Examination of sensory system
Sensory modalities to be tested are:
2. Pain Superficial
Deep pain I pressure pain
3. Temperature < Warmth
4. Sense of position, Sense of movement
6. Vibration sense
7. Any abnormal sensations - parasthesia.
Before proceeding to the examination, explain to the subject, the nature of the test to be conducted, so as to get maximum cooperation from the subject. During examination ask him to close his eyes and do the tests on both sides of the body and compare. All sensations should be tested in all the areas of the body. Negative tests should be given in between.
1. Touch or tactile sensibility:
Light touch is tested by touching the skin surface using a wisp of cotton or a fine hair brush. Instruct the patient to say ‘Yes’ every time he feels the touch, with his eyes closed. Corresponding points on both sides of the body are. compared. Occasionally negative tests should be applied and ask him whether he can feel the touch.
Light Pressure touch: is tested by touching with a blunt object. (with head of a pin) without applying too much pressure.
Tactile localisation: When the subject says that he can appreciate the sense of touch, ask him to localise the site, by touching the corresponding site on the opposite side.
Tactile discrimination or two point discrimination
It is the ability to discriminate between 2 points touched simultaneously, as two separate points. This can be tested using blunt dividers or weber’s compasses. Ask the subject whether he is touched with one point or 2 points. A minimum separation of the two points by about 1 - 2mm is enough to be appreciated in highly sensitive areas like fingertip. Whereas a separation of about 5-6 cms is needed in less sensitive areas like back. This test is particularly useful in lesions of posterior column or parietal cortex and in some peripheral nerve lesions (carpel tunnel syndrome).
Abnormalities of touch sensation
1. Anaesthesia - Complete loss of touch sensation
2. Hypoaesthesia - Partial loss of touch sensation
3. Hyperaesthesia -Touch is perceived as pain, irritating ortingling sensation
4. Delayed conduction - Touch is appreciated only after some time
5. Defective localisation -Allochiria
Superficial pain: The point of a pin may be used to test this. Make sure that the patient is not confusing between pain and sharpness of the point. Even in the absence of pain sensation, the subject may be able to detect the sharpness of the point object.
Pressure pain: This is tested by squeezing the muscles or pinching the tendo achilles. In tabes dorsalis the most prominent sensory involvement is loss of pressure pain.
Analgesia - Absence of pain sensitivity
Hypoalgesia - Partial loss of pain sensitivity
Hyperalgesia - Increased sensitivity to pain
3.Temperature: This is examined using two test tubes containing hot and cold water. The part to be tested is touched with both the tubes in turn and ask him which is hot and which is cold. Too hot or cold water should not be used because they produce only pain sensation. Negative tests should be applied occasionally. This is the first sensation that is lost in leprosy.
4. Sense of position: This is the ability to describe or imitate (In the opposite side of the body with the eyes closed, the position in which one limb has been placed. Ask the subject to close his eyes and keep his limbswill relaxed. Hold one of his limbs move it passively in various directions and finally keep it in a particular position. Then ask the subject to keep the opposite limb also in the same position. If he is not able to do the same, then his sense of position is defective.
Joint sense or Appreciation of passive movement:
Gradually move a part or whole of a limb into a new position and ask him to say ‘Yes’ as soon as he recognizes the movement. Movements of less than 100 can be appreciated at all normal joints. If the sense of movement is defective, the angle through which the movement isto be carried out for the subject to recognize is greater. Ask the subject the oirection of movement i.e. whether up or down, after moving a digit into a new position.
5. Stereognosis: This is the ability to recognize with eyes closed, common familiar objects from their size shape and form, when placed in hand.
To test size, two objects of different size, but same shape are placed in his palm and ask him to say which is the larger. Small rods or match sticks of different lengths can be used.
To test recognition of shape, familiar objects like coin, key, pen etc are given and ask to identify them, Loss of this sense is known as astereognosis. This can occur with parietal lobe lesions and posterior column lesions. In parietal lobe lesions, position sense and light touch are normal, whereas in posterior column lesions, position sense, vibration sense and light touch are profoundly disturbed.
6. Vibration sense
If the foot of a vibrating tuning fork is placed on the surface of the body at any bony prominence, the vibrations can be felt, provided they are sufficiently strong. If the subject perceives the vibration, ask him to say when he ceases to feel it. If the examiner can still perceive it; the patient’s perception of vibration is impaired. This is a valuable test, as the ability to appreciate vibration may be lost in various diseases, like tabes dorsalis, peripheral neuritis and posterior column disorders. There is often some loss of vibration sense in the feet and legs, in old age. A tuning fork of 128 Hz should be used. Vibrations of higher frequency are more difficult to be perceived.
7. Test the sensory cranial nerves - I, II, V, VII, IX & X
8. Any abnormal sensations
These are experienced by the patient even without any external stimulus. Eg. pins and needles, numbness, tingling sensation, crawling of insects, itching, tightness or pressure.
Other disturbances of sensation
Ask the subject to close his eyes. Corresponding points on both sides of body are simultaneously stimulated by painful, tactile orthermal stimuli. Ask him to saywhich side is stimulated. In sensory inattention he fails to appreciate the stimulus on one side of the body. This is seen in parietal lobe lesion, on the opposite side of body.
Sensory loss: Sensations could be lost in lesions of sensory pathways at any level. Cortical sensations like tactile localisation, tactile discrimination and stereognosis are lost in lesions of parietal cortex, whereas the sensations like crude touch, pain and temperature probably appreciated at the thalamic level are preserved.
Name: Age: Sex: Occupation: Address:
2. General Examination
Build & nourishment
Clubbing of fingers
General appearance and behaviour
Level of consciousness
Mental & emotional state
Rt. I Lt. handed
Delusions and Hallucinations
Orientation in place, time and person
3. Sensory system examination
Trace the different Sensory pathways.
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