8.3 neuropathology

Question 1

how can microorganisms gain entry into the CNS?

Answer 1

Direct spread (from middle ear, basal skull fracture, even through ethmoid bone)

blood borne in sepsis of infective endocarditis

latrogenic (post neurosurgery, ventriculoperitoneal shunt, lumbar puncture)

Question 2

what is a sign of septicaemia in meningitis?

Answer 2

a non blanching rash = meningococcal septicaemia

Question 3

what are the causative organisms of meningitis in different age groups?

Answer 3

Neonates - E. coli, L. monocytogenes

2-5 yrs - H influenza type B

5-30 yrs - N meningitides

over 30 yrs - S. pneumoniae

Question 4

what are the properties of chronic meningitis?

Answer 4

caused by M tuberclosis

granulomas

meningeal fibrosis

cranial nerve entrapment

bilateral adrenal haemorrhage can be a complication

Question 5

what are the complications of local meningitis?

Answer 5

• death due to raised intracranial pressure
• cerebral infarction (stroke)
• cerebral abscess
• subdural empyema
• epilepsy (due to direct irritation of brain)

Question 6

under what circumstances can you get systemic effects resulting from meningitis?

Answer 6

if you have septicaemia

Question 7

what is encephalitis and its usual causative organism?

Answer 7

inflammation of brain parenchyma and not meninges (but can occur as a complication of meningitis)

usually viral. it kills neurones causing inflammation

NB: Herpes affects temporal lobe

Question 8

what is inflamed in meningitis?

Answer 8

the leptomeninges

Question 9

what is a prion? and how can it mutate?

Answer 9

a normal constituent of synapse function

mutation can be sporadic, familiar or ingested
will then interact with normal prion protein to undergo a post translation conformational change to form a very stable structure

(isn’t susceptible to immune damage as seen as a self antigen)

Question 10

what is prion disease?

Answer 10

when mutated prions aggregate together which destroy neurones and create holes in the grey matter

brain takes on a sponge like appearance = spongiform encephalopathies
(e.g mad cow disease)

Question 11

what is Alzheimers disease (dementia)?

Answer 11

loss of cortical neurones

leads to cortical atrophy and decreased brain weight
damage caused by neurofibrillary tangles and plaques

Question 12

how can neurofibrillary tangles and plaques cause damage in Alzheimers dementia?

Answer 12

tangles

• twist tau protein
• tau normally binds to microtubules
• hyperphosphorlylation = tangle

plaques

• foci of enlarged axons, synaptic terminals and dendrites
• amyloid deposition in centre of plaque associated with vessels
• trisomy 21 associated with Alzheimers disease

Question 13

what is normal intracranial pressure and how is it maintained?

Answer 13

0-10mmHg is normal

coughing/straining can increase it to 20mmHg

compensatory mechanisms in place to compensate for ant rise

• reduced blood and CSF volume
• brain atrophy if chronically elevated

Question 14

how do space occupying lesions affect the brain?

Answer 14

deforms or destroys surrounding brain

displaces midline structures e.g loss of symmetry, midline shift

can cause brain herniation

Question 15

what types of herniations can space occupying lesions in the brain cause?

Answer 15

subfalcine herniation

• cingulate gyrus is pushed under free edge of faux cerebri
• can become ischaemic due to compression of anterior cerebral artery

tentorial herniation

• medial temporal lobe is pushed down through the tectorial notch ( free edge of tentorium cerebella)
• can compress ipsilateral oculomotor nerve and ipsilateral cerebral peduncle = ipsilateral third nerve palsy and contralateral UMN signs int he limbs
• a mode of death

Question 16

what is a benign brain tumour?

Answer 16

meningioma (from meninges)

Question 17

what is a malignant drain tumour?

Answer 17

astrocytoma (astrocytes)
slow growing but difficult to remove

super rare

Question 18

what is a stroke?

Answer 18

a sudden event producing a disturbance of CNS function due to vascular disease

Question 19

what are the risk factors for a stroke?

Answer 19

hyperlipidaemia
hypertension
smoking
diabetes

as its a vascular disease

Question 20

what is the pathogenesis for a stroke?

Answer 20

embolism (most common)

• Heart AF
• atheromatous debris (carotids)
• thrombus over ruptured plaque
• aneurysm

thrombosis
- over atheromatous plaque

Question 21

what is a cerebral infarction?

Answer 21

most common
rupture of a vessel

can be:

regional
- in the territory of a band cerebral artery

Lacunar

• small
• associated with hypertension
• commonly affects basal ganglia and internal capsule

Question 22

what is a cerebral haemorrhage?

Answer 22

usually spontaneous
less common

can be:

intracerebral haemorrhage

• associated with increasing age, hypertensive vessel damage and amyloid deposition in vessels
• get a space occupying lesion

subarachnoid

• rupture of berry aneurysms at branch points of the circle of willis
• can cause secondary spasm of cerebral arteries

Question 23

what are the associations and symptoms of a subarachnoid cerebral haemorrhage?

Answer 23

associations

• male
• hypertension
• atheroscleorisis
• linked to other disorders

symptoms

• thunderclap headache
• preceeded by a senile headache
• loss of consciousness
• often instantly fatal