What is the clinical examination of sensory nerve?

CLINICAL EXAMINATION OF SENSORY SYSTEM

During examination of the sensory system, test various types of sensations.

 Peripheral nervous system functions (PNSF)

1. Tactile sensibility

2 Pain

3. Temperature

4. Sense of position

5 Vibrations

6. Presence of any abnormal sensation

Cortical sensory functions:

1. Point localization

2. Two point discrimination

3. Recognition of size, weight, shapes and form of objects (Sterorignotis)

4 Graph aesthesia

5. Extinction phenomenon

Before starting the examination, introduce yourself and explain the nature of the test to be performed to the patient to get his full cooperation. The eyes should then be closed, and the test should elicit different forms of sensations. Always compare corresponding points on both sides of the body

It routinely involves assessing the sensation of the hands, lower arms, abdomen, feet, and lower legs. Facial sensation is tested during the evaluation of cranial nerves

PRINCIPLES OF SENSORY ASSESSMENT:

The sensations are evaluated with the patient's eyes closed The stimulatipiki is presented minimally at first, and then its intensity is increased until the patient becomes aware of the stimulation. The sensations should be compared on both sides of the body, and they should be of equal intensity. The stimuli should have the correct location and correct identification. Sensory impairments should be mapped on a "body-figure" which represents the dermatomes

Peripheral Nervous System (PNS) Functions Testing

1. Tactile Sensibility 

i.  Light Touch

Use a wisp of cotton wool or hair aesthesiometer Tell the patient to say yes every time they feel a touch, comparing corresponding points on both sides of the body.

ii. Pressure Touch (Sense)

Repeat the above test with the tip of a finger or any blunt object the temperature of which does not differ much from that of the skin. Loss of tactile sensation is called anaesthesia if it is partial loss, it is called hypoesthesia; if it is exaggerated it is called hyperaesthesia

2 Pain sensation

i. Superficial Pain

Use the point of a sterile steel pin or a needle to test superficial pain sensation (Figure 35). Allow several seconds between stimuli. Ask the patient to identify where the sensation is felt, and ask the patient whether the pain is sharp or dull. The technique is almost the same as that used for touch.

ii. Pressure Pain

It is tested by squeezing the muscle the biceps, triceps, and calf muscles, or the lendo achilles can also be done with the help of Algometer With the help of this instrument, we can measure the threshold pressure that causes the pressure pain. Absence of sensibility to pain termed analgesia, partial loss of pain sensation is called as hypoalgesia, and exaggerated pain sensibility is known as hyperalgesia

3 Temperature (Thermal) Sensibility

It is tested using test tubes containing hot and cold water The part to be tested is touched with each in turn, and the patient says whether each tube feels hot or cold, and if he felt same intensity on both sides

4. Sense of Position.

It can be checked by two methods.

i. Ask the patient to close his eyes, take hold of one of his limbs, and move it about in various directions through the air, finally leaving it in some definite position, say semi-flexed and slightly elevated. ask him to put the corresponding limb in a similar position if the subject is able to place the other limb in the same position; a sense of position is intact.

ii. In case of foot, there may be fold that the great toe will be placed pointing upwards or downwards and he is asked to tell where it is

Patients with a defective sense of position may not be able to manipulate small objects without visually observing their movements (sensory ataxia).

5. Vibration Sense

A Tuning fork (218 Hz) is made to vibrate by striking the prong gently on a firm bus The rubber pad or wooden tales fact is then placed on the bony prominences of toes, shins, finger joints, wrists, elbows, shoulders, and sternum. Ask the patient to say 'yes' and where the vibration is felt The ankle is a commonly tested see Ascertain if the patient received the Vibrations and if so, ask him to say once again when he ceases to feel them. The force is transferred to the same region of the observer for comparison. of the examiner still perceive the vibrations, the patient's perception of vibration is impaired There is often loss of vibration sense in the feet and legs in old age Vibration sensibility may be lost in tables dorsalis, peripheral neuritis, and posterior column disorders.

6. Presence of any Abnormal Sensations

This is termed as paresthesia and consists of various sensations experienced by the patient in the absence of outside stimulus. The commonest of these are feeling of 'pins and needles, of numbness as heats of chills, of pressure or tightness, of itching sometimes termed pruritis or a feeling if insects were crawling over the body (formication)it can be due to CNS disorders (stroke, encephalitis) or disorders of peripheral nervous system (carpal tunnel syndrome)

Cortical Sensory Functions Testing

i. Point localization and two point discrimination

The skin of the patient is touched, and the stimulus is withdrawn. The patient is asked to tell the area of the skin touched after you have removed stimulus Normal subjects feel no difficulty in identifying the site touched

It is not enough to find out that the patient can feel the touch One should find out whether he can localize it and whether he can discriminate between two points (Two point discrimination). It is done with the help of a compass aesthesiometer. Normally two mm of separation of points can be appreciated on the palmar surface of the thumb and fingers. This distance depends upon the number of tactile receptors in the area (density of receptors), as below

Part of the Body and their minimal distance (mm)

Palms and hands➡ 8-12 mm

Toes➡ 3-8mm

Fingertips➡ 2-8mm

Tongue➡ 1mm

Chest and forearms➡ 40mm

Upper arms and thighs➡ 75mm

Back➡ 40-70mm

ii. Recognition of size, shape, weight and form (stereognosis) 

These faculties can be tested most accurately in both hands one by one with the eyes closed To test size, place in the patient's palm objects of same shape but of different sizes for example small rods of different lengths Ask him to say which is the larger. To test recognition of shape, familiar objects such as coins, a pencil, scissors, keys, etc., are placed in the hand, and the patient is asked to identify them by manipulation. Loss of this faculty is known as astereognosis

It may occur with patient lesions when position sense and light touch normal, although there is usually some defect in these modalities When astereognosis occurs, posterior column lesions position sense, vibration sense, and light touch are invariably profoundly disturbed.

iii. Graphesthesia

In this test, a stick of a cotton applicator is used to draw or write a number or letter on the palm of the patient's hand. The patient is asked to identify the number or letter Repeat this procedure with different numbers or letters on the other hand. The patient should be able to recognize the number or letter.

iv. Extinction Phenomenon

The patient is touched on the same body parts bilaterally with a sterile needlepoint. The patient should be able to detect both stimuli and to identify their locations