Pathological, clinical, and manipulative considerations - Europe PMC

Lateral nerve root entrapment: Pathological, clinical, and manipulative considerations* Silvano A. Mior, DCt J. David Cassidy, DC, FCCS(C)i

The importance of degenerative disease of the lumbar posterior joints and intervertebral disc in the pathogenesis of acquired stenosis of the lateral recess has been recognized for many years. In 1927 Putti wrote, "A diseased (posterior) joint, by its swelling and deformity changes the shape of the foramen, thus irritating and compressing the nerve within it"'. Later, Verbiest described the clinical symptoms of neurogenic claudication which result from encroachment of the spinal canal by hypertrophic articular processes2. These findings were further supported by MacNab, Epstein, and Crock; who all emphasized the importance of degenerative posterior joints in the pathogenesis of nerve root entrapment3A45 . More recently, Kirkaldy-Willis has outlined the pathological factors contributing to low-back pain6. He has proposed a possible mechanism of nerve root entrapment produced by arthrosis and subluxation of the posterior joints. When such changes are present, most commonly in conjunction with degenerative changes of the intervertebral disc, entrapment of the spinal nerve roots in the narrowed lateral recess may occur. In fact, this syndrome is becoming increasingly recognized as an important cause of low-back pain. Furthermore, Kirkaldy-Willis and Hill have classified the lateral entrapment syndrome as one of the five most common syndromes responsible for low-back pain and leg pain 7. The purpose of this article is essentially threefold: firstly, to outline the pathologic anatomy responsible for entrapment of the lumbar roots; secondly, to illustrate its clinical presentation; and thirdly to review the effectiveness of spinal manipulative therapy in the management of lateral entrapment syndrome. We have included two case studies to illustrate some of the main features of this syndrome.

feriorly and laterally towards the intervertebral foramen. The canal itself is bound by superior, inferior, anterior, and posterior walls. The superior and inferior walls are formed by the inferior pedicle of the vertebra above and the superior pedicle of the vertebra below. The anterior wall is formed by the posterior aspect of the vertebral body superiorly and the annulus fibrosis inferiorly. The ligamentum flavum, the superior aspect of the lamina corresponding to the related nerve root, and the superior articular process of the vertebra below form the posterior wall of the recess8. The anterior and posterior walls play the most important role in the pathogenesis of nerve root entrapment (Figure 1).

Anatomy of the lateral recess The conical-shaped lateral recess, also known as the nerve root canal, begins at the point where the nerve root leaves the dural sac and continues obliquely to extend in-

Figure 1: The nerve root canal contains the mixed spinal nerve (SN) and dorsal root ganglion. Its anterior border is the disc (D) and its posterior border is the superior articular process (SAP) of the vertebra below.

*

Part of this study was made possible through a grant from the Foundation for Chiropractic Education and Research, Des Moines, Iowa, U.S.A.

t Resident III, Chiropractic Science, CMCC, 1900 Bayview Avenue, Toronto, Ontario t Research Associate, Department of Orthopaedics, University Hospital, Saskatoon, Saskatchewan S7N OXO

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Lateral nerve root entrapment

Figure 2: Cross-sectional view of a normal lateral recess

(arrow) at the lower lumbar level.

Pathogenesis of entrapment Normally, the lateral recess is of sufficient diameter to allow the nerve root to exit freely (Figure 2). The recess may, however, be compromised by degenerative changes affecting the posterior joints and the intervertebral disc. Disruption and degeneration of the disc leads to a loss of disc height, subperiosteal new bone formation, and osteophytic reaction at the posterior aspect of the vertebral body. At the same time, the posterior joints undergo degenerative changes similar to those seen in other diarthrodial joints. These changes include the breakdown of articular cartilage and subsequent subperiosteal new bone formation. This can result in the enlargement and deformation of the articular processes which may eventually bulge into the nerve root canal6. As a result of these proliferative changes in the intervertebral disc anteriorly and the superior articular process posteriorly, there is a decrease in the anteroposterior dimensions of the lateral recess giving a trefoil appearance to the spinal canal (Figure 3). A. Dynamic lateral entrapment As a result of degenerative thinning of the intervertebral disc, there is an accompanying anterosuperior subluxation of the superior articular process at the same level. The incongruous joint surfaces stretch and may even disrupt the surrounding capsular structures leading to segmental instability9. When segmental instability is superimposed on hypertrophic changes, certain body movements may result in an intermittent or dynamic narrowing of the lateral 14

Figure 3: Cross-sectional view of a pathologically narrowed lateral recess (arrow). Note the enlargement and irregularity of the superior articular process (SAP) on the right. recess 10 . Dynamic lateral nerve root entrapment responds more readily to manipulation than the more advanced or fixed variety. Nevertheless, it is a difficult problem to manage and reoccurrences of entrapment are common, especially if there is a marked degree of associated segmental

instability (Figure 4). B. Fixed lateral entrapment Recurrent strains to an unstable segment can lead to further degeneration of the intervertebral disc and degenerative hypertrophy of the articular processes69. With time, the disc and posterior joints tend to fibrose and stabilize, which may create a fixed or permanent narrowing of the lateral recess (Figure 5). If the encroachment progresses to the point of entrapment, surgical decompression may become necessary as manipulation is less likely to have any affect on this situation.

Clinical presentation of entrapment The clinical presentation of lateral nerve root entrapment is characterized by a history of intermittent attacks of pain noted over several years. Occasionally, however, patients may present with a spontaneous onset of symptoms similar to an acute joint strain. The pain is most frequently localized to the lower lumbar and upper sacral segments with radiation into the buttock, trochanteric region, and posterior thigh - extending distally as far as The Journal of the CCA/Volume 26 No. 1 /March 1982

Lateral nerve root entrapment

Figure 4: Flexion-extension study of the lumbar spine showing segmental instability at the L4-5 level (arrows) in a patient with recurrent dynamic lateral nerve root entrapment.

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Figure 5: (a) Pathological specimen demonstrating the lateral recesses at L5-S1 with the L5 nerve roots in place (arrows). The left recess is narrowed by degenerative changes in the disc anteriorly, and the posterior joints posteriorly. (b) Same specimen showing narrowing of the lateral recess on the left with indentation of the nerve root (arrow) caused by the compression.

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Lateral nerve root entrapment

the calf and foot. Often, there is little or no back pain and these patients more commonly complain of distal leg pain. At times, the pain is diffuse and patchy, covering several dermatomes, but it is more often localized to a lower lumbar or upper sacral nerve root distribution. Examination of the lumbar spine may not be that remarkable 7. Movements tend to be diminished in all planes, but most noticeably in flexion and extension. Not infrequently, motion palpation reveals restricted movement in the lower lumbar posterior joints and the sacroiliac joints. Occasionally, anteroposterior instability can be detected at the lower lumbar levels9. Straight leg raising is often diminished and frequently accompanied by signs of nerve root tension (bowstring and Braggard's sign). The sciatic nerve is usually sensitive to pressure at the sciatic notch and popliteal fossa. The neurological examination of the lower extremities is characteristic of a single nerve root lesion. The patients may experience mild to moderate sensory deficits extending over a single dermatome, frequently accompanied by a diminished or absent Achilles or hamstring reflex. A mild to moderate degree of weakness may be noted in muscles supplied by the involved nerve root 7. Unfortunately, this syndrome shares many of the signs and symptoms of other common low-back pain syndromes. This can complicate the diagnosis of nerve root entrapment, particularly in the early stages of the syndrome. This difficulty may be further compounded by the presence of other symptom-producing lesions including sacroiliac and posterior joint dysfunction. Consequently, a trial of manipulations to relieve joint dysfunction may be required to confirm the diagnosis of nerve root entrapment. In such cases, a poor response to conservative therapy may clinch the diagnosis. Nevertheless, all such patients should be given a trial of therapy prior to operative intervention.

Radiographic evaluation The evaluation of routine and stress radiographs provides additional information which may contribute to, the diagnosis of nerve root entrapment. In fact, this diagnosis should be suspected when diminished intervertebral disc height and other degenerative changes are seen on routine lateral radiographs of the lumbar spine 7. Further information obtained from stress radiographs (lateral views taken in flexion and extension, and anteroposterior views taken in left and right lateral bending) is helpful in determining the presence of instability and/or lack of movement at intersegmental levels. For example, lateral radiographs taken in flexion and extension may reveal retrograde movement of the vertebra above with respect to the one below. This type of instability decreases the dimensions of the lateral recess and is a common cause of intermittent dynamic lateral entrapment. Anteroposterior radiographs obtained in right and left lateral bending are more useful in determining levels of rotational 16

deformity and decreased intersegmental motion9. In any case, the x-ray findings must be correlated to the physical findings, since x-ray evidence of degenerative lumbar disease is not in itself diagnostic of nerve root entrapment. In some cases, the patient may present with clinical signs and symptoms characteristic of lateral entrapment, but routine and stress radiographs fail to reveal any structural or motion abnormalities. In such cases, the use of the computed tomographic scan (C.T. scan) is a most valuable tool in confirming the diagnosis 10 . The C.T. scan gives a clear sectional horizontal view of the spinal canal and lateral recesses. In entrapment syndromes, the C.T. scan frequently reveals the presence of a hypertrophic superior articular process narrowing the lateral recess at the same level. C.T. scanning in flexion, extension and rotation has also been used at this centre to confirm the presence of dynamic lateral nerve root entrapment 10 . Although chiropractors do not usually have direct accessibility to the C.T. scan, the diagnosis of lateral nerve root entrapment can, in most cases, be made on clinical grounds with the aid of plain film radiographs.

Case presentations Case 1: A 64-year-old caucasian female was seen in the Low-Back Pain Clinic with complaints of episodic low-back pain of approximately two years duration. The pain was dull in character, localized to the left posterior superior iliac spine with burning and tingling radiations into the buttock and posterolateral aspect of the left leg to the ankle. The pain was aggravated by walking and relieved by rest. She also complained of pain at night which was relieved by getting up from bed and walking about for several minutes. There was no significant history of trauma, although she did have a history of several similar episodes of pain over the past five years. She was otherwise in good general health. On examination, the range of movement of the lumbar spine was full and painless, except for extension and lateral bending to the left which were decreased by 50% and 25% respectively. Motion palpation revealed tenderness and dysfunction of the left L4-5 and L5-S1 posterior joints, as well as the left sacroiliac joint. She could straight leg raise to 90 degrees on the right, but was limited to 70 degrees on the left. There was a diminished left Achilles reflex, some loss of sensation over the left L5 dermatome, and slight weakness of dorsiflexion of the left great toe, graded at 4/5. Lateral stress radiographs in flexion and extension revealed moderate osteophytic formation throughout the lumbar spine, most marked at the L4-5 level. There was marked narrowing of the disc spaces from L3 to SI, as well as a mild degree of retrospondylolisthesis of L4 and LS in extension (Figure 6). There was no evidence of marked segmental instability. Anteroposterior right and left lateral bending films revealed decreased movement to the left throughout the lumbar spine and slight misalignment of the L4-5 spinous processes sugestive of a fixed rotation deformity (Figure 7). The C.T. scan showed narrowing of the left lateral recess at the L5-S1 level by the enlarged osteophytic superior articular process of Si (arrow: Figure 8). No disc abnormality could be seen. The Journal of the CCA/Volume 26 No. 1 /March 1982

Lateral nerve root entrapment

Figure 6: Lateral radiographs of lumbar spine of a 64-year-old female in (a) flexion and (b) extension, respectively, demonstrating mild retrograde movement of LA on L with extension. This is suggestive of some instability at this level.

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Figure 7: Lateral bending radiographs of the same patient as Figure 6, demonstrating a marked loss of movement to the left at L4-5 and L5-S1. There is slight misalignment of the spinous processes at L4-5 suggestive of fixed rotational deformity. 17 The Journal of the CCA/Volume 26 No. 1 /March 1982

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A clinical diagnosis of L5 nerve root entrapment was made and the patient was treated daily for ten consecutive days with manipulations directed to the left L4-5 and L5-S1 posterior joints and the left sacroiliac joint. The initial manipulation caused some discomfort, but by the tenth day her symptoms were greatly improved. Her night pain was significantly decreased in both frequency and intensity and she was able to walk without difficulty. She did experience a recurrence of her symptoms several weeks later, but improved again with subsequent manipulations. Follow-up care included a vigorous regime of flexion exercises with periodic manipulations when indicated.

Case 2: A fifty-two-year-old caucasian female was referred to our clinic complaining of low-back and leg pain of approximately three years duration. The pain was insidious in onset and described as a numbness localized to the lumbosacral level with radiation into both lower extremities. The leg discomfort was much worse than the low-back pain and more marked on the right side. The pain was aggravated by movement and relieved by rest. Her past history included a chemonucleolysis at the L4-5 and L5-S1 levels, an epidural block several months later, and spinal manipulations with only temporary benefit. There was no history of trauma and she was otherwise in good general health. On examination the lumbar spine was moderately restricted by pain in forward flexion and left lateral bending. Extension was markedly restricted and very painful. Motion palpation revealed

ligure 5: C.1. scan of same patient as Figures 6 and 7, demonstrating hypertrophy of the superior articular process of S1 and narrowing of the left lateral recess at the L5-S1 level.

Figure 9: Lateral radiographs of lumbar spine of a 52-year-old female showing loss of disc height at L4-5 and L5-S1. Note the contrast medium in the subarachnoid space. The Journal of the CCA/Volume 26 No. 1 /March 1982 18

Lateral nerve root entrapment

Figure 10: Lateral bending radiographs of the lumbar spine to the right and left demonstrating marked loss of motion of L4 and L5 on left lateral flexion. bilateral joint dysfunction at the L4-5 and L5-Sl posterior joints, as well as bilateral sacroiliac joint fixation. There was marked fixation at the L4-5 level on left lateral bending. Straight leg raising was 60 on the left and 70 degrees on the right. There was bilateral weakness of the plantar flexors of the feet (graded 3/5) and the Achilles reflex was absent bilaterally. X-rays of the lumbar spine revealed marked thinning of the discs at L4-5 and L5-S1. The patient underwent a regime of manipulations directed to the lumbosacral and sacroiliac joints for suspected bilateral SI nerve root entrapment. Her response to treatment was poor and she subsequently underwent a separate bilateral approach for decompression of the Si roots at the L5-S1 level. Her postoperative condition was good until the second month. At that time, she developed right lower-lumbar pain with radiation into the right buttock and posterior thigh to the level of the knee. Examination at that time revealed a good range of motion in the lumbar spine, but bilateral sacroiliac joint dysfunction was still present. There was a mild sensory deficit along the L5 dermatome extending to the dorsum of her right foot. Motor power in the lower extremities was within normal limits. The Achilles reflexes were still absent. X-rays of the lumbar spine were repeated. The flexion-extension films revealed marked narrowing of the L4-5 and L5-S1 disc The Journal of the CCA/Volume 26 No. 1 /March 1982

spaces, but no evidence of instability (Figure 9). Anteroposterior lateral bending films revealed a decrease in movement to the left throughout the lumbar spine, most marked at the L4-5 level (Figure 10). Contrast medium from a previous myelographic study could be seen in the subarachnoid space along with evidence of a previous laminectomy at L5. This patient again underwent a regime of spinal manipulations for sacroiliac and posterior joint dysfunction and slowly improved over the course of two months. Two years postoperatively, she continues to experience occasional episodes of low-back and leg pain which have been successfully managed by specific spinal manipulative therapy.

Manipulative management of lateral entrapment syndrome Although complete relief is not always possible, spinal manipulative therapy can play an important role in the treatment and management of this common syndrome. Over the past five years, one of us (JDC) has been involved in a prospective study of the results of spinal manipulation of patients with chronic low-back and leg pain. These 19

Lateral nerve root entrapment

patients were classified into different diagnostic categories (including lateral nerve root entrapment) according to predetermined criteria. The final results of this study are now available and will be published in the near future. Seventy patients with nerve root entrapment were treated over the five-year period with an average follow-up of approximately one year. Although these patients had been unresponsive to other forms of conservative therapy, approximately 50% showed significant improvement after spinal manipulative therapy'1. The overall response to this treatment was somewhat better in patients with the dynamic form of lateral entrapment. It should be emphasized that this study focused on a very select group of difficult patients, seen in a very specialized Low-Back Pain Clinic and may not be representative of the general practice experience of most chiropractors. The success of spinal manipulative therapy in this condition is related to the type and degree of entrapment encountered. It has been our experience that the dynamic form of lateral entrapment is more responsive to manipulation than the fixed form. In the former instance, there remains the possibility of either directly or indirectly reducing tension and/or compression on the nerve root with properly applied manipulations. In the latter instance, the nerve root is compressed by rigid structures and usually requires surgical decompression. Dynamic entrapment with marked instability requires careful assessment, for manipulations may be contraindicated at that level, and in most cases, must be directed to the hypomobile levels above and below the lesion9. This is especially important to remember when treating patients who have undergone decompression by an extensive laminectomy and may have some associated instability. In all cases, management is difficult and frequently complicated by recurrent episodes of low-back and leg pain. With the exception of acute herniation of the nucleus pulposus, most cases of lateral nerve root entrapment represent an end-stage of a long-standing process. The vast majority of these patients have a long history of back pain. As such, they tend to suffer from chronic posterior joint and sacroiliac dysfunction, as well as, lateral nerve root entrapment. Manipulations should be directed towards these associated lesions which are themselves pain-producing. Moreover, the correction of such lesions is often associated with a marked improvement of the low-back pain, but less improvement of the leg pain. It is the distal sciatic component of this syndrome which is the most difficult to manage. Nevertheless, chiropractic therapy can play an important role in the interdisciplinary management of pat'Ints with lateral nerve root entrapment.

Summary 1. Hypertrophic changes of the superior articular process in conjunction with degenerative changes of the interverte-

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bral disc may diminish the anterior-posterior dimensions of the lateral recess and result in entrapment of the nerve root. 2. The clinical presentation is usually that of one-level nerve root involvement with pain commonly localized to the lower lumbar and upper sacral segments radiating distally into the leg. Lumbar spinal movements may be diminished in all ranges and most notably in extension. Straight leg raising is frequently diminished with signs of nerve root tension. 3. Manipulation is of both diagnostic and therapeutic value in cases of lateral nerve root entrapment. There is a tendency for recurrence of symptoms and patients may require continuing care and /or surgical decompression.

Acknowledgement The authors would like to acknowledge the cooperation and assistance of the Department of Orthopaedic Surgery at the University of Saskatchewan, and in particular the kind assistance of Dr. W. H. Kirkaldy-Willis. The authors would also like to acknowledge the technical assistance of Mr. D. Manderville, Mr. R. Van den Beucken and Mr. J. Junor in the preparation of x-rays and pathological specimens, and Elaine Riekman for typing the manuscript.

References 1. Ghormley R. Low-back pain with special reference to the articular facets, with presentation of an operative procedure. JAMA 1954;

101:1773-7. 2. Verbiest H. Radicular syndrome from developmental narrowing of the lumbar vertebral canal. J Bone Jt Surg 1954; 36B:230-7. 3. MacNab I: Negative disc exploration - an analysis of the causes of nerve root involvement in 68 patients. J Bone Jt Surg 1971; 53.A: 891-903. 4. Epstein J, Epstein B, Lavine L, Carras R, Rosenthal A and Sommer P. Lumbar nerve root compression at the intervertebral foramina caused by arthritis of the posterior facets. J Neurosurg 1973; 39: 362-9. 5. Crock HV. Isolated lumbar disc resorption as a cause of nerve root canal stenosis. Clin Orthop 1976; 109-15. 6. Kirkaldy-Willis WH, Wedge JH, Jong-Hing K and Reilly J. Pathology and pathogenesis of lumbar spondylosis and stenosis. Spine 1978; 3:319-38. 7. Kirkaldy-Willis WH and Hill RJ. A more precise diagnosis for lowback pain. Spine 1979; 4:102-9. 8. Reilly J, Yong-Hing K, MacKay R and Kirkaldy-Willis WH. Pathological anatomy of the lumbar spine. In: Helfet, A and Gruebel Lee, D (eds). Disorders of the lumbar spine. JB Lippincott Co, Toronto, 1978. 9. Cassidy JD and Potter GE. Motion examination of the lumbar spine. J Manipulative and Physiological Therapeutics 1979; 2:151-8. 10. Burton CV, Heithoff KB, Kirkaldy-Willis WH and Ray CD. Computed tomographic scanning and the lumbar spine, Part II: Clinical considerations. Spine 1979; 4:356-68. 11. Cassidy JD, Kirkaldy-Willis WH and McGregor M. Spinal manipulation for the treatment of chronic low-back and leg pain: A five-year experience. Accepted for reading at the proceedings of the International Society for the Study of the Lumbar Spine Toronto June 1982. Department of Orthopaedics, University of Saskatchewan, Saskatoon, 1982.

The Journal of the CCA/Volume 26 No. 1 /March 1982