By: Sana U. Khan, M.D., Ph.D., Radiologist/Neurophysiologist
Magnetic Resonance Imaging (MRI) is a noninvasive and radiation-free medical test conducted by physicians to look inside the human body. MRIs use powerful magnetic fields and radio signals to produce an image of the targeted body part. With review by a specially trained radiologist, images produced by an MRI can provide clear indicators of why the patient was having certain symptoms and lead to proper treatment.
The initial design of MRIs was tunnel-like where patients would lay down in a circular, enclosed tube. Due to a large number of patients experiencing claustrophobia and a “sensation of being buried,” MRI manufacturers produced machines designed with magnets placed above and below with the sides open. These machines are commonly known as “open MRIs.” However, patients are still lying down with a very heavy magnet inches from their face and even though these machines do decrease the “buried” effect, many patients continued to complain of claustrophobia.
It is a simple, yet fundamental observation that many human musculoskeletal conditions are impacted by gravity, and that many patients experience signs and symptoms in weight bearing positions even when they do not in the recumbent one. Conventional magnetic resonance imaging systems are limited to acquiring scans with patients in the recumbent position. Thus, recumbent imaging alone may not demonstrate the full degree of pathology, due to muscle and ligament relaxation and in the case of the spine, disc retraction. Smith et al. (2006) performed a study on 25 patients with low back pain and sciatica. These patients were referred for lumbar spine MRIs following at least one prior “normal” recumbent MRI within 6 months of referral. In this study, 13 patients demonstrated abnormalities in one or more of the seated postures that was not evident in the supine positioned MRI. That’s a 52% missed rate. Would you send a loved one to do mammography on a machine that missed pathology 52% of the time?
Positional MRI is a continued evolution in the design of this technology. The magnets are vertically placed on the sides which results in a front open design virtually eliminating any claustrophobia as patients can watch television while the MRI exam is being performed. From a medical perspective, a major advantage emerged from this front and top open design. Patients can actually be placed in varying positions rather than “supine only” which is the limitation with other MRIs. Unlike the traditional MRIs where the patient only had their injury imaged in a relaxed state while lying down, the Positional MRI system allows upright, angled (slanted) and recumbent imaging, replicating partial or full weight bearing conditions. It also allows kinetic maneuvers of the patient’s whole body or any body part which results in images acquired in position of normal everyday stress, across the limits of normal range of motion. Most importantly, imaging is performed in the specific position of the patient’s clinical symptomatology.
Musculoskeletal injuries are common in motor vehicle accidents (MVA) and work related traumas. Several published scientific studies and reviews have established that positional MRI often reveals pathology that is clinically relevant but radiologically occult when imaged in a single position. Though the majority of the research has been published on the spine, Positional MRIs results are significant on other body regions as well. Patel et al. (2004) concluded that “MR imaging allows excellent non-invasive evaluation of knee joint kinematics with weight bearing. This tool may potentially be used for assessing knee kinematics in patients with knee pathology.” In addition, Niitsu et al. (2001) reported that visualization of the moving normal and torn anterior cruciate ligaments indicates that kinematic MR imaging of the moving knee is advantageous in evaluating the continuity and tension in the cruciate ligaments. Carpal tunnel syndrome (CTS) is the most common of the nerve entrapment syndromes. It has been shown that flexion and extension MRI can accurately image the contents of the carpal tunnel and the anatomic relationships between these structures, Skie et al. (1990).
In spinal imaging, the American Medical Association (AMA) Guides to the Evaluation of Permanent Impairment, 5th Edition (page 378) clearly states that “The dominant motions at both the lower cervical and entire lumbar spine, where most clinical pathology occurs, are flexion-extension.” So according to the AMA, if flexion and extension views are not acquired then we may be missing most of the clinical pathology on a patient. Kahn et al. (2002) evaluated 200 disc levels in 50 patients and showed that 33% of patients progressed from a non-critical to a critical stenosis of the dural sac (75mm²) with axial loading. Importantly, 25% of patients with one critical stenotic level developed a second critically stenotic level with axial loading. In another study, Jenkins et al. (2002), reported significant alterations on Positional MRI demonstrating fluctuating anterior and posterior disc herniations, hypermobile spinal instability, central spinal canal and spinal neural foramen stenosis and general sagittal spinal contour changes. They concluded that the potential relative beneficial aspects of Positional spinal imaging on this system over that of recumbent MRI include: the revelation of occult disease dependent on true axial loading, the unmasking of kinetic-dependent disease, and the ability to scan the patient in the position of clinically relevant signs and symptoms. As pointed out by Hitawashi et al. (2004), Axial loading during MR imaging of the lumbar spine can influence neurosurgeons in their treatment decisions for symptomatic spinal stenosis. Vincenzo et al. (2002) recommend the flexion and extension MRI protocol as an adjunctive procedure in the clinical setting of subacute cervical spine trauma as the procedure optimizes the detection of segmental motion abnormalities and injuries of the discoligamentous complex and the biomechanical changes in the herniated disk. The literature indicates that Positional MRI provides a more sensitive evaluation of spinal pathology. This in turn may provide the referring physician with a more relevant diagnosis, especially in cases where the pain is worse in a sitting or standing position.
Motor vehicle accidents often produce forceful back-and-forth displacement (Whiplash) of the head on the neck. When the head moves backward the ligaments in the front of the cervical spine are stretched and the bones and joints in the back of the neck are compressed. Forceful forward movement of the head compresses the discs and may produce considerable pain and instability. Plain cervical radiographs are usually normal following whiplash injury. The injuries are best identified using MRI techniques specifically designed for the evaluation of post-traumatic injuries. The exam may be called “MRI of the Cranio-Vertebral Junction” and is a completely separate exam from a routine cervical spine study.
A general biomechanical principle includes the understanding that there is a trade-off between mobility and stability. The upper cervical spine and the cranial-cervical junction are a mechanically unique region of the spinal column with greater vulnerability to injury because, while 5% of the rotation of the cervical spine occurs at the Occiput-C1 joint and 40% of the rotation of the cervical spine occurs at C2-C7, 55% of cervical spine (neck) rotation (turning to the right or left) occurs at the atlas-axis joint (C1-C2). This joint possesses great mobility, but at a price of reduced stability and increased vulnerability to injury. A main stabilizing ligament of the cranial-cervical region is called the alar ligament. The alar ligaments connect the odontoid process (dens) of the axis vertebrae (C2) to the occipital condyles of the occiput bone of the skull. Alar Ligaments consist primarily of collagen proteins with a few elastic fibers. In contrast to elastic fibers which can tolerate elongation up to 200% before failure, collagen ligaments will fail at only 8% elongation, consequently the alar ligaments are particularly vulnerable to traumatic stretching loads. The alar ligaments are particularly vulnerable to neck trauma when the head is rotated at the moment of impact. When the head rotates, the alar ligaments twist around the dens. Reaching 90° rotation, these ligaments are maximally tightened and obtain an anteroposterior orientation. Not unexpected, such tightened anteroposteriorly oriented alar ligaments are more vulnerable to hyperextension-hyperflexion trauma than relaxed, transversely oriented ligaments. Acutely, injured ligament permits influx of edema or hemorrhage which, on MRI, is seen as bright areas interspersed within dark collagen fibers.
Numerous research studies have been published looking at acute and long term consequences of whiplash injuries. Vetti et al (2009) have shown that there is strong evidence for causal relationship between trauma and alar ligament lesions. Alar ligament changes were unrelated to age, type of trauma, spinal degeneration and signal lesions may persist for months to years. In a study looking at long-term status of whiplash-injured patients (Gargan, 1990), researchers reviewed 43 patients who had sustained soft-tissue injuries of the neck after a mean 10.8 years. Of these, only 12% had recovered completely and 88% suffered from residual symptoms. Of these residual symptoms, 28% were intrusive and 12% were severe indicting that 40% of whiplash-injured patients continued to suffer from significant residual symptoms more than a decade after being injured. In fact, after two years, symptoms did not alter with further passage of time, remaining chronic.
A 1996 study by Squires et al. reviewed the long-term status of whiplash-injured patients 15.5 years after injury. The authors documented that 70% of the patients continued to complain of symptoms referable to the original accident. Bunketorp et al. (2002) looked at the health status of whiplash-injured patients 17 years after injury. At the time, this was the longest follow-up study on whiplash-injured patients published. The authors documented that 55% of the patients still suffered from pain caused by the original trauma 17 years later. Bannister et al. (2009) reviewed 15 studies pertaining to whiplash-injury outcomes and reported that whiplash-injured patients are 5 times more likely to suffer from chronic neck pain than control populations. They also concluded that the view suggesting a whiplash-injured patient’s symptoms will improve once litigation has finished “is unsupported by the literature.”
Chronicity of symptoms for many patients following whiplash trauma has been well established scientifically. Consequently, numerous clinical investigations have been performed in the assessment of the tissue origin of these symptoms. These investigations have included the careful fluoroscopic insertions of anesthetic needles using gold-standard protocols and techniques. The majority of these studies have focused on the tissues of the lower cervical spine. In their 1993 study Bogduk and Aprill, demonstrated that the facet joints of the lower cervical spine and the annulus of the disc are significant tissue sources for chronic whiplash injury symptoms.
More recently, researchers have turned their attention to the tissues of the upper cervical spine (C1-C2) as a source of chronic symptoms following whiplash trauma, especially if the symptom complex includes headaches. Because of the lack of a disc and the horizontal nature of the facet joints, the stability of the atlanto-axial complex depends mainly on the ligaments and muscles. Cranial cervical junction ligament injury may prove to be the structural substrate for the chronic whiplash syndrome. Specifically, these researchers have focused on the alar ligaments since they show the most consistency with disability scores and it was the structure with the most frequent high-grade MRI abnormalities. Recent advances in MR imaging have enhanced the assessment of the health of the alar ligaments. Structural changes in the alar ligaments in the late stage of whiplash injuries can be characterized and classified using high resolution proton density weighted MRI. The alar ligaments are the most injured from neck trauma, especially if the head is rotated at time of accident. The alar ligaments could be irreversibly overstretched or ruptured when the head is rotated and bent by the impact of whiplash trauma. An abnormal alar ligament is the strongest predictor for severity of subjective symptoms and functional disability in whiplash-injured patients. Alar ligament damage can take up to 2 years for complete healing. Whiplash injury to the upper cervical spine can cause balance disturbance, dizziness, visual problems and jaw problems. Chronic whiplash patient symptoms attributable to Occiput-C1-C2, include, neck pain, headache, upper limb symptoms, lower limb symptoms, loss of balance, some tongue numbness. Women appear to be more injured, perhaps due to the fact that the neck muscles are weaker in females, thus making their neck structures more vulnerable when under the influence of abrupt external forces. (Krakenes et al., 2002)
Alar ligament problems pose both mechanical and proprioceptive problems for the patient and treatment is often sought. Ice to the neck helps reduce acute pain and swelling. Painkillers or other drugs Non-steroidal anti-inflammatory drugs (NSAIDs), like ibuprofen (Advil, Motrin) or naproxen (Aleve) help with pain and swelling. However, these medicines or other prescription painkillers and muscle relaxants can have side effects and should not be taken unless under a doctor’s supervision. A neck brace or collar can add support, if a doctor recommends it. However, they are not recommended for long-term use, because they can actually weaken the muscles of the neck. Moist heat to the neck using warm wet towels may help but only after 2-3 days of icing it first. Heat should be used on the neck only after the initial swelling has gone down.
Experience indicates that carefully applied chiropractic adjustments to this sensitive spinal region can significantly improve and help manage these otherwise very difficult chronic injuries. Chiropractors commonly employ different chiropractic treatments for whiplash, often including manipulation, muscle relaxation and/or stimulation, various exercises, ergonomic and lifestyle changes. The primary whiplash treatment for joint dysfunction, spinal manipulation involves the chiropractor gently moving the involved joint into the direction in which it is restricted. Also known as a chiropractic adjustment, spinal manipulation may involve the application of a short thrust in that direction. In many cases, instead of a thrust, a slow mobilizing movement consisting of gentle stretches to the muscle that has excessive tension or repeated contractions of the muscle that is inhibited. If the muscle is very tight, a more vigorous stretch may be applied by the chiropractor. Gentle finger pressure techniques may be applied to trigger points to relieve the pain associated with the tight muscles.
In summary, Since the late 1980s it has been known that the alar ligaments could be injured from neck trauma. An abnormal alar ligament is the strongest predictor for severity of subjective symptoms and functional disability in whiplash-injured patients. Alar ligament injuries are often permanent. The best diagnostic tool to assess injury to the upper cervical ligaments and membranes is the proton density-weighted MRI examination. The increasing severity of MRI findings of soft tissue structures in the upper cervical spine is related to increasing levels of neck pain and functional disability, as experienced by persons with a diagnosis of whiplash injury. A whiplash injury should not be ignored and professional care should be sought.
American Medical Association (AMA) Guides to the Evaluation of Permanent Impairment, 5th Edition, (page 378), Linda Cocchiarella, Chief Editor
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