S8 L3 Introduction to neuropathology Flashcards
What is meant by infections of the CNS?
CNS is normally sterile
No commensal bacteria
Immune privileged site
How can micro-organisms gain access to the CNS?
- Direct spread → Middle ear infection, base of skull fracture
- Blood-borne → sepsis, infective endocarditis
- Iatrogenic → VP shunt, surgery, lumbar puncture
What is meningitis?
Inflammation of the leptomeninges → pia and arachnoid mater (inner layers)
With or without septicaemia- non blanching rash (sign of meningococcal septicaemia not meningitis)
Prompt diagnosis and treatment is life saving → acute inflammation, oedema, swells the brain, congestion of BV, neutrophils and pus → ↑ICP → death if not treated
What are the causative organisms of bacteria meningitis?
Different age groups different prominent bacteria
Various ones in immunocompromised individuals e.g. fungi
DONT need to learn- just be aware
1. Neonates → E.Coli, L.monocytogenes
2. 2-5 years → H. influenzae type B (HiB)
3. 5-30 years → N. Meningitides (types)
4. Oer 30 years - S. pneumoniae
What is chronic meningitis?
Rare disease Chronic clinical course M. tuberculosis → Granulomatous formation → Fibrosis of the meninges → Nerve entrapment If left untreated or in immunocompromised patients→ more progression → cranial nerve problems
What are the complications of meningitis?
Local
- Death (swelling → RICP)
- Cerebral infarction → neurological defect
- Cerebral abscess → bit of infection becomes walled off, antibiotics unable to reach it
- Subdural empyema → infection (pus) in potential space between meninges
- Epilepsy → damages particular areas of the brain
Systemic (if associated with septicaemia)
What is encephalitis?
Classically viral not bacterial
Inflammation of the brain parenchyma not the meninges → can occur as a complication of meningitis
- Neuronal cell death by virus → inflammation and presence of inclusion bodies
- Lymphocytic infiltrate typical → chronic inflammation- swelling of the brain
- Different areas of the brain affected by different viruses
→ Temporal lobe affected by Herpesvirusus (most common)
→ Spinal cord affected by polio (now eradicated)
→ Brainstem affected by rabies (very rare)
What is prions disease?
- Prion protein (PrP) → normally found in synapses (unknown function)
- Mutated PrP → PrPsc
- Sporadic, familial or ingested
- Mutated PrP (PrPsc) can interact with normal PrP - undergoes post translational conformational change by protein-protein interactions alone
- PrPsc is extremely stable - resistant to disinfectants, irradiation etc…, not susceptible to immune attacks- ‘self protein’
- Forms aggregates in the brain which results in damage
What does prions disease result in?
Spongiform encephalopathies - brain looks like a sponge
- Scrapie in sheep
- BSE in cows
- Kuru in tribes of New Guinea
- Variant Creutzfeld-Jacob disease (vCJD)
What is variant Creutzfeld-Jacob disease?
- Linked to ingestion of prions
- Much higher prion load compared to classical CJD
- Earlier age death (28 years)
- More prominent psychiatric symptoms
- Prolonged incubation period 15+ years
Is prion disease an infection?
Unclear
Does not fulfil Koch’s postulate
- Microorganism must be found in abundance in all organisms suffering from disease but not found in healthy organisms
- Must be isolated from diseased organism and grown in pure culture
- Cultured microorganism should cause disease when introduced into a healthy organism
- Organisms must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent
What is dementia?
Acquired global impairment of intellect reason and personality without impairment if consciousness
- AD → 50% → Sporadic/familial, early/late
- Vascular dementia → 20% → Not enough blood getting to the brain
- Lewy body
- Picks disease
What is Alzheimers disease?
- Exaggerated aging process
- Loss of cortical neurones → ↓brain weight, cortical atrophy (shrinkage)
- Due to ↑neuronal damage → neurofibrillary tangles, senile plaques
- Amyloid deposition central to pathogenesis
What is a tangle in Alzheimer’s disease?
- Intracellular twisted filament of Tau protein
- Tau normally binds and stabilises microtubules
- Tau becomes hyperphosphorylated in AD
- Tauopathy
What is a senile plaque in AD?
- Foci of enlarged axons, synaptic terminals and dendrites
- Amyloid deposition in centre of plaque associated with BV
- Builds up around BV → abnormal and fragile → reduced blood flow to brain → ischaemia
What is the familial cause of AD?
Trisomy 21 associated - Down syndrome
Early onset AD
Mutation in 3 genes in chromosome 21
- Amyloid precursor protein (APP) gene
- Presenilin (PS) genes 1 and 2 code for components of secretase enzyme
Incomplete breakdown of amyloid precursor protein → amyloid deposited → where they build up determines pathology
What is normal intracranial pressure?
- 0-10mmHg
- Coughing/straining can increase it to 20mmHg
- Compensatory mechanism in place to deal with fluctuations
→ ↓blood flow
→ ↓ CSF volume
→ Chronic elevation → brain atrophy - Cerebral blood flow can be maintained as long as the ICP < 60 mmHg
What is a space occupying lesion?
e.g. tumour, haemorrhage
Deforms or destroys surrounding brain tissue
Displacement of midline structures - loss of symmetry, midline shift
Can result in brain herniation
- Subfalcine herniation
- Tentorial herniation
What is a hernia?
Protrusion of an organ or part of an organ through wall that normally contains it
What is subfalcine herniation?
- Cingulate gyrus pushed under the free edge of the falx cerebri
- Herniated brain can become ischaemic due to compression of anterior cerebral artery
- Normally loops up around the corpus callosum
What is a tentorial herniation?
- Medial part of temporal lobe - uncus- pushed down through the tentorial notch - free edge of tentorium cerebelli
- Compress ipsilateral oculomotor nerve → down and out eye
- Ipsilateral cerebral peduncle causing ipsilateral third nerve palsy but contralateral UMN signs in limbs?????????
- Complicated by brainstem haemorrhage (Duret haemorrhage) → often fatal
- Usual mode of death for those with large brain tumours or severe intracranial haemorrhage
What is a tonsilar herniation?
Cerebral tonsils pushed into the foramen magnum compressing the brainstem
What is Cushing reflex?
- Physiological response to ↑ICP
- Blood vessels compressed so body unable to get -blood to brain
- Detects the ↑systemic pressure to try and push more and more blood to the brain → ↑ICP even more → sustainable for short period of time → herniation of brain
- Compress cardiorespiratory centres in the brainstem → Bradycardia
Reflex bradycardia - ↑↑ BP ↓HR
Brain coning
What are brain tumours?
Generally rare
- Benign
→ Meningioma - meningeal origin, often accidental finding or develop epilepsy then find it
- Malignant
→ Astrocyte origin - astrocytoma (grade 1- 4)
Others
- Neurofibroma (Schwann cell origin PNS or cranial nerves)
- Ependymoma (ependymal cells lining ventricular system)
- Neuronal tumours (from neurones, extremely rare)
- Non-CNS tissue
→ Lymphoma
→ Metastases (most common of all brain tumours)
