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