The "scratch test", or "direction of scratch" test, examines perception of the direction (up or down) of a scratch applied to the anterior shin (for example, with the sharp margin of a paper clip). It has been claimed as a reliable test of posterior column function of the spinal cord. Errors in this test correlate with central conduction times and vibration perception threshold.
Hankey GJ, Edis R. The utility of testing tactile perception of direction of scratch as a sensitive clinical sign of posterior column dysfunction in spinal cord disorders. Journal of Neurology, Neurosurgeryand Psychiatry 1989; 52: 395-398
Motoi Y, Matsumoto H, Kaneshige Y, Chiba S. A reappraisal of "direction of scratch" test: using somatosensory evoked potentials and vibration perception. Journal of Neurology, Neurosurgery andPsychiatry 1992; 55: 509-510