MRI analysis of the size and shape of the oropharynx in chronic whiplash

Shape modelling of the oropharynx distinguishes associations with body morphology but not whiplash-associated disorder

Characterization of the oropharynx, a subdivision of the pharynx between the soft palate and the epiglottis, is limited to simple measurements. Structural changes in the oropharynx in whiplash-associated disorder (WAD) cohorts have been quantified using two-dimensional (2D) and three-dimensional (3D) measures but the results are inconsistent. Statistical shape modelling (SSM) may be a more useful tool for systematically comparing morphometric features between cohorts. This technique has been used to quantify the variability in boney and soft tissue structures, but has not been used to examine a hollow cavity such as the oropharynx. The primary aim of this project was to examine the utility of SSM for comparing the oropharynx between WAD cohorts and control; and WAD severity cohorts. The secondary aim was to determine whether shape is associated with sex, height, weight and neck length. Magnetic resonance (MR) T1-weighted images were obtained from healthy control (n = 20), acute WAD (n = 14) and chronic WAD (n = 14) participants aged 18-39 years. Demographic, WAD severity (neck disability index) and body morphometry data were collected from each participant. Manual segmentation of the oropharynx was undertaken by blinded researchers between the top of the soft palate and tip of the epiglottis. Digital 3D oropharynx models were constructed from the segmented images and principal component (PC) analysis was performed with the PC weights normalized to z-scores for consistency. Statistical analyses were undertaken using multivariate linear models. In the first statistical model the independent variable was group (acute WAD, chronic WAD, control); and in the second model the independent variable was WAD severity (recovered/mild, moderate/severe). The covariates for both models included height, weight, average neck length and sex. Shape models were constructed to visualize the effect of perturbing these covariates for each relevant mode. The shape model revealed five modes which explained 90% of the variance: mode 1 explained 59% of the variance and primarily described differences in isometric size of the oropharynx, including elongation; mode 2 (13%) primarily described lateral (width) and AP (depth) dimensions; mode 3 (8%) described retroglossal AP dimension; mode 4 (6%) described lateral dimensions at the retropalatal-retroglossal junction and mode 5 (4%) described the lateral dimension at the inferior retroglossal region. There was no difference in shape (mode 1 p = 0.52; mode 2 p = 0.96; mode 3 p = 0.07; mode 4 p = 0.54; mode 5 p = 0.74) between control, acute WAD and chronic WAD groups. There were no statistical differences for any mode (mode 1 p = 0.12; mode 2 p = 0.29; mode 3 p = 0.56; mode 4 p = 0.99; mode 5 p = 0.96) between recovered/mild and moderate/severe WAD. Sex was not significant in any of the models but for mode 1 there was a significant association with height (p = 0.007), mode 2 neck length (p = 0.044) and in mode 3 weight (p = 0.027). Although SSM did not detect differences between WAD cohorts, it did detect associations with body morphology indicating that it may be a useful tool for examining differences in the oropharynx.

Self-reported Dysphagia and Pharyngeal Volume Following Whiplash Injury

Difficulty swallowing has been reported following whiplash injury; however, the reasons remain poorly understood. A possible factor may be the observed changes in pharyngeal volume. The current exploratory study was designed to examine the prevalence of self-reported dysphagia after whiplash and the relationship with recovery status and change in pharyngeal volume. Data were available from a longitudinal study of adults with whiplash. Data included magnetic resonance imaging (MRI) of the cervical spine, the Dysphagia Handicap Index (DHI), and Neck Disability Index (NDI) collected over four timepoints (< 1 week, 2 weeks, 3 months, and 12 months post-injury). Initial cross-sectional analysis examined 60 patients with DHI data from at least one timepoint. A second, longitudinal analysis was conducted on 31 participants with MRI, NDI, and DHI data at both early (< 1-2 weeks) and late (3-12 months) timepoints. The pharynx was contoured on axial T2-weighted MRI slices using OsiriX image processing software and pharyngeal volume (mm³) was quantified. In the 60-patient cohort, prevalence of self-reported dysphagia (DHI ≥ 3) was observed in 50% of participants at least once in 12 months (M = 4.9, SD 8.16, range 0-40). In the longitudinal cohort (n = 31), mean total DHI significantly (p = 0.006) increased between early and late stages. There was no relationship (p = 1.0) between dysphagia and recovery status, per the NDI% score. Pharyngeal volume remained stable and there was no relationship between dysphagia and pharyngeal volume change (p = 1.0). This exploratory study supports the need for further work to understand the nature of dysphagia, extent of functional compromise, and the underlying pathophysiology post-whiplash.

[Dysphagia in cervical spine diseases]

Dysphagia is a common symptom and can be indicative of a variety of heterogeneous diseases. "Classical" diseases of the head and neck region, such as acute tonsillitis, peritonsillar abscesses, diverticula, and benign or malignant tumors are common causes of dysphagia. However, it can also occur in the context of neurological diseases, e.g., as a result of stroke or as an age-related phenomenon (presbyphagia). Pathologies of the cervical spine can also be a cause of dysphagia. In this context, congenital or acquired diseases, inflammatory or degenerative processes, cervical spine surgery, and (malignant) masses of the cervical spine should be taken into account. Particular dysphagia with a positive history of previous operative interventions on the cervical spine or symptoms such as chronic back pain and trauma should give rise to consideration of a cervical spine-related cause.

Whiplash-Associated Dysphagia: Considerations of Potential Incidence and Mechanisms

Non-specific self-reports of dysphagia have been described in people with whiplash-associated disorders (WAD) following motor vehicle collision (MVC); however, incidence and mechanistic drivers remain poorly understood. Alterations in oropharyngeal dimensions on magnetic resonance imaging (MRI), along with heightened levels of stress, pain, and changes in stress-dependent microRNA expression (e.g., miR-320a) have been also associated with WAD, suggesting multi-factorial issues may underpin any potential swallowing changes. In this exploratory paper, we examine key biopsychosocial parameters in three patients with persistent WAD reporting swallowing change and three nominating full recovery after whiplash with no reported swallowing change. Parameters included (1) oropharyngeal volume with 3D MRI, (2) peritraumatic miR-320a expression, and (3) psychological distress. These factors were explored to highlight the complexity of patient presentation and propose future considerations in relation to a potential deglutition disorder following WAD. The three participants reporting changes in swallowing all had smaller oropharyngeal volumes at < 1 week and at 3 months post injury and lower levels of peritraumatic miR-320a. At 3 months post MVC, oropharyngeal volumes between groups indicated a large effect size (Hedge's g = 0.96). Higher levels of distress were reported at both time points for those with persistent symptomatology, including self-reported dysphagia, however, this was not featured in those nominating recovery. This paper considers current evidence for dysphagia as a potentially under-recognized feature of WAD and highlights the need for future, larger-scaled, multidimensional investigation into the incidence and mechanisms of whiplash-associated dysphagia.

How Do We Meet the Challenge of Whiplash?

A previous special issue of JOSPT (October 2016) discussed whiplash in terms of the clinical problems and current research surrounding prevention, biomechanics of injury, emergent care, imaging advancements, recovery pathways and prognosis, pathogenesis of posttrauma pain, acute and chronic management, and new predictive clinical tools. While great strides have been made in the field of whiplash and are continuing in earnest, a key group of clinicians and academics have recognized that inconsistent outcomes in published literature hamper our ability to meaningfully synthesize research findings, leading to results of systematic reviews that provide very few concrete clinical recommendations. We are optimistic that improved outcomes for people with whiplash-associated disorder (WAD) are attainable in the near future, as interdisciplinary research efforts continue to align internationally, new mechanisms are identified and explored, and advanced statistical techniques allow complex questions to be answered in clinically meaningful ways. J Orthop Sports Phys Ther 2017;47(7):444-446. doi:10.2519/jospt.2017.0106.

Advancements in Imaging Technology: Do They (or Will They) Equate to Advancements in Our Knowledge of Recovery in Whiplash?

Synopsis It is generally accepted that up to 50% of those with a whiplash injury following a motor vehicle collision will fail to fully recover. Twenty-five percent of these patients will demonstrate a markedly complex clinical picture that includes severe pain-related disability, sensory and motor disturbances, and psychological distress. A number of psychosocial factors have shown prognostic value for recovery following whiplash from a motor vehicle collision. To date, no management approach (eg, physical therapies, education, psychological interventions, or interdisciplinary strategies) for acute whiplash has positively influenced recovery rates. For many of the probable pathoanatomical lesions (eg, fracture, ligamentous rupture, disc injury), there remains a lack of available clinical tests for identifying their presence. Fractures, particularly at the craniovertebral and cervicothoracic junctions, may be radiographically occult. While high-resolution computed tomography scans can detect fractures, there remains a lack of prevalence data for fractures in this population. Conventional magnetic resonance imaging has not consistently revealed lesions in patients with acute or chronic whiplash, a "failure" that may be due to limitations in the resolution of available devices and the use of standard sequences. The technological evolution of imaging techniques and sequences eventually might provide greater resolution to reveal currently elusive anatomical lesions (or, perhaps more importantly, temporal changes in physiological responses to assumed lesions) in those patients at risk of poor recovery. Preliminary findings from 2 prospective cohort studies in 2 different countries suggest that this is so, as evidenced by changes to the structure of skeletal muscles in those who do not fully recover. In this clinical commentary, we will briefly introduce the available imaging decision rules and the current knowledge underlying the pathomechanics and pathophysiology of whiplash. We will then acknowledge known prognostic factors underlying functional recovery. Last, we will highlight emerging evidence regarding the pathobiology of muscle degeneration/regeneration, as well as advancements in neuroimaging and musculoskeletal imaging techniques (eg, functional magnetic resonance imaging, magnetization transfer imaging, spectroscopy, diffusion-weighted imaging) that may be used as noninvasive and objective complements to known prognostic factors associated with whiplash recovery, in particular, poor functional recovery. J Orthop Sports Phys Ther 2016;46(10):861-872. doi:10.2519/jospt.2016.6735.

Magnetic resonance imaging atlas of the cervical spine musculature

The anatomy of the cervical spine musculature visible on magnetic resonance (MR) images is poorly described in the literature. However, the correct identification of individual muscles is clinically important because certain conditions of the cervical spine, for example whiplash associated disorders, idiopathic neck pain, cervical nerve root avulsion and cervical spondylotic myelopathy, are associated with different morphological changes in specific muscles visible on MR images. Knowledge of the precise structure of different cervical spine muscles is crucial when comparisons with the contralateral side or with normal are required for accurate description of imaging pathology, management and assessment of treatment efficacy. However, learning the intricate arrangement of 27 muscles is challenging. A multi-level cross-sectional depiction combined with three-dimensional reconstructions could facilitate the understanding of this anatomically complex area. This paper presents a comprehensive series of labeled axial MR images from one individual and serves as a reference atlas of the cervical spine musculature to guide clinicians, researchers, and anatomists in the accurate identification of these muscles on MR imaging. Clin. Anat. 29:643-659, 2016. © 2016 Wiley Periodicals, Inc.

Magnetic resonance imaging changes in the size and shape of the oropharynx following acute whiplash injury

STUDY DESIGN

Prospective longitudinal.

OBJECTIVE

To quantify the temporal development of magnetic resonance imaging changes in oropharyngeal morphometry in subjects with varying levels of disability following a whiplash injury.

BACKGROUND

A recent cross-sectional investigation has identified reductions in the size and shape of the oropharynx in subjects with chronic whiplash-related disability when compared to healthy controls. The temporal development of such changes and their relationship to persistent disability have yet to be investigated.

METHODS

Forty-one subjects (30 women) with acute whiplash injury were included. Repeated measures T1-weighted magnetic resonance imaging was used to measure and compare cross-sectional area (CSA) in square millimeters and shape ratio (SR) of the oropharynx at 4 weeks, 3 months, and 6 months postinjury. Subjects were classified at 6 months by their Neck Disability Index scores into the following categories: recovered (less than 8%), mild disability (10%-28%), and moderate/severe disability (greater than 30%). The effects of time and group and the interaction effect of group by time on oropharynx morphometry (CSA, SR) were investigated using repeated-measures, linear, mixed-model analysis. Based on previous research findings, age, gender, and body mass index were entered into the analyses as covariates. Where significant main or interaction effects were detected, pairwise comparisons were performed to investigate specific differences in the dependent variable between groups and within groups over time.

RESULTS

There was a significant interaction effect for group by time for both the CSA and SR values. Age significantly influenced SR (P = .024) and body mass index significantly influenced CSA (P = .001). There was no difference in CSA or SR across all groups at 4 weeks postinjury. However, at 6 months, CSA was significantly different between the recovered group and the moderate/severe group (P = .001). The recovered group demonstrated a significant increase in CSA (P = .04) over time, whereas the moderate/severe group significantly decreased (P = .01). At 6 months, the moderate/severe group had a reduced SR compared to the mild group (P = .03). No differences in CSA or SR of the oropharynx were found between the mild and recovered groups throughout the study.

CONCLUSION

Temporal reductions in CSA of the oropharynx occur following whiplash and persist to a greater extent in those with moderate/severe symptoms at 6 months postinjury. Studies are planned (1) to better investigate the underlying mechanisms of CSA reductions, (2) to determine their relevance to functional recovery and production of voice following whiplash, and (3) to evaluate multidisciplinary assessment and management of these patients.

Considerations in the physical rehabilitation of patients with whiplash-associated disorders

STUDY DESIGN

Review of research identifying physical impairments in the neuromuscular system in subjects with whiplash-associated disorders.

OBJECTIVE

Review the impairments in movement and neuromuscular function toward constructing research informed exercise programs.

SUMMARY OF BACKGROUND DATA

Pain and injury to the musculoskeletal system result in loss of motion and impaired neuromuscular function which impacts on functional activities, work and quality of life. Therapeutic exercise is a mainstay of rehabilitation, but the nature of the exercises prescribed are currently various and the effect sizes of current programs for patients with whiplash-associated disorders are modest at best.

METHODS

A review was undertaken of research investigating the changes in cervical motion and neuromuscular function to better inform exercise prescription and identify areas for future research. RESULTS.: Reduced range of movement as well as pathological movement patterns (reduced acceleration and velocity, reduced smoothness and irregular axes of neck movement) have been documented in subjects with whiplash-associated disorders. In relation to neuromuscular control, changes have been demonstrated in neck muscles' spatial and temporal relationships as well as in their strength and endurance. The presence or not and the extent of changes is highly variable between individuals and appears to have some relationship to pain intensity. It appears that there is a need for specificity in exercise prescription to address particular impairments rather than the use of generic programs. High pain intensity can modify effects of a therapeutic exercise program.

CONCLUSION

Pain and injury result in reorganization of the motor control strategies of neck muscles and movement. Further research is required to determine if outcomes after a whiplash injury can be improved by using research informed, individually prescribed exercise programs matched to the individual's presentation. Research into best methods of pain management is also required to facilitate physical rehabilitation.