# Therapy of Neurophysiological Changes after Oral and Maxillofacial Surgery--A Systematic Review
## 4 Discussion
### Limitations of the Work  
In general, due to the huge heterogeneity of the studies of surgical procedures, as well as in diagnosis, timepoint of diagnosis, and measurement of nerve lesions, conclusions from this review should be carefully interpreted.  
The surgical procedures ranged from extraction of mandibular teeth in four cases [48] to mandibular advancement procedures in six patients [42]. Degree of nerve impairment and potential to recover was not related to a surgical procedure. Other factors not clearly declared in the studies were factors such as expertise of surgeon (experienced surgeon,surgeon in training, student) or anatomic individualities causing persistent neuropathic pain. These factors, as well as male gender, older age, and root curvature, were found to be risk factors for paresthesia in third molar removal [61]. Only one study dealing with neurophysiological changes and implant placement met the final inclusion criteria.  
In this review, the different time points of reevaluation (e.g., after 2 years in [PERSON] et al. [45], 1 week after surgery [46], directly after surgery in [PERSON] et al. [42]) prevent a correct comparability because of the known time impact of nerve injuries [62]. [PERSON] et al. [63] described that persisting functional nerval disorders exceeding one year are of poor prognosis. [PERSON] and [PERSON] [29] recommended an early diagnosis within the first 36 h after injury. As a clinical implication, it is necessary to emphasize the need for early referral and intervention when nerve injuries occur [63,64]. In the study of [PERSON] et al. [45], revealing neurophysiological disturbances of >2 years, LLL provided a significant improvement concerning sensory perception compared to placebo-LLL. This may point to potential procedures capable to improve long-term nerval disturbances, although thermal parameters did not recover after >2 years.  
The studies, in general, did not differ between sensory nerve impairment and traumatically caused nerve injury. As described in the introduction, the first mentioned may develop without an injury of anatomically relevant structures and has a high spontaneous remission rate. In literature, altered sensation was found to be associated with pain in 45% of the cases [26]. Therefore, to evaluate a whole neurosensory profile, the neurophysiological changes and their correlation with neuropathic pain must be described [26,65]. Only one study [46] evaluated pain states and their potential to recover. Patients' subjective assessment of the situation was analyzed in six studies [18,41,42,43,45,46] but not in comparable ways. This is necessary to deliver a whole reproducible profile of neurophysiological disturbances. Studies providing standardized quantitative sensory testing, including a standardized thermode, investigating cold and warm detection thresholds using the methods of limits are able to provide information on neurophysiological disorders ([PERSON] et al. [45], [PERSON] et al. [42], [PERSON] et al. [48]). Some of the studies use the contralateral, unaffected side as reference, others use identical areas at a healthy control group. By using the contralateral side as a control, one may argue that patient-specific errors may occur [41]. The studies did not specify the \"recovery\" precisely and homogenously (e.g., four studies performing QST after therapy and involving objective measurements such as neurometry). Others identified the neurophysiological changes according to clinical findings [44]. The interpretation of the outcome, even stated as significantly improved, \"seemed\" not to be reliable. This concerns primary and secondary outcome as well. There is also a considerable heterogeneity concerning evaluation of IANI or LNI [41].