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Neurology > Radiology and Investigations > Flashcards

Radiology and Investigations Flashcards

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

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

A

T2

25
Q

What is an EEG

A

Electroencephalogram

It is a way of monitoring electrical activity in the brain.

26
Q

What are EEGs used for

A

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
Q

What aspects of an EEG require consent

A

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
Q

Why are EEG recorded on video

A

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
Q

How are the electrodes placed in an EEG

A

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
Q

An ECG is recorded at the same time as an EEG - true or false

A

True

A lead 1 ECG is also recorded – there is an overlay between syncope events and seizures.

31
Q

How does an EEG work

A

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
Q

What are montages in relation to an EEG

A

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
Q

Which procedures can be used to provoke signs on an EEG

A

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
Q

Which types of waves are seen on a normal EEG and what affects them

A

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
Q

What are the contraindications for using hyperventilation to provoke an EEG

A

Aged over 65

Respiratory or cardiovascular disease

Raised intracranial pressure

Cerebrovascular disease

Recent cerebrovascular accident

Moya Moya disease

36
Q

What can cause an artefact on an EEG

A

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
Q

A normal EEG excludes epilepsy = true or false

A

False

Epilepsy is an electro-clinical diagnosis and the clinical background should take precedence over the EEG findings

38
Q

Nerve conduction studies are used in the diagnosis of which types of disorders

A

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
Q

List disorders which affect nerves distal to the main plexus

A

Mononeuropathy - e.g. entrapment

Mononeuritis multiplex - inflammatory process

Polyneuropathy - more diffuse damage, usually length dependant

40
Q

How are sensory nerve conduction tests carried out

A

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
Q

Which types of fibres are tested in sensory nerve action potenital tests

A

Only large fibre function can be measured

42
Q

How do post-ganglionic lesions present on SNAP tests

A

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
Q

How do pre-ganglionic lesions present on SNAP tests

A

In pre ganglionic lesions the SNAP will be normal

Seen in radicular pathology and anterior horn cell lesions

44
Q

How are motot nerve conduction studies carried out

A

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
Q

How are motot nerve conduction studies used

A

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
Q

How would axonal loss present on a motor nerve conduction study

A

Loss of amplitude

This is because amp represents number of axons

47
Q

How does demyelination present on motor nerve conduction studies

A

Slowed conduction or increased latency

48
Q

What are repetitive nerve stimulation tests used for

A

This is a specialist test used to investigate myasthenia

49
Q

How would myasthenia present on repetitive nerve stimulation tests

A

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
Q

What are needle EMG tests used for

A

To look for evidence of myopathy

Assess the health of the nerve supplying the muscle that is affected/being sampled

51
Q

How are needle EMG tests carried out

A

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
Q

What are the benefits of needle EMG tests

A

Needle can assess muscle directly

Can test areas not accessible to standard nerve conduction

Can localise the pathology

53
Q

How would neuropathy present on a needle EMG test

A

APs would have long duration, fast firing, high amplitude

54
Q

How would myopathy present on needle EMG

A

APs would have short duration, low amplitude, polyphasic

55
Q

What is the most common use of nerve conduction studies

A

Diagnosis of carpal tunnel syndrome (median nerve entrapment)

This is also the most common type of nerve entrapment

56
Q

List some physical barriers to nerve conduction tests

A

Obesity, oedema, emollients, thickened skin etc

57
Q

What are the limitation of using nerve conduciton studies to assess ulnar neuropathy

A

ulnar sensory response can only be measured at risk, distal to actual pathology (usually around the elbow)

Neurology (18 decks)

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