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Neurology > Radiology and Investigations > Flashcards

Radiology and Investigations Flashcards

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1
Q

What are the indications for brains imaging

A

Headache
Raised ICP
Seizures
Weakness or signs of stroke
Trauma
Loss of consciousness
Neurological deficit
Post-operative

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2
Q

What are the advantages of CT for head scans

A

CT is quick
Can be used in the emergency settings and ICU
Provides great bone detail (good for trauma cases)
Will show up acute bleeds

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3
Q

What are the disadvantages of using CT for head scans

A

Poor soft tissue detail and contrast
Older bleeds cannot be seen
Radiation exposure

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4
Q

What are the advantages of using MRI for head scans

A

Best contrast and soft tissue resolution
Shows up marrow and cord pathologies
Can view the cranial nerves

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5
Q

What are the disadvantages of using MRI for head scans

A

Less bony detail
Not compatible for pacemakers and implants
Takes a lot longer
Not compatible with ICU/emergency equipment

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6
Q

How many sequences do you need for a MRI

A

Usually need at least 3 sets
Usually T1, T2 and then FLAIR (water suppressed)
Gives a more complete picture

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7
Q

What are the two types of MRI

A

T1 and T2 weighted
Show up different materials as light and dark

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8
Q

Describe a T1 MRI

A

Bright sections are fat, methaemoglobin, mineral deposition, melanin and mush (fat and 4M’s)
Contrast will also show up bright if used

Dark areas are water, air and cortical bone, high flow areas (arteries)

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9
Q

Describe a T2 MRI

A

Bright areas are water, areas with less tissue and fat
Dark areas are blood products, mineral deposition, air and cortical bone, high flow areas

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10
Q

What are the features of ischaemic stroke on a brain scan

A

Thrombus visible in vessel - will be dense on CT
Areas of ischaemic tissue (blurring of white and grey matter border)

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11
Q

How do haemorrhages appear on brain scans

A

CT will show up acute bleeds (few hours)
MRI will show up for years

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12
Q

What is the best investigation for brain aneurysm

A

CT angiogram
Inject contrast

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13
Q

What is the best investigation for skull trauma

A

CT is the most sensitive

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14
Q

How does a subdural haematoma appear on scans

A

Concave/crescent shape that follows the brain outline

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15
Q

How does a extradural haematoma appear on scans

A

Convex/lens shape pushing in towards the brain

The dura is pushed away from the skull by accumulating blood

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16
Q

What is an extra-axial tumour

A

One found outside of the brain

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17
Q

What is an intra-axial tumour

A

One found inside the brain

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18
Q

What type of tumour is a pituitary adenoma

A

Extra-axial - in the pituitary gland not brain
Can be functional and produce hormones
Non-functional and will be silent until they cause mass effect

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19
Q

How does hydrocephalus present on a brain scan

A

Dilation of the ventricles

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20
Q

What is a Chiari malformation

A

Congenital brain malformation
Leads to flow obstruction from the 4th ventricle - hydrocephalus (accumulation of CSF)
Leads to mixed upper and lower MN signs

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21
Q

What is cortical dysplasia

A

Issue that occurs in brain development – cortex is not formed properly
Abnormality seen on scans

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22
Q

What is polymicrogyria

A

The gyri are small and too numerous

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23
Q

What is Creutzfeldt–Jakob disease

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A

Brain condition caused by prions - can be sporadic, familial or acquired from beef
Patient presents gradually with memory and behavioural changes
Will then progress to coma and death

24
Q

Water is white on which type of MRI scan

25
What is an EEG
Electroencephalogram It is a way of monitoring electrical activity in the brain.
26
What are EEGs used for
To characterise or help diagnose a range of conditions, particularly epilepsy. It suuports the diagnosis of epilepsy but is NOT a definitve test It can help differentiate between seizure type to guide treatment options.
27
What aspects of an EEG require consent
The first is for hyperventilation and photic stimulation as these have a small chance of evoking a seizure. The second is for the use of video recording during the test - further consent needed to use these videos for teaching etc.
28
Why are EEG recorded on video
We see lots of movement and muscle artefact on the recording and use the video recording to confirm what the patient was doing at that time. If a patient was to have an event during the recording, you have both the video recording and EEG to analyse
29
How are the electrodes placed in an EEG
An EEG requires 23 electrodes to be accurately attached to the head Electrodes record from specific lobes of the brain There is a system of specific measurements taken from landmarks on the head which ensure they are in the correct placed Skin is rubbed with an exfoliator to lower resistance and then the electrodes are attached using an electrolyte paste
30
An ECG is recorded at the same time as an EEG - true or false
True A lead 1 ECG is also recorded – there is an overlay between syncope events and seizures.
31
How does an EEG work
The electrodes pick up the electrical activity produced by the brain on the scalp. These tiny signals are amplified and sent to the computer to be analysed. The computer then sorts these electrodes into pre-defined pairs. The waveforms seen are representing the potential difference between two electrodes
32
What are montages in relation to an EEG
Chains of electrode pairs created by the computer programme Can be bipolar or reference In bipolar montages each channel represents the voltage difference between two “poles” on the scalp. These are the standard montages used as they give a wider picture of the electrical activity in the brain Reference montages compare “point of interest” electrodes to another electrode somewhere else on the body. often used to highlight abnormalities
33
Which procedures can be used to provoke signs on an EEG
Hypereventilation - Vigorous, deep breathing for 3 minutes results in a transient respiratory alkalosis leading to constriction of the small cerebral blood vessels decreasing O2 supply to the brain Photic stimualtion - Stimulation with flashes of light to elicit visual responses in the occipital region
34
Which types of waves are seen on a normal EEG and what affects them
Alpha - most prominent when the eyes are closed and the patient is relaxed Beta - Augmented by barbiturates and benzodiazepines Theta - Increases in abundance with drowsiness and light sleep Delta - Occurs in sleep at all ages but prominent in chidlren Lamda waves - Can be evoked by looking at colourful patterns and attenuated by looking at blank paper (sharp waves from occipital area)
35
What are the contraindications for using hyperventilation to provoke an EEG
Aged over 65 Respiratory or cardiovascular disease Raised intracranial pressure Cerebrovascular disease Recent cerebrovascular accident Moya Moya disease
36
What can cause an artefact on an EEG
Electrical interference from beds, drips, oximeters and other machinery around the patient. Movement of eyes, eyebrows, head Jaw clenching Rapid blinking Talking Yawning and ciughing
37
A normal EEG excludes epilepsy = true or false
False Epilepsy is an electro-clinical diagnosis and the clinical background should take precedence over the EEG findings
38
Nerve conduction studies are used in the diagnosis of which types of disorders
Used for neuromuscular disorders Includes pathology in the nerve cell bodies or axon, at the NMJ or in the muscle itself Disorders of the nerve itself is the most common clinical application Includes anterior horn, roots, plexus and nerves distant to the plexus
39
List disorders which affect nerves distal to the main plexus
Mononeuropathy - e.g. entrapment Mononeuritis multiplex - inflammatory process Polyneuropathy - more diffuse damage, usually length dependant
40
How are sensory nerve conduction tests carried out
Measure SNAP - Sensory nerve action potential Apply a stimulus to the sensory area If stimulus is enough then an AP is generated which is picked up by electrode This AP can be measured (speed of onset, voltage of response, duration) Can measure conduction velocity as well
41
Which types of fibres are tested in sensory nerve action potenital tests
Only large fibre function can be measured
42
How do post-ganglionic lesions present on SNAP tests
In post ganglionic lesions the SNAP will be abnormal Seen if there are lesions in pleuxus, nerves distal to plexus or in sensory ganglion
43
How do pre-ganglionic lesions present on SNAP tests
In pre ganglionic lesions the SNAP will be normal Seen in radicular pathology and anterior horn cell lesions
44
How are motot nerve conduction studies carried out
Motor tests are more varied but most basic is the compound muscle action potential You stimulate the nerve and measure the output at a distal muscle innervated by that nerve (electrodes placed on muscle) CMAP - sum response of action potentials generated by the various muscle fibres contracting Measure onset, velocity, amplitude etc
45
How are motot nerve conduction studies used
Can be used to localise and determine the severity of abnormality Also specific patterns associated with axonal loss and different types of demyelination (relevant for polyneuropathies as may have genetic and treatment implications)
46
How would axonal loss present on a motor nerve conduction study
Loss of amplitude This is because amp represents number of axons
47
How does demyelination present on motor nerve conduction studies
Slowed conduction or increased latency
48
What are repetitive nerve stimulation tests used for
This is a specialist test used to investigate myasthenia
49
How would myasthenia present on repetitive nerve stimulation tests
You stimulate the same nerve multiple times Will see a reduction in amplitude with repeated stimulus (CMAP decrease \>10%) Usually biggest drop between 4-5th stimulus
50
What are needle EMG tests used for
To look for evidence of myopathy Assess the health of the nerve supplying the muscle that is affected/being sampled
51
How are needle EMG tests carried out
Place needle into the muscle Assess muscle at rest and then under voluntary movement Resting muscle should be electrically silent Muscle activity generates a waveform and associated sound
52
What are the benefits of needle EMG tests
Needle can assess muscle directly Can test areas not accessible to standard nerve conduction Can localise the pathology
53
How would neuropathy present on a needle EMG test
APs would have long duration, fast firing, high amplitude
54
How would myopathy present on needle EMG
APs would have short duration, low amplitude, polyphasic
55
What is the most common use of nerve conduction studies
Diagnosis of carpal tunnel syndrome (median nerve entrapment) This is also the most common type of nerve entrapment
56
List some physical barriers to nerve conduction tests
Obesity, oedema, emollients, thickened skin etc
57
What are the limitation of using nerve conduciton studies to assess ulnar neuropathy
ulnar sensory response can only be measured at risk, distal to actual pathology (usually around the elbow)

Neurology (18 decks)

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