Quantitative assessment of facial sensation in leprosy

The trigeminal and great auricular nerves which supply sensation to the face are affected in leprosy. No objective sensory testing methods have been devised for testing sensation in the face. Testing for corneal sensation to ascertain trigeminal nerve or visualization and palpation of the great auricular nerve alone may not be enough to establish the involvement of these nerves. In a sample of leprosy patients, face sensation threshold measurements were done using a set of three Semmes-Weinstein (SW) monofilaments that gave a force of 0.05-0.07, 0.2 and 2 g. Sensation was tested by three examiners and intra- and inter-observer testing was used as a means to validate the findings. Within the limitations of this study, the results indicate that use of SW monofilaments is a fairly reliable and repeatable method for sensory testing in the face. During follow up, a single filament with a force of 0.5-0.7 g (2.83 marking number in SW filament or any other filament with a corresponding gram force) could be used to assess sensation. A simple procedure of quantifying sensation in these nerves is suggested. A method to incorporate trigeminal or great auricular nerve sensory testing into the existing sensory assessment charts is also discussed.