Block 12 - Musculoskeletal and nervous system (nervous 2) Flashcards
What are the colours on a CT scan?
Black = fluid
Grey = brain
White = bone
Bright white = blood
Where is an extradural bleed?
What shape is it?
In the extradural space (outside the dura)
Lens shaped bleed
Where is subdural bleed?
What shape is it?
Between the dura
Bioconcave shape
Give 3 examples of diffuse brain injuries
Swelling/inflammation
Hypoxia (neurones damages > reduced oxygen)
Axonal injury > decreased consciousness
What can sheering forces cause to happen after a brain injury?
2 other ways progressive damage occurs
Sheering forces tear the lipid bilayer at the BBB > flux of elements (Ca), inflammation and axon death
Metabolic changes
Free radical formation
Give 4 examples of secondary brain injuries
Increased intracranial pressure
Hypoxia/Ischaemia
Seizures/fits
Infection
Which fracture has increased risk of infection?
Why?
Basal skull fracture
Bacteria enter through tympanic membrane
Explain what happens to cerebral blood flow after a brain injury
Increased ICP in the brain due to increased mass
Brain loses CSF > spinal cord and blood to SVC to balance pressure
Eventually you can balance no more and pressure rises
How does death occur in a brain injury?
Uncus of brain herniates though tentorium causing pressure on the brainstem
Brainstem cones through the foramen magnum
Which nerves will the brain push on first?
What will this do to the eye?
Push on the parasympathetic (they’re outside)
Eye will dilate
Why must you maintain blood pressure during a brain injury?
Blood Pressure - Intracranial Pressure = Cerebral Perfusion Pressure
Must maintain CPP and ICP is increased so BP needs to also increase
What is Cushing’s reflex?
Increased blood pressure when the ICP increases
Define lucid
No symptoms
How long does an MRI scan take?
How expensive is it?
The scan is quick but there’s a little preparation time
The scanner is expensive but scans are cheap
What is the resolution and sensitivity like in an MRI scanner?
Poor time resolution but good spatial resolution
Poor sensitivity
Define precission
When does it occur
Change in the orientation of the rotational axis of a rotating body
Happens to protons in an MRI scanner
How do you obtain an MRI image?
- Apply an electromagnetic radiofrequency pulse at the precision frequency
- Protons absorb energy and change their alignment in respect to the external field (same/opposite direction)
- Remove the RF pulse > protons realign with the external field and emit energy to the scanner to form an image
What is the difference between a T1 and T2 weighted MRI?
T1: white matter white, grey matter grey, CSF dark
T2: white matter dark, grey matter light, CSF very white
What can you use MRI contrast to look specifically for? (4)
Blood flow and volume
Vessel permeability and extracellular volume
Cell density and water movement
Biochemistry and metabolite disruption
What happens to blood vessel permeability as a tumour develops?
Vessels become more ‘leaky’ and haemorrhage more
What does water motion tell you about a cell?
Increased water motion = increased cell density
What does magnetic resonance spectroscopy look at?
Chemicals and metabolites in the brain
What is the spacial resolution of MRS like?
Low spacial resolution as it targets a specific area
What do levels of choline and lactate indicate?
Choline shows normal cell division and density
Lactate indicates anaerobic respiration (tumour)
What is PET?
How does it work?
Proton emission tomography
Patient injected with radioactive isotopes (e.g. glucose)
Brain uses lots of glucose so can see affected areas
What is PET dependent on?
The isotope half life
Long enough for scanning but short for the patient
(amino acids better than glucose but shorter half life)
Resolution, sensitivity and safety or PET
Low spacial resolution
High sensitivity
One scan a lifetime (risky)
What is SPECT?
How does it work?
Single photon emission computed tomography
Same as PET but photon not positron
Resolution, expense and safety or SPECT
Low spacial resolution
Less expensive (isotopes have longer half lives)
Less invasive
How long does an EEG take?
A long time, has a long preparation time
What is the resolution of an EEG?
Good time resolution
Poor spatial resolution (don’t know where signals originate)
What is ECoG?
Electrocorticography
What is the resolution of an ECoG?
Good time resolution
Better spatial resolution
How does an MEG work?
Current flow from neurones > magnetic field on sensors > computer interpretation
What is the resolution of an MEG?
How much does it cost? (what does this mean?)
How long does it take?
Good time and better spatial resolution
Expensive (not clinically established)
Quicker (reduced prep time)
What is the BOLD response?
What is its purpose?
Which imaging technique measures it?
Blood Oxygen Level Dependent response
Exploits the different magnetic properties of Hb and its oxygen status
fMRI
What is fMRI combined with?
EEG/MEG to improve information about neuronal actiivty
What imaging techniques does York University have?
MEG
fMRI
What is brain plasticity and when does it occur?
When the brain recovers from a tumour, other parts of the brain take over the role of the damaged brain
What is fNIRS?
Explain how it works
Function Near-Infrared Spectroscopy
Uses infrared light to measure blood flow by the different absorption properties of oxy / deoxy haemaglobin
Sensor detects the amount of infrared reflected
When is fNIRS used?
In research
In children who cannot stay still in an MRI
Define hyperpolarisation (MRI)
Increased protons aligning with the field
Explain the purpose of single shot hyperpolarised MRI
What is the sensitivity and resolution like (compared to normal MRI)
Enhances structural images based on proton distribution
Increased sensitivity and resolution
Define primary prevention
How can you do it?
Avoidance of disease before sign/symptoms develop
e.g. genome sequencing
Define secondary prevention
Avoiding progression in people who already have signs and symptoms
2 risk factors for cardioembolism in the young
Patent foramen ovale
Endocarditis
2 recreational drugs which increase the risk of stroke
How?
Cocaine: vasoconstricts and increased bp
Amphetamine: increases blood pressure and irregular heart beat
How do you measure stroke risk?
CHADS2-VASc score
2 ways by which smoking increases the risk of stroke
Accelerates atherosclerosis
Increases platelet adhesion
Explain why an effective large study may not actually benefit in a population?
1000 people = 100 benefit but in your 50 patients only 5 will benefit from the drug
What happens in a haemodynamic event?
2 symptoms
When you quicky stand up your blood pressure is not high enough to reach all of your arteries
Pale and clammy
What is reducing lipids better at preventing than stroke?
Better at preventing heart disease
What happens to the core of the plaque in atherosclerosis?
Becomes soft and unstable due to inflammation so parts break off`
Which part of the homulculus does the middle and anterior cerebral artery supply?
Cervical = middle Sacral = anterior
Define dysgraphasthesia
Can feel but cannot interpret what an object is
Where is a lacunar stroke?
Basal ganglia
Define ischaemia penumbra
The brain is short of blood but the cells are not dead yet
The brain is electrically silent but can be recovered
What are the 3 main causes of ischaemic stoke and %
50% atheromatous plaque
25% heart related (e.g. AF and endocarditis)
25% small end arteries
What are the 2 types of haemorrhages in strokes?
Which has the worse prognosis and why?
Subarachnoid
Parenchymal (poor prognosis as in the middle of the brain)
6 causes of haemorrhagic stroke
Aneurysm Artero-venous malformation Cerebral amyloid angiopathy (amyloid deposits weaken vessels) Coagulation disorders/medication Haemorrhage Hypertension
Explain the 4 types of stroke
TACI: Total anterior circulation infarct
PACI: Partial anterior circulation infarct
LACI: Lacunar infarct
POCI: Posterior circulation infarct
What happens in a TACI?
Corticol dysfunction
Hemianopia
Hemi motor and sensory deficit
What happens in a PACI?
Corticol dysfunction (with or without hemianopia and hemi motor and hemi sensory deficit)
What happens in a LACI?
Pure motor or sensory loss
Dysarthria (clumsy hand)
Ataxic hemiparesis (pyramidal signs on one side and cerebellar on the other)
What happens in a POCI?
Ataxia (cerebellar syndrome)
A/Dyspraxia (lack of motor integration and sequencing)
Vertigo
Hemianopia
Define hemiplegia
Paralysis (motor loss) in one side of the body
Define pyramidal symptoms
Increase in the muscle tone in the lower limb
Hyperreflexia
Positive Babinski
Decrease in fine motor coordination
What are the signs if there is a stroke in the middle cerebral artery?
Contralateral motor, sensory and vision loss
Agnosia (cannot integrate sensory information)
Dominant: Agraphia, Acalculia, Aphasia
Non-dominant: Neglect, dressing apraxia, cannot recognise faces
What are the signs if there is a large vessel occlusion in the carotid?
Contralateral motor and sensory loss
Ipsilateral homonymous hemianopia
Global aphasia
Gaze palsy
Hemianopia
Blindness in half the field of vision
What are the 8 stages of stroke rehabilitation?
Admission > Assessment > Goal setting > Education > Reassessment (may go back) > Monitor progress > Plan discharge > Discharge
Define early onset dementia
Diagnosed before the age of 65
What does normal and abnormal amyloid do?
Normal: Protects nerves from Ca and glutamate toxicity
Abnormal: Ca influx and plaques around nerves > inflammation and death
What does normal and abnormal tau do?
Normal: Maintains brain cell strcrure and communication
Abnormal: hyperphosphorylated tau disrupts cell integrity and function > reduced communication
8 symptoms of Alzheimer’s
Anxiety and withdrawal Cannot perform everyday tasks or recognise faces Disorientation in time and place Frontal lobe problems Language difficulties Mild symptoms which gradually worsen Recall recent events but not past ones Reduced spatial awareness
4 risk factors for Alzheimer’s
Is it preventable?
Above 65 and Female
Poor physical health e.g. uncontrolled diabetes or heart disease
Lifestyle e.g. smoking, alcohol, exercise
It is preventable
4 risk factors of Vascular dementia
Above 65 and Male
Family history and poor physical health
What are Lewy bodies?
What do they do?
Proteins which disrupt how brain cells communicate by reducing nerve cell connections and reducing Ach/dopamine
7 symptoms of dementia with lewy bodies
Fluctuating alertness Frontal lobe problems Mood changes Reduced memory Reduced spatial awareness Sleep disturbance Visual hallucinations and delusional beliefs (upsetting
Which type of dementia has parkinson features?
Lewy Body
2 risk factors for dementia with Lewy bodies
3 ways of prevention
Above 65 and equal
Rare genetic mutations
Can be prevented by being socially active, hearing/eye checks, sleep routine and physical health
Which dementia is linked to genetics so cannot be modified?
What age does it occur at?
Frontotemporal dementia
Diagnosed between 45 and 65
What causes frontotemporal dementia?
Mutation in tau gene
Nerves in the frontal and temporal lobes die> reduction in chemical messengers and lobe shrinkage
What are the 3 main types of frontotemporal dementia?
Behavioural variant frontotemporal dementia
Primary progressive aphasia
- Semantic dementia
- Progressive non-fluent aphasia
What is Behavioural variant frontotemporal dementia also known as?
What symptoms does it have?
5 examples
Pick’s disease
Frontal and temporal lobe changes
e.g. emotional blunting, withdrawal
e.g. rude, personality change, sweet tooth
Main symptom in Primary progressive aphasia
3 examples
Speech and language difficulties
Cannot understand, speak gramatically correct or recognise objects/people
Explain what happens in Semantic dementia (3)
Describe objects as they don’t know the name
Fluent speech but doesn’t understand meaning
Cannot recognise people
Explain what happens in Progressive non-fluent aphasia (3)
Slow and hesitant speech with gramatical errors
Telegraphic speech (leave out linking words)
Know the words but not the sentences
How many seizures do you need to have in a year to be diagnosed with epilepsy?
2
4 characteristics of an epileptic seizure
Spontaneous, Brief, Stereotypical, Non-situational
What is the most common origin of an epileptic seizure?
Temporal lobe
3 characteristics of status epilepticus
Active part of the seiure lasts 5 mins or longer
Person goes into the 2nd seizure with no recovery from the 1st
Repeated seizures for 30 minutes or longer
7 causes of epilepsy
Cerebrovascular disease Corticol development malformations Genetic Hippocampal sclerosis Trauma Tumour Vascular malformations
3 characteristics of a frontal lobe seizure
Twitching and shaking
Consciousness retained
Difficulty speaking
2 characteristics of a parietal lobe seizure
Body tingling
Reduced motor control in the affected area
4 characteristics of the visual disturbances in occipital lobe seizures
Unformed, circular, coloured and continued to 1 hemisphere
11 symptoms which occur DURING a temporal lobe seizure
Dejavu Fear Hallicuinations (all senses) Lip smacking, fidgeting, undressing Motionless stare Pallor/flushed - heart rate increase/decrease Speech arrest/repeitive speech
4 symptoms which occur after a temporal lobe seizure
Confusion, headache, dysphasia, nose rubbing
How long do seizures usually last?
How many happen a month?
2-5 minutes
2-10 times a month
3 characteristics of visual disturbances in a migraine
Zigzag, black and white, transverse visual fields
Define postural hypotension
Blood pressure decreases when you stand up
7 red flags for epilepsy
Auras/dejavu Drugs/alcohol Event sequence Early morning myoclonic jerks Family history Other medical problems Trauma
Explain the history of someone who experiences a single seizure
Feeling strange for a few days Aura for seconds > minutes Tonic: cry and fall Clonic movements for a minute Altered consciousness
4 investigations for epilepsy
Blood
CT (reliable)
MRI (reliable)
EEG (not reliable)
What does the EEG look like in epilepsy?
Double wave
What is the ‘pacemaker’ used to treat epilepsy called?
What does it do?
Vagus nerve stimulator
Controls brain electrical waves
Define sleep
Period of rest with reduced bodily functions
Immune and reduced (but reversible) sensitivity to the environment
Define sedation
When is it used?
Verbal contact maintained but reduced anxiety and discomfort
Toleration of unpleasant procedures
Define coma
Extreme unresponsiveness
No voluntary behaviour
4 characteristics of general anaesthesia
Coma, Hypnosis, Areflexia, Analgesia
What happened in anaesthesia development in the: 1500s 1700s 1800s 1900s
1500s Curare discovered
1700s NO discovered as laughing gas
1800s Curare if maintain ventilation, Ether, Chloroform (childbirth)
1900s Rapid development e.g. propofol
What was discovered in the polio epidemic
Positive pressure ventilation
Which receptors do GA target?
GABA - A
4 side effects of anaesthesia
Reduced heart contractility and blood pressure
Sympathetic inhibition
Respiratory depression
Brain functions depressed
What is the onset of volatile anaesthetics?
Why?
Slow - alveolar gas exchange
What are the characteristics of A, B and C fibres?
A = large and myelinated B = small and myelinated C = small and unmyelinated
Which fibres do you lose first?
C fibres then B then A
What are the 3 types of A fibres?
alpha = motor and proprioception beta = light touch and pressure delta = pain and temperature
What do you administer when you overdose on local anaesthetic?
Lipid solution to dissolve the anaesthetic
‘Intralipid’
Which Ach receptor is blocked by NMJ blocking drugs?
Nicotinic (sympathetic)
6 risks of GA
CNS, CVS, RS depression
Aspiration of gastric contents
Can be hard to ventilate (e.g. asthma/airway problem)
Post op nauesea, vomiting and resp problems
Continued awareness (rare)
Death (very rate)
4 benefits of GA
Patient unconsciousness
Surgical access
Total control of the patient
Easily treated complications
6 risks of LA
Often not suitable Contraindications Anticoagulation Nerve injury > paralysis (e.g. epidural) Can fail Toxicity
5 benefits of LA
Avoid GA risks Post op analgesia Reduced blood loss Reduced DVT risk Reduced death
3 ways to know that someone is asleep
Clinical signs
Measure exhaled anaesthetic concentrations
Bispectral index monitor (EEG on the forehead)
3 examples of reliable signs
4 examples of unreliable signs
Reliable: heart rate, resp rate and bp
Unreliable: movement, muscle tone, eye reflexes, lacrimation
What are the 4 stages of anaesthesia
- Induction
- Excitement
- Surgical/Operative
- Overdose/Danger
Explain what happens in induction
Analgesi > Amnesia
Patients can talk
Ends when patient unconscious
Explain what happens in excitement
Excited after loss of consciousness
Irregular heart and resp rate
Uncontrolled movements e.g. vomiting, pupil dilation, holding breath
Can lead to airway compromise
Explain what happens in surgical/operative
Muscles relax and vomiting stops
Resp depression
Eye movements slow and stop
- eyes roll > fixed
- loss of corneal and laryngeal reflex
- pupils dilate and lose light reflex
- intercostal paralysis > shallow abdominal resp
Explain what happens in overdose/danger
Brain stem depression
Stop breathing
Cardiovascular collapse
