Two-point discrimination tester

LETTERS TO THE EDITOR Two-point discrimination tester To the Editor: Bravo ... the better mousetrap! Drs. Mackinnon and Dellon extend the prongs of two-point discriminatory testing yet another 5 mm (J HAND SURG lOA:906-7, 1985). Have we not flogged static and dynamic two-point testing long enough? A review of the literature reveals that this aspect of the sensory examination was known to S. Weir Mitchell, M.D., who wrote in 1872 of a similar device, "For numerical appreciations, we make use of the aesthesiometer, which consists of a compass the points of which are covered with little rounded balls, a scale placed above enabling us to learn how far apart are the points." He continues, "Above all, it is essential, in every examination of sensation, to see that the patient does not move the part during the time of testing it . . . if he be allowed to stir the part ever so little, the answer he makes will often prove correct when in the absence of motion it would have been defective.'" Regardless of the latest innovations described in the Department of Technique, it has always seemed reasonable to follow the teaching of this classical American neurologist, who over 100 years ago advised, "Ordinary compasses and a rule on which to ascertain the extent of separation of their parts, answer every purpose." The sincere desire to publish articles of significance motivates authors and editors alike, but we must exercise some awareness of the advice offered by professor C. Northcoate Parkinson, citing Parkinson's, "Rule Six" as follows, "Don't take yourself too seriously. "2 Richard M. Braun. M.D. 6699 Alvarado Rd. #2302 San Diego. CA 92120

testing instruments, which were introduced more than a century ago. As rehabilitation of the sensory function of the hand has been introduced recently,' lagging far behind the greater awareness for motor rehabilitation, sensory testing instruments have also lagged behind those for the motor system in scientific testing and standardization. To date, only normative data have been compiled for two-point discrimination. 2,3 In contrast to the increasing efforts in the 1980's to refine evaluation of the motor system by studying validity and reliability of pinch and grip testing instruments ,4, 5 there has not been one study reported that evaluates these criteria for standardization of any sensory testing instrument. In particular, no instrument presently available permits an examiner to evaluate, and therefore to record and report, two-point discrimination at a controlled (defined) stimulus intensity (pressure). Until we have an instrument to measure two-point discrimination that is manufactured with product control, has normative data, permits reporting the observed two-point limen at a given stimulus intensity, and has been demonstrated by the scientific method to be both reliable and valid, only then will we have an instrument to measure sensation in the hand. "Sensory assessment instrumentation is in an early developmental phase. Representing a final frontier that should be given a high priority, the generation of instruments that better evaluate sensibility of the hand will significantly influence the scope and direction of the profession in the next several decades."7 A "better mousetrap," Dr. Braun, yes, but the "best mousetrap" is yet to come. This is a goal we should all take seriously. A. Lee Delton. M.D. Susan E, Mackinnon. M.D. The Hampton Plaza 300 E. Joppa Rd. Towson. MD 21204

REFERENCES 1. Mitchell SW: Injuries of nerves and their consequences. 1872. American Academy of Neurology Reprint Series. New York, 1965, Dover 2. Train J: Parkinson's "rule six." Forbes Magazine, vol 127, No.1, 1981

Reply To the Editor: Thank you for the opportunity to reply to Dr. Braun's letter. He questions the necessity in the 1980's for making technical improvements "Two-point discrimination tester." (J HAND SURG I OA:906-7, 1985) in the sensory

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THE JOURNAL OF HAND SURGERY

REFERENCES 1. Dellon AL: Evaluation of sensibility and re-education of sensation in the hand. Baltimore, 1981, The Williams & Wilkins Co 2. Gillis M, Pool R: Two-point discrimination distances in the normal hand and forearm. Plast Reconstr Surg 59:5762, 1977 3. Louis OS, Greene TC, Jacobson KE, et al: Evaluation of normal values for stationary and moving two-point discrimination in the hand. J HAND SURG 9A:552-5, 1984 4. Mathiowetz V, Weber K, Volland G, et al: Reliability and