Transcript 01-Sensory Exam2008-11

RAMLA A. SANDAG – JAILANI, M.D.
Physiology department
kkuh
Somatosensory system
(Somatovisceral Sensory System)
- transmits sensations from receptor
organs
in the skin, muscles, joints and viscera
to the brain.
* Two (2) main pathways:
1. Posterior (Dorsal) Column Lemniscal tract
- fine touch, two-point discrimination,
vibration and position sensations, fine
pressure
2. Spinothalamic (Anterolateral) tract
- pain and thermal sensations, crude
touch, crude pressure, tickle and itch
OBJECTIVES:
To be able to reasonably acquire the skill of
testing the following general sensation:
1. tactile sensations – light touch, pressure, tactile
localization and discrimination
2. joint position sense
3. recognition of size, shape, weight forms and
textures of objects
4. vibration sense
5. pain sensations
6. temperature sense
REQUIREMENTS:
Cotton wools
Thin bristles
Calipers, pins or disposable toothpicks
Test tubes with warm and cold water
Flat base tuning forks
Different weights
TACTILE LOCALIZATION:
1. Ask the subject to close
her eyes.
2. Touch different parts of
the body with cotton wool.
3. Ask her to acknowledge
whether she feels the touch
and ask her to locate the
exact area touched.
4. Note whether there is
abnormality like hypoaesthesia or hyperaesthesia.
* Hypoaesthesia – touch sensation is reduced.
* Hyperaesthesia – sensations produced is either
painful, irritating, or tingling.
Spinothalamic tract interruption
- increase touch threshold
- decrease in no. of touch spots in
the skin
- slight touch deficit
- normal touch localization
Dorsal columns destroyed
-
vibration and proprioception sense are lost
increase touch threshold
no. of touch-sensitive areas in the skin
impaired localization of touch sensation
TWO-POINT DISCRIMINATION:
1. Ask the subject to close
her eyes.
2. With the calipers wide
apart, touch two areas
of the back of the hand.
3. Ask the subject to say
whether she feels two
points of touch or a
single point.
4. Now decrease the distance between two limbs of the
caliper and measure in millimeter(mm) the minimum
distance that can be recognized as two distinct
points.
* Two-point threshold
– is the minimum distance at which two points
of contact can be felt.
– is impaired in: dorsal column and parietal
cortical (somatosensory cortex) lesions
5. Determine two-point threshold in the following areas
– palm of the hand, fingertip, leg and back of the
neck.
RECOGNITION OF SIZE, SHAPE AND FORMS:
1. Ask the subject to close
her eyes.
2. Place any common object
like coins, keys, pen, etc.
in her palm and ask her to
identify the object without
looking towards it.
* Stereognosis – ability to recognize
objects.
* Astereognosis – loss of recognition of
objects.
– early sign of damage to cerebral
cortex.
– if without defect in touch and
pressure sensation
(Parietal lobe lesion posterior to
postcentral gyrus)
RECOGNITION OF WEIGHT DISCRIMINATION:
1. Ask the subject to close
her eyes and place her
hand on the table.
2. Place different weighs
in his hands.
3. Ask her to indicate if
she could identify the
variations in the weights
placed on her hand.
Weight discrimination – the ability to assess the
weight of an object.
* An increase in intensity of stimuli is transmitted
to the brain in the form of:
a. an increase in the number of afferent fibers
stimulated
b. increased frequency of action potentials in
these fibers
… These two features are perceived as an
indication of the strength of the stimulus.
VIBRATION SENSE:
1. Ask the subject to close
her eyes.
2. Strike the tuning fork
(128 – 250 cps) and place
it successively over identical
body areas on each side of
the body.
3. Ask the subject to acknowledge
whether she feels the vibration
and whether it is of the same
intensity on the two sides.
4. Proceed from the upper part of the body downwards
– the clavicle, tip of the shoulder, elbow, wrist,
dorsum of the hand, anterior chest wall, anterior
superior iliac spine, patella, tibial tuberosity,
lateral and medial malleoli and the base of the
big toe.
5. Test if the subject can accurately identify when the
vibration stops.
Vibration – a pattern of rhythmic pressure stimuli
… receptors involved: touch receptors especially
Pacinian corpuscles
… pathway: dorsal column
… degeneration occurs in:
- poorly controlled diabetes
- pernicious anemia
- some vitamin deficiencies
JOINT POSITION SENSE:
1. Ask the subject to close
her eyes.
2. Hold her finger or toe
and make it up and down
and ask her to recognize:
a. movement of the joint
by saying NOW
b. direction of the fingers
whether up or down.
PAIN SENSATION:
* SUPERFICIAL
… With the prick of
a pin, elicit the
sensation of pain
on a willing partner.
* PRESSURE
… Put pressure on deep
structures such as
muscles, tendoachilles
or bones, superior
orbital margin, etc and
ask her whether she
feels pain.
TEMPERATURE SENSE:
1. With two test-tubes
containing warm and
cold water, touch at
different sites of the
body of your subject.
2. Ask her to identify the
temperature differences.