Pedretti Ch. 23 -- Assessment of Sensation

Question 1

Sensation

Answer 1

Bodily function, component of client factors that influences both the motor and processing aspects of performance skills

All clients with sensory dysfunction should be evaluated to determine the occupational impact of loss

• Tests selected depend on whether the diagnosis is CNS or PNS in origin
• CNS injury is more likely to have deficits in proprioception and stereognosis
• PNS injury is more likely to have deficits in touch pressure awareness and two point discrimination

Question 2

Somatosensory System

Answer 2

Somatosensory system handles sensory input from superficial sources (skin) and deep sources (musculoskeletal system)

Question 3

Somatosensory System Receptors

Answer 3

Mechanoreceptors – respond to touch, pressure, stretch and vibration; are stimulated by mechanical deformation

Chemoreceptors – respond to cell injury or damage; stimulated by substances that the damaged cells release

Thermoreceptors – stimulation of heating or cooling

Nociceptors – in each of these above, and stimulated by pain

Question 4

Disturbances in somatosensory system may be manifested as:

Answer 4

Paresthesia: tingling, electrical, tickling sensation

Hyperalgesia: increased pain, may occur during nerve regeneration

Hypersensitivity: increased sensory pain; normalized by desensitization

Dysesthesia: unpleasant sensation that may be spontaneous or stimulated

Allodynia: pain in response to a stimulus that is not normally painful

Question 5

Dermatome

Answer 5

area of the skin supplied by one dorsal root and its spinal nerve

Question 6

Neuropathy

Answer 6

Dysfunction of the PNS

Typical order of sensory impairment associated with peripheral neuropathy loss is in the following sequence: light touch, cold, heat, pain.

Order is reversed for sensory recovery

Question 7

Superficial Sensation

Answer 7

Includes pain, temperature and touch

Distal parts have higher density of receptors than the more proximal parts

In people with sensory issues, healing is slowed by lack of nutrition and vascularity

Lack of sweating correlates to a lack of discriminative sensation

Nerve damage results in atrophy of soft tissue → increases the tissue’s susceptibility to injury

UE sensory fibers and Sympathetic nervous system fibers follow the same pathways → sympathetic phenomena may correlate with sensory function

Before sensory testing, history should be obtained (interview and chart review)

Question 8

Most accurate sensory testing environment

Answer 8

Most accurate sensory testing environment: no background noise, good instruments, consistent testing techniques, cooperative clients and competent testers

Client’s eyes should be occluded

Question 9

Pain Sensation

Answer 9

Experience of pain is subjective and multidimensional

Can be tested with pin prick or pinching the digit firmly

Question 10

Test for Pain (Protective Sensation)

Answer 10

Procedure: sterilized safety pin, assess the amount of pressure needed to elicit pain response on uninvolved hand; alternate randomly between dull and sharp sides and ensure that each spot has one sharp and one dull

Response: client indicates sharp or dull

Scoring: correct response to both sharp and dull indicates intact protective sensation; incorrect to both sharp and dull indicates absent protective sensation

Question 11

Temperature Awareness

Answer 11

Thermal receptors are critical for a person to determine safe water for bathing

Clients who lack temperature awareness must learn compensatory strategies

Question 12

Test for Temperature Awareness (Protective Sensation)

Answer 12

Procedure: apply test tubes filled with hot or cold fluid randomly to areas of the involved hand

Response: client indicates “hot” or “cold” after application

Scoring: a correct response to both cold and hot indicates intact temperature awareness; incorrect response to either or both indicates impaired temperature awareness

Question 13

Testing for Touch Sensation – Two-Point discrimination

Answer 13

Test for receptor density; good test for mapping improvement following nerve repair

Moving two-point discrimination returns before static two-point discrimination

Criticism: variability in the force of application during testing

Question 14

Touch Sensation – Test for Static Two-Point Discrimination

Answer 14

Procedure: use device such as disk-criminator or boley guage with blunt testing ends; test only the fingertips (because this is the area of the hand used for exploration of objects); begin with a distance of 5mm between testing points; randomly test one or two points from the radial and ulnar aspects of each finger for 10 applications; pressure is applied lightly stop just when the skin begins to blanch

Response: client will respond “one” or “two” or “I don’t know” following application

Scoring: The client responds accurately to 7 of 10 applications at that number of millimeters of distance between the two points

Norms are as follows:
1 to 5 mm indicates normal static two-point discrimination
6 to 10 mm indicates fair static two-point discrimination
11 to 15 mm indicates poor static two-point discrimination

• one point perceived indicates protective sensation only
• no points perceived indicates an anesthetic area

Question 15

Touch Sensation – Test for Moving Two-Point discrimination

Answer 15

Procedure: Begin with a distance of 8mm between points; randomly select one or two points and move proximal to distal on the distal phalanx parallel to the longitudinal axis of the finger so that the adjacent digital nerve is not stimulated; the pressure applied is just enough for the client to appreciate the stimulus
- If the client responds accurately, decrease the distance between the points and repeat the sequence until you can find the smallest distance that the client can perceive accurately

Response: client says “one” “two” or “I don’t know”

Scoring: The client responds accurately to 7 out of 10 applications

Norms:
2 to 4mm for ages 4 to 60 indicates normal moving two-point discrimination
4 to 6mm for ages 4 to 60 and older indicates normal moving two-point discrimination

Question 16

Touch Pressure

Answer 16

Light touch is perceived by receptors on the skin
- Important for fine discriminatory hand use

Pressure (deep touch) is perceived by receptors in the subcutaneous and deeper tissue
- Important as a form of protective sensation

Touch pressure testing (ranges from light to deep) good for clients with nerve entrapment

Having intact light touch is an indicator of better sensation than having only deep touch

Touch pressure is tested with a set of 20 monofilaments (varying thicknesses; color coded to correspond with the 5 threshold categories)

Question 17

Touch Pressure Testing

Answer 17

Begin with monofilament 1.65; apply for 1 to 1.5 seconds (at the pressure needed to bow the monofilament); hold 1 to 1.5 seconds; lift in 1 to 1.5 seconds; repeat this 3x for monofilaments 1.65 to 4.08 (monofilaments higher than 4.08 are applied only once)

Randomly select areas of the hand to test; change the interval of time between the application

If the client does not perceive the monofilament proceed to the next thicker one and repeat the sequence until 6.65

If the client does not perceive the monofilament, record this number on the hand grid and proceed to the next area

Response: client says “touch” when they feel it

Scoring: client responds to at least 1 of 3 applications of the monofilament
Green (1.65 to 2.83) indicates normal light touch
Blue (3.22 to 3.61) indicates diminished light touch
Purple (3.84 to 4. 31) indicates diminished protective sensation
Red (4.56 to 6.65) indicates loss of protective sensation
Untestable indicates unable to feel the largest monofilament

Question 18

Proprioception

Answer 18

Definition: awareness of joint position in space

Conscious proprioception: derives from receptors found in muscles, tendons, and joints

It is through cerebral integration of information that objects can be identified by tactile cues and pressure

Ex: pressure needed when holding a paper cup

Question 19

Test for Proprioception

Answer 19

Procedure: Hold the lateral aspect of the elbow, wrist, or digit; move body part into flexion or extension

Response: Client indicates whether body part is moved “up” or “down”

Scoring: accurate response indicates proprioception

Question 20

Kinesthesia

Answer 20

defined as awareness of joint movement

Test for: moving the unaffected limb in a certain position and having the client move the affected side with eyes closed

Question 21

Stereognosis

Answer 21

Use of both proprioceptive information and touch information to identify an item with vision occluded

Question 22

The Dellon Modification of Moberg Pickup Test

Answer 22

For stereognosis

Good test for clients with injuries involving the median and/or ulnar nerves; requires the client to have the ability to participate motorically (so motor loss or weakness should be factored into choice of assessment)

Procedure: Begin with a group of 12 standardized items; if the ulnar nerve is not involved tape the two fingers to the client’s palm if possible

Test 1
The client places the items one at a time into a box as quickly as possible; record the time for two trials

Test 2 (initiate test two only if the client’s deficits do not appear to be too severe during test 1)

• With client’s vision occluded, the examiner places the items in the client’s radial three digits at one time
• The examiner records the time that it takes to identify each (30 sec max for each item); each item is placed into the client’s hand two times

Response:

• Test 1: Client places items into the box as quickly as possible with radial three digits
• Test 2: Time that it takes to identify all the items

Scoring:

• Test 1: time it takes to place all items into the box
• Test 2: time it takes to identify all items

Question 23

Localization of Touch

Answer 23

Test of functional sensation

Important to perform following nerve damage → determines client’s baseline and projected functional prognosis

Can be done with a static or moving touch

Tactile discrimination requires cortical processing

Question 24

Test for Localization of Touch

Answer 24

Procedure: Apply the finest monofilament that clients can perceive to the center of the corresponding zone on the hand grid; once the client feels the touch have them open their eyes and point to the exact area the stimulus was felt
- Place dot on hand grid for correct response; if incorrect place arrow from site of actual stimulation to the identified site

Response: client attempts to identify exact location of stimulus

Scoring: correct identification of area within 1 cm of actual placement indicates intact touch localization

Question 25

Somatotopic Arrangement

Answer 25

Sensory info is received and organized in the primary somatosensory cortex

Homunculus: areas of large cortical representation indicate high density of sensory receptors

Inherent capacity for plasticity involving circuitry

Topographic reorganization of the cerebral cortex occurs following injury and can be influenced by sensory input and learning experience

Question 26

Neuroplasticity

Answer 26

Our brain has the plasticity to mechanically induce neuronal reorganization

Process of habituation, learning, memory and cellular recovery following an injury

There are also changes in non-neuronal cells

Sensory perception is a dynamic process that is experienced by the CNS
Receptor morphology is affected by hand use; “use it or lose it”
- Immobilization or disuse → retrogressive modification in receptors
- Promoting normal use may stimulate new receptors

There is an overlap of the receptive fields of various nerve fibers → single stimulus can excite different receptors

Neurons may die following CNS injuries, but the nervous system accommodates for injuries with behavioral, physiologic and anatomical changes

Over time CNS can adapt by altering the strength of neural transmission through modifications in structure and function of neurons and synapses

Question 27

Desensitization

Answer 27

Existence or persistence of hypersensitivity will often limit use of affected body part and may prevent sensory re-education from proceeding

Desensitization is a form of treatment → aims to elicit habituation and reduce hypersensitivity
- Habituation: decrease in response following repeated benign stimuli

Uses graded stimulation with procedures and modalities that are slightly averse but tolerable

Question 28

Sensory Re-education

Answer 28

Children have greater capacity for neural regeneration and neuroplasticity than older adults

Motivation and the ability to concentrate enhance the results

Has been shown to improve the sensation of fingertip replantations even without repair of nerves

Question 29

Protective Sensory Re-education

Answer 29

People who lack protective sensation are at risk for serious injury because they cannot feel hot or cold sensation

Question 30

Instructions for re-education

Answer 30

• Protect from being exposed to sharp items or cold/heat
• Try to soften the amount of force used when gripping an object
• Use built up handles on objects → distribute gripping pressure
• Do not persist in activities for a long period of time
• Visually examine skin for blisters, edema… etc.
• If there is tissue damage try to avoid infection
• Maintain skin suppleness by applying moisturizer

Question 31

Discriminative Sensory Re-education

Answer 31

Eligible if they have intact protective sensation with a recognition of at least 4.31 to touch pressure
- A client who is not able to localize the stimulus but can still feel it is a candidate

Graded initially by grossly dissimilar objects → progressing over time to more similar objects (ex: spoon and penny then penny and dime)

Best to identify short term goals that are achievable and that will enhance function

Involves training in both localization and graded discrimination

Question 32

Localization

Answer 32

Localization of moving touch returns before static touch

Retraining is done for both

Use the previously described test for localization of touch but you can use your finger or a pencil eraser

Activity in the visual cortex is enhanced when the touch of the hand is added to visual stimulation (as long as touch is provided to the same side as the visual stimulation)

As the client improves, stimulus is changed to lighter and smaller touch

Question 33

Graded Discrimination

Answer 33

Graded from requiring gross discrimination to requiring fine discrimination

Discrimination are represented through sequencing of the following three categories:

1. Same or different
2. How they are same or different
3. Identification of the material or object

Stimulus is applied to the skin in an area corresponding to the hand grid
- various textures can be used

Another version: tracing a geometric shape, letter or number on the fingertip or small area of hand → client identifies