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Thomas L.1, Chan K.1
1University of Queensland, School of Health and Rehabilitation Sciences, St Lucia, Australia
Background: Dissection of the cervical arteries has in rare cases been associated with cervical manipulative therapy but screening methods including physical tests of blood flow are limited their ability to predict those at greater risk. Increased stiffness of the cervical arterial wall may increase vulnerability to environmental stresses such as minor neck strain. Measurement of arterial stiffness has been shown to be a reliable indicator of some arterial diseases and could provide a method of evaluating underlying arterial susceptibility in dissection. Recently, ultrasound elastography has been used to measure the stiffness of various tissues including the carotid artery. Measurement of wall stiffness could provide a useful means to screen the cervical arteries prior to manipulative treatment. Individuals with stiffer arteries might be at greater risk from minor neck trauma.
Purpose: To investigate the ability of ultrasound elastography to assess the mechanical properties of the cervical arterial wall and to determine any change in wall stiffness between the neutral and contralateral head positions
Methods: This was an observational study investigating wall stiffness in the cervical arteries in 2 head positions. The right internal carotid and vertebral arteries of 30 healthy participants were scanned in B-mode ultrasound, Doppler, and shear wave elastography modes with an Acuson Siemens S3000 ultrasound system using a 9 MHz linear transducer. Measurements of arterial wall thickness (mm), blood flow velocities (cms-1), and wall stiffness (cms-1) were taken proximally at C3-4 and distally at C1-2, in the neutral head position and at end range contralateral rotation. Repeatability of stiffness measures was assessed. Linear regression analysis was used to compare wall stiffness between arteries and the neutral and contralateral head rotation positions.
Results: Thirty participants (16 male) mean age 29.8 years (SD12.8, range 20-62) entered the study and full sets of wall stiffness measures were obtained from 28 participants. Inter-rater reliability was good (ICC ICA 0.71, VA 0.61). The vertebral arterial wall was significantly stiffer (3.45 cm/s) than internal carotid (2.45cm/s) in the neutral head position (p 0.001), and became stiffer in contralateral rotation (p=0.043). The internal carotid wall became less stiff in contralateral rotation (p=0.038). Lumen diameter of the vertebral artery decreased in contralateral rotation. There was a moderate negative correlation (r = - 0.5) between vertebral artery lumen diameter and wall stiffness, with stiffness increasing as the lumen diameter decreased.
Conclusion(s): Ultrasound elastography can be utilised to measure arterial wall stiffness in the cervical arteries in both neutral and rotated head positions. Stiffness appears to be different between ICA and VA which may have implications for relative arterial susceptibility when exposed to environmental stresses such as extreme head positions or minor strain.
Implications: Ultrasound elastography has potential to provide insight into cervical arterial wall compliance and the effect of different head positions. Future research should investigate patient populations to determine stiffness in those with dissection. Elastography may have potential for use as a clinical screening tool prior to cervical manipulative therapy in the future.
Funding acknowledgements: The University of Queensland
Topic: Musculoskeletal: spine
Ethics approval: Medical Research Ethics Committee, The University of Queensland, ref. 2015000326
All authors, affiliations and abstracts have been published as submitted.
