Neck Retractions, Cervical Root Decompression, and Radicular Pain

Transcription

1 Journal of Orthopaedic & Sports Physical Therapy 2000;30(1):4-12 Neck Retractions, Cervical Root Decompression, and Radicular Pain Sami S. Abdulwahab, PhD, PT1 Mohamed Sabbahi, PhD, P7; ECSZ Study Design: Two-group repeated measures. Objectives: To evaluate the changes in the flexor carpi radialis H reflex after reading and neck retraction exercises and to correlate reflex changes with the intensity of radicular pain. Background: Repeated neck retraction movements have been routinely prescribed for patients with neck pain. Methods and Measures: Ten nonimpaired subjects (mean age, 27 t 4 years) and 13 patients (mean age, 35 t 9 years) with C7 radiculopathy volunteered for the study. The flexor carpi radialis H reflex was elicited by electrical stimulation of the median nerve at the cubital fossa before and after 20 minutes of reading and after 20 repetitive neck retractions. Subjective intensity of the radicular pain was reported before and after each condition using an analog scale. Results: For patients with radiculopathy, a repeated-measures analysis of variance showed a significant decrease in the H reflex amplitude (from 0.81 t 0.4 to mv), an increase in radicular symptoms after reading (from 4.2 t 1.3 to 5.6 t 1.4 on the visual analog scale), an increase in the H reflex amplitude (from to 1.Ol mv), and a decrease in pain intensity (from 5.6 t 1.4 to ) after repeated neck retractions. There was an association between cervical root compression (smaller H reflexes) and increased pain during reading and between cervical root decompression (larger H reflex) and reduced pain (r = to -0.60). Exacerbation of symptoms was found with a reading posture. There were no significant changes in the H reflex amplitude in the nonimpaired group. No changes were found in reflex latency for either groups. Conclusions: Neck retractions appeared to alter H reflex amplitude. These exercises might promote cervical root decompression and reduce radicular pain in patients with C7 radiculopathy. The opposite effect (an exacerbation of symptoms) was found with the reading posture. 1 Orthop Sports Phys Ther 2000;30:4-12. Key Words: electromyography, H reflex, neck pain, posture Texas Woman's University, School of Physical Therapy, Houston, Tex. * Texas Woman's University, School of Physical Therapy, Houston, Tex. Pdrtially presented at the Combined Section Meeting of the APTA in Send correspondence to Mohamed Sabbahi, Texas Woman's University, School of Physical Therapy, 1130 M. D. Anderson Boulevard, Houston, TX HFSabbahi@twu.edu T he anatomical and biomechanical nature of the cervical spine encourages mobility at the expense of stability and strength.23 That is why cervical pain and dysfunction are common, particularly as a result of and poor spinal pos ture.12 Cervical pain and dysfunction appear to affect many pee ple.1.2."7j0 The sixth and seventh cervical vertebral roots were reported to be the sites most commonly affected, representing 60 and 25%, respectively, of cervical nerve root impingement.'4j"24 Reading for long periods has been considered a risk factor for neck pain.g Clinically, patients with neck pain usually report aggravation of their symptoms with reading. This indicates possible compromise of the neuromusculoskeleta1 structures of the neck. There are several techniques used to treat patients with neck pain. Neck retraction was first recommended by McKen~ie~~J~ and Stevens and McKenziezZ to treat cervical pain. It involves pulling the head and neck posteriorly into a position in which the head is aligned more directly over the thorax, while the head and eyes remain level. The end position is maintained for a short period, and then the neck is allowed to relax into a resting posture. During this movement, the lower cer-

2 vical segments move toward an extended position, while the upper segments move toward a more flexed position.12j5 It is believed that neck retraction may increase cervical range of motion, improve resting neck post~re,~~.~~ relieve neck or radicular pain, and possibly move the nucleus pulposus to a more anterior position and prevent recurrences of pain.12js.22 This immediate response to repeated neck retractions (particularly changes in the distribution and intensity of the referred symptoms from distal to a more central location) could indicate a decompres sion effect on the impinged nerve root. Recently, online H reflex monitoring has been reported to be a useful method to evaluate and monitor treatment effects in patients with lumbosacral radiculopathy.17j8 The idea behind this method was that postural modification could cause either further H reflex suppression, indicating more compression on the nerve root causing more pain, or H reflex recovery, indicating decompression of the impinged nerve root leading to pain reduction. This technique could also be useful to monitor the treatment effect of neck retractions, if such mechanical movement would compress then decompress the cervical nerve roots. The H reflex has been a useful electrophysiologic procedure for evaluation of root entrapment in radiculopathy. Therefore, the purpose of this study was to investigate the influence of reading and subsequent neck retractions on the flexor carpi radialis (FCR) H reflex and cervical radicular pain intensity. Radicular or radiating pain has been defined herein as arm and neck pain. MATERIALS AND METHODS Subjects Patient group Thirteen subjects volunteered and consented to participate in the study (8 men and 5 women; mean age, years). They complained of frequent neck, shoulder, and scapular stabbing or burning pain associated with arm, forearm, hand paresthesia, and a "pins and needles" type of pain for the last 6 months. The pain was exacerbated during intensive work or reading and was absent or reduced at rest. Their medical histories showed C7 radiculopathy, with one or more of the following symptoms: weakness in triceps muscle, numbness in the middle finger (and C7 dermatome), and reduction in triceps muscle tendon reflex. Clinical reports from the referring physician confirmed the level of cervical spinal involvement. None had cervical spine surgery or stenosis, metabolic systemic disorders, or cancer. They were screened to rule out other causes, such as thoracic outlet or carpal tunnel syndromes. They all showed poor head alignment, which was a moderate forward head posture according to the criteria of Griegel-Morris et al.5 Patients signed a consent form approved by the Human Subject Review Committee of Texas Woman's University. Comparison group Ten nonimpared subjects (5 women and 5 men; mean age, years) with no history of constant neck or radiating radicular symp toms in the last 12 months participated in this study. This group of subjects may have experienced occasional neck pain but never reported whiplash injury, metabolic systemic disorders, or cancer. Experimental Procedure The subjects were asked to sit on a chair with their lower backs supported, using a lumbar roll, and buttocks against the chair back. The subjects' forearms rested on a pillow in the lap with the elbows slightly flexed. A silver-silver chloride surface bar electrode with coupling gel was placed on the medial surface of the lower third of the arm above the median nerve just proximal to the cubital fossa. The bar electrode was positioned with the cathode electrode proximal to the anode electrode and in line with the median nerve, usually about 2 in proximal to the medial epicondyle. Stimulation at this site usually causes twitches in thumb flexion. Stimulation pararneters were a 0.5millisecond pulse duration at a frequency of 0.2 pulses per second with an intensity that elicited H reflex maximum. The H reflex of the FCR was recorded using a Cadwell 5200A electromyogram unit (Kennewick, Wash). The procedure for recording was as follows. The skin was washed and cleaned with alcohol. A silver-silver chloride surface bar electrode with coupling gel was connected to the electromyogram unit for signal recording; the negative-up and positive-up electrodes were positioned on the belly of the FCR muscle and 2 cm laterally, respectively. To identify the belly of the FCR muscle, the subject was asked to flex the wrist-thumb component with the thumb and little finger in opposition, and the examiner provided mild resistance to the flexed wrist at the thenar muscle. This maneuver caused contraction of the FCR, and the muscle belly bulged at the middle point of the upper third of the forearm. A ground surface metal electrode (3 cm in diameter) was positioned on the cubital fossa between the stimulation and recording sites (Figure). The H reflex was monitored by the minimal M response, which is usually recorded with the maximum H reflex, to ascertain that there were no changes in the stimulation or recording condition^.^ The minimal M response was monitored visually and was almost identical during recording throughout the whole testing period. All signals were amplified X using differential amplification and were filtered using a HZ bandwidth. J Orthop Sports Phys Ther*Volume SO. Number 1 *January 2000

3 and after 20 minutes of reading and after 20 repetitions of neck retraction. A new visual analog scale line was provided for each testing condition. Using this procedure, a total of 3 measurements were carried out before and after reading and after neck retraction. Stimulation and recording arrangement for the flexor carpi radialis H reflex. % and % refer to the distance on the arm with respect to the medial epicondyle. S indicates stimulation; G, ground; and R, recording. Three-minute practice trials of elicited H reflexes were obtained to familiarize the subject with the H reflex stimulation and recordings. Then 4 readings of the maximum H reflex were recorded and averaged before and after 20 minutes of reading a magazine, to exacerbate pain, and after 20 repetitions of neck retractions. During recording, the subject was asked to look straight ahead at a horizontal level. Subjects were asked to read for 20 minutes in their own relaxed style. The neck retractions were requested to be at full range with the head and eyes leveled as described by McKenzie.lJ The retraction position was maintained for 1 second each time, and subjects were asked to move the head and neck further with each successive repetition. Neck, arm, and forearm radicular pain intensity was evaluated using a l km visual analog scale, with 0 set as no pain and 10 as the worst imaginable pain. Subjects were instructed to rate their pain before Signal and Data Analyses The peak-to-peak amplitude and latency to the deflection of the action potential were measured and averaged for 4 consecutive, successful H reflex representations. Within-group, repeated-measures analysis of variance was used to determine if there was significant difference among the H reflex recordings and radicular pain intensities (visual analog scale) before and after reading and neck retractions, followed by simple contrast tests. Each dependent variable was also evaluated with a between-group general linear model multivariate analysis of variance. The Spearman rank order correlation coefficient was also used to measure the degree of association between the changes in the H reflex amplitude and the intensity of radicular pain. The SPSS software statistical program (SPSS, Chicago, Ill) was used to analyze the data. RESULTS Within-Group Comparisons The differences in the H reflex amplitude and latency and radicular pain intensity within groups are shown in Tables 1 through 3. In the patient group, the peak-to-peak amplitude of the H reflex was significantly (P <.001) decreased after 20 minutes of reading (Table 1). Subsequently, the H reflex amplitude was significantly (P <.001) increased after neck retraction (Table 1). In the comparison group, the H reflex changes were similar to those recorded in the patient group, except these changes were not statistically significant (P <.59). In both groups, no significant difference (P <.64) was detected among the H reflex latency in the 3 conditions (Table 2). The intensity of the radicular symptoms was significantly increased after reading (P <.01) and decreased after neck retraction in the patient group (P <.001) (Table 3). TABLE 1. The mean and standard deviation of the H reflex amplitude (in millivolts) recorded before and after 20 minutes of reading and 20 neck retractions for the nonimpaired comparison groups and patient Between group Within group Comparison Patient Condition (n = 10) (n = 13) df F ratio Pvalue df F ratio Pvalue Before reading , After reading ? , , After retraction 1.13? , , J Orthop Sports Phys Ther-Volume 3O.Number 1.January 2000

4 TABLE 2. The mean and standard deviation of the H reflex latency (in milliseconds) recorded before and after 20 minutes of reading and 20 neck retractions for the nonimpaired comparison group and the patient groups. Between group Within group Comparison Patient Condition (n = 10) (n = 13) df F ratio Pvalue df F ratio Pvalue Before reading , After 20 minutes of reading , , After 20 neck retractions , , The H reflex amplitude and cervical radicular pain intensity during the 3 conditions were inversely related (r = to -0.86) (Table 4). This means that the increased H reflex amplitude was associated with reduced radicular symptoms. Between-Group Comparisons The. peak-to-peak amplitude of the H reflex behaves similarly in both groups. It decreased after reading and increased after neck retractions, but the difference between the patient and the comparison groups was not statistically significant (.08 < P <.61). This is mainly due to the large variability in the H reflex amplitude between patients and nonimpaired subjects (Table 1). No statistically significant difference in the latency of the H reflex was found between groups (Table 2). DISCUSSION This study showed that a reading posture exacerbated cervical and radicular pain and reduced H reflex amplitude in the patient group. Neck retraction, however, caused immediate reduction or relief of radicular pain and increased the H reflex amplitude in the patient group. This could indicate that reading probably caused further mechanical compression on the neural elements of the nerve root. In contrast, neck retraction may have decompressed the cervical nerve root. Postures of the neck during reading cause neck flexion. Observation of all our subiects., showed consistent neck flexion during reading. Neck flexion and forward head posture are postulated by Mc- Kenzie to cause movement of the nucleus pulposus to a more posterior positioni3" as a result of increased mechanical compression on the anterior surface of the intervertebral disk. This posterior transla- tion of the disk and soft tissues toward the spinal root could be the explanation for the reduction of the H reflex amplitude and increased radicular pain. These findings suggest that it may be beneficial to carefully restrict neck flexion movement in patients with cervical radiculopathy to avoid further nerve root compression. Lau et aly reported that spending more time reading is considered a risk factor for neck pain and our results support this point of view. Repetitive neck retractions caused an immediate increase in the H reflex amplitude and a decrease in the intensity of cervical radicular pain. This was most likely due to a decompression effect on the compromised spinal root or dorsal root ganglia.'' Neck retraction has been documented to cause extension of the lower cervical region and to promote the resting neck po~ture.'".'~~~ Extension of the lower cervical region is proposed to move the nucleus pulposus to a more anterior position, causing decompression and reduction of cervical radicular The reported neck resting posture following neck retraction1" could reduce the mechanical forces on the intervertebral disk, leading to decompression effect and pain reduction. It was speculated that minimum correction of neck resting posture (as a result of maintained retracted neck position) could relieve pain.i5 Results of our study provide preliminary support for the beneficial clinical effect of neck retraction.ij A significant inverse relationship (r = to -0.60) was found between the H reflex amplitude and the intensity of radicular pain. This means that increasing H reflex amplitude was associated with a reduction of radicular symptoms (such as after neck retraction), and decreasing H reflex amplitude was associated with increased neck pain and radiating radicular symptoms (such as after reading). The association of reflex changes with pain validates the use of the H reflex for online monitoring of root com- TABLE 3. Cervical radicular pain intensity expressed (in centimeters) on the visual analog scale before and after 20 minutes of reading and 20 neck retractions for the nonimpaired comparison group and the patient group. Between Croup Within group Comparison Patient Condition (n = 10) (n = 13) df F ratio Pvalue df F ratio Pvalue Before reading ? 1.3 1, After 20 minutes of reading , , After 20 neck retractions , , J Orthop Sports Phys Ther.Volume 30. Number 1.January

5 TABLE 4. Pearson correlation coefficient between the H reflex amplitude and the visual analog scale values for the patient group before and after 20 minutes of reading and 20 neck retractions. Condition Before 20 minutes of reading After 20 minutes of reading After 20 neck retractions Correlation coefficient -0.86' -0.74' -0.60t ditions could be successfully obtained by postural exercises. This study raises the question of whether neck retraction is the only movement to cause cervical neural decompression and to reduce the pain. We do not know if there is any optimum movement or posture of the cervical spine to recover the comprm mised H reflex and reduced radicular symptoms, as reported in the lumbosacral region.17jr Exploring this issue will be the basis for a future study. pression and decompression phenomena with associated radicular sympt~ms.'~j~ A previous report, which included fresh cadavers of old subjects, related the changes in the compression and decompression forces on the nerve roots to the changes in foraminal dimension during neck movements.ll Our results did not support those findings. The significant increase in the H reflex amplitude and reduction of radicular pain intensity in this study indicated that the lower cervical extension during retraction did not lead to a significant reduction in foraminal dimension that might cause root compression." This was not surprising, because it has been reported that nerve root impingement in the younger population (up to 50 years of age) most likely resulted from disk herniation, whereas in older populations (older than 50 or 60 years), it often resulted from foraminal narrowing due to osteophyte formati~n.~ Subjects in our study were relatively young, and their cervical pain was possibly due to some degree of disk protrusion. If neck retraction causes significant foraminal narrowing, the H reflex of the nonimpaired comparison group should be suppressed. This reflex suppression was not found in our study for the nonimpaired comparison group. Neck retractions seemed to have no immediate affect on the H reflex latency in the patient group. This could be due to the fact that there was no significant demyelination in the nerve root and the mean H reflex latency in the study fell within the normal range Nonimpaired subjects in the control group showed H reflex and neck pain behavior similar to those recorded in the patient group, but the results were not statistically significant. Reading posture resulted in reduction of H reflex amplitude with appearance of neck ache. Neck retraction caused an increased H reflex amplitude and alleviation of the neck ache. These results imply a relative degree of compression and decompression effect on the neural element. Although this relative compression did not cause a pathologic condition, it indicates a resilience and flexibility of the diskal components during movements and postures. Results from our current study provide evidence for the mechanical basis of spinal radicul~pathyl~-~~ and suggest that treatment for these pathologic con- CONCLUSIONS Repeated neck retraction might be an effective exercise to recover the FCR H reflex amplitude, decompress cervical neural elements, and reduce cervical and radicular pain. The study also confirms the feasibility of using the H reflex to evaluate patients with neck pain. However, additional studies with a larger sample population in a randomized controlled trial should be conducted to confirm these results. REFERENCES 1. Ahlgren BD, Garfin SR. Cervical radiculopathy. Orthop Clin North Am. 1996;27: Barnsley L, Lord S, Wallis B, Bogduk N. The prevalence of chronic cervical zygopophyseal joint pain after whiplash. Spine. 1995;20:2& Bogduk N. The anatomy and pathophysiology of whip lash. Clin Biomech. 1986;1: Deans GT, Magalliard JN, Kerr M, Rutherford WH. Neck sprain: a major disability following car accidents. Br JAccident Surg. 1987;18: Griegel-Morris P, Larson K, Mueller-Klaus K, Oatis C. Incidence of common postural abnormalities in the cervical, shoulder and thoracic regions and their association with pain in two age groups of healthy subjects. Phys Ther. 1992;72: Holmstrom E. Low back pain and necwshoulder pain in construction workers, part 2: relationship to neck and shoulder pain. Spine. 1992;17: lnufusa A, An H, Lim T, Hasegawa T, Haughton V, Nowicki B. Anatomic changes of the spinal canal and intervertebral foramen associated with flexion-extension movement. Spine. 1996;21: Jabre J. Surface recording of the H-reflex of the flexor carpi radialis. Muscle Nerve ;4: Lau E, Sham A, Wong K. The prevalence of and risk factors for neck pain in Hong Kong. Chin I Public Health Med. 1996;18: Makela M, Heliovaara M, Sievers K, lmpivaara 0, Knekt P, Aromaa A. Prevalence, determinants and consequences of chronic neck pain in Finland. Am J Epidemiol. 1991; 134~ Malanga G. The diagnosis and treatment of cervical radiculopathy. Med Sci Sports Exerc. 1997;29:~ McKenzie R. Treat Your Own Neck. Lower Hutt, New Zealand: Spinal Publications; McKenzie RA. The Cervical and Thoracic Spine: Mechanical Diagnosis and Therapy. Waikanae, New Zealand: Spinal Publications Ltd; Murphey F, Simmons JC, Brunson B. Ruptured cervical discs, 1939 to Clin Neurosurg. 1973;20:9-17. J Orthop Sports Phys Ther.Volume SO Number 1.January 2000

6 15. Peanon N, Walmsley R. Trial into the effects of repeated neck retractions in normal subjects. Spine. 1995;20: Radhakrishnan K, Litchy W, O'Fallon W, Kurland L. Epidemiology of cervical radiculopathy: a population-based study from Rochester, Minnesota, 1976 through Brain. 1994;117: Sabbahi M. Fixing lumbosacral radiculopathy with postural modification: a new method for evaluation and treatment based on electrodiagnostic testing. J Neurol Orthop Med Surg. 1997;17: Sabbahi M. Electrodiagnosis directed treatment of lumbosacral radiculopathy after spinal surgery. J Neurol Orthop Med Surg. 1997;17: Sabbahi MA, Khalil M. Segmental H-reflex studies in upper and lower limbs of healthy subjects. Arch Phys Med Rehabil. l990;71: Sabbahi MA, Khalil M. Segmental H-reflex studies in upper and lower limbs of patients with radiculopathy. Arch Phys Med Rehabil. 1990;71: Saunders H, Saunden R. Evaluation, Treatment and Prevention of Musculoskeletal Disorders. Vol 1. 3rd ed. Chaska, Minn: Saunden Group Co; 1995: Stevens BJ, McKenzie RA. Mechanical diagnosis and self treatment of cervical spine. In: Grant R, ed. Physical Therapy of the Cervical and Thoracic Spines. New York, NY: Churchill Livingstone; 1988: Walmsley R, Kimber P, Culham E. The effect of initial head position on active cervical axial rotation range of motion in two age populations. Spine. 1996;21: Ward R, Basmajian J, Nyberg N. Myofascial release concepts. In: Rational Manual Therapies. Baltimore, Md: Williams & Wilkins; 1993: J Orthop Sports Phys Ther-Volume 30.Number 1.January 2000

7 Invited Commentarv Sami S. Abdulwahab, PhD, PT, and Mohamed Sabbahi, PhD, PT, have begun to address the rationale underlying a commonly used treatment technique in the treatment of putative C7 radicular pain. They measured pain using the VAS and the flexor carpi radialis H reflex in 2 groups of subjects on 3 occasions: baseline, after 20 minutes of reading, and following 20 neck retraction manoeuvres. They concluded that neck retraction movements reduced radicular pain and increased the amplitude of the H reflex (which had decreased following sustained neck flexion). Dr Abdulwahab and Dr Sabbahi then sought, by inference, to conclude that these neck retraction manoeuvres promoted cervical root decompression. When attempting to establish the rationale for a technique, the putative source of pain is of interest. The authors have used the terms radicular pain and referred pain interchangeably, yet these terms are not synonymous. Radicular pain is pain arising from the roots of a spinal nerve. It is evoked by ectopic impulses generated in the dorsal root or its ganglion. Referred (somatic) pain is evoked by the noxious stimulation of nerve endings, which may be found in any of the structures of the neck (ie, the annulus fibrosus, ligaments, zygapophysial joint structures, or muscles).:'s4 Studies have indicated that pain in the neck, shoulder, and scapular region associated with pain radiating into the arm and forearm is as likely to be referred somatic pain as it is radicular pain.5." " The extent to which the pain reported by patients in their study is due to radiculopathy or to a somatic source, therefore, is unclear. Drawing an inference about nerve root pathology would be sub stantiated better by showing resolution of paraesthesias and numbness rather than improvement of VAS. It is perplexing why Drs Abdulwahab and Sabbahi did not refer or allude to their work that was recently published in Spine.I4 In that study, they demonstrated that H reflex amplitude increased in all head positions (extension, lateral bending, retraction and protraction) except for flexion. Given such findings, it is curious that the authors only chose to include retraction as a treatment technique in this study. Their failure to include a further treatment group who undertook different neck movements gives cause for reflection. Furthermore, there is a substantial difference in amplitude of the H reflex in the nonimpaired comparison group in this study and the previously studied nonimpaired subjects. Amplitudes are about 22% greater, yet the latencies in this and the previous study are identical. Was the present comparison group more sensitive than normal? If so, the significance in comparison to the patient group is diminished. In the introduction, the authors stated that H reflex amplitude suppression indicated more compression on the nerve root, causing more pain. However, therapists should be aware that H reflex does not directly evaluate the neurologic mechanisms associated with pain generation.' Study of H reflexes is undertaken to assess conduction in group la sensory afferents that innervate muscle spindles and does not assess conduction along the C fibers that transmit pain. Readers should not be overawed by conclusions because they sound technically impressive. Finally, the authors have invoked a clinical theory postulated by McKenzieH to provide a biological rationale for their findings. McKenzie's model is based on the concept of a gelatinous nucleus pulposus whose change in shape or position is held responsible for the "centralization" and "peripheralization" of ~ymptorns.~ Movements or sustained positions of the spine are proposed to affect the position of the nucleus pulposus only as long as the anulus fibrosus is intact.i7 Dr Abdulwahab and Dr Sabbahi have suggested that this directional movement of the nucleus pulposus is responsible for the changes in H reflex amplitude; however, the form and function of the adult cervical intervertebral disc has been demonstrated to be unlike its lumbar counterpart. The anulus fibrosus of the adult cervical intervertebral disc does not form a ring surrounding a gelatinous nucleus pulposus. It has been found to consist of 4 distinct components: an anterior anulus fibrosus forming a thick crescentshaped mass tapering and eventually vanishing laterally; a thin, vertically-oriented posterior anulus fibrosus; a lateral, thin periosteofascia1 component overlying the uncovertebral cleft; and a central fibrocartilaginous core, which exhibits transverse fissures of variable extent "12.15.'k19 Studies also indicate that the cervical nucleus pulposus shows signs of fibrosis by the midteens and is entirely composed of fibrocartilage by early adult- h~od.~.~~j!' Clearly, the adult cervical intervertebral disc does not consist of an intact anulus fibrosus encircling a gelatinous nucleus pulposus. Physical therapists are in need of sound science on which to base their treatment approaches. Use of clinical hypotheses that have not been validated by controlled experiments published in peer-reviewed publications will not further the progress towards a rigorous and justifiable scientific foundation of our profession. J Orthop Sports Phys Ther.Volume 30. Number 1.January 2000

8 Susan Mercer, PhD, PT Senior Lecturer Department of Anatomy and Structural Biology School of Medical Sciences University of Otago Dunedin, New Zealand REFERENCES 1. Andersson GB, Brown MD, Dvorak J, et al. Consensus summary on the diagnosis and treatment of lumbar disc herniation. Spine. 1996;21 (suppl):75>78s. 2. Bland J, Boushey DR. Anatomy and physiology of the cervical spine. Semin Arthritis Rheum. 1990;20: Bogduk N. Innervation and pain patterns of the cervical spine. In: Grant R, ed. Physical Therapy of the Cervical and Thoracic Spine. London: Churchill Livingstone; 1994: Bogduk N. Medical Management of Acute Cervical Radicular kin: An Evidence-based Approach. Newcastle: Newcastle Bone and Joint Institute; Dwyer A, Aprill C, Bogduk N. Cervical zygapophyseal joint pain patterns. I: A study in normal volunteers. Spine. 1990;15: Feinstein B, Langton JNK, Jameson RM, Schiller F. Experiments on pain referred from deep somatic tissues. J Bone Joint Surg. 1954;35A: Hirsch C. Some morphological changes in the cervical spine during ageing. In: Hirsch C, Zotterman Y, eds. Cervical kin. Oxford: Pergamon Press; McKenzie RA. The Cervical and Thoracic Spine. Mechanical Diagnosis and Therapy. Wai kanae: Spinal Publ ications Ltd; Mercer, SR, Bogduk N. The ligaments and anulus fibrosus Author Response Susan Mercer, PhD, PT, has raised a number of points in her comments. In responding to these comments, I emphasize that one should be familiar with the methodology and limitations of the H reflexes in order to correctly interpret the results of our paper.'," It is also important to be familiar with the neurophysiologic mechanisms of the H reflex in nonimpaired and impaired subjects when interpreting the possible mechanistic changes that might occur with neck movement and postures.'." Dr Mercer questioned our results on nonimpaired subjects in this paper as compared to our previous paper," where the reflex amplitude of one group was 22% greater than the other group. One has to be careful, however, when comparing the H reflex amplitude between subject groups because subjects are tested during 2 different recording sessions. It is somewhat erroneous to compare the H reflex amplitude of 2 groups of nonimpaired subjects at 2 differ- of human adult cervical intervertebral discs. Spine. 1999; 4: Mercer SR, lull GA. Morphology of the cervical intervertebral disc: implications for McKenzie's model of the disc derangement syndrome. Man Ther. 1996;2: Murphey F, Simmons JCH, Brunson B. Surgical treatment of laterally ruptured disc: review of 648 cases, 1939 to Neurosurg. 1973;38: Oda J, Tanaka H, Tsuzuki N. Intervertebral disc changes with aging of human cervical vertebra. From the neonate to the eighties. Spine. 1988;13: Pooni JS, Hukins DWL, Harris PF, Hilton RC, Davies KE. Comparison of the structure of human intervertebral discs in the cervical, thoracic and lumbar regions of the spine. Surg Radio1 Anat. 1986;8: Sabbahi M, Abdulwahab S. Cervical root compression monitoring by flexor carpi radialis H-reflex in healthy subjects. Spine ;24: Schellhas KP, Smith MD, Gundry CR, Pollei SR. Cervical discogenic pain: prospective correlation of magnetic resonance imaging and discography in asymptomatic subjects and pain sufferers. Spine. 1996;21: Slipman CW, Plastaras CT, Palmitier RA, Huston CW, Sterenfeld EB. Symptom provocation of fluroscopically guided cervical nerve root stimulation: are dynatomal maps identical to dermatomal maps? Spine. 1998;23: Stevens BJ, McKenzie RA. Mechanical diagnosis and self treatment of the cervical spine. In: Grant R, ed. Physical Therapy of the Cervical and Thoracic Spine. Edinburgh: Churchill Livingstone; 1988: Taylor JR. Growth and Development of the Human Intervertebral Disc [dissertation]. university of Edinburgh, Edinburgh, Scotland, Tondury G. The behaviour of the cervical discs during life. In: Hirsch C, Zotterman Y, eds. Cervical kin. Oxford: Pergamon Press; 1971 : ent recording sessions, then call the group with larger amplitude "more sensitive." The value of the H reflex amplitude varies between subjects with no back or neck pain. This is based upon the excitability level of the alpha-motoneuron pool at that time of te~ting.~ There is, however, a statistically significant difference in the H reflex amplitude between patients with neck and back pain and nonimpaired sub jects.vhere is also selective reduction in the amplitude of the H reflex in the symptomatic compared to the non-symptomatic limb of the patients with low back and neck pain. This is where the validity of the H reflex is dernon~trated.~ The main objectives, sample subjects, and methodology of this study were different from the previous ~tudy.~ In the current study, we compared the H reflex amplitude in response to specific mechanical manoeuvres (reading and head retractions) in impaired and nonimpaired groups. The purpose was to test the neck when subjected to J Orthop Sports Phys Ther-Volume 3O.Number 1.January

9 provocative activity (reading) and after alleviating such posture with neck retraction exercise. The purpose of the previous study in S'nB was not to provoke a change in the H-reflex with postural changes, but rather monitor the reflex changes in different extreme postures for a short period of time (30 seconds); therefore, data from both studies cannot be compared. In our opinion Dr Mercer was partially correct when she cautioned therapists about the use of the H reflex amplitude as a direct measure of pain or neurologic mechanisms associated with pain. It is true that the H reflex is elicited by stimulation of the la sensory afferent fibers and does not asses the conduction along the C fibers. The H reflex amplitude is a measure of the output of the alpha-motoneurons. Such output is dependent on the cumulative input of different sensory afferents including C fibers. When there is a compression on the spinal nerve roots, causing reduction of Gfiber input to the alpha-motoneurons and testing the excitability via any other pathway (la fibers) would evaluate the total output of the alpha-motoneurons. This is because the threshold level of the spinal neurons would. be different (possibly be decreased) after inputs are compromised. An example that supports this notion is the results of our previous study using topical anes the~ia.~ Desensitization of the skin with topical anesthesia resulted in a significant increase in the amplitude of the soleus H reflex. The cutaneous receptors were desensitized and the excitability of the alphamotoneurons was increased through the input of the la-spindle afferent stimuli (H reflex), not by stimulation of cutaneous receptors. This input-output relationship is a central focus of our studies of patients with neck and back pain using the H reflex; therefore, we proposed the use of H reflex amplitude to reflect compression or decompression phenomena on the neural element (root or ganglia) and not as a direct measure of pain. Our results can only be interpreted by reflection on the compression or decompression of the neural element (root or ganglion). The source of this compression may vary (discal, other soft tissue, or even bony structures). Unless imaging is performed, we cannot be certain which structures are causing symp toms. The fact is that the H reflex test is a technique that evaluates the directional changes (unilateral or bilateral) of the presumed compressive forces (increase or decrease) on the neural elements. Finally, Dr Mercer criticized our use of the terms radicular pain and referred pain, suggesting the use of "parasthesias" and "numbness" as better terms for describing root pathology. Unfortunately, not all patients report numbness or parasthesias and such symptoms are not common in nonimpaired subjects after holding a reading position. It is always enlightening to receive constructive comments that promote scientific advance of physical therapy, but care must be taken when interpreting the results of studies reporting electro-physiological data. Mohamed A. Sabbahi, PhD, PT, ECS REFERENCES 1. Fisher MA. AAEM Minimonograph #13. H reflexes and F waves: physiology and clinical indications. Muscle Nerve. 1992;15: Jankus WR, Robertson LR, Little JW. Normal limits of sideto-side H-reflex amplitude variability. Arch Phys Med Rehabil. 1994;75: Sabbahi M, Abdulwahab S. Cervical root compression monitoring by flexor carpi radialis H-reflex in healthy subjects. Spine. 1999;24: Sabbahi M, DeLuca C. Topical anesthesia: modulation of the monosynaptic reflexes by desensitization of the skin. EEG. Clin Neurophysiol. 1982;54: Sabbahi M, Khalil M. Segmental H-reflex studies in upper and lower limbs of patients with radiculopathy. Arch Phys Med Rehabil. 1990;71: Troni W. The value and limits of the H-reflex as a diagnostic tool in SI root compression. Electromyogr Clin Neurophysiol. 1983;23: J Orthop Sports Phys Ther.Volume 30. Number 1.January 2000