- Volume 73 , Number 3
- Page: 219–22
Quantitative measurement of sensory impairment in referral centers
This department is for the publication of informal communications that are of interest because they are informative and stimulating, and for the discussion of controversial matters. The mandate of the JOURNAL is to disseminate information relating to leprosy in particular and also other mycobacterial diseases. Dissident comment or interpretation on published research is of course valid, but personality attacks on individuals would seem unnecessary. Political comments, valid or not, also are unwelcome. They might result in interference with the distribution of the JOURNAL and thus interfere with its prime purpose.
To the Editor:
In 1998, we had suggested the quantitative method of sensory assessment of face and testing sites for the limbs (4). The following improvement to the original method may be required and this is based on our clinical experience in using this technique in a referral center with specialists and time available.
The 10 sites for testing sensation on the face, hands, and feet are unchanged. We suggest two changes with the Semmes-Weinstein monofilaments as a result of the recent understanding of the normal sensation of the hands and feet. Similarly, the method to score sensory nerve status is also altered. This is because the clinicians expressed that the norms for muscle grading are: "zero" indicating flaccidity, and a maximum score of 5 given for normal musculature; this was reversed in our quantitative sensory testing. In order to have a uniformity between sensory and muscle testing, we recommend the changes depicted in the following assessment form. In the revised form, 0 to 4 sensory grading system is followed for the hands. For the foot, 0 to 3 grading system is used because their sensory function is less than that of hands, which have to manipulate objects and require well developed sensory nerve endings. For the face, a 0 to 3 grade sensory threshold scale was used with the interpretations suggested by Premkumar, et al. (4).
The interpretations presented for the foot and hand are also based on the following previous scientific studies. Krotoski published the details on interpretation for the hands (1). Similarly, Birke, et al. interpreted 10 g filament as the level of protective sensation in leprosy patients (2). Kets, et al. study demonstrated that the touch sensibility monofilament threshold screening in healthy Nepalese population were 0.2 g for hands and 2 g for feet (3). Since all of the South Asian population is likely to be similar to that of Nepalese, we had taken the interpretation of this study and made a small modification to Krotoski's hand sensory battery by removing 0.05 to 0.07 g filament as an instrument to test normal sensation. In the original neurological mappings by Weinstein demonstrated the higher sensitivity in the face; the mean threshold of males to be 0.02 g; females, 0.018 g (5). Despite the above work in neurology, in the facial sensation assessment we suggest using a filament that gives a force of 0.05 to 0.07 g. It will be higher than the threshold for the face and will avoid false negative responses for the following reason: The lowest sensory threshold in normal individuals quoted in the Weinstein article is in the laboratory situation, which cannot be duplicated in clinics. Therefore, the next higher threshold may be required to increase the test sensitivity.
We are also aware that more studies are needed to answer the following research questions arising from this work. For instance, the lack of testing the corneal sensation to an extent limits the usefulness of testing facial sensation. Since this study confines in using the instrument of S-W filaments in testing only the skin in the limbs and face, and not the cornea, it is beyond the scope of this work. In the previous work on facial sensory testing, the authors hypothesized that the corneal sensation assesses only the ophthalmic branch of the trigeminal nerve (4). The other two branches of the nerve usually go unexamined. Facial sensory testing, we have suggested, will give quantitative sensory information for all three branches of the trigeminal nerve. Hence, the specific research question would be whether testing the facial sensation around the eyes could indicate corneal insensitivity?
The Figure
There is also a research question related to the testing sites: whether further reduction in the number of testing points would be more beneficial than the 25 sites we proposed? Our suggestion for further testing sites reduction is to 10; for example, two each for facial, great auricular, ulnar, median and posterior tibial. A further scrutiny is also needed into the validity of the facial sensory loss and its interpretation to function that we have suggested in our previous work (4), in a larger population.
Method used to score sensory nerves supplying face, hand and feet
Ten testing sites have been selected for each hand, foot and face. Three testing points have been identified for each trigeminal and 2 for each great auricular nerve: 4 for ulnar, 6 for median and 10 for posterior tibial. If the patient feels 0.05 g filaments in the face and 0.2 g in hands or 2 g filaments in feet on each point, three score is given to that site for face and foot. Four score is given to that site in hand as four filaments are used for the palmar surface: two for not feeling that filament in face and foot and so forth.
Thus, total loss of sensation at a point will be scored as zero for the face, hand, and feet; i.e., since there are 3 testing points for trigeminal, the maximum sensory loss per this nerve is scored, as 0 + 0 + 0, which is 0. Normal sensation will be scored as 3 + 3 + 3 = 9. The maximum score for normal sensation of the following nerves are stated below and these are indicated as denominators in the first Table.
- Ramaswamy Premkumar, Ph.D., Pichaimuthu Rajan, BOT, Ebenezer Daniel, MS, MPH
Schieffelin Leprosy Research and TrainingCentre, Karigiri - 632106, Tamil Nadu, India.
REFERENCES
1. BELL-KROTOSKI, J. A. Sensibility testing: current concepts. In: Rehabilitation of the Hand: Surgery and Therapy, 4th edn. St. Louis: Mosby-Year Book, Inc., 1995. pp. 109-128.
2. BIRKE, J. A., and SIMS, D. S. Plantar sensory threshold in the ulcerative foot. Lepr. Rev. 57 (1986) 261-267.
3. KETS, C. M., VAN LEERDAM, M. E., VAN BRAKEL, W. H., DEVILLE, W., and BERTELSMANN, F. W. Reference values for touch sensibility thresholds in healthy Nepalese volunteers. Lepr. Rev. 67 (1996) 28-38.
4. PREMKUMAR, R., DANIEL, E., SUNEETHA, S., and YOVAN, P. Quantitative assessment of facial sensation in leprosy. Int. J. Lepr. Other Mycobact. Dis. 66 (1998) 348-355.
5. WEINSTEIN, S. Intensive and extensive aspects of tactile sensitivity as a function of body part, sex and laterality. In: The Skin Senses. Springfield, IL: Charles C. Thomas Publishers, 1968. pp. 193-218.