Ultrasonic Anatomical Basis Of Optic Nerve Sheath And Ultrasonic Measurement Of Opyic Nerve Sheath Diameter To Evaluate The Increase Of Intracranial Pressure

Objective : The purpose of this study was to understand the ultrasound anatomical images of the optic nerve sheath,and explore the normal range of adult optic nerve sheath diameter(ONSD)and its influencing factors.According to the correlation between ONSD and intracranial pressure(ICP),the optimal ONSD threshold for the diagnosis of intracranial hypertension would be determined.Methods:(1)Three eyeballs,with which the optic nerve and rouge body connected to,were removed from the cadaver specimen.Ultrasound was performed in axial,longitudinal and transverse scans to record the ultrasonographic features of optic nerve sheath on different section surfaces.(2)102 normal adults who underwent ultrasound from the Department of Ultrasound,the First Affiliated Hospital of Guangxi Medical University fromJuly 2018 to February 2019,were regarded as volunteers and included in the normal control group.Ultrasound was used to measure the ONSD of each volunteer,and some information were collected such as gender,age,height and weight.The body mass index(BMI)was calculated according to height and weight.The aim was to search the normal range of normal adult ONSD and analyze the related influencing factors of normal ONSD.(3)From July 2018 to February 2019,87 patients with cranial brain disease were enrolled,who were hospitalized in the Department of Neurology and Infectious Diseases of the First Affiliated Hospital of Guangxi Medical University.Ultrasound was used to measure the ONSD of each patient and collect the information such as gender,age,height,weight,and BMI.The patient’s ICP was measured by lumbar puncture within 12 hours after the ultrasound examination.According to the results of lumbar puncture ICP measurement,patients were divided into normal ICP group and high ICP group.The correlation between ONSD and gender,age,height,weight,BMI,ICP was analyzed,and the optimal threshold value for the diagnosis of ONSD was determined.Results:(1)The longitudinal and transverse scans could clearly show the optic nerve sheath and intrathecal tissue by ultrasound.There was a three-layer structure surrounding the dark area of the optic nerve,which showed an strong-low-strong echo from the inside to the outside.Axial scanning could not clearly distinguish the three-layer structure,and only a layer of thick echoes surrounding the optic nerve was showed instead.(2)The axial scanning of adultoptic nerve sheath was consistent with the axial scanning of optic nerve specimen.Without ICP increasing nor disc edema,the strong echo surrounding the optic nerve was relatively thin.In patients with ICP,the strong echogenic layer surrounding the optic nerve was thickened to varying degrees.In this situation,12 patients had optic disc edema,and the average thickness of the optic disc was(1.65±0.31)mm,which showed a flat prominent strong echo spot at the optic nerve head.(3)The mean value of ONSD in 102 normal adults was(4.21±0.36)mm,and the 95% confidence interval was 4.14~4.28 mm.The maximum was 4.95 mm,and the minimum was 3.17 mm.The 95% medical reference range was form 3.51 to 4.90 mm.(4)The ONSD values of the high ICP group,the normal ICP group and the normal control group were(5.55±0.57)mm,(4.45±0.27)mm,and(4.21±0.36)mm,respectively.The ONSD value of the high ICP group was significantly higher than that of the normal ICP group(P<0.001)and the normal control group(P<0.001).The ONSD value of the normal ICP group was higher than that of the normal control group(P<0.001).(5)Establishing the ROC curve to determine the optimal threshold value of the ONSD for the diagnosis of ICP increase.The area under the ROC curve was0.980,95% confidence interval(0.957,1.000),and the optimal threshold for the diagnosis of ICP was 4.9 mm.When ONSD≥4.9 mm,the diagnosis was ICP ascending.The sensitivity was 93.1% and the specificity was 96.6%.(6)The results about the analysis of ONSD-related factors showed that ONSD was positively correlated with ICP,and the correlation coefficient was r=0.794,P<0.001.Gender,age,height,weight,and BMI were not associated with normal adult ONSD.Conclusions : Ultrasound can clearly show the structure of optic nerve sheath.Ultrasound measurement of ONSD can preferably evaluate the increase of intracranial pressure.This is a convenient,effective,non-invasiveand safe method for monitoring intracranial pressure.It has a higher clinical application value.