MRI Study On The Cut-Off Value Of Muscle Thickness Related To Thoracic Outlet Syndrome

Background:Most of the factors that cause thoracic outlet syndrome are as follows:(1)Soft tissue factors account for 70%of TOS compression factors.Anterior scalene muscle hypertrophy,edema,and degeneration are the most common factors that cause neurovascular compression.Because the anterior scalene muscle is very close to the brachial plexus anatomically,the anterior scalene syndrome is the most common.(2)Bone factors account for 30%of TOS compression factors.Common bony compression factors include the first rib,cervical ribs,and the excessively long seventh cervical vertebra transverse process.(3)There are a few other factors,most of which are space-occupying factors,such as tumors and bone hyperplasia.None of the current methods for diagnosing thoracic outlet syndrome is 100%sensitive or specific.The clinical diagnosis of thoracic outlet syndrome(TOS)is still controversial and challenging.Medical imaging,especially MRI,has a good evaluation value for brachial plexus and surrounding soft tissues due to its excellent soft-tissue contrast.Purpose:In this study,intraoperatively seen related muscle hypertrophy leading to thoracic outlet syndrome was used as the diagnostic reference standard.Through the measurement of related muscles on the MRI T1WI sagittal image,it was predicted that the best diagnostic cut-off value for judging relative muscle hypertrophy on MRI,which provides important clinical guidance.Materials and methods:We retrospectively studied 98 patients(108 sides),all of whom underwent surgery after an MRI examination.The MRI scan for this study was examined by a professional radiologist who did not know the intraoperative results.The relative muscle hypertrophy seen during the operation was used as the reference standard.Among them,34 anterior scalene muscle hypertrophy and 25 subclavius muscle hypertrophy were used to predict the best diagnostic cut-off value for judging relative muscle hypertrophy on MRI.Results:There was a statistically significant difference between the related muscle hypertrophy on the affected side and the non-hypertrophy on the contralateral side and during the operation(P<0.05).The data was obtained by measuring the MRI T1WI sagittal image.The best cut-off point for diagnosing male anterior scalene muscle hypertrophy is 11.6mm,the best cut-off point for female anterior scalene muscle hypertrophy is11.695mm,and the best cut-off point for subclavius muscle hypertrophy is 11.785mm.Conclusion:When the patient takes the supine position,the hypertrophy of the anterior scalene muscle and subclavian muscle on the MRI T1WI sagittal image is correlated with the muscle hypertrophy seen during the operation,combined with the intraoperative findings and the MRI T1WI sagittal image to measure the male front scalene muscle the thickness is11.600mm,the thickness of the female anterior scalene muscle is11.695mm and the thickness of the subclavian muscle is 11.785mm.