Mechanosensory and thermosensory changes across the border of impaired sensitivity to pinprick after mandibular nerve injury

Purpose: The study goal was to determine how sensory function varies across the border of impaired sensitivity to pinprick in patients with mandibular nerve injuries. Patients and Methods: Borders of decreased sensitivity to pinprick were mapped in 15 patients who reported altered sensation. Four mechanoreceptive, 2 thermoreceptive, and 2 thermonociceptive functions were studied at 5 sites separated by 0.6 cm across the border. The tests were repeated to evaluate day-to-day consistency in the pattern of variation for each sensory measure. Results: The estimates of sensory function were not found to vary in a systematic manner from outside to inside the pinprick-impaired area for all patients for any of the 8 tests. However, for every test, some patients exhibited large variations. On average, the magnitudes of loss in contact detection, subjective intensity of light touch, and direction discrimination were greatest; the magnitudes of loss in 2-point perception and in heat and cold pain perception were least. Some patients provided no evidence of impairment on certain tests. For some patients, the estimates suggested increased sensitivity within the pinprick-impaired area (eg, to noxious cold stimuli). Conclusions: Although certain patients exhibit impairment, there is no obligatory loss in light touch, 2-point perception, direction discrimination, or temperature perception across the border of decreased sensitivity to pinprick. The differences among patients suggest that the data from individual patients should be evaluated in clinical studies and in clinical practice. Researchers should not rely solely on average values and summary statistics. (C) 2002 American Association of Oral and Maxillofacial Surgeons.