Primary sensation - asymmetry, sensory level

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Light touch is best tested with a cotton-tipped swab, but a light finger touch will often suffice, as long as care is taken to make the stimulus fairly reproducible. You can test the relative sharpness of pain by randomly alternating stimuli with the sharp or dull end of a safety pin (always use a new pin for each patient).

70. Pin Prick


Temperature sensation can be tested with a cool piece of metal such as a tuning fork.

71. Temperature


Test vibration sense by placing a vibrating tuning fork on the ball of the patient's right or left large toe or fingers and asking him to report when the vibration stops. Take care not to place the tuning fork on a bone, since bones conduct the vibration to much more proximal sites, where they can be detected by nerves far from the location being tested.

72. Vibration Sense


Test joint position sense by moving one of the patient's fingers or toes up and down and asking the patient to report which way it moves. Hold the digit lightly by the sides while doing this so that tactile inputs don't provide significant clues to the direction of movement. The digit should be moved very slightly because normal individuals can detect movements that are barely perceptible by eye.

73. Joint Position Test


Two-point discrimination can be tested with a special pair of calipers, or a bent paper clip, alternating randomly between touching the patient with one or both points. The minimal separation (in millimeters) at which the patient can distinguish these stimuli should be recorded in each extremity.

74. Two-Point Discrimination Test


As in other parts of the exam, the patient's deficits, as well as the anatomy of the nerves, nerve roots, and central pathways, should be used to guide the exam (see Neuroanatomy through Clinical Cases Chapters 7, 8, and 9). Comparisons should be made from one side of the body to the other and from proximal to distal on each extremity. Note especially if there is a sensory level corresponding to a particular spinal segment below which sensation abruptly changes, since such a change may indicate a spinal cord lesion requiring emergency intervention. Whenever there are uncertainties in the sensory exam, or other parts of the exam, a good strategy is to repeat the relevant portions of the exam several times.

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