Sensation Flashcards
How is sensation transmitted from a stimuli to the cortex?
1) Receptors or free nerve endings on the skin, in muscle spindles or golgi tendon organs pick up sensory stimuli.
2) Transmit stimuli via peripheral nerves.
3) Enters SC through dorsal root ganglion
4) Travels through spinal ascending pathways to the thalamus then the primary somatosensory cortex or post central gyrus.
Receptors-spinal cord-cortex
What are the types of sensory receptors?
- Touch receptors
- Free nerve endings for pain and temperature
- Specialized terminal ads of axons for touch) - Proprioceptors:
- Muscle spindles
- Golgi tendon organs
What are the spinal tracts for the sensory system?
Dorsal Columns (Fasiculus gracilis and Fasiculus cuneatus): Carries touch, pressure, vibration, proprioception and visceral pain.
Spinothalamic tract or anterolateral pathway: carries pain and temperature.
Where is the somatosensory cortex?
Parietal lobe
Postcentral gyrus
What are the 4 major subdivisions of sensation?
- Pain: includes mechanical pain such as cutting and heat-pain.
- Temperature: mediates warm and cold thermal senses, but not heat pain
- Touch: Includes light touch, deep touch/pressure and vibration sense.
- Proprioception: Muscle and joint position (stationary position), muscle length and tension provides movement sense (kinaesthesia)
Where do the sensory spinal tracts cross over?
Spinothalamic tract: immediately crosses over within a few segments in a spinal cord
Dorsal Column: Fibers cross at brainstem
When sensory exams are an essential component of neurological eval?
- To determine the extent of sensory loss
- To help id the source of sensory loss in order to establish a more precise differential diagnosis: By examining the pattern of distribution you may determine if the underlying cause is from a peripheral and/or central nervous system dysfunction
- To help determine impact on function and activity level
- To more effectively determine prognosis and follow recovery
- To help determine plan of care and develop treatment: Develop strategies/compensations if protective sensation is absent. Determine which modality to train (sensory re-education) if recovery is expected.
What are the three types of sensation that can be tested?
Exteroception: superficial sensation
Proprioception: deep sensation
Discriminatory sensation: requires cortical integration in order to interpret the meaning of sensory input
What are the categories of sensory test?
- presence/absence or discrimination tests (PT)
- Threshold tests (some clinics and research)
- Nerve integrity tests (medical)
- Objective Tests
- Subjective (functional test)
What are the types of presence/absence or discrimination tests?
Touch-LT
Pain or nociception: pin-prick or sharp and dull discrimination
Temperature: hot and cold detection/discrimination
Vibration-tuning fork on bony prominences
Proprioception and kinaesthesia: joint position and movement sense
What is a threshold test?
What is a nerve integrity test?
Threshold: determine the min stimulus that the patient can perceive. Pain threshold and tolerance (dolorimeter)
NIT: Nerve conduction test-velocity of impulses, sensory evoked potentials.
What is the difference between objective and subjective tests?
Objective: Requires no active participation of pt; no subjective interpretation (NCV, sensory evoked potentials).
Most tests are subjective and required the pt to be attentive and participate in test to respond to stimuli.
Subjective:
Assess ability to feel or perceive a sensory modality
Assess the quality of sensibility.
What are the three areas for sensory distribution or mapping?
- Peripheral Nerves
- Spinal nerve or dorsal nerve root
- Primary somatosensory cortex
What are peripheral nerve distributions?
Each nerve has a specific mapped area of innervation. A single nerve may represent multiple spinal segments. (i.e. ulnar nerve C8 and T1)
See UE and LE PN distributions.
What are spinal nerve or dorsal nerve root distributions?
Represents 1 particular segment of the spinal cord (one nerve root may affect many peripheral nerves. (Ie C5 has many peripheral nerves)
Ie dermatomes-ASIA (dermatomes specialized to SCI)
How is sensation mapped in the primary somatosensory cortex?
Body representation related to the amount of brain area devoted to that body part.
Ie Sensory Homunculus: picture representation of the amount of cortex devoted to innervating particular body parts/areas.
Nottingham sensory scale: 3 standardized points per region and score (0,1,2) used for Stroke, TBI or ABI.
What are the components of a sensory assessment?
History Taking
Selecting the appropriate test
Administering the test
Knowledgeable interoperation of results.
What are the important aspects of history for sensory assessment?
Sensory symptoms: pain, numbness, paresthesia. Subjective description of loss or partial loss of sensory appreciation or sensory abnormalities. Where is it?
Motor symptoms: secondary to sensory loss
- Clumsy movements
- Difficulty with complex coordinated tasks
- Difficulty or inability to perform movements without visual feedback.
How do you select an appropriate test?
- Diagnosis or medical conditions (PNS or CNS)
- History: (Subjective complaints, hand dominance, age, occupation)
- Observation and information gathered (frequent cuts, bruises or falls may lead clinician to suspect sensory problems)
What are important components of test administration?
- Quite area
- Expose area
- Support area
- Quick scan of area w/ EO (how does it feel), then EC
- Constant speed and pressure
- Avoid manual contacts that may give cues
- Multiple random trials
- Chart using body maps or dermatomes
- Interpret information- sensation normal, impaired (partially, hypo or hyper) or completely impaired (full loss).
What are characteristics of peripheral level changes in sensation?
Common conditions?
Depends on the nerve and the site and extend of the nerve injury. How injury happened (stretch, compression, cut)
Loss or reduction in all sensory modalities can occur.
1) Diabetic neuropathy-usually starts distal
2) Nerve Palsies Bells-Facial, peroneal, carpal tunnel.
Changes in sensation at the level of the spinal cord:
- Central lesions
- Other conditions/diseases
- SCI
- Syringomyelia(cysts): sensory loss mainly pean and temp in UE and neck
Stenosis: cervical or lumbar often related to OA - Vit B12 deficiency posterior column, poisons/toxins, spina bifida
- 1) Complete transection: loss of all sensation bilat below lesion
2) Hemi-section: loss of pain/temp on contralateral side and joint position on the ipsilateral side.
Changes in sensation at the cerebral level?
Cortical stroke: complete sensory loss is rare: often appears on contralateral side of face and body.
Thalamic storkes: increase sensory problems often pain
Brainstem strokes: Pattern of sensory loss usually ipsilateral face and contralateral body.
TBI: variable depend on site and extent of injury.
What are the general effects of impaired sensation?
1. Postural Control and Gait?
- UE and hand function?
- imbalance or general balance problems
- Increase sway in standing (esp without vision)
- +Romberg’s test (more unsteady w/ EC)
- Difficulty walking
- Increase difficulty without visual feedback
- Falls.
- Clumsiness, dropping things
- Akward or strange movements
- Difficulty with fine motor control or coordination
Why do these changes in posture and UE function occur?
Superficial sensory loss: Impaired cutaneous feedback from hands or feet.
Deep sensory loss: impart proprioceptive feedback from ankles and legs (balance and gate) or from hand/fingers can all lead to problems with sensory-motor integration.
What are treatment strategies for sensory deficits?
- Education on skin care and safety issues:
- Avoid sharp objects, excessive hot or cold
- Check temp w/ intact limb
- Regular inspection of feet and hands
- Wear gloves or footwear - Compensation/strategies:
- Use vision more and cognition - Depending on prognosis may include monitoring and some sensory retraining
What are some standardized measures for sensation?
- Generally not standardized and unreliable.
- Only a few assessments exist for all sensory modalities
- Nottingham Sensory assessment
What is the EmNSA?
Erasmus MC Nottingham Sensory Assessment.
Neurological conditions (Stroke, TBI)
LT, pressure, pain, sharp/blunt discrimination and proprioception.
Standardized locations and points: face, trunk, shoulder, elbow, wrist, hand, hip, knee, ankle, foot
0=absent, 1=impaired 1=normal
Test 3 points for each body area, 3 reps per point
How is touch awareness or light touch assessed?
- Equipment
- Procedure
- Interpert
Equipment: Cotton Ball
-Demonstrate procedure on normal side first, prior to involved segment and ensure pt understands test.
- Fully support area being tested. Occlude vision.
- Use a random sequence to apply 10 stimuli. Vary between LT w/ the cotton ball and not touching.
- A fixed contact (stationary) or moving contact of the cotton ball can be used. Keep in mind that moving is easier to sense. So if pt cannot sense fixed contact try stroke contact. - Record the # of correct responses.
- Interpert:
Normal or Intact: 7/10 correct
Impaired: Pt sometimes feels the stimuli but did not manage 7/10
Absent: Pt never felt stimuli.
- In OSCE scenario right down random sequence before you go in the room, so then you can cross it off as you go.
How is temperature discrimination assessed?
- Equipment
- Procedure
- Interpretation
Equipment: Test tubes w/ hot and cold water; extreme temps not required.
-Demonstrate procedure on normal side first, prior to involved segment and ensure pt understands test.
- Fill test tubes
- Occlude Vision
- Randomly apply hot or cold test tube to skin area to be tested. Do not apply hot/cold stimuli immediately after each other on the exact same area.
- Ask pt to id if stimulus was hot or cold.
- Note time required for correct identification as slow or normal.
- Note the # of correct responses out of the total number of stimuli.
- # of reps: at least 1 hot and 1 cold in each zone.
Interpretation
Intact or Normal=100% correct
Anything else=Abnormal (impaired)
How do you assess for nociception (pain)
- Equipment
- Procedure
- Interpretation
Equipment: Opened paper clip or toothpick
-Demonstrate procedure on normal side first, prior to involved segment and ensure pt understands test.
- Occlude vision
- Randomly apply the sharp and dull end of paper clip to zone being tested.
- Pt reports if the stimulus was sharp or dull.
- Random sequence up to 10 reps of stimuli.
Interpretation:
Intact= 100% success
Hyperalgesia: over sensitivity
Hypoalgesia: decreased pain awareness
What is the difference between proprioception and kinaesthesia?
Proprioception is position sense- where a body part is in space
Kinaesthesia is movement sense- sensation that a body part has moved.
How are proprioception and kinaesthesia assessed?
- Equipment
- Procedure: proprioception
- Procedure: Kinaesthesia
Equipment: None
Demonstrate procedure on normal side first, prior to involved segment and ensure pt understands test.
- Occlude vision.
- Passively move limb/joint being tested. Use manual contracts that minimize tactile or directional cues (don’t change position when moving; hold from the side of the joint; try to avoid joint contact w/ support surfaces).
Proprioception : Pt has to correctly identify or correctly imitate the end position of a joint.
1) Ask pt to identify which joint segment was moved.
2) Ask pt to identify the direction of movement (up or down)- move joint and hold in one final position.
3) Ask pt to copy final position: move joint or body segment and ask pt to imitate or copy movement endpoint w/ their uninvolved side. “Show me the position w/ your other side”
Kinaesthesia: Pt reports a sense of joint movement or correctly copies movement of a joint.
1) Ask pt if they are able to feel if a joint is moved
2) Ask pt to id which joint was moved
3) Ask pt to copy movement; move joint and ask pt to imitate or copy movement w/ uninvolved side. “Show me the movement w/ your other side”- same speed and range.
Test false positive: Do not move a joint and check if pt id movement.
Intact- 100% success
Absent or impaired.
- What is the EmNSA?
- What does it test?
- EmNSA testing procedures?
- Standardized sensory test specifically in CNS lesions (Stroke, TBI)
2. Tactile sensation (light touch, temp discrimination, pp) Kinaesthesia Stereognosis 0,1,2 scale
- Pt supine. Demo on unaffected side as needed. Start distally.
Each body segment tested once at 3 distinct points.
Tactile sense: LT, pressure, PP
-Each defined point of contact is stimulated 3 times.
Sharp-blunt discrimination
-Each defined point stimulate 6 times (3 sharp and 3 dull)
Two-Point discrimination:
-2 points on thenar eminence an index finger
Proprioception:
- Passive movements
- Large joints move through 1/4 of their range. Small jointed moved through full available ROM.
- 3 practice movement w/ EO allowed.
- Move each joint 3 times. Id direction of movement.
What are the points of contact for proprioception (EmNSA)- these points do not have to be used for general proprioceptive testing, but can be useful to know manual contacts.
Pt in supine w/ forearm supination.
-Refer back to picture
Always have one fixing hand and one moving hand (PT).
Fingers: Distal phalanx of the thumb.
Wrist: Flex and extend
Elbow: Flex and extend elbow
Shoulder: Abduction and adduction of the shoulder w/ below 90 degrees of flexion.
Toes: Flexion and extension of the 1st MTP joint
Ankle: Flexion and extension
Knee: Flexion and extension of knee w/ hip in 90 degrees of flexion
Hip: Flex and extend, starting in 90 degrees of flexion.
What is the sensory homunculus?
Topographical mapping of sensation by body segment in the cortex.
What are the general principles of sensory testing?
- Pt should be positioned comfortably so that all tested areas are accessible: Supine.
- Test procedure should be explained to the pt before beginning the examination: demonstrate where sensation is intact.
- Pt vision should be obscured
- Exam should be initiated in areas of impaired or absent sensation and progress towards areas of normal sensation. The allows for a better visualization of the lines of demarcation between impaired and intact sensation.
- Areas of the patient’s skin where sensation is normal should be used as standard.
- Sensory deficits should be carefully noted.
