Pathology of the Brain Flashcards
What commensal bacteria is normally found in the central nervous system?
NONE
CNS is normally sterile!
How can microorganisms gain entry the CNS?
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
What are the leptomeningies and how are they affected in meningitis?
inner two meningeal layers
(arachnoid and pia mater)
inflammed in meningitis with collection of pus (neutrophil infiltration)
Patients with meningitis must always have a non-blanching rash?
TRUE / FALSE
FALSE
meningitis can exist with or without a septicaemia (causing a non-blanching rash)
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)
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
Why may patients with chronic meningitis caused by TB present with cranial nerve palsies?
TB causes granulomatous inflammation
meningies become fibrosed/scarred
cranial nerves become compressed as they exit the foramina
What are 3 potential complications of meningitis?
Death
Raised ICP
Cerebral Infarction
Cerebral Abscess
Subdural Empyema
What pathogen commonly causes encephalitis?
Viruses
What is the underlying pathology in encephalitis?
disease of brain parenchyma
(not meningies)
neuroncal cell death cause by virus replication and cell rupture
How may a patient present with encephalitis?
Headache
Nausea and Vomiting
Confusion
Seizures
Neurological Deficit
Altered Level of Consciousness
What is a prion?
a protein
normal constituent of synapse with unclear function
How do mutated prions cause disease and how can they get into the body?
mutated prions can occur via 3 mechanisms:
- sporadic mutation
- familial inheritance
- ingested
mutated prions interact with normal prions and cause a post translational conformational change
What is the effect of the post translational conformational change that occurs following fusion of a prion with a mutated prion?
aggregations form within neuronal cells that lead to cell death
holes appear in grey matter of the brain
(spongiform encephalopathies - due to appearance)
Give two examples of prion disease
BSE
in Cows
Variant Creutzfeld-Jacob Disease (vCJD)
in humans
Provide a definition of dementia
acquired global impairment of intellect, reason and personality without impairment of consciousness
Give two examples of types dementia
Alzheimer’s Dementia
Vascular Dementia
Lewy Body Dementia
Outline the role of Tau proteins in Alzheimer’s disease
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
What are senile plaques seen on histological sample of patients with Alzheimer’s disease?
plaques around neurones, formed of aggregated amyloid protein
Other than Tau protein, name another protein that can build up in cells and vessels that contributes to Alzheimer’s disease
Amyloid
due to abnormal mutations on 3 genes on chromosome 21
What is the normal range for intracranial pressure?
0 - 10mmHg
How can the body’s normal physiological responses help to reduce ICP?
Reduced Blood Flow/Volume to Brain
(can compensate up to an ICP <60mmHg)
Reduced CSF Volume
Brain Atrophy
(longer term)
What is Cushing’s reflex?
Significant Hypertension
&
Reflex Bradycardia
(due to compression of medulla)
all in response to a rising ICP > in an attempt to maintain perfusion
What are 3 potential anatomical effects of a space occupying lesion in the skull?
displacement of midline structures
deformation or destruction of brain around lesion
internal herniation
What is a subfalcine herniation?
cingulate gyrus pushed under the free edge of the falx cerebri
causes ischaemia of medial parts of brain in frontal and parietal lobe
Which cerebral artery is typically damaged in a subfalcine herniation?
Anterior Cerebral Artery
Which area of the brain moves significantly during a tentorial herniation?
uncus/medial part of parahippocampal gyrus moves over the tentorial notch
Which strucutres are at signifcant risk with a tentorial herniation?
occulomotor nerve (CN III)
posterior cerebral and superior cerebellar arteries
What is a Duret haemorrhage that frequently occurs with a tentorial herniation?
secondary haemorrhage into the brainstem (midbrain/pons)
What is a tonsillar herniaton?
cerebellar tonsils are pushed into the foramen magnum > compressing the brianstem
Why are primary brain tumours rare in adults?
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)
Is a meningioma a malignant or benign neoplasm?
Benign
Which supporting cells in the CNS commonly cause malignant neoplasms?
Astrocytes
(cause astrocytomas)
What is the most common cause of malignany neoplasms in the CNS?
metastasis
commonly from colon or lung
What are the two broad classifications of stroke?
Cerebral Infarction (ischameic)
Cerebral Haemorrhage
What common risk factors are shared between stroke and MI, and why?
common risk factors as both are vascular diseases
Hyperlipidaemia
Hypertension
Diabetes
Male
What are 2 pathological processes that can lead to an interupted blood supply to the brain and cause stroke?
Embolism
(mural thrombus, atrial fibrillation)
Thrombosis
(forming over an atheromatous plaque in carotid arteries)
e.g. thrombus occuring in basilar artery
Within which 2 locations can a cerebral haemorrage cause stroke?
Intracerebral Haemorrhage
Subarachnoid Haemorrahe
What condition prediposes patients to intracerebral haemorrhages?
Hypertension
(hypertensive vessel damage)
Deposition of Amyloid
(cause vessels walls to become weakened)
What is the common source of bleeding in a subarachnoid haemorrhage?
rupture of ‘berry’ aneurysms
found at branching points of the Circle of Willis
How many a patient present with a subarachnoid haemorrhage?
DEATH
Thunderclap Headache
Loss of Consciousness
Sentinal Headache
(worsening due to rising ICP/bleeding)
