Sarcopenia diagnosed using masseter muscle area predictive of early mortality following severe traumatic brain injury

Traumatic brain injury（TBI）represents a global pandemic and is currently a leading cause of injury related death worldwide.Unfortunately,those who survive initial injury often suffer devastating functional,social,and economic consequences.

Changes following denervation to the masseter muscle

BACKGROUND： Masseter muscle nerve is often injured in mandible osteotomy. What changes in food intake and masseter muscle will be brought after masseter muscle nerve injury？ OBJECTIVE： This study was designed to selectively establish animal models of denervated masseter muscle and investigate the effects of severing masseter muscular nerve on masseter muscle and animal＇s food intake. DESIGN, TIME AND SETTING： A randomized controlled animal experiment was performed at the Laboratory Animal Center, Nanfang Hospital, Southern Medical University from September to November 2005. MATERIALS： A total of 50 healthy, adult, SPF-grade, New Zealand rabbits, of both genders, were used to develop an animal model of selectively denervated masseter muscle. METHODS： Five rabbits were randomly selected as normal controls. According to various mutilation methods, the remaining animals were randomly divided into 3 experimental groups, with 15 rabbits in each group： masseter muscular neural stem denervated, masseter muscular neural superior branch-denervated, and masseter muscular neural inferior brancb-denervated groups. Self-control comparison was performed on each animal. The right masseter muscle served as the experimental side, and the left masseter muscle served as the control side. In each group, 3 time points （2, 8, and 24 weeks post-surgery） were allotted for observation. MAIN OUTCOME MEASURES： At the pre-set time points, masseter muscular thickness was measured with a Logic 500 color Doppler ultrasonic diagnostic apparatus. Masseter muscle tissue was resected for hematoxylin eosin staining. Masseter muscular fiber diameter and area were measured with an optical microscope. Masseter muscle tissue was sectioned and nicotinamide adenine dinucleotide tetrazolium oxidoreductase （NADH-TR） and adenosine triphosphatase staining were performed. Following staining, the sections were quantitatively analyzed using an IBAS200 image analyzer. RESULTS： Post-surgery food intake： No abnormal food intake was found after surgery among the three groups. Intragroup comparison： In each experimental group, following denervation, masseter muscular thickness was decreased （P 〈 0.05） and masseter muscular fiber cross-section area was reduced in the experimental side compared to the control side （P 〈 0.05）. Inter-group comparison： There was a significant difference in masseter muscular thickness and masseter fiber cross-section area among the three experimental groups （P 〈 0.05）. There was no significant difference in masseter fiber type between the control side of the three experimental groups and the normal control group （P 〉 0.05）. CONCLUSION： Following various methods of masseter muscle denervation, masseter muscle thickness and masseter fiber cross-section area was reduced by varying degrees. Denervated masseter muscle did not influence food intake of experimental animals or alter masseter muscle fiber ratio.

Effect of Botubinum toxin type A injection into the masseter muscle on mandibular development in rats

Objective To investigate the effect of Botulinum toxin type A(Botox)injection into the masseter muscle on mandibular development in rats.Methods 1228-day-old Wistar rats were divided into two groups as Botox group(n=6)and control group(n=6)

Vestibular-evoked myogenic potentials recorded from miniature pigs and rats

Objective:To report vestibular evoked myogenic potentials from different recording sites(neck extensor or masseter muscles) in miniature pigs and rats.Methods:Potentials were recorded using 1000 Hz tone bursts from the neck extensor muscle or masseter muscle in normal adult Bama miniature pigs and rats anesthetized with 3%pentobarbital sodium and Sumianxin Ⅱ.Results:At 80 dB SPL,the first positive wave(P wave) of VEMPs was recognizable in 58%of rats with a latency of 6.45±0.23 ms and an amplitude of 1.45±0.49 μV when recorded from the neck extensor muscle,and in 50%of rats with a latency of 6.38±0.34 ms and an amplitude of 1.57±0.35 μV when recorded from the masseter muscle.In miniature pigs,at the same stimulus intensity,P wave was recognizable in 58%of the animals with a latency of 7.65±0.64 ms and an amplitude of 1.66±0.34 μV when recorded from the neck extensor muscle,and in 50%of the animals with a latency of 7.65±0.64 ms and an amplitude of 0.31±0.28 μV when recorded from the masseter muscle.Conclusion:VEMP can be induced from both neck extensor and masseter muscles in the miniature pig and rat.For a given species,the site of recording affects P wave induction rate and amplitude but not latency.Consistency and repeatability analysis suggests that the masseter muscle is a better recording site in miniature pigs while the cervical extensor is a better recording site in rats.For a given recording site,both latency and amplitude of the P wave are slightly greater in miniature pigs than in rats.

Effect of occlusal splints for the management of patients with myofascial pain： a randomized, controlled, double-blind study

Background Occlusal splints have been the preferred modalities in the management of myofascial temporomandibular disorders （TMDs）,but now controversy exists in reporting whether they are successful for TMDs treatments.The aim of this study was to give objective evidence to the assessment of treatment effect of occlusal splints for myofascial TMDs patients by clinical assessments and surface electromyography （sEMG） measurements of masseter muscles （MM）.Methods Thirty-six patients （12 males and 24 females） aged 16-57 （38±11） years participated in the study.All participants diagnosed with myofascial TMD were randomized into two groups （18 of each）.Patients in the first group （A） were treated with occlusal splints for 1 month,while patients in the second group （B） were treated with placebo （non-occluding palatal） splints.Clinical assessments were performed at the beginning of the study and 1 month after treatment.sEMG measurements for MM were performed at mandibular postural position （MPP） and maximum intercuspal contacted position （ICP） 1 month after the treatment.The root mean square （RMS） and the median frequency （MF） as linear indices of sEMG data were used to demonstrate muscle activity and muscle fatigue.Data were analyzed by ANOVA and post hoc SNK test.The differences were considered significant at P 〈0.05.Results It was found that 89% of group A either completely recovered （39%） or clinically improved （50%）,while only 22% of group B had a spontaneous improvement.sEMG analysis showed that at MPP,the mean of RMS value of MM in group A was lower than that of group B,which shows statistical differences （P 〈0.01）.At ICP,the RMS value of MM in group A was higher than that of group B,which shows statistical differences （P 〈0.01）.At MPP,MF value of MM in group A was higher than that of group B （P 〈0.05）.At ICP,MF value of MM was lower than that of group B （P 〈0.01）.Conclusions Occlusal splint could eliminate or improve the signs and symptoms of TMD patients with myofascial pain.sEMG analysis indicates that the wearing of occlusal splints may reduce the degree of fatigue of the masticatory muscles.The splint therapy outcome has a correlation with the electromyographic changes in the masticatory muscles.