ORIGINAL ARTICLE Is There Altered Activity of the Extensor Muscles in Chronic Mechanical Neck Pain? A Functional Magnetic Resonance Imaging Study Shaun O’Leary, PT, PhD, Barbara Cagnie, PT, PhD, Ashton Reeve, BSc, Gwendolen Jull, PT, PhD, James M. Elliott, PT, PhD ABSTRACT. O’Leary S, Cagnie B, Reeve A, Jull G, Elliott JM. Is there altered activity of the extensor muscles in chronic mechanical neck pain? A functional magnetic resonance imag- ing study. Arch Phys Med Rehabil 2011;92:929-34. Objective: To compare the pattern of neck extensor muscle use in participants with chronic mechanical neck pain to that of healthy controls during 2 different extension exercises by use of muscle functional magnetic resonance imaging (mfMRI). Design: Cross-sectional. Setting: University laboratory. Participants: Data recorded from subjects with chronic mechanical neck pain (n=12; 10 women, 2 men) were com- pared with previously recorded data from healthy subjects (n=11; 7 men, 4 women). Interventions: Not applicable. Main Outcome Measures: mfMRI measures of shifts in T2 relaxation were made for the multifidus, semispinalis cervicis, semispinalis capitis, and splenius capitis muscles, at C2-3, C5-6, and C7-T1 levels, prior and immediately after 2 different exercises: cervical extension in craniocervical neutral (CCN) and cervical extension in craniocervical extension. T2 shift values (difference between pre- and postexercise T2 relaxation values) for each muscle and exercise condition were used for analysis. Results: While there were observed differences in differen- tial activation of the extensor muscles in participants with mechanical neck pain compared with controls, these differ- ences were only evident for the CCN exercise condition and were only observed for 3 out of the 7 muscle regions of interest during this exercise. Conclusions: Results of this study suggest some alteration in the differential activation of the cervical extensors in patients with mechanical neck pain and indicate that further investiga- tion of this muscle group in mechanical neck pain disorders is warranted. Key Words: Cervical vertebrae; Exercise; Magnetic reso- nance imaging; Rehabilitation. © 2011 by the American Congress of Rehabilitation Medicine I MPAIRMENT IN MUSCLE function is a feature of chronic mechanical neck pain and has been implicated as a signif- icant factor in the maintenance of this disorder that is charac- terized by periods of remission and exacerbation. 1 Impairments of the cervical extensor muscles have been identified in patients with mechanical neck pain disorders 2-6 and exercise to train and improve their performance is advocated in management. 7 However, there is a paucity of studies investigating their role in mechanical neck pain. Further information on the topic could be useful to better inform decision making in the clinical management of neck pain. Studies investigating the neck extensor muscles in patients with mechanical neck pain have observed changes in their physical structure, including alterations in cross-sectional area, 3,5,8 and changes in fiber type. 9 Studies have also identified deficiencies in extensor muscle strength 10,11 and endurance 12,13 in patients with neck pain compared with healthy subjects. However, while clinical evidence exists for the flexors, 14,15 there has been little exploration into the effect of painful neck disorders on the differential activation of the extensor muscles. Within the multiple layers of the cervical extensor muscle group, there is a distinct division between the superficial cer- vical muscles (splenius capitis [SpC] and semispinalis capitis [SCa]), which span the entire cervical spine and the deeper layered muscles (semispinalis cervicis [SCe] and the multifidus [Mul]), which span only the typical cervical vertebrae (C2-7). While imaging studies have attempted to quantify changes in cervical extensor muscle activity in response to exercise, 16,17 no studies to date have compared the activity patterns of the different cervical extensor muscles in patients with and without chronic mechanical neck pain disorders. It is therefore perti- nent to compare the differential activity of the extensors in From the Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, Division of Physiotherapy (O’Leary, Jull), the Centre for Advanced Imaging (Reeve, Elliott), and the Centre of National Research on Disability and Rehabilitation Medicine (Reeve, Elliott), The University of Queensland, Brisbane, QLD, Australia; the Physiotherapy Department, Royal Brisbane and Women’s Hospital, Brisbane, QLD, Australia (O’Leary); Department of Rehabilitation Sciences and Physiotherapy, Ghent University, Ghent, Belgium (Cagnie). No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organi- zation with which the authors are associated. Reprint requests to Shaun O’Leary, PT, PhD, Principal Research Fellow, Physio- therapy Dept, Royal Brisbane and Womens Hospital, Royal Brisbane Post Office, Brisbane, QLD, 4029 Australia, e-mail: shaun_oleary@health.qld.gov.au. Published online April 29, 2011 at www.archives-pmr.org. 0003-9993/11/9206-01070$36.00/0 doi:10.1016/j.apmr.2010.12.021 List of Abbreviations BMI body mass index CCE craniocervical extension CCN craniocervical neutral mfMRI muscle functional magnetic resonance imaging MRI magnetic resonance imaging Mul multifidus MVC maximal voluntary contraction ROI region of interest SCa semispinalis capitis SCe semispinalis cervicis SpC splenius capitis 929 Arch Phys Med Rehabil Vol 92, June 2011