ZweiPunktDiskriminationsTests

Zweipunktdiskrimination, also called two-point discrimination, is the smallest distance at which two simultaneous tactile stimuli on the skin are perceived as two distinct points. It is a standard measure of tactile acuity and varies across body regions according to sensory receptor density and cortical representation.

The underlying mechanism lies in the distribution of mechanoreceptors in the skin (for example, Merkel cells and Meissner corpuscles) and the arrangement of their receptive fields in the somatosensory cortex. Receptive fields in fingertips are small and densely packed, yielding high acuity, whereas areas like the back have large receptive fields and low acuity.

Measurement is typically performed with an aesthesiometer or calipers. The examiner alternates between one and two-point stimuli and asks the patient to report whether they feel one or two points, or which sensation they perceive. The distance at which two points are reliably perceived as separate is recorded as the two-point threshold. Normative values depend on the body site.

Clinical relevance: The test helps assess peripheral nerve function and somatosensory pathway integrity. Abnormal thresholds can indicate neuropathies, nerve compression, diabetes-related neuropathy, or post-traumatic injury. Age-related decline in acuity is also observed.

Limitations include examiner technique, patient attention, and instrument calibration. Standardized protocols and site-specific norms improve reliability and comparability.

See also: tactile acuity, somatosensory system, sensory thresholds.