Case 5 Flashcards
What is a stroke?
Sudden attack of weakness usually affecting one side of the body due to interrupted flow of blood to the brain
Deficit Lasts more than 24hrs or leads to death
What are the two types of stroke?
Ischaemic - thrombus/embolism prevents flow (80%)
Haemorrhagic - rupture of a cerebral artery wall
What are stroke risk factors?
Asian and black African
Age (>40)
Male
Hypertension
Hypercholesterolemia
Diabetes
Cigarette smoking
Family history
CVD
What is ischaemic strokes linked to?
Neurological deficits, headaches, seizures
What is the penumbra?
Area surrounding immediate area of infarct
Blood supply is compromised but not cut off and cells are not dead but under threat
What three things cause ischaemic damage?
Neurotransmitters - glutamate
Ions - calcium and sodium
Free radicals - abnormal oxygen molecules
The mechanisms that lead to ischaemic damage are?
Excitotoxicity
Reperfusion injury
Free radical formation (oxidative stress)
Apoptosis
Inflammation
Peri-infarct depolarisation
What is excitotoxicity?
Hypoxia leads to decrease ATP production hence failure of pump channels
Influx of calcium and sodium ions causes increase glutamate release
Calcium ions cause formation of free radicals
Results in necrosis at onset of injury
How does calcium ion overload lead to free radical production?
Mitochondrial injury
Increased production of Nitric Oxide
Protease Activation
Phospholipase activation
All these lead to cell death via apoptosis
What does the production of free radicals result in?
Lipid ms and proteins peroxidation
DNA damage
How does apoptosis occur?
Oxidative stress > mitochondrial injury > cytochrome C released from mitochondria > paracaspases activated to cascades > DNA damage and apoptosis
Why does inflammation occur?
Due to potent inflammatory response caused by brain damage
What is the charesteristic of inflammation?
Heat (Calor); redness (rubor); swelling (tumor); pain (dolor); lost of function (function laesa)
What are investigations for stroke?
- FAST
- CT and MRI - CT best for haemorrhage, MRI for infarction
What are the clinical features of a stroke?
Limb weakness on contralateral side, contralateral hemiplegia/hemiparesis w/ facial weakness, aphasia (when dominant hemisphere is affected); extensor plantar response
What is a Doppler ultrasound for?
Assessing blood flow to neck and head - if internal carotid artery stereos is present a carotid bruit is heard
Electrocardiogram identifies cardioembolic source
Echocardiogram looks for structural abnormalities or thrombi
Blood test for cardiac enzymes to detect myocardial infarction
How is an ischaemic stroke treated?
Drugs for hypertension, heart disease and diabetes (propranolol and ramipril)
Endarterectomy
Speech therapy
Anticoagulants (warfarin/heparin)
Antiplatelet agents (aspirin)
Thrombolysis (rule out haemorrhage with CT and then administer tPA w/in 4.5hrs of stroke onset)
How to treat haemorrhage stroke?
Anticonvulsant
Antihypertensive (reduce BP and other risks of heart disease)
Osmotic diuretic (reduce intracranial pressure)
What is a Transient Ischaemic Attack?
Focal neurological deficit lasting less than 24hrs and causing temporary ischaemia
What is amauroses fungax?
Sudden loss of vision in one eye due to embolus in retinal arteries
What is transient global amnesia?
Episodes of amnesia/confusion lasting several hrs due to posterior circulation ischaemia
More common in over 65yo
Over what period of time do some patients regain function affected by stroke?
3-6months
What is neuroplasticity?
Extraordinary ability of the brain to modify its own structure and function following changes within the body or in external environment
It is strongest during childhood (this is a why childhood stroke recovers quickly)
This is built upon synaptic pruning - removing weak synaptic connections and keeping strong ones
Where are ischaemic events more common?
Middle cerebral artery
What is the different types of intracranial haemorrhages?
- subarachnoid: headaches, Nuchal rigidity, photophobia, neurologic deficits
- subdural: headaches, drowsiness, confusion caused by rupture of bridging veins
- extradural: ipsilateral dilated pupil and contralateral hemiparesis caused by rupture of middle meningeal artery second to temporal bone fractures
What is carotid stenosis ?
Narrowing of internal carotid caused by atherosclerotic disease or sudden drop in systemic blood pressure
Leads to:
MCA - contralateral face-arm or face-arm-leg weakness
ACA - leg weakness
Ophathalmic artery - amauroses Fungax
What is muscle tone?
Continuous and passive partial contraction of muscles
Where are skeletal muscle movements initiated?
Lower motor neurones in the spinal cord and brainstem that directly innervate skeletal muscles
What are gamma motor neurones?
They innervate specialised intramural muscle fibres and function to regulate sensory input by setting the intramural muscle fibres to an appropriate length
Muscle tone and tension
What are intrafusal muscle fibres?
aka muscle spindles
Specialised muscle fibres that serve proprioceptors
What are alpha motor neurones?
They innervate extrafusal muscle fibres for posture and skeletal movement
Muscle Power and Strength
What is a motor unit?
A single alpha motor neurone and all the muscles fibres it innervates
What are slow twitch muscle fibres?
Slow oxidative fibres (Type I)
Innervated by small alpha motor neurones
Rich blood and myoglobin supply
Lots of mitochondria
Resistant to fatigue
Good for posture maintenance
What are intermediate muscle fibres?
Fast oxidative-glycolytic fibres (Type IIA)
ATP generated by substrate-level phosphorylation (glucose > lactic acid)
Used in walking and slow pace running
What are fast twitch muscle fibres?
Type IIB - fast glycolytic fibres
Innervated by large alpha motor
Release energy via glycolysis
Fewer mitochondria
Easily fatigued
Used for jumping and running
How do stretch reflex work?
type Ia and type II afferent neurones innervate spindle > info relayed to alpha motor neurones (one to extensor and other to flexor muscle) > muscle tone
Gamma motor fibres maintain the contraction (tension) in the intrafusal fibre
What is the job of golgi tendon organs?
These are proprioceptive that sense muscle tension caused by active contraction of the muscle
How does the golgi tendon circuit work?
1b axons to 1b inhibitory interneurones > alpha motor neurones to the same muscle
Negative feedback regulating muscle tension
What is the flexion reflex pathway?
A sensory stimulus via a nociceptor (A-delta afferent fibre) causes motor neurones to extensor and flexor muscles (one inhibits and other excites) to withdraw the foot from stimulus
The opposite thing happens on the contralateral half to allow for postural support
What does damage to lower motor neurones cause?
Paralysis/paresis in affected muscle
Loss of reflexes
Loss in muscle tone
Atrophy of affected muscles
Fibrillations and fasciculations (spontaneous twitches)
What is the premotor cortex?
Area of motor cortex lying within frontal lobe
It uses information from other cortical regions to select movements appropriate to the context of the action
What does medial premotor cortex do?
It mediates selection of movement
It responds more so to internal cues rather than external
What does an Upper Motor Neurone Déficit cause?
Weakness of muscle on contralateral side
Abnormal babinski sign
Increased muscle tone (spasticity)
Hyperactive reflexes
Clonus (sustained)
[the later 3 causes loss of ability to perform fine movements]
What is the babinski sign?
Stroking the sole of the foot resulting in flexion of big toe
UMN damage causes extension of big toe and fanning of the other toes
What does clonus mean?
Involuntary contractions and relaxations of muscles in response to muscle stretching
What is decerebrate rigidity?
Extensive UMN damage causes rigidity of extensor muscle of the leg and flexor muscle of the arm
When does anxiety become abnormal?
When it is:
• excessively intense/ disproportionate to stimulus
- continues beyond exposure to danger
- triggered by harmless situations
- occurs without cause
- can’t be controlled
- impairs function
What structure is anxiety disorder associated with?
Dysfunction of the amygdala
What are the different types of anxiety?
Panic disorder, phobias, OCD, generalised anxiety disorder (GAD) and PTSD
Each include symptoms of anxiety
What is GAD?
a state of inappropriate and sometimes severe anxiety, without adequate cause that lasts for at least six month
It’s long term condition
What are the characteristics of GAD?
free floating anxiety not linked to a specific cause or situation
Excessive, uncontrollable and often irrational worry about everyday things - disproportionate to the actual source of worry
When is the common onset of GAD?
20s
What are the causes of GAD?
Genetics, anxious personality, negative life events, childhood traumas, major stress in life, physical illness and drug harm (alcohol)
What are the three types of signs and symptoms seen with GAD?
Psychological
Physical
Behavioural
How is GAD diagnoses?
Operation diagnoses - a person must experience a number of symptoms for a minimum amount of time and symptoms must cause: significant disease and be associated with impairment in everyday function
DSM-5
ICD-10
How does ICD-10 diagnose GAD?
6 out of 12 diagnostic criteria in ICD-10
Symptoms >6months in DSM-5
Not restricted or focused to a particular circumstance
How is GAD treated?
- Short-term treatment = benzodiazepines
- long-term = beta-blockers/SSRI/SNRI
- long term = Pregabalin
What is the stress response?
Reaction to stressors (threatening stimuli)
Avoidance behaviour, increased vigilance and arousal, activation of sympathetic division of ANS, release of cortisol (stress hormone) from adrenal glands
What responses is the hypothalamus involved in?
Humoral
Visceromotor
Somatic motor
Which structures control the Corticotrophin-releasing-hormone (CRH) neurones of the hypothalamus?
Amygdala - fear response
Hypocampus - suppresses CRH release
What does Benzodiazepines do?
Increases the inhibitory effect of GABA between gamma-2 and alpha-1 subunits of the GABA-A receptor
Diazepam is the choice for acute anxiety
What is memory?
Mental capacity to store and later recall or recognise events that were previously experienced
What is the process of memory?
Receive, encode, modify and retrieve information
Stage:
Perception, storage and retrieval
What is short term memory?
Lasts seconds to minutes
Limited capacity 7 (+/- 2) pieces of information
Acoustic code (Engram)
Areas of activity include frontal and parietal lobe
What is long term memory?
Capacity is possibly unlimited
Semantic code
Activity spread throughout the brain but hippocampus is essential for consolidation (learning)
What are the four types of memory?
- Procedural - memory for actions, skills (acquired through practicing)
- Declarative - conscious effort of explicit information
- implicit - non-conscious form of learning from unaware experiences
- explicit - conscious process of remembering (attention is crucial)
