Aetiology Flashcards
How is each common carotid artery separated?
Separate into the external and internal carotid (system is replicated on right and left side)
What is the external carotid?
Blood supply to the face
What is the internal carotid?
Blood supply to anterior portions of the brain (frontal and middle brain areas)
What are the branches of the internal carotid?
The anterior cerebral artery and middle cerebral artery
What is the other artery that provides cerebral blood supply?
The vertebral artery
What is the vertebral artery?
Vertebral arteries from each side of the body merge at the base of the brain to form the basilar artery
What is the basilar artery?
The basilar artery separates into two posterior cerebral arteries, one for each hemisphere
What are the posterior cerebral arteries?
Blood supply for the posterior portions of the brain
What does the ACA supply?
Lateral superior frontal, medial frontal and parietal lobes
What does the MCA supply?
Lateral inferior frontal/parietal and superior temporal
lobes
What does the PCA supply?
Lateral posterior parietal/occipital and inferior temporal lobes
What are strokes?
A cerebrovascular accident. Has a very sudden onset and occurs when the blood supply to part of the brain is interrupted
What happens when the brain blood supply is reduced?
Brain uses 20% of oxygen we breathe so reduced blood supply means reduced oxygen to brain. Neurons are damaged or destroyed
What is a cerebral infatction?
Death of brain tissue. An infarct is the area of dead tissue
What is an ischaemic stroke?
A blood clot forms, blocking the artery and preventing blood flow to the territories served by that part of the cerebrovascular system, which in turn leads to infarction
What are two types of ischaemic stroke?
Thrombotic (blood clot formed in the brain) and embolic (blood clot formed somewhere else and then travels until it gets stuck)
What are ischaemic strokes associated with?
Atherosclerosis
What is atherosclerosis?
Hardening of the arteries due to a build up of fat, cholesterol and other substances in artery walls. It causes stenosed arteries due to the build-up (narrowing) which makes them more easy to block (ischaemic stroke)
How common are ischaemic strokes?
88% of strokes are ischaemic
What are risk factors for ischaemic stroke?
Smoking, hypertension, obesity, high cholesterol, excessive alcohol consumption
How do ischaemic strokes present (clinical characteristics)?
Infarct is wedge-shaped and more clearly defined. Neurological effects are limited to the part of the brain supplied by that artery (this could be territories of the main artery or sub-arteries, depending on where the clot is)
Why is an understanding of the cerebrovascular system and vascular territories clinically useful?
For localisation of common strike syndromes, as well as prompt diagnosis and intervention
What was the FAST campaign?
Face, arms, speech and time. A campaign that aimed to improve detection of stroke and therefore improve time for help to be given to those that suffered a major stroke. Not all strokes show effects in motor control though (FAS part) and so it had no effect on TIA patients
What is TIA?
Transient ischaemic attack, or, mini stroke, which is a temporary blockage of an artery without acute infarction, resulting in transient episode of neurological impairment
What makes TIA’s less dangerous?
The majority resolve within the first hour and so there is no neuronal death, but also makes them hard to identify
Why is it important to identify TIAs?
They are major risk factors for an ischaemic stroke. 150,000 in the UK have a TIA annually, and of this, 5% will have a major stroke within 24 hours, 17% within 3 months, and 35% within 5 years
What is an intracerebral haemorrhage/intracranial haematoma?
A blood vessel within the brain bursts, allowing blood to leak inside the brain, compressing neuronal tissue. The sudden disruption to blood supply and increase in pressure causes atrophy
How do intracerebral haemorrhages present (clinical characteristics)?
The infarct border is less clearly defined and effects are not limited to the part of the brain supplied by the artery (focal deficits but damage associated with anatomical proximity in addition to vascular territory borders). Symptoms are also progressive as compression increases
What are the risk factors for an intracerebral haemorrhage?
Hypertension (as this can make the vessels weak), smoking, excessive alcohol consumption, males, increasing age, damaged or weakened arteries
What are the mortality rates for ischaemic strokes?
27.9% within 1 month. 40% within 1 year. 69% within 5 years
What are the mortality rates for intracerebral haemorrhage?
58.3% 1 month. 62% 1 year. 76% 5 years
What are predictors of mortality?
Better survival among younger patients. Additional health conditions such as heart diseases/diabetes predict mortality
What are subarachnoid haemorrhages?
Blood vessel just outside the brain bursts, causing blood to leak into the brain and apply sudden direct pressure onto the brain, thereby damaging cells
What are subarachnoid haemorrhages associated with?
Usually result from a cerebral aneurysm (75-80% cases) which is irregular swelling of artery which makes the blood vessel weak and prone to rupture
What are the symptoms of a cerebral aneurysm?
Headache, focal neurological deficits dependent on the location, impaired consciousness, coma and death (immediate death in 43% of cases as many occur near the brainstem)
What are some predictors/risk factors for subarachnoid haemorrhages?
Most are under 60 years old. Women are 1.6x more likely. 5-20% have a family history (the cerebral aneurysm is the hereditary part)
What is the prognosis for subarachnoid haemorrhages?
1/3 remain dependent. Only 19% of those who are independent report no significant decline in quality of life
What are traumatic brain injuries?
Damage to the brain tissue caused by an external force
What are the leading causes of TBI?
Motor vehicle accidents, acts of violence, falls, sports and recreational injuries, lightning strikes and electric shocks (generally more common in males as they are more associated with these causes)
What are the two types of TBI?
Penetrating head trauma and closed head trauma
What is a penetrating head trauma?
Direct tissue injury, eg a gunshot wound
What is a closed head injury?
Blunt head injury and acceleration/deceleration injury (eg in car accidents) causing traumatic haemorrhage and contusion (‘bruising’ in the brain)
What is concussion?
Reversible impairment of neurologic function for a period of minutes to hours following TBI. It is the main first symptom of brain injury
What are the symptoms of concussion?
Loss of consciousness, seeing ‘stars’ (phosphenes caused by change in blood flow/pressure around optic nerve), headache, dizziness, nausea/vomiting, and can be accompanied by retro and anterograde amnesia for a period of several hours surrounding injury
Where do contusions occur?
Regions where gyri touch the ridges of the skull. Often near the temporal pole and frontal pole due to fossa at the bottom the skull
What are two types of injuries that occur from TBI?
Coup and countercoup injury
What are coup injuries?
Damage on the side of impact. Inertia causes mobile brain to slam into skull wall (at the side of the injury)
What are countercoup injuries?
Damage on the opposite side to impact. Mobile brain rebounds and slams into back of skill wall
What impairments occur following TBI?
Depend on the site of the injury
What is tortion?
Mechanical torsion tears white matter fibres deep in the brain (corpus-callosum). Particular type of closed head trauma, eg when a car flips and hemispheres momentarily move in opposite directions)
What are two types of tumour?
Primary CNS tumours which originate in the brain or spinal cord, and metastatic tumours arise from other tissue and spread to the brain
What are examples of tumours?
Meningiomas, gliomas, adenomas, lymphomas, schwannomas
What are symptoms of brain tumours?
Symptoms are closely related to location of the tumour. They aren’t bound by territories so can cross over into other areas. Because damage occurs as the tumour grows, the progression of symptoms/impairments is gradual
What are symptoms of a frontal lobe tumour?
Dysexecutive syndrome
What are symptoms of a parietal lobe tumour?
Left side would be apraxia. RIght side would be neglect
What are symptoms of an occipital lobe tumour?
Contralateral visual impairments
What are symptoms of a temporal lobe tumour?
Memory impairments
What are symptoms of a cerebellar tumour?
Poor coordination
What is an example of an impairment that indicates a highly localised tumour?
Bilateral hemianopia. Occurs when a tumour develops in the pituitary gland (adenoma - close to base of skull so grows upwards towards optic chiasm). Leads to loss of visual information from the nasal half of each retina (temporal visual hemifields)
What is multiple sclerosis?
Autoimmune inflammatory disorder affecting central (not peripheral) nervous system myelin. Discrete plaques of demyelination and inflammatory response appear and disappear in multiple locations over time, causing periods of remission and worsening until it eventually becomes chronic progressive
How prevalent is MS?
0.1% prevalence with a 2:1 female ratio. Peak onset between 20 and 40 years old
What deficits can MS cause?
Can affect numerous nervous systems: motor, visual sensory. Symptoms depend on the affected area and severity varies for individuals
What is the classical definition for MS?
Two or more deficits separated in neuroanatomical space and time
What are two examples of a neurodegenerative disorder?
Alzheimer’s disease and Parkinson’s disease
What is Alzheimers?
A type of dementia (group of symptoms associated with a decline in the way the brain functions, affecting memory and behaviour)
How common is Alzheimer’s?
<65 years is 1%. >85 years is 40%. Slightly more common in females but this is explained by their slightly increased life expectancy
What pathological changes occur in Alzheimers?
Accumulation of a protein (beta-amyloid) which leads to cerebral atrophy. Atrophy is most severe in medial temporal and frontal lobes. Because of this, primary motor, somatosensory, visual and auditory cortices are relatively spared
What are the symptoms of Alzheimers?
Memory loss (particular for recent memories) due to the medial temporal damage, and worsens over time. Anomia and apraxia due to temporo-parietal damage. Behavioural abnormalities due to frontal lobe damage, Advanced Alzheimer’s can have other symptoms that are not included in dementia
How common is Parkinsons?
Affects around 0.15% of the population with a mean onset of 60 years
What is Parkinsons?
A hypokinetic movement disorder (reduced movement)
What are the symptoms of Parkinsons?
Asymmetrical resting tremor (can become bilateral with progression). Cogwheel rigidity (lack of fluidity of movement when moved by someone else). Akinesia (initiation of movement problems). Bradykinesia (slow movement). Postural instability (stooped). Masked facial expressions (hypomimia-have emotional capacity but struggle to move face to express it) and impaired movement sequencing (shuffling gait)
How is movement affected overall?
Unequally. Patients may not be able to run usually, but can when there is a fire. Shuffling fait is improved by putting lines on the floor for the patient to step over. This is because self-initiation of action is the greatest impairment and so movement is better with cues
How can Parkinsons progress?
As it progresses, atrophy also occurs in the cortex, resulting in dementia. Around 29% of patients develop dementia, and presence is correlated with degree of rigidity and hypokinesia (correlated with their motor symptoms)