Week 7 - CNS Pathology Flashcards
In relation to the dura, where do dural arteries run?
Above the dura mater
What are the major differences between extradural and subdural haemorrhage?
Subdural = bridging veins between arachnoid and dura mater, drain into venous sinuses. Bleeds from tears in subdural space. Dura intact.
Extradural = dural arteries (i.e. middle meningeal artery) torn by traumatic fracture –> blood under arterial pressure and causing dura to separate from periosteum of skull
What are the 3 different mechanisms of stroke?
1) Thrombosis
2) Embolism
3) Haemorrhage
What % of CO and O2 consumption is the brain responsible for?
15% CO
20% O2 consumption
What are different ways in which hypoxia of brain tissue can occur?
Decreased partial pressure of O2
Reduced O2 carrying capacity of blood
Inhibition of O2 utilisation in tissue
Ischaemia
How does ischaemia lead to injury in CNS?
Reduction in ATP can lead to inappropriate release of excitatory amino acids (glutamate) and cell damage via excessive Ca2+ influx into cells (free radical generation and mitochondrial injury)
What is penumbra?
At risk tissue surrounding core necrotic area, which can undergo recovery with restoration of blood flow, or may progress to apoptosis if injury too severe/non reversible
Where does watershed ischaemic impact the brain?
Most distal aspects of arterial supply - in cerebral hemispheres this is between anterior and middle cerebral artery distributions
What pathological process is responsible for the majority of thrombosis related stroke?
Atherosclerosis
What are the most common sites of primary thrombosis in CNS?
Carotid bifurcation
Origin of MCA
Either end of basilar artery
What distribution do EMBOLIC phenomena usually affect?
MCA
What is the clinical presentation of MCA stroke?
Contralateral weakness and sensory loss of face and arms
IF left hemisphere, dysphasia, motor aphasia, receptive aphasia
IF right hemisphere, heme-neglect
**Eye deviation towards side of lesion and away from weak side
What is clinical presentation of ACA stroke?
Contralateral leg paresis and sensory loss
What is clinical presentation of PCA stroke?
Contralateral hemianopia or quadrantanopia
CN III and IV palsy
What are neurological symptoms suggestive of anterior circulation occlusion/TIA?
Amaurosis fugax
Aphasia
Hemiparesis
Hemisensory loss
Hemianopia visual loss
What are neurological symptoms associated with posterior circulation occlusion/TIA?
Diplopia
Vertigo
Vomiting
Choking/dysarthria
Ataxia
Transient global amnesia
What is subfalcine herniation? What symptoms can it cause?
Below falx cerebri —> causes herniation of singular gyrus below the fall and compresses anterior cerebral artery
Can cause gait/motor disturbance
What is uncle herniation and what symptoms does it cause?
Uncus = part of temporal lobe
Herniation is uncut through tentorium cerebelli
Can cause compression of oculomotor nerve, and post ganglionic parasympathetic fibres –> causing ‘down and out’ appearance of eye due to compression of sympathetic supply to the eye –> mydriasis
What is tonsillar herniation? What does this cause?
Cerebellar tonsils herniate through foramen magnum (coning)
Cardiorespiratory centres compressed –> arrest
What is the most common subtype of aneurysm?
Berry/Saccular
Where are aneurysms most commonly found?
Major arterial branch points of anterior circulation (i.e. junction of anterior cerebral artery and anterior communicating artery
Are aneurysms congenital?
No - but can be genetically predisposed or have environmental risk factors
- Genetic: PCKD, Ehler’s Danlos, Marfans, NF
- Environmental: HTN, Smoking
What space do aneurysms bleed into when ruptured?
Subarachnoid space
What are the acute CNS pathologies linked to acute hypertension?
- Lacunar infarct
- Slit haemorrhage
- Hypertensive encephalopathy
- Intracranial haemorrhage
What is the mechanism of lacunar infarct in HTN?
Deep penetrating arteries to the basal ganglia can develop arteriolar stenosis and become occluded, leading to small cavity infarcts/lacunae. Occur in thalamus, internal capsule, caudate nucleus and pons.
What are the symptoms of hypertensive encephalopathy?
- Headaches
- Vomiting
- Confusion
- Seizure
What types of intracranial haemorrhages are considered primary hypertensive bleeds?
Intraparenchymal
Subarachnoid
Other than HTN, what other factors can contribute to spontaneous intraparenchymal haemorrhage?
Coagulopathy
Neoplasm
Vasculitis
Aneurysm
Vascular malformations
What are the different routes of CNS infection?
1) Haematogenous spread
2) Direct implantation (trauma, surgery)
3) Local extension (sinuses, nasal cavity, teeth, cranial OM)
4) Transport along peripheral nervous system (rabies, VZV)
What is meningitis? How is it classified?
Inflammation of the leptomeninges and CSF within subarachnoid space.
Acute pyogenic (bacterial)
Aseptic (viral)
Chronic (TB, cryptococcus)
What are causative organisms in acute pyogenic meningitis in neonates?
E. coli
Group B strep
S. aureus
What are causative organisms in acute pyogenic meningitis in infants?
Haemophilus influenzae
Strep pneumoniae
What are causative organisms in acute pyogenic meningitis in adolescents?
N. meningitidis
What are causative organisms in acute pyogenic meningitis in elderly?
Strep pneumoniae
Listeria monocytogenes
What are the characteristic CSF findings of bacterial meningitis?
High neutrophil count
High protein count
Low glucose
What are common causative organisms in aseptic meningitis?
What about encephalitis?
Meningitis = Enterovirus, measles, influenzae
Encephalitis = HSV 1 and 2, CMV, HIV
What is the CSF characteristics of viral meningitis?
elevated lymphocytes
moderate protein
normal glucose
What is the most common CNS tumour < 15 years?
Astrocytoma
< 15 more commonly infratentorial
> 15 = 80 % supratentorial tumours
What is the clinical triad of Parkinson’s disease?
Bradykinesia
Rigidity
Tremor
What is the pathogenesis of Parkinson’s disease?
Loss of dopaminergic neurons in substantial Nigra = functional decrease in dopamine content
What other neurocognitive/autonomic symptoms accompany Parkinson’s disease?
Autonomic: postural hypotension, urinary and faecal incontinence
Cognitive: dementia, hallucinations
What is Guillain-Barre Syndrome?
Disease of PNS, characterised by ascending neuropathy
What is the pathogenesis of Guillian Barre?
Acute onset immune mediated de-myelinating neuropathy - Type II hypersensitivity reaction.
Usually after recovering from an acute, influenza like illness
What are organisms are implicated in Guillian barre?
Campylobacter
CMV
EBV
Mycoplasma pneumoniae
What is the clinical presentation of Gillian barre?
Ascending paralysis
Loss of deep tendon reflexes
CSF: high protein, low pleocytosis/cell count
What is Wernicke’s syndrome?
Alcohol induced amnesic disorder characterised by lack of Thiamine (B1) resulting in necrotic lesions in thalamus, brainstem
What is the triad of Wernicke’s syndrome?
- Nystagmus
- Ataxia
- Confusion
**Acute and reversible process
What is Korsakoff’s?
chronic, only partially reversible disease of EtOH with anterograde amnesia, confabulation, persisting beyond intoxication and withdrawal.
