The Three-dimensional Quantitative Measurement Of The Reflex Movements Of The Eyelids And The Auricles In Rats

Facial paralysis affects thousands of people every year.The assessment of its severity is the basis for its diagnosis,treatment and prognosis estimation.In the studies of facial nerve in animals,the methods for measurement of facial nerve function can be mainly divided into three types,the morphological methods,the electrophysiological methods and motor behavior methods.The motor behavior methods have advantages over the other two because they can directly measure the dysfunctions of muscular movements,which would be the consequences after facial nerve paralysis,and the goal of treatments to restore the facial nerve’s complex and delicate innervations for the target muscles.However,there are difficulties in the objectivity and accuracy of these assessments.In the previous studies,the measurements of the muscular movement innervated by facial nerve are stuck in the two-dimensional plane level.In the present study,we try to use an analysis system based on motion capture and three-dimensional reconstruction techniques,which were preliminarily validated in the measurements among healthy people and patients,to assess the motor parameters in rats with facial paralysis in a three-dimensional,dynamic and quantitative way.The movements of eyelids and auricles are included in the present study.Blink reflex is an important protective reflection,with relatively large amplitude and simple forms.In humans and animals,the structures related to its nerve pathways and the muscles involved are consistent.Auricular movement is important for auditory orientation.Because the directions of the auricular movements are variable and not in the same plane,the previous methods couldn’t describe the positions of the auricles accurately and quantitatively.Objective:(1)To adjust the analysis system,and to develop the methods and data processing programs for the quantitative assessment of facial nerve function among animals.(2)To explore the motor parameters which are fit for the assessment of reflex eyelids movements,and to obtain their normal values and changes between the facial paralysis side and the normal side.(3)To quantitatively describe the reflex auricles movements in rats,and to compare the differences of the motor parameters between the facial paralysis side and normal side.Method:Healthy adult female Wistar rats accept the surgery to become the unilateral facial nerve paralysis models.They are fixed within a fixed box before movement capture processes and placed in front of the analysis system.We paste the mark points in the sites to be measured.We use the air flow against the cornea to induce eyelids reflex movement.And we use a sound source,which is placed below the rat in its midsagittal plane,to produce a sudden strong noise to induce the auricular reflex movement.The movements of the markers are captured by the analysis system among the entire process.Then we output the three-dimensional data of the markers,set and calculate the motor parameters,and analyze the ranges and the trends of changes of those parameters statistically.Results:1 Eyelids movements:(1)In eyelids reflex movements,after the air flow stimulation,the distance between the markers on the middle of the upper eyelid of both sides is the only one which become larger than static state.In the control group the maximum distance is 21.5-23.2mm,and in the experimental group the distance is 20.1-22.2mm,which is significantly smaller than the control group.(2)The maximum change of distances takes place between the upper and lower eyelid midpoints,closed state accounted for 0.58-0.60 of the resting static state,and the minimum distance is 5.5-6.5mm,the velocity of the distance changing is about 40-55mm/s.For the facial paralysis side,the ratio is 0.78-0.92,the velocity is 16mm/s.The distance of the eyelids movement of the facial paralysis side is about a quarter of the distance of the contralateral healthy side,and the velocity of movement is significantly lower than the contralateral.(3)The minimum medial canthus angle is 40-50°,accounting for 0.64-0.67 of the resting state,and the change of the angle is 22-25° among blink reflex.In facial paralysis side,the ratio is 0.86,which is significantly greater than the contralateral healthy side,and the change of the angle is about 10°,which is significantly less than the contralateral.(4)The medial canthus angle has the largest angular changing velocity,the median is about 160-320°/s,and in the facial paralysis side is 116°/s,which is significantly lower than the contralateral.2 Auricles movements:(1)After the sudden stimulation of the sound,the distance between the markers on the apex of the auricle of both sides reduce to 0.78-0.98 of the rest state,while the distance from the nose to the apex of auricle increased and the ratio is 1.07-1.11.∠FOf reduced,and the angular rate is 170-340°/s.So the apex of the auricles moves medially and caudally.(2)The distance from the root to the apex of the auricle is increased,1.06 to 1.08 to the resting state,which means the auricle stretching among the reflex,the relative velocity is 90-115mm/s.(3)The relative velocity between the medial canthus and the root of the auricle is 50-110mm/s,and the distance increased,show the caudal movement of the auricular root.The relative velocity between the medial canthus and the apex of the auricle is 40-60mm/s,which is lower than that of the auricular root.(4)In the experimental group,the facial paralysis side,the distance between the root and the apex of the auricle,the medial canthus and the apex,the medial canthus and the root,and the nose and the apex all become smaller after sound stimulation than in resting state.The ratios are 0.95-0.97,and the velocities are 10-30mm/s,with the direction of the movement opposite to and much smaller than that of the contralateral side.There are no obvious peak/valley changes in the angle curve of facial paralysis side,and the angular rate was significantly smaller than that of the contralateral.3 To assess the movements of the markers on medial canthus of both sides and nose,the distance,angle and other changes are relatively small.They may be considered as reference points.Conclusions:This analysis system can be applied to the three-dimensional and quantitative measurement of eyelids and auricles movement in small animals such as rats.The animals were well adapted during the measurements.There are significant differences between the control group and the experimental group,or between the facial paralysis side and the contralateral healthy side,in all the motor parameters chosen.