Aesthesiometers

Aesthesiometers are instruments used to quantify sensory thresholds of the somatosensory system. They are employed in clinical and research settings to measure tactile, thermal, and vibration sensitivity on the skin, supporting the evaluation of peripheral nerve function, spinal and brain injuries, and conditions such as diabetes mellitus–related neuropathy. The measurements are typically expressed as the smallest stimulus perceived or as the smallest distance at which two points are resolved.

Mechanical tactile aesthesiometers include Semmes-Weinstein monofilaments, a graded set of nylon filaments that bend at known forces. The examiner applies each filament perpendicularly to the skin until it bends, recording whether the stimulus is felt. This method yields a force threshold and is widely used to map cutaneous sensation, particularly for screening diabetic neuropathy and in wound or pressure ulcer risk assessment.

Two-point discrimination aesthesiometers use a pair of pointed tips mounted on a handle or caliper. By adjusting the distance between the points and asking the patient to identify one point versus two, clinicians determine spatial acuity thresholds on different body regions, most commonly the fingertips and face.

Vibrotactile aesthesiometers and thermal aesthesiometers provide other stimulus modalities. Vibroesthesiometers (including devices such as biothesiometers) deliver controlled vibration to measure vibration or tactile thresholds. Thermal aesthesiometers, often employing Peltier elements, assess warm and cold detection and thermal pain thresholds.

Limitations include subjective responses, learning effects, skin condition, and examiner technique. Standardized protocols and training are essential, and results are typically interpreted within the broader framework of quantitative sensory testing (QST) to profile somatosensory function across modalities.