A Clinical Study On Evaluating Facial Nerve Function By Electrodiagnosis

ObjectiveThe electrodiagnostic methods can be used in facial nerve functional estimating system through the detection of eletroneurography (ENoG) before and after parotid gland surgery. Hope to provide objective electrodiagnostic parameters to facial nerve functional estimating standard, and to reflect the clinical application value of ENoG as an objective method on estimating facial nerve function. Then discuss the clinical potential applications of surface electromyography (sEMG) as a new method to analysis myoelectric activity of facial expression muscle and to estimate facial nerve function.Methods1. Eletroneurography (ENoG) was applied to52patients with unilateral parotid gland tumor at the time of24hours before operation and7-14days (average10days) after surgery. Parameters included amplitude (Am), latency time (LT), and degeneration rate (DR) were calculated. At the same time point, the facial nerve functions of patients before and after surgery were evaluated subjectively by regional facial nerve functional evaluation system.2.10normal people were elected as control group and11patients with different classification of postoperative facial nerve function as the experimental group. Meanwhile, the estimated number of motor unit action potential (MUAP) and inter-pulse interval (IPI) of MUAP were achieved based on sEMG signals acquired from the two groups. Results1. Parameters results of detected ENoG display:①There was no statistically significant difference of LT before and after surgery and between the healthy and affected sides in each facial nerve (P>0.05);②At the healthy side, there was no statistically significant difference of Am before and after surgery in each facial nerve (P>0.05);③At the affected side, there was significant decrease of Am after surgery in each facial nerve (P <0.05);④After surgery, there was significant decrease of Am at the affected side in each facial nerve;⑤DR parameters of patients almost to zero before surgery, but DR parameters of46.3%postoperative patients≥40%.2. Correlation analysis between regional facial nerve function evaluation results and DR parameters:∥Preoperative evaluation of the facial nerve function in patients with I level accounted for92.3%, but postoperative facial nerve function evaluation greater than I level accounted for88.5%.②There was higher correlation in statistics between regional facial nerve function evaluation results and DR parameters.③The higher level of facial nerve function evaluated after surgery, the bigger DR parameter. Postoperative evaluation of the facial nerve function in patients with IV-V levels, whose DR parameters were75%～99%.3. Analysis results of collected sEMG display:①In the control group, corresponding activities of a muscle contraction distinguished by muscle movement around the mouth were symmetrical and the signal amplitude almost the same.②In the experimental group corresponding activities of a muscle contraction distinguished by muscle movement around the mouth were unsymmetrical and the signal amplitude in healthy side was lower than in affected side.③The comparison of sEMG parameters between the experimental group and control group, difference was different in different cases of facial paralysis. The number ratios of MUAP between the healthy and affected sides and IPI of the affected side had significant changes in Ⅳ～Ⅴ levels compared to normal. 4. Analysis of postoperative facial nerve function evaluation results and patients’ clinical factors:Parotid gland tumors located in the deep lobe, greater than3cm in diameter, row second operation and the sacrifice of facial nerve and parotid gland resection in patients, whose postoperative facial nerve function were poor. Patients with parotid gland malignancy, whose postoperative facial nerve function were the worst.Conclusions1. Am and DR parameters acquired by ENoG can reflect the damage degree of the postoperative facial nerve, and can be used to evaluate facial nerve function in the clinical as objective parameters, and can consider take DR parameters into facial nerve evaluation system (FNES).2. Amplitude changes of sEMG between the healthy and affected sides are consistent with the results of ENoG, and parameters of sEMG have difference when reflect the serious facial paralysis situations. Meanwhile sEMG as a new method in evaluating facial nerve function field needs further study.3. Parotid gland surgery way depends on location, size and characteristics of the tumors, row parotid gland resection or secondary surgery lead to the relatively high risk and degree of facial nerve injury.