouchard aneurysm rupture
BV amyloid deposition in elderly

Question 33

Causes of subarachnoid haemorrhage

Answer 33

Rupture of berry aneurysm (at branching points of circle of Willis)