Reference Values For CSA Of Peripheral Nerves And Distinctive Pattern Of Sonographic Nerve Enlargement In Guillain-Barré Syndrome

Part 1 Reference values for CSA of peripheral nerves and cervical nerve rootsObjective: The aim of this study was to determine normal reference values for cross sectional area（CSA）and the correlation between demographic factors and CSA in the peripheral nerves and cervical nerve roots using high resolution ultrasonography（HRUS）.Methods: This study was performed form January 2018 to January 2019 and was approved by the ethics committee（19k074-001）.One hundred healthy volunteers had HRUS of median,ulnar,tibial,fibular,C₅,C₆ at defined sites.The CSA was measured and the effects of age,hight,wight and body mass index（BMI）were evaluated.Results: CSA values in healthy subjects were described.No statistical differences were found in bilateral CSA of 11 sites.Compared between different genders,it was found that the CSA of males were larger.The CSA of peripheral nerves positively correlated with height,weight and BMI,among which the most significant correlation was with weight.The CSA in mid-forearm of ulnar nerve,the tibial nerve,the C₅ and C₆ roots positively correlated with age.However,the absolute value of the side-toside difference had no significant correlation with demographic factors.Conclusion: This study provides normative values for HRUS,which can be used as the reference criteria for the diagnosis of peripheral nervous diseases.Part 2 Distinctive pattern of sonographic nerve enlargement in Guillain-Barré syndromeObjective: To investigate the use of HRUS in the early stage of GuillainBarré syndrome（GBS）and to perform a sonographic comparison of different subtypes.The relationship between nerve conduction studies（NCS）,sonographic data,and clinical parameters were analysed.Methods: This study was performed form November 2018 to October 2019,in the ultrasonography center in the Department of Neurology at the First Hospital of Jilin University.It was approved by the ethics committee of the First Hospital of Jilin University（19K081-001）.Thirty-eight prospectively hospitalized patients suffered from acute GBS in three weeks as confirmed by clinical,laboratory,and electrophysiological examinations were recruited in the study.Ultrasonic CSA of peripheral nerves,vagus nerve,and cervical nerve roots were prospectively recorded within 3 weeks of disease onset.A similar number of healthy subjects（n=40）enrolled from our working environment without neurological deficits served as controls.Results: Ultrasonic CSA exhibited significant enlargement in most nerves of patients compared to that in healthy controls,and this was most prominent in cervical nerves.The CSA tended to be larger in acute inflammatory demyelinating polyneuropathy（AIDP）than in acute motor axonal neuropathy/acute motor and sensory axonal neuropathy（AMAN/AMSAN）,especially in C₅ [（7.0±1.7）mm² vs.（5.9±1.7）mm² ,P=0.042],C₆ [（12.0±2.1）mm² vs.（10.5±1.8）mm² ,P=0.033].The vagal nerve was more pronounced in patients with autonomic dysfunction than in patients without [（2.3±1.0）mm² vs.（1.4±0.5）mm² ,P=0.003].There was no correlation between CSA and their corresponding motor conduction velocities or functional disability.Conclusion: We observed that pathological structural changes were prominent in cervical nerves and occurred to a lesser degree in peripheral nerve trunks.With regard to different subtypes,AIDP tended to show more significant nerve thickening in cervical nerves compared to that of AMAN/AMSAN.Moreover,vagus enlargement could supplement clinical presentation for assessing autonomic dysfunction.HRUS of the peripheral nervous system is able to demonstrate specific changes in cervical nerves and inaccessible vagus nerve in GBS patients.HRUS may be of adjunctive diagnostic value in GBS assessment.