Week 10: Sensory Testing

Question 1

Abnormal sensation can be divided into 2 categories:

1. Positive

Answer 1

1. Positive
2. Usually result from trains of impulses generated at sites of lowered threshold or
   heightened excitability along a peripheral or central pathway 2. These types of sensations are described as;
   1. Tingling
3. Pricking
4. Band like
5. Lightning like, shooting (lancinating) 5. Aching
6. Knifelike
7. Twisting
8. Drawing
9. Pulling
10. Tightening 11. Burning
11. Searing
12. Electrical
13. Rawfeelings
14. The nature and severity depends on the number, rate, timing of impulses and the type and function of nervous tissue in which they arise.

As this category is due to excessive activity in sensory pathways they are not necessarily associated with a sensory deficit on examination

Question 2

Abnormal sensation can be divided into 2 categories:

1. Negative

Answer 2

1. Represent a loss of sensory function
2. They are characterised by diminished or absent feeling.
3. They are often experienced as numbness.
4. They often have abnormal findings on sensory examination
5. It is estimated that at least 50% of afferent axons innervating a particular site are lost or functionless before a sensory deficit can be demonstrated by clinical examination (rate of loss ? ).
6. Sensory findings on examination are always a measure of negative phenomena.

Question 3

Terminology: 
Dysaesthesia
Paraesthesia 
Hypaesthesia or Hypoasthesia 
Anaesthesia 
Analgesia or hypalgesia 
Hyperaesthesia
Allodynia 
Hyperalgesia

Answer 3

1. Dysaesthesia
   o All types of abnormal sensations
2. Paraesthesia
   o Typically refers to tingling or pins and needles
   o May include other sensory sensations except pain
3. Hypaesthesia or Hypoasthesia
   o Reduction of cutaneous sensation to a specific type of testing such as pressure, light touch, warm or cold stimuli
4. Anaesthesia
   o Complete absence of skin sensation to pressure, light touch, warm or cold stimuli and pain.
5. Analgesia or hypalgesia
   o Reduced or absent pain sensation
6. Hyperaesthesia
   o Pain or increased sensitivity to touch
7. Allodynia
   o Anormallynonpainfulstimulusisnowperceivedaspainful
8. Hyperalgesia
   o Severepaintoamildlynoxiousstimulus

Question 4

What are some sensory abnormalities arising from muscle spindles, tendons and joints- as they are located deeply
6

Answer 4

1. Affect proprioception (position sense) 2. Includes
2. Imbalance – particularly when no visual input
3. Clumsiness of precision movements
4. Unsteadiness of gait
5. Reduced or absent joint position sense and vibration 5. Absent DTR
6. (+)ve Rombergs
7. Pseudoathetosis – continuous involuntary movements of the outstretched hands and fingers, particularly when the eyes are closed.

Question 5

Describe the anatomy of sensation i.e. What are the 2 main pathways for sensation?
What are the types of cutaneous afferent nerve endings?
Be able to label the diagram on slide 8

Answer 5

1. Cutaneous afferent innervation is conveyed by a large variety of
   nerve endings both naked and encapsulated.
2. Naked – nociceptors and thermoreceptors
3. Encapsulated –mechanoreceptors
4. Each type of receptor has it’s own set of sensitivities to specific stimuli, size and distinctness of receptive fields and adaptational qualities.
5. All afferent fibres in the peripheral nerve trunks pass through the dorsal roots and enter the dorsal horns
6. The two main pathways for sensation are;
7. Spinothalamic tract or anterolateral system
8. Posterior column-medial lemniscal pathway

Question 6

The anterolateral Fasiculus (ALF)/ Spinothalamic tract conveys?
Slide 10

Answer 6

1. Conveys
2. Nociception
3. Temperature
4. Crude Touch
5. Itch
6. Consists of unmyelinated and small myelinated fibres
7. The pathway decussates at the spinal cord usually 1-2 levels above the entry point.
8. A unilateral lesion usually causes contralateral anaesthesia which will normally begin 1-2 segments below the level of the lesion, affecting all caudal body areas.

Question 7

Posterior column- medial lemniscal pathway coneys?

Answer 7

Conveys:

1. Fine touch
2. Vibration
3. Proprioception
4. Tactile pressure
5. Barognosis (evaluating weight of objects)
6. Graphesthesia (writing on skin)
7. Stereognosis (sensing objects in hand)
8. Recognition of texture
9. Kinesthesia and
10. Two-point discrimination
11. Consists of large myelinated fibres
12. The pathway decussates at the medulla.
13. Lesions to the posterior column-medial lemniscus pathway below the decussation of its fibres produce loss of sensation on the same side of the body as the lesion. Above the decussation produces loss of sensation on the opposite side of the body than the lesion

Question 8

Look at the table on slide 12 to examine the sensory system.

Answer 8

h

Question 9

How do you examine Pain?

Answer 9

1. A screen can be completed first. Each dermatome should have at least one point tested.
2. If any abnormal sensation noted a full dermatomal or peripheral nerve mapping should be completed.
3. To map the area of hypalgesia – start from the area of most hypalgesic site and work outwards.
4. Remember to test if the patient can feel the sharpness/pain on an area not suspected of being hypalgesic.
5. Ensure when testing the suspect area that the patient has there eyes closed.
6. Ensure to ask the patient if the sharpness/pain feels the same on both sides.

Question 10

How do you examine Temperature

14

Answer 10

Temperature – usually using small containers filled with water of the desired temperatures. This is not really practical however so using a metal object such as a tuning fork that is cold and then warmed using water can be used.

1. A screen can be completed first. Each dermatome should have at least one point tested.
2. If any abnormal sensation noted a full dermatomal or peripheral nerve mapping should be completed.
3. To map the area of hypalgesia – start from the area of most hypalgesic site and work outwards.
4. Remember to test if the patient can feel the warmth/cold on an area not suspected of being hypalgesic.
5. Ensure when testing the suspect area that the patient has there eyes closed.
6. Ensure to ask the patient if the warmth/cold feels the same on both sides.
7. Both warmth and cold should be tested as they have different receptors.

Question 11

How do you examine Touch?

Answer 11

• Touch – usually using cotton wool. You can use the backs of your fingers as well although hygiene may be an issue if the patient or yourself have any lesions on the skin.

1. A screen can be completed first. Each dermatome should have at least one point tested.
2. If any abnormal sensation noted a full dermatomal or peripheral nerve mapping should be completed.
3. To map the area of hypalgesia – start from the area of most hypalgesic site and work outwards.
4. Remember to test if the patient can feel the touch on an area not suspected of being hypalgesic.
5. Ensure when testing the suspect area that the patient has there eyes closed.
6. Ensure to ask the patient if the touch feels the same on both sides.
7. Hairy skin is not as reliable for light touch due to the excess of sensory endings that surround each hair follicle

Question 12

How do you examine joint position testing?

16

Answer 12

Joint position testing – measures proprioception. It is usually performed by holding the distal interphalangeal joint of the big toe and fingers.

1. A screen can be completed first by testing just the distal interphalangeal joints.
2. If any abnormal sensation noted move proximally until the patient has no abnormality.
3. Ensure when testing the suspect area that the patient has there eyes closed.
4. Ensure to ask the patient if the touch feels the same on both sides.

Question 13

How do you examine vibration testing?

17

Answer 13

1. A screen can be completed first by testing just the distal bony points, dorsal surface of the distal phalanx of the big toes. Then the malleoli of the ankles. In the hands the distal phalanx of the fingers is used.
2. If any abnormal sensation noted move proximally until the patient has no abnormality.
3. Ensure when testing the suspect area that the patient has there eyes closed.
4. Ask the patient if they can feel the vibration, if they can ask them to tell you when it stops. At some point you stop the vibration by placing your fingers on the prongs of the tuning fork.
5. Compare sides.

Question 14

How to examine spinal nerve roots? and Sensory pathways i.e. Dermatomes?
Slide 18

Answer 14

v

Question 15

What is garrisons summary?

The primary Modalities?

The secondary or cortical modalities?

Answer 15

• Is it symmetrical (most likely metabolic eg Diabetic neuropathy) or
asymmetrical (more likely to be a nerve entrapment eg Carpal tunnel)
• Where did it begin ?
The length rule eg a diabetic neuropathy “my feet burn”
• If not then its not an axonal or dendritic disease, must be demyelinating or CNS (not peripheral at all)
• The pace of the illness – acute or chronic is important

The Primary modalities
1. Nociception – pain and thermal sensation,
potentially tissue damaging in C-fibres (slow conducting via spinothalamic tracts)
2. Non noxious – vibration & touch & position via large myelinated nerves (fast conducting via dorsal column medial lemiscus)
The Secondary or Cortical Modalities (brain interprets the info )
Myelopathy Versus Neuropathy: myelopathy will produce a changes above and below a specific level on the trunk, a neuropathy produces “the sternal Christmas tree”.