10. Neuropathology

Question 1

Via what 3 routes can microorganisms gain entry to the CNS? Give an example of each.

Answer 1

Direct spread eg middle ear infection or base of skull fracture.
Blood-borne eg sepsis or infective endocarditis.
Iatrogenic eg lumbar puncture, surgery or ventriculoperitoneal shunt.

Question 2

What are the 2 main causative organisms of meningitis in neonates?

Answer 2

E. coli and L. monocytogenes.

Question 3

What is the main causative organism of meningitis in 2-5 year olds?

Answer 3

H. influenzae type B.

Question 4

What is the main causative organism of meningitis in 5-30 year olds?

Answer 4

N. meningitides.

Question 5

What is the main causative organism of meningitis in the over 30s?

Answer 5

S. pneumoniae.

Question 6

What is the causative organism of chronic meningitis?

Answer 6

M. tuberculosis.

Question 7

What is seen pathologically in chronic meningitis?

Answer 7

Granulomatous inflammation.
Fibrosis of meninges.
Nerve entrapment.

Question 8

Name 3 complications of meningitis

Answer 8

Death due to raised intracranial pressure.
Cerebral infarction leading to neurological deficit.
Cerebral abscess.
Subdural empyema.
Epilepsy.
Septicaemia.

Question 9

What is encephalitis?

Answer 9

Viral infection of the parenchyma of the brain.

Question 10

What causes spongiform encephalopathies?

Answer 10

Mutated prion aggregates causing neuronal death and holes in grey matter.

Question 11

What is the definition of dementia?

Answer 11

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

Question 12

What is seen pathologically in Alzheimer’s disease?

Answer 12

Loss of cortical neurones - decreased brain weight and cortical (gyral) atrophy. Marked ventricular dilation, reflecting the loss of white matter.
Neurofibrillary tangles - intracellular twisted filaments of Tau protein which has become hyperphosphorylated.
Senile plaques - form at the foci of enlarged axons, synaptic terminals and dendrites, with amyloid deposition in vessels in the centre of the plaque (amyloid-beta plaques).

Question 13

What is normal intracranial pressure?

Answer 13

0-10mmHg.

Question 14

What 3 compensation mechanisms maintain normal intracranial pressure?

Answer 14

Reduced blood volume - maintain cerebral blood flow as long as ICP <60mmHg.
Reduced CSF volume.
Brain atrophy.

Question 15

What happens pathologically in a subfalcine herniation?

Answer 15

Herniation occurs on the same side as the mass. The cingulate gyrus pushes under the free edge of the flax cerebri. The anterior cerebral artery becomes compressed, leading to ischaemia of the medial parts of the frontal and parietal lobe and corpus collosum and so results in infarction.

Question 16

What happens pathologically in a tentorial herniation?

Answer 16

The uncus/medial parahippocampal gyrus herniates through the tentorial notch. Leads to damage to the oculomotor nerve on the same side (blown pupil) and occlusion of blood flow in the posterior cerebral and superior cerebellar arteries.

Question 17

Why can tentorial herniation be fatal?

Answer 17

Secondary haemorrhage into the brainstem - duret haemorrhage.

Question 18

Tentorial herniation is a common mode of death in patients with what brain pathologies?

Answer 18

Large brain tumours and intracranial haemorrhage.

Question 19

What happens in a tonsilar herniation?

Answer 19

Cerebellar tonsils are pushed into the foramen magnum compressing the brainstem.

Question 20

What is the most common benign brain tumour?

Answer 20

Meningioma.

Question 21

Astrocytomas are the most common primary malignant tumours of the brain, how do they spread?

Answer 21

Spread along the nerve tracts and through the sub arachnoid space.

Question 22

How to astrocytomas often present?

Answer 22

With a spinal secondary.

Question 23

What is the definition of a stroke?

Answer 23

Sudden event producing a disturbance of the CNS function due to vascular disease.

Question 24

Considering a stroke is a vascular disease, name 2 risk factors.

Answer 24

Hyperlipidaemia.
Hypertension.
Diabetes mellitus.

Question 25

Give 3 of the most common causes of embolism and thrombosis leading to a stroke.

Answer 25

Embolism - AF, mural thrombus, atheromatous debris, thrombus over ruptured atheromatous plaque, aneurysm.
Thrombosis - over atheromatous plaque.

Question 26

What is a lacuna infarct?

Answer 26

An infarct of less than 1cm. Is associated with hypertension and commonly affects the basal ganglia.

Question 27

What are intracerebral haemorrhages causing a stroke associated with?

Answer 27

Hypertensive vessel damage.
Charcot-Bouchard aneurysms.
Deposition of amyloid around cerebral vessels in the elderly.

Question 28

What are subarachnoid haemorrhages causing a stroke associated with?

Answer 28

Rupture of berry aneurysms at branching points in the Circle of Willis.

Question 29

Give 2 risk factors for subarachnoid haemorrhage.

Answer 29

Male.
Hypertension.
Atheroma.
Has links to other diseases.

Question 30

What is seen clinically in a subarachnoid haemorrhage leading to stroke?

Answer 30

Sentinel headache leading to a sudden severe ‘thunderclap’ headache.
Loss of consciousness.
Often instantly fatal.