Session 3.3 - Group Work Flashcards
1a) You help a plaster technician to apply a cast to a patient’s leg. He complains initially of some skin irritation but when you see him in fracture clinic the following day he states he feels comfortable, with no irritation.
What is the neurophysiological mechanism for this
phenomenon?
Rapidly adapting receptors adapt
1b) You help a plaster technician to apply a cast to a patient’s leg. He complains initially of some skin irritation but when you see him in fracture clinic the following day he states he feels comfortable, with no irritation.
Can you think of any everyday phenomena that can be
explained by this concept? This video might help
https://www.youtube.com/watch?v=MlCS0k16ESs
- Sitting in a chair
- Feeling your clothes
- Having a shower
2a) You are assisting in theatre with a resection of a brain tumour arising from the cerebral cortex. The neurosurgeon states that the patient’s sensory function in their right hand is likely to be impaired.
Ascertain as precisely as possible where in the brain the tumour is likely to be.
On the left-hand side in the post-central gyrus, superolaterally
2b) You are assisting in theatre with a resection of a brain tumour arising from the cerebral cortex. The neurosurgeon states that the patient’s sensory function in their right hand is likely to be impaired.
Why is the hand particularly vulnerable?
The hand occupies a large surface area in the cerebral cortex homunculus.
2c) You are assisting in theatre with a resection of a brain tumour arising from the cerebral cortex. The neurosurgeon states that the patient’s sensory function in their right hand is likely to be impaired.
Assuming the neurosurgeon’s prognosis is accurate, which modalities will be affected?
All of the modalities, because the lesion is in the cortex so you’ve lost everything
2d) You are assisting in theatre with a resection of a brain tumour arising from the cerebral cortex. The neurosurgeon states that the patient’s sensory function in their right hand is likely to be impaired.
Speculate on what other functions might be affected by the tumour or following the operation.
- Areas around the sensory cortex
- Motor affection
- Power of speech is close by
3a) A patient with diabetic neuropathy is found to have bilateral ‘glove and stocking’ paraesthesia in both hands and feet.
Can this pattern be explained by a single lesion affecting the sensory homunculus in the primary sensory cortex?
No, because the hands and feet are not adjcanet within the homunculus so they would need more than one nerve lesion. Secondally, it is bilateral, so it would need to be on both sides of the primary sensory cortex.
3b) A patient with diabetic neuropathy is found to have bilateral ‘glove and stocking’ paraesthesia in both hands and feet.
Further examination of the same patient reveals that they have complete sensory loss (all modalities) in the S1 dermatome on the right side.
Where is the S1 dermatome (can you answer this without looking it up?!)
Little toe and heel
Dorsum of the foot
3c) A patient with diabetic neuropathy is found to have bilateral ‘glove and stocking’ paraesthesia in both hands and feet.
Further examination of the same patient reveals that they have complete sensory loss (all modalities) in the S1 dermatome on the right side.
Which structure(s) might have been damaged to cause this isolated dermatomal loss? Draw a diagram showing these potential sites.
- Damage to the dorsal horn of the spinal root
- of the primary order neurone
- Dorsal root ganglion
Has to be more distal than the cord because we’ve lost all modalities - Spinal nerve
On the right side
3d) A patient with diabetic neuropathy is found to have bilateral ‘glove and stocking’ paraesthesia in both hands and feet.
Further examination of the same patient reveals that they have complete sensory loss (all modalities) in the S1 dermatome on the right side.
The patient is found to have weakness in plantarflexion?
Using this additional piece of information, state precisely where the lesion is.
The lesion would need to be at the S1 spinal nerve to affect both sensory and motor (it can’t be at the DRG)
4a) A vegan man is seen in the neurology outpatient department. His MRI scan of the cervical spinal cord on admission looked like this:
Label the images with anterior, posterior, superior,
inferior, left and right
Left: anterior (left), posterior (right)
Right: anterior (top), left (right), posterior (bottom), right (left)
4b) A vegan man is seen in the neurology outpatient department. His MRI scan of the cervical spinal cord on admission looked like this:
Which region of the cord has been affected?
C2-C4 posterior grey matter in the dorsal aspect - dorsal cord
(You can see the odontoid peg which is C2)
4c) A vegan man is seen in the neurology outpatient department. His MRI scan of the cervical spinal cord on admission looked like this:
Why is his dietary history important?
He doesn’t eat meat or dairy so he is lacking (deficient) in B12, iron and folate (and could therefore have megaloblastic anaemia)
Subacute combined degeneration of the cord
4d) A vegan man is seen in the neurology outpatient department. His MRI scan of the cervical spinal cord on admission looked like this:
Which cord levels have been affected?
C2-C4
4e) A vegan man is seen in the neurology outpatient department. His MRI scan of the cervical spinal cord on admission looked like this:
How might he have presented initially?
Posterior so sensory loss to C2-C4 dermatomes which is loss of sensation (paraesthesia) in the neck, upper torso and ears both anteriorly and posteriorly.
4f) A vegan man is seen in the neurology outpatient department. His MRI scan of the cervical spinal cord on admission looked like this:
What might be found during clinical examination of the
sensory system in this man? What might a full blood count show?
Sensory ataxia when your eyes are closed (hence loss of proprioception - vision and proprioception can be used to overcome ataxia when there are problems in the cerebellum)
Pronator drift - arms out shut your eyes, pronator muscles pronate the arms because these muscles are stronger but patient thinks they’re holding their arms out still
Rhomberg’s test -
Microcytic anaemia (megaloblastic anaemia)
5a) A 30 year old woman presents to the neurology clinic with ‘numbness’ affecting both of her upper limbs and the upper half of her chest.
Sensory examination reveals she has bilateral loss of pinprick and temperature sensation in the totality of her C4-T2 dermatomes. Vibration, light touch and two point discrimination are preserved.
Which sensory system is affected?
Spinothalamic pathway
5b) A 30 year old woman presents to the neurology clinic with ‘numbness’ affecting both of her upper limbs and the upper half of her chest.
Sensory examination reveals she has bilateral loss of pinprick and temperature sensation in the totality of her C4-T2 dermatomes. Vibration, light touch and two point discrimination are preserved.
Can you explain the bilateral nature of her symptoms and signs?
Central lesion that affects the decussation of the spinothalamic tracts
5c) A 30 year old woman presents to the neurology clinic with ‘numbness’ affecting both of her upper limbs and the upper half of her chest.
Sensory examination reveals she has bilateral loss of pinprick and temperature sensation in the totality of her C4-T2 dermatomes. Vibration, light touch and two point discrimination are preserved.
Why are there no signs at levels below T2?
A central lesion will only affect the dermatomes that run medially, but any other dermatomes further below the spinal cord level of T2 will be too lateral so the lesion will not affect this area.
5d) A 30 year old woman presents to the neurology clinic with ‘numbness’ affecting both of her upper limbs and the upper half of her chest.
Sensory examination reveals she has bilateral loss of pinprick and temperature sensation in the totality of her C4-T2 dermatomes. Vibration, light touch and two point discrimination are preserved.
If the lesion continues to expand, how might her clinical picture change? Think about the location and somatotopic organisation of the sensory tracts. Focus on the sensory system but feel free to speculate about other systems!
- Firstly, we’d expect the spinothalamic to progress until eventually we might lose the tract altogether
- ## The dorsal column (DCML) might get squished because it’s at the back
6a) In the 1999 James Bond film The World Is Not Enough the main villain, Renard, was shot in the head and recovered to find that he could not feel any pain anywhere in his body. Otherwise he was completely neurologically normal. Watch this video from
1: 50
https://www.youtube.com/watch?v=0NsNYC6Ye24
What do you make of the explanation given in the video? Is this even possible?!
It is not possible as the damage is not confined to the medulla
6b) In the 1999 James Bond film The World Is Not Enough the main villain, Renard, was shot in the head and recovered to find that he could not feel any pain anywhere in his body. Otherwise he was completely neurologically normal. Watch this video from
1: 50
https://www.youtube.com/watch?v=0NsNYC6Ye24
Are there any other (real…) causes for insensitivity to pain?
Release of endorphins which cause an increase in firing of the inhibitory fibres which inhibit the action of the C fibres which cause the pain sensation.
7a) Watch this video
https: //www.youtube.com/watch?v=Ff_PiYWrakM
Speculate about the neurological mechanism for this remarkable phenomenon. Does it have any current clinical applications?
Central inhibition, upregulation of the inhibitory pathway - gate-control theory (direct synaptic interactions where pain fibres synapse.
7b) Watch this video
https: //www.youtube.com/watch?v=Ff_PiYWrakM
Why does rubbing a painful area of skin relive the pain?
Firing of the neurones downregulate pain neurones. Tactile sensation relieves the pressure.
The C fibres are slowly conducting C fibres. There are also mechanoreceptors which when you rub the skin become activated as well: these A fibres synapse onto inhibitory interneurons (black neurone on picture) it inhibits the second order neurone, if you activate the mechanoreceptors you inhibit the interneurons producing pain
8a) A soldier has been shot in the back, completely destroying the right half of his C5 cord segment.
Predict the sensory disturbance that he is likely to suffer from. A diagram might help.
Dorsal root decussates at the medulla so it’s contralateral pain, temperature modalities that are affected (left side in spinothalamic).
Further reading: what motor weakness would you get with Brown-Sequard syndrome?
