Pedretti Ch. 23 -- Assessment of Sensation Flashcards
Sensation
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
Somatosensory System
Somatosensory system handles sensory input from superficial sources (skin) and deep sources (musculoskeletal system)
Somatosensory System Receptors
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
Disturbances in somatosensory system may be manifested as:
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
Dermatome
area of the skin supplied by one dorsal root and its spinal nerve
Neuropathy
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
Superficial Sensation
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)
Most accurate sensory testing environment
Most accurate sensory testing environment: no background noise, good instruments, consistent testing techniques, cooperative clients and competent testers
Client’s eyes should be occluded
Pain Sensation
Experience of pain is subjective and multidimensional
Can be tested with pin prick or pinching the digit firmly
Test for Pain (Protective Sensation)
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
Temperature Awareness
Thermal receptors are critical for a person to determine safe water for bathing
Clients who lack temperature awareness must learn compensatory strategies
Test for Temperature Awareness (Protective Sensation)
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
Testing for Touch Sensation – Two-Point discrimination
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
Touch Sensation – Test for Static Two-Point Discrimination
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
Touch Sensation – Test for Moving Two-Point discrimination
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
Touch Pressure
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)
Touch Pressure Testing
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
Proprioception
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
Test for Proprioception
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
Kinesthesia
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
Stereognosis
Use of both proprioceptive information and touch information to identify an item with vision occluded
The Dellon Modification of Moberg Pickup Test
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
Localization of Touch
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
Test for Localization of Touch
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
Somatotopic Arrangement
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
Neuroplasticity
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
Desensitization
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
Sensory Re-education
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
Protective Sensory Re-education
People who lack protective sensation are at risk for serious injury because they cannot feel hot or cold sensation
Instructions for re-education
- 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
Discriminative Sensory Re-education
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
Localization
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
Graded Discrimination
Graded from requiring gross discrimination to requiring fine discrimination
Discrimination are represented through sequencing of the following three categories:
- Same or different
- How they are same or different
- 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
