Microneural reconstruction after iatrogenic lesions of the lingual nerve and the inferior alveolar nerve. Critical evaluation

Abstract

As microneural repair techniques of the sensory mandibular branches enter the third decade of their clinical use, there are but a few long-term investigations into the value of these procedures in the treatment of iatrogenic injury to the lingual (LN), inferior alveolar (IAN) or mental (MN) nerve. To establish the efficacy of microneural repair in lesions of the LN, IAN or MN with loss of continuity, the outcome of sensory recovery was evaluated in a series of 92 patients (LN: direct coaptation n = 39, coaptation + sural nerve grafting n = 23; IAN: direct coaptation n = 11 coaptation + sural nerve grafting n = 10; MN: direct coaptation n = 11). The minimum duration of follow-up was 14 months postoperatively. The persistent sensory deficit was assessed using standardized neurosensory testing and gustometric stimuli. In addition the patients answered a multiple-choice questionnaire containing a list of complaints. To obtain a numeric estimate for interindividual and intergroup comparison the information from clinical measurements and patient reports was condensed into a 'neurological score' and a 'complaint score', respectively. Furthermore, adequate items from both scores were combined to affirm or deny the return of sensory function in terms of protective and discriminative sensation. The overall results show a broad range of variation in the scores, sometimes reflecting severe degrees of persistent sensory impairment. The lowest scores, corresponding to the best regeneration, were found after direct coaptation of the LN, IAN and NM, but even the best results did not provide sensory recovery to a preinjury level. After direct coaptation of LN 69% of the patients exhibited protective sensation and 41% regained discriminative function. In contrast, LN grafting was ensued from restoration of protective function in 39% and discriminative function in 17% of the patients. More striking differences were found between coaptation and grafting of the IAN (IAN coaptation: 91% protective function; 18% discriminative function; IAN grafting: 60% protective function, 0% discriminative function). In the LN coaptation group low scores and improved taste perception were convincingly associated with short periods since injury (i.e. timing of repair). In conclusion, we feel there is sufficient justification to optimize the potential results of microneural repair by immediate (LN/MN) or early (IAN) reexposure of the injured site in order to clarify the precise nature of the underlying nerve damage and prevent delay, if patients present with complete loss of sensory function subsequent to dentoalveolar or oral surgery. However, clinical and electrophysiologic findings suggesting impairment or partial loss of sensory function are considered a contraindication to microneural intervention, in view of the limited prospects of sensory recovery after surgical repair.