Sensation

Original Editors - Naomi O'Reilly Top Contributors - Naomi O'Reilly, Kim Jackson, Kakshya Rupakheti and Claire Knott

Introduction

According to Jones (2011)[1] sensation is complex consisting of several modalities including our four special senses including Vision, Hearing, Smell, and Taste, and our Somatosensory Senses including tactile - light touch and pressure, proprioception, temperature and pain. Sensation plays a huge role in how we perceive our environment, impacts on our control of movement, maintaining arousal, and provides warning of potential danger[1]. The evaluation of sensation, or any sensory modality for that matter, is highly dependent on the ability and desire of the patient to cooperate. Sensation belongs to the patient (i.e., is subjective) and the examiner must therefore depend almost entirely on their reliability. Sensory changes that are unassociated with any other abnormalities (i.e., motor, reflex, cranial, hemispheric dysfunctions) must be considered weak evidence of disease unless a pattern of loss in a classical sensory pattern is elicited e.g. in a typical pattern of peripheral nerve or nerve root distribution. Therefore, one of the principle goals of the sensory exam is to identify meaningful patterns of sensory loss. Basic testing should sample the major functional subdivisions of the sensory systems. The patient's eyes should be closed throughout the sensory examination.

Sensory Receptor Nerve Fibre Sensory Pathway
Light Touch

Meissner's Corpuscle

Merkel's Discs

Aβ Fibers Spinothalamic
Pressure

Pacinian Corposcles

Aβ Fibers
Pain / Pin Prick

Free Nerve Endings

Aδ Fibers (Nociceptors of Neospinothalamic Tract)
C Fibers (Nociceptors of Paleospinothalamic Tract)
Temperature

Thermoreceptors

Aδ Fibers (Cold Receptors)
C Fibers (Warmth Receptors)
Vibration

Meissner's Corpuscle

Pacinian Corposcles

Aβ Fibers Dorsal Column
Proprioception

Muscle Spindle

Ruffini Endings

Aβ Fibers
Touch Localization

Meissner's Corpuscle

Merkel's Discs

Aβ Fibers
Stereognosis Hemispheric
Graphesthesia


Sensory Examination[2]

At first, Superficial(Exteroceptive) sensation is examined which is followed by Proprioceptive(deep) sensation, and then, the combined cortical sensations.If the superficial sensation is impaired then some impairment is also seen in deep and combined sensations. Sensory tests are done from the distal to the proximal direction.

Superficial Sensation Deep Sensation Combined Cortical Sensation
  1. Pain Perception
  2. Temperature Awareness
  3. Touch Awareness
  4. Pressure Perception
  1. Kinesthesia Awareness
  2. Vibration Perception
  1. Stereognosis Perception
  2. Tactile Localization
  3. Two-Point Discrimination
  4. Double Simultaneous Stimulation
  5. Graphesthesia
  6. Recognition of Texture
  7. Barognosis

Pain Perception

It is also known as sharp/dull discrimination. To test this sensation, the sharp and dull end of any objects like a safety pin, a reshaped paperclip, or neurological pin is used. The sharp and dull end is randomly applied perpendicular to the skin, should not be applied too close to each other or in a too rapid manner to avoid the summation of impulses. The patient is asked verbally to indicate sharp/dull when a stimulus is felt. All areas of the body should be tested. After testing the instrument should be sterilized or disposed.

Temperature Awareness

Two test tubes with stoppers are required for this examination; one should be filled with the cold water (between 5°C to 10°C) and warm water( 40°C to 45°C). It should be taken care that the temperature should remain within this range for accuracy. The test tubes are randomly placed in contact with the skin area to be tested. All skin surfaces should be tested. The patient is asked to respond hot and cold after each stimulus application.

[3]

Touch Awareness

A piece of cotton, camel-hair brush, or tissue is used to perceive the tactile touch input. Light touch or stroke is applied in the area to be tested. The patient is asked to indicate where he/she recognizes that a stimulus has been applied .

[4]

Pressure Perception

The therapist's fingertip or a double-tipped cotton swab is used to apply a firm pressure on the skin surface. This test can also be administered using the thumb and finger to squeeze the Achilles tendon. The patient is asked to indicate when an applied stimulus is recognized.

Kinesthesia Awareness

Awareness of movement is known as kinesthesia. The Therapist passively moves a joint through a relatively small range of motion and the patient is asked to describe the direction of movement. The patient can also respond by simultaneously duplicating the movement with the opposite extremity.

Proprioception Awareness

Proprioception includes position sense and awareness of joint at rest. The joint is moved through a range of motion and held in static position by the therapist, the patient is asked to describe the position either verbally or by demonstrating on another limb.

Vibration Perception

The perception of a vibratory stimulus is tested by placing the base of the vibrating tuning fork on the bony prominence( sternum, elbow, ankle). Generally, the tuning fork should be of 128Hz. If there is impairment patient will be unable to distinguish between a vibrating and nonvibrating tuning fork. Therefore, there should be a random application of vibrating and nonvibrating stimuli.

[5]


Stereognosis Perception

Tactile object recognition is determined in this test. A familiar object of different shape and size are required like keys, coins, combs, safety pins, pencils). A single object is placed in a hand and the patient manipulates it to identify the object and say it verbally. For speech impairment patients sensory testing shield can be used.

[6]


Tactile Localization

The test checks the ability to localize touch sensation on the skin.This test is not performed in isolated manner rather it is done in combination with pressure perception or touch awareness.

Two-Point Discrimination

It determines the ability to perceive two points applied to the skin simultaneously. Aesthesiometer or the circular two-point discriminator are the devices to test. The two tips of the instrument are applied to the skin simultaneously with the tip spread apart. With each successive application, the two tips are gradually brought closer together until the stimuli are perceived as one. The small est distance between the stimuli that is still perceived as two distinct points is measured.

Double Simultaneous Stimulation(DSS)

DSS examines the ability to perceive a simultaneous touch stimulus on opposite sides of the body; proximally and distally on a single extremity; or proximally and distally on one side of the body.

Graphesthesia(Traced Figure Identification)

The ability to recognize letters, numbers, or designs traced on the skin is examined using fingertip or the eraser end of the pencil. the patient is asked verbally the figures drawn on the skin.

Recognition of Texture

The test examine the ability to differentiate among various textures like cotton, wool, or silk.

Barognosis( Recognition of weight)

For the test different weights are used. the therapist may choose to place a seres of different weights in the same hand one at a time, place a different weight in each hand simultaneously.

[7]


Vision

Vision plays an important role in balance and movement, therefore any deficits may have a huge impact on functional activities. As many as 40% of individuals with Stroke will present with visual deficits post-Stroke.
Eyesight in the Older Person

Hearing

The sense of hearing is of paramount importance in spoken communication, and hearing loss can lead to porblems with communication, decreased awareness of environmental clues and even social isolation.
Hearing in the Older Person

References

  1. 1.0 1.1 Jones K. Neurological Assessment: A Clinician's Guide. Elsevier Health Sciences; 2011 Nov 29.
  2. O'Sullivan SB, Schmitz TJ. Physical rehabilitation fifth edition. FA Davis.
  3. Clinical Examinations Videos. Temperature perception test - Spinothalamic tracts test. Available from:https://www.youtube.com/watch?v=7it5E9OBl2k [last accessed 21/12/2020]
  4. Clinical Examinations Videos. Neurological sensory examination- Light touch and pain(pin prick test). Available from: https://www.youtube.com/watch?v=XVOVpq-41BY [last accessed 21/12/2020]
  5. Clinical Examinations Videos. Neurological peripheral vibration test. Available from:https://www.youtube.com/watch?v=iEfyHSm2fCA [last accessed 21/12/2020]
  6. Onlinemedicalvideo. Normal Sensory Exam ; Stereognosis. Available from:https://www.youtube.com/watch?v=6fyiGUAg2GY [last accessed 21/12/2020]
  7. Clinical Examinations Videos . Two point discrimination - Graphesthesia - Stereognosis. Available from:https://www.youtube.com/watch?v=xhygnHkC-9Y [last accessed 21/12/2020]