J Manipulative Physiol Ther 2013 (Oct); 36 (8): 461–467 ~ FULL TEXT
Cynthia K. Peterson, RN, DC, M.Med.Ed, Christof Schmid, DC, Serafin Leemann, DC,
Bernard Anklin, DC, B. Kim Humphreys, DC, PhD
Professor, Department of Chiropractic Medicine,
Faculty of Medicine, Orthopedic University Hospital Balgrist,
University of Zürich,
OBJECTIVE: The purpose of this study was to investigate outcomes of patients with cervical radiculopathy from cervical disk herniation (CDH) who are treated with spinal manipulative therapy.
METHODS: Adult Swiss patients with neck pain and dermatomal arm pain; sensory, motor, or reflex changes corresponding to the involved nerve root; and at least 1 positive orthopaedic test for cervical radiculopathy were included. Magnetic resonance imaging-confirmed CDH linked with symptoms was required. Baseline data included 2 pain numeric rating scales (NRSs), for neck and arm, and the Neck Disability Index (NDI). At 2 weeks, 1 month, and 3 months after initial consultation, patients were contacted by telephone, and the NDI, NRSs, and patient's global impression of change data were collected. High-velocity, low-amplitude spinal manipulations were administered by experienced doctors of chiropractic. The proportion of patients responding "better" or "much better" on the patient's global impression of change scale was calculated. Pretreatment and posttreatment NRSs and NDIs were compared using the Wilcoxon test. Acute vs subacute/chronic patients' NRSs and NDIs were compared using the Mann-Whitney U test.
RESULTS: Fifty patients were included. At 2 weeks, 55.3% were "improved," 68.9% at 1 month and 85.7% at 3 months. Statistically significant decreases in neck pain, arm pain, and NDI scores were noted at 1 and 3 months compared with baseline scores (P < .0001). Of the subacute/chronic patients, 76.2% were improved at 3 months.
CONCLUSIONS: Most patients in this study, including subacute/chronic patients, with symptomatic magnetic resonance imaging-confirmed CDH treated with spinal manipulative therapy, reported significant improvement with no adverse events.
From the FULL TEXT Article:
Symptomatic compression of a cervical nerve root occurs in approximately 83.2 of every 100000 persons and is caused by disk herniations, degenerative spondylosis, or a combination of the . Degenerative stenosis leading to narrowing of the intervertebral foramen is reported to be the most common cause of nerve root compression.  The C6 and C7 nerve roots are most frequently involved, often resulting in severe pain and disability. [1, 2] Symptoms can arise from the nerve root compression, inflammation, or both and include pain in a radicular distribution, paresthesias in a dermatomal pattern, decreased relevant reflex, and weakness of the muscles innervated by the nerve root. 
Patients with radiculopathy from cervical disk herniations (CDHs), the second most common cause of cervical nerve root compression, typically have acute neck pain with associated arm pain following the distribution of the involved nerve root, although the arm pain may be the predominant symptom. [3, 4] However, it is important to recognize that disk protrusions are also a common finding on magnetic resonance imaging (MRI) scans of asymptomatic people. [5-7] One study found that 63% of asymptomatic athletic males older than 40 years had protruding disks in the cervical spine.  In another study, disk protrusion with demonstrable spinal cord compression was noted in 7.6% of asymptomatic subjects over the age of 50 years.  However, extruded disk herniations and cord compression are unusual findings in asymptomatic individuals. 
The treatment of patients with cervical radiculopathy is often surgical if conservative therapies fail. [2-4, 8] Conservative treatments of patients with CDH are not well described or studied but may include lifestyle changes, pain medications, physiotherapy, epidural steroid injections, or spinal manipulative therapy (SMT). [2, 3, 8, 9-12] Like most of the conservative treatments other than epidural steroid injections, the research evidence supporting SMT as a treatment for CDHs is lacking. Three systematic reviews on manipulation for various neck disorders found insufficient evidence to support this therapy for patients with neck pain and radiculopathy. [9-11] However, it is known that some doctors of chiropractic (DCs) and other manual therapists treat CDH patients with SMT in spite of the lack of supporting evidence. [11, 13] Therefore, the purpose of this study is to investigate the clinical outcomes of patients with cervical radiculopathy from MRI-confirmed CDH who are treated with high-velocity, low-amplitude SMT in an outpatient chiropractic practice.
Most patients in this study with MRI-proven symptomatic CDHs who were treated with high-velocity, low-amplitude spinal manipulation reported clinically significant improvement at all time points, particularly at 3 months. The PGIC responses of much better and better have previously been shown to indicate clinically relevant improvement, whereas slightly better is not clinically relevant. [16, 17] In addition, the large reductions in NRS neck and arm pain scores as well as the NDI scores at 3 months of approximately between 66% and 75% far exceed the threshold of 30% to 35% pain reduction considered clinically relevant.  Because of the paucity of research into SMT for patients with CDHs, comparisons with other studies cannot be directly made. However, a recent large prospective outcomes study on Swiss neck pain patients undergoing chiropractic treatment found that the presence of radiculopathy was not a negative predictor of improvement.  In that study, however, the specific treatment method was not determined, and the diagnosis of radiculopathy was made by numerous different treating DCs and not necessarily linked to MRI findings.
It is important to point out that even the subacute/chronic patients in this study with symptoms lasting longer than 4 weeks (mean duration, 298.73 days) reported high levels of clinically significant improvement. This is clinically important as the chronic patients are the ones who are usually the most costly in terms of health care use and quality-of-life disruption. [19-21] Although the natural history of acute patients with radiculopathy from CDHs has been reported to be quite favorable, this only applies to patients with symptoms of less than 4 to 8 weeks. [22, 23] The most recent review on the natural history of radiculopathy states that the clinical course of cervical radiculopathy is poorly documented.  Indeed, it is virtually impossible to extract reliable figures on the natural history of this condition from the few published studies for acute CDH patients with radiculopathy who have not had any type of treatment at all. [2, 24] The results of this current study can, therefore, only be compared with those published, which involved another treatment for patients with CDH and radiculopathy. Kolstad et al  studied 21 chronic (symptoms >3 months) CDH patients with radiculopathy who received 2 cervical nerve root blocks consisting of a corticosteroid and anesthetic. They reported that 24% of these patients (5/21) had clinically relevant reduction in their symptoms, that is, a 25% reduction in their NRS score, at 6 weeks and 4 months after injection. The results of this current study using SMT for the subacute/chronic patients had substantially better results with more than 76% reporting clinically relevant improvement and a 65% reduction in arm pain as well as a 59% reduction in neck pain NRS scores at 3 months. However, the patients in this current study included those with symptoms between 4 and 12 weeks as well as those whose symptoms were longer than 3 months, and this may have favorably influenced the results. The mean duration of the symptoms in this subacute/chronic cohort was over 298 days however.
One patient reported being slightly worse at 1 month, but by 3 months, no patients were worse. No cases of serious adverse events occurred. Risks of SMT to the cervical spine in general include fainting/dizziness/light-headedness (at worse 16/1000 treatment consultations), headache (at worse 4/100 treatments), and numbness/tingling in upper limbs (at worse 15/1000 treatments).  Serious adverse events such as dissection of the vertebral artery or serious neurologic deficits are so rare that accurate estimations of the frequency cannot be calculated but are estimated at 1 of 200000 to 1 of several million treatments. [25, 26] The most common adverse events are transient local pain and stiffness. [27, 28] Other uncommon adverse events include tiredness, dizziness, nausea, and ringing in the ears. [27, 28]
An advantage to this study is that the treatment was standardized to a high-velocity, low-amplitude manipulative procedure, based on the location of the disk herniation as seen on the MRI scans and correlated with the clinical signs and symptoms. In addition, patients whose herniation had penetrated through the peripheral annular fibers, the posterior longitudinal ligament, or were sequestered were not excluded from being treated with SMT. However, no studies have been conducted to determine whether there is a difference in outcome based on the choice of the specific manipulative procedure or the type and location of disk herniation. Future studies should address these issues.
There are several limitations to this study. As a cohort outcomes study and not a randomized controlled clinical trial, the outcomes reported here cannot be directly attributed to the SMT treatment. Additional research comparing SMT with other treatments, for example, therapeutic nerve root infiltrations using the randomized controlled clinical trial methodology, needs to be done. Furthermore, all patients in this study were examined and treated in a single chiropractic practice in Zürich, Switzerland, by any 1 of the 3 DCs working there using a standardized treatment approach. Thus, the results obtained may not be representative of other chiropractic practices or other practitioners using SMT. The relatively small sample size for the subgroup of CDH patients whose symptoms were “subacute/chronic” (24 patients) is another limitation.
Additional limitations include the fact that all outcomes were self-reported, consistent with many other research studies. No attempt was made to confirm the reality of the information given to the research assistants. However, the DCs themselves monitored and documented the patients' progress, including their neurologic evaluations as outlined in the methodology. Furthermore, the fact that the follow-up outcomes were obtained by telephone interviews, whereas the baseline data were completed by the patient in a written format, may also influence the results. However, all patients were handled in the same way, and there was no mixture of telephone and written questionnaire follow-up data collection.  In addition, the primary outcome measure of the PGIC can only be collected after treatment, and thus, there was no “baseline” data for this scale. By conducting the telephone interviews at the university hospital by research assistants unknown to the patients rather than collecting the data at the practice site itself, an attempt was made to avoid a positive bias.
A high proportion of acute and most importantly subacute/chronic patients with MRI-confirmed symptomatic cervical disk herniations treated with high-velocity, low-amplitude cervical spine manipulation reported clinically relevant improvement at 1 and 3 months after the first treatment. There were no adverse events reported for patients in this study.
Patients with symptomatic MRI-confirmed cervical disk herniations treated with SMT to the level of herniation reported high levels of clinically relevant improvement at 2 weeks, 1 month, and 3 months after the first treatment.
A higher proportion of acute patients improve, and this improvement is faster than those patients who are subacute or chronic.
Of the subacute/chronic patients, 76.2% reported clinically relevant improvement at 3 months.
There were no adverse events.