Sensory functions

Three screening tests are available for the assessment of sensory function. Two-point discrimination (2PD), pin prick test and cold-warm discrimination; it is not essential to carry out the 2PD and the pin prick test. If the 2PD shows no damage, the pin prick test need not be carried out. In case of noticeable findings in the screening tests, the Semmes-Weinstein monofilament test (SWMT) is carried out as a supplementary test.

Two-point discrimination

Screening (1)

Required material: 2-Point discriminator with own weight

The examiner rests the patient’s hands in supination, the examination is carried out for ten possible areas (N1-N10 right/ left hand). Only those areas suspected of being afflicted need be tested.

Procedure: The test begins with the healthy side with a 4mm separation between the points (normal range). The order in which the examiner tests with single or double points is random. With the instrument laid along the long axis without imposing additional pressure on the finger, the measurement is taken on the fingertip. The instrument remains in place for 5 seconds, after which the patient must say whether they sensed one or two points. Should the patient fail to sense two points, the instrument is adjusted to the next larger distance. The distance between the points that the patient recognises as two separate points is documented.

Pin prick test

Screening (2)

Required material: Paperclip

Procedure: Touch the skin in the area to be examined with a sharp and blunt object (for instance the sharp and blunt ends of a paperclip). The patient is asked to differentiate between the different ends. Only as much pressure as is required to achieve the correct answer on the healthy side needs be used. The test is repeated three times per area. The frequency of the patient’s correct answers is recorded (see documentation example).

Cold-warm discrimination

Screening (3)

Required material: E.g. test tubes

Procedure: For the test, test tubes are filled with water at different temperatures. The skin areas to be examined (N1-N10) are touched alternately with the hot and cold objects. The patient is asked to respond on the temperature of each touch. The test is repeated three times per area. The frequency of the patient’s correct answers is recorded (see documentation example).

Documentation example:

07_sensory

Semmes-Weinstein monofilament test / Weinstein enhanced monofilament test

Supplementary testing

Required material: Case with monofilaments according to Semmes-Weinstein

The SWMT tests sensitivity in up to 23 areas on the palm and the back of the hand. Not all of these areas need to be tested, only those areas that are presumed to be afflicted. The patient’s hand is laid supine, such that they cannot see it. The test begins on the distal side of the palm of the unimpaired hand. If the patient senses the stimulation, the afflicted hand is then tested.

Procedure: The test starts with the 2.83 filament (= normal sensitivity). Held upright, the monofilament is pressed into the area to be tested until it bends. The patient responds as soon as they recognise the touch. All identified test areas are then examined with the same filament. Should the 2.83 monofilament not be felt, the test is repeated with the next largest filament. Monofilaments of the range 1.65 to 4.31 are each applied three times to the same spot, the remaining filaments are just applied once to the skin. Each application lasts 1.5 seconds, with a 1.5 second pause between applications. The size of the experienced monofilaments is recorded.