Should sensory function after median nerve injury and repair be quantified using two-point discrimination as the critical measure?

Two-point discrimination (2PD) is widely used for evaluating outcome from peripheral nerve injury and repair. It is the only quantifiable measure used in the British Medical Research Council (MRC) classification that was developed by Highet in 1954. This paper reports the results of a study of 41 patients with complete median nerve lacerations to the wrist or forearm. Two-point discrimination thresholds were assessed together with locognosia (locognosia is the ability to localise a sensory stimulus on the body's surface), tactile gnosis, and touch threshold. Using the MRC classification 29 (71%) patients had a result of S2 or below, 11 (27%) were S3, and only one scored S3+. Patients scored much better on the other tests and showed progressive recovery. It remains too difficult for patients to obtain a measurable threshold value on 2PD and the test therefore lacks responsiveness. The rating of outcome from peripheral nerve repair should not be based solely on 2PD testing and must include other tests of tactile sensibility.