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The International Journal of Adult Orthodontics & Orthogathic Surgery
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International Journal of Adult Orthodontics and Orthognathic Surgery

Year 1990
Volume 5 , Issue 1

Pages: 35 - 42

Comparison of methods to assess neurosensory alterations following orthognathic surgery


Orthognathic surgery may damage branches of the trigeminal nerve, resulting in postoperative neurosensory disturbances. Alterations may be due to surgical edema, stretching, or direct trauma to the nerve. Lack of a standard and objective method of assessment hinders efforts to study and/or reduce the incidence of neurosensory disturbances in patients who underwent bilateral mandibular ramus sagittal split osteotomies. Forty patients (26 female, 14 male) ranging in age from 23 to 47 years particpated in the study. All of the patients had bilateral mandibular ramus sagittal split osteotomies and were stabilized with rigid skeletal fixation. Neurosensory testing was performed prior to surgery, and at 2 weeks, 1 month, 3 months, 6 months, and 1 year following surgery. Methods of assessment included two-point discrimination, threshold to electrical stimulation, and somatosensory evoked potentials. Threshold to electrical stimulation and two-point discrimination were obtained by the two-alternate forced choice technique. Somatosensory evoked potentials testing used surface electrodes over the area of the mental foramina for stimulation and recording electrodes at vertex an d inion. Analysis of variance revealed significant (P < .001) changes in each measure across time, indicating that all three techniques were sensitive to some degree of neurosensory disturbances. The techniques were compared by measuring the length of time required postsurgically for each to return consistently to within 10% of the presurgical level. One-way analysis of variance revealed significant (P < .05) differences among measures. Pairwise comparisons revealed that somatosensory evo ked potentials respnses required a significantly longer period of time to return to presurgical levels than did either threshold to electrical stimulation or two-point discrimination. No significant difference was noted in recovery times between threshold to electrical stimulation and two-point discrimination. The following conclusions were reached: (1) most patients who subjectively reported postsurgical neurosensory disturbances also exhibited them when tested with any of the three methods, but the correlation was higher with somatosensory evoked potentials responses than with threshold to electrical stimulation and two-point discrmination; (2) in patients not reporting neurosensory disturbances, somatosensory evoked potentials testing revealed a higher percentage of results differing from baseline levels; and (3) somatosensory evoked potentials responses required a significantly longer time to return to presurgical baseline, which is presumably indicative of greater sensitivity to subclinical neurosensory disturbances


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