Pathology of the Brain

Question 1

What commensal bacteria is normally found in the central nervous system?

Answer 1

NONE

CNS is normally sterile!

Question 2

How can microorganisms gain entry the CNS?

Answer 2

Direct Spread

middle ear infection / basal skull #
(photo shows abcess from middle ear inf)

Haematogenous Spread

sepsis / infective endocarditis

Iatrogenic

V-P shunt / lumbar puncture

Question 3

What are the leptomeningies and how are they affected in meningitis?

Answer 3

inner two meningeal layers
(arachnoid and pia mater)

inflammed in meningitis with collection of pus (neutrophil infiltration)

Question 4

Patients with meningitis must always have a non-blanching rash?

TRUE / FALSE

Answer 4

FALSE

meningitis can exist with or without a septicaemia (causing a non-blanching rash)

Question 5

What are the common causative organisms of meningitis in the following age groups:

Neonates

2-5 Years (toddlers)

5-30 Years (adolescents)

Over 30 Years (older adult)

Answer 5

Neonates

• E. coli

2-5 Years (toddlers)

• H. influenzae type B (HiB)

5-30 Years (adolescents)

• N. meningitidis (gm -ve diplococci, intracellular)

Over 30 Years (older adult)

• S. pneumoniae

Question 6

Why may patients with chronic meningitis caused by TB present with cranial nerve palsies?

Answer 6

TB causes granulomatous inflammation

meningies become fibrosed/scarred

cranial nerves become compressed as they exit the foramina

Question 7

What are 3 potential complications of meningitis?

Answer 7

Death

Raised ICP

Cerebral Infarction

Cerebral Abscess

Subdural Empyema

Question 8

What pathogen commonly causes encephalitis?

Answer 8

Viruses

Question 9

What is the underlying pathology in encephalitis?

Answer 9

disease of brain parenchyma
(not meningies)

neuroncal cell death cause by virus replication and cell rupture

Question 10

How may a patient present with encephalitis?

Answer 10

Headache

Nausea and Vomiting

Confusion

Seizures

Neurological Deficit

Altered Level of Consciousness

Question 11

What is a prion?

Answer 11

a protein

normal constituent of synapse with unclear function

Question 12

How do mutated prions cause disease and how can they get into the body?

Answer 12

mutated prions can occur via 3 mechanisms:

1. sporadic mutation
2. familial inheritance
3. ingested

mutated prions interact with normal prions and cause a post translational conformational change

Question 13

What is the effect of the post translational conformational change that occurs following fusion of a prion with a mutated prion?

Answer 13

aggregations form within neuronal cells that lead to cell death

holes appear in grey matter of the brain

(spongiform encephalopathies - due to appearance)

Question 14

Give two examples of prion disease

Answer 14

BSE
in Cows

Variant Creutzfeld-Jacob Disease (vCJD)
in humans

Question 15

Provide a definition of dementia

Answer 15

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

Question 16

Give two examples of types dementia

Answer 16

Alzheimer’s Dementia

Vascular Dementia

Lewy Body Dementia

Question 17

Outline the role of Tau proteins in Alzheimer’s disease

Answer 17

loss of cortical neurones due to abnormally phosphorylated tau proteins that would normally stabalise microtubules in neurones

abnormal tau aggregates to form collections witin neurones > then unable to function and die

Question 18

What are senile plaques seen on histological sample of patients with Alzheimer’s disease?

Answer 18

plaques around neurones, formed of aggregated amyloid protein

Question 19

Other than Tau protein, name another protein that can build up in cells and vessels that contributes to Alzheimer’s disease

Answer 19

Amyloid

due to abnormal mutations on 3 genes on chromosome 21

Question 20

What is the normal range for intracranial pressure?

Answer 20

0 - 10mmHg

Question 21

How can the body’s normal physiological responses help to reduce ICP?

Answer 21

Reduced Blood Flow/Volume to Brain
(can compensate up to an ICP <60mmHg)

Reduced CSF Volume

Brain Atrophy
(longer term)

Question 22

What is Cushing’s reflex?

Answer 22

Significant Hypertension

&

Reflex Bradycardia
(due to compression of medulla)

all in response to a rising ICP > in an attempt to maintain perfusion

Question 23

What are 3 potential anatomical effects of a space occupying lesion in the skull?

Answer 23

displacement of midline structures

deformation or destruction of brain around lesion

internal herniation

Question 24

What is a subfalcine herniation?

Answer 24

cingulate gyrus pushed under the free edge of the falx cerebri

causes ischaemia of medial parts of brain in frontal and parietal lobe

Question 25

Which cerebral artery is typically damaged in a subfalcine herniation?

Answer 25

Anterior Cerebral Artery

Question 26

Which area of the brain moves significantly during a tentorial herniation?

Answer 26

uncus/medial part of parahippocampal gyrus moves over the tentorial notch

Question 27

Which strucutres are at signifcant risk with a tentorial herniation?

Answer 27

occulomotor nerve (CN III) posterior cerebral and superior cerebellar arteries

Question 28

What is a Duret haemorrhage that frequently occurs with a tentorial herniation?

Answer 28

secondary haemorrhage into the brainstem (midbrain/pons)

Question 29

What is a tonsillar herniaton?

Answer 29

cerebellar tonsils are pushed into the foramen magnum \> compressing the brianstem

Question 30

Why are primary brain tumours rare in adults?

Answer 30

CNS contains permenant tissue \> therefore as it does not divide, tumours do not commonly occur *(this is not the case in children due to growth and development)*

Question 31

Is a meningioma a malignant or benign neoplasm?

Answer 31

Benign

Question 32

Which supporting cells in the CNS commonly cause malignant neoplasms?

Answer 32

Astrocytes *(cause astrocytomas)*

Question 33

What is the most common cause of malignany neoplasms in the CNS?

Answer 33

metastasis *commonly from colon or lung*

Question 34

What are the two broad classifications of stroke?

Answer 34

Cerebral Infarction (ischameic) Cerebral Haemorrhage

Question 35

What common risk factors are shared between stroke and MI, and why?

Answer 35

common risk factors as both are vascular diseases Hyperlipidaemia Hypertension Diabetes Male

Question 36

What are 2 pathological processes that can lead to an interupted blood supply to the brain and cause stroke?

Answer 36

Embolism *(mural thrombus, atrial fibrillation)* Thrombosis *(forming over an atheromatous plaque in carotid arteries)* *e.g. thrombus occuring in basilar artery*

Question 37

Within which 2 locations can a cerebral haemorrage cause stroke?

Answer 37

Intracerebral Haemorrhage Subarachnoid Haemorrahe

Question 38

What condition prediposes patients to intracerebral haemorrhages?

Answer 38

Hypertension *(hypertensive vessel damage)* Deposition of Amyloid *(cause vessels walls to become weakened)*

Question 39

What is the common source of bleeding in a subarachnoid haemorrhage?

Answer 39

rupture of '**berry**' aneurysms found at branching points of the **Circle of Willis**

Question 40

How many a patient present with a subarachnoid haemorrhage?

Answer 40

DEATH Thunderclap Headache Loss of Consciousness Sentinal Headache *(worsening due to rising ICP/bleeding)*