Transcript The Sensory System - Faculty Web Pages

The Sensory System
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Examining the sensory system provides
information regarding the integrity of the
Spinothalamic Tract, posterior columns of
the spinal cord and parietal lobes of the
brain.
Client preparation
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Examination gown
Sit comfortably on bed or exam table
Explain re position changes
Reassure and provide with clear directions
Equipment
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Cotton ball
Objects to feel, quarter or key etc.
Test tubes with hot/cold H2O
Tuning fork, low pitched
Screening Test
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Only necessary to evaluate the following
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Lateral aspect of upper thighs
Inner aspect of upper arms
Dorsal or palmer surface of hands
Bottom or dorsal surface of feet
Neural Pathways
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Sensory impulses travel to the brain via
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2 ascending neural pathways
1.
2.
Spinothalamic tract
Posterior columns
Impulses originate in the afferent fibers of the
peripheral nerves, are carried through the
posterior dorsal root into the spinal cord.
Lateral Spinothalamic Tract
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Pain
Temperature
Crude & Light Touch
Posterior Columns
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Position
Vibration
Fine touch
Assessment
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Scatter stimuli over the distal and proximal
parts of all extremities and trunk to cover
most of the dermatomes.
Abnormal symptoms may indicate need to
test the entire body surface
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Pain
Numbness
Tingling
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Compare sensations on symmetric parts of
the body
If decrease in sensation
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Systematic testing
From point of decreased sensation toward
sensitive area
Note where sensation changes
Map borders of deficient area, Diagram
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Note if the pattern of sensory loss is “distal”
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Glove & stocking ( hands & feet)
Dermatones
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C3- front of neck
T4 - nipples
T10 – umbilicus
C6 – thumb
L1 inguinal
Dermatones
L4 – Knee
 L5 – Anterior ankle & foot
Dermatone = bandof skin innervated by the
sensory root of a single spinal nerve.
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Light Touch Sensation
Use wisp of cotton
Ask clients to close both eyes and tell you
what they feel and where
 Normal Findings
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Correctly identifies light touch
In some older clients light touch and pain
sensations may be decreased
Abnormal findings
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Disorders that can alter perception of
sensations
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Peripheral neuropathies due to:
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Diabetes
Folic acid deficiencies
Alcoholism
Lesions of the ascending spinal cord, brain stem,
cranial nerves, and cerebral cortex
Abnormal findings to Touch
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Anesthesia = absent
Hypoesthesia = decreased
Hyperesthesia = increased
Pain Sensation
Pin prick
 Tongue blade, dull & sharp
 Ask to distinguish
2 sec. b/t each stimulus to avoid summation
(frequent consecutive stimuli percieved as
one strong stimulus)
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Abnormalities to pain
Analgesia = absence of pain sensation
 Hypalgesia = decreased
 Hyperalgesia = increased
Apply lightest pressure to obtain response
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Temperature
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Only tested when pain sensation is
abnormal.
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Temp. & pain travel in the lateral spinothalamic
tract
Test tubes, hot & cold H2O
Vibration
Low pitched tuning fork (128Hz)
 Distal interphalangeal joint (finger & big
toe)
Ask what the patient feels. Ask to tell when
the vibration stops and then touch the fork
to stop it. If impaired- proceed to more
proximal joints or bony prominances.
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Posterior Column Tract
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Vibration – often first sense to be lost in
peripheral neuropathy.
Loss = posterior column disease, lesion of
peripheral nerve or root
Position ( Kinesthesia)
Passive movement of extremity
 Finger or big toe up and down
 Hold by sides b/t thumb and index finger
 If position sense is impaired, move
proximally to next joint
If position sense intact distally , then it is
OK proximally.
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Tactile Discrimination
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Sensory cortex
Eyes closed during testing
Stereognosis= identification of an object by
feel
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Astereognosis, inability to recognize objects
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Number identification= Graphesthesia
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Used when stereognosis prevented due to motor
impairment for ex. In arthritis
Use blunt end of pen/pencil to draw number
Two-point discrimination
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Alternate double with single stimulus
Minimal distance1 from 2 points= less than 5mm
on finger pads
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Point Localization
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Touch pt’s skin
Open eyes and point to where touched
Useful trunk & legs
Extinction
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Simultaneously stimulate same area both sides
of body
Ask how many points felt and where
charting
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If normal
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Identifies light touch, dull and sharp sensations
to trunk and extremities.
Vibratory sensation, stereognosis,
graphesthesia, two-point discrimination intact.
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Abnormal results in these tests indicate
lesions of the sensory cortex.
These tests not done on children 6 yrs and
younger.
65yrs &older
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loss of sensation of vibration at the ankle
Position sense in big toe may be lost
Tactile sensation impaired
Infants and toddlers
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Little sensory testing
Hypoesthesia
Responds to pain by crying
General reflex withdrawal of all limbs
7 – 9mos.can localize stimulus