is Associate Professor of Radiology at the University of Arkansas for Medical Sci- ences, Little Rock. He received his M.D. degree from the University of Tennessee in Memphis and completed training in Ra- diology at the University of Minnesota. Dr. Holder’s special interests include radio- graphic contrast material and spinal ra- diology. is Assistant Professor of Radiology at the University of Arkansas for Medical Sci- ences. He received his M.D. degree at the same institution in 1976. Dr. Fitz- Randolph’s interests are bone radiology and teaching. is Professor of Neurosurgery and Chair- man of the Department at University of Arkansas for Medical Sciences, Little Rock. He is a graduate of the Washington University School of Medicine in St. Louis, trained in Surgery and Neurosurgery at Yale, and was on the faculty there until his transfer to Arkansas in 1967. Dr. Flan- igan has a particular interest in disorders of the spinal cord and spinal roots. SPINAL STENOSIS as a pathologic entity has been known and described in the literature since 1934, for the lumbar area, and since 1943 for the cervical region.‘, 2 These early reports, how- ever, dealt with disc disease and this has tended to overshadow 6
Transcript
is Associate Professor of Radiology at the University of Arkansas for Medical Sci- ences, Little Rock. He received his M.D. degree from the University of Tennessee in Memphis and completed training in Ra- diology at the University of Minnesota. Dr. Holder’s special interests include radio- graphic contrast material and spinal ra- diology.
is Assistant Professor of Radiology at the University of Arkansas for Medical Sci- ences. He received his M.D. degree at the same institution in 1976. Dr. Fitz- Randolph’s interests are bone radiology and teaching.
is Professor of Neurosurgery and Chair- man of the Department at University of Arkansas for Medical Sciences, Little Rock. He is a graduate of the Washington University School of Medicine in St. Louis, trained in Surgery and Neurosurgery at Yale, and was on the faculty there until his transfer to Arkansas in 1967. Dr. Flan- igan has a particular interest in disorders of the spinal cord and spinal roots.
SPINAL STENOSIS as a pathologic entity has been known and described in the literature since 1934, for the lumbar area, and since 1943 for the cervical region.‘, 2 These early reports, how- ever, dealt with disc disease and this has tended to overshadow
6
the appreciation of spinal stenosis in otherwise normal patients as an isolated entity. In 1953 Taveras and Schlesinger were the first to describe patients who presented with symptoms of cauda equina compression and multiple levels of involvement. These patients had both bulging lumbar discs and decreased sagittal dimensions in the lumbar region. Later reports showed that con- genitally small canals alone without disc bulging may be symp- tomatic. Subsequent reports have stressed that an AP diameter of 15 mm or less is critical in determining which patients are at risk for lumbar symptoms secondary to degenerative disease. In fact, some authors in recent years have taken the position that only patients with lumbar spinal stenosis (localized or general- ized) will develop symptomatic disease.3’ 4
The condition of congenital cervical spinal stenosis was first suggested in 1957.5 Subsequently numerous articles have been published presenting small series of patients with this condi- tion.6-16 From these reports it has become clear that males are predominantly involved. A large percentage of patients who present with symptoms of myelopathy as opposed to radiculopa- thy secondary to degenerative disease have a degree of spinal stenosis. In the cervical region, 12 mm is thought to be the lower limit of normal for the AP sagittal diameter.7, l5
The importance of familiarity with congenital spinal stenosis is in the need for proper diagnosis. Many patients with stenosis in the lumbar region have been initially misdiagnosed as having vascular insufficiency of the lower extremities or multiple nerve root compressions. In the cervical region the diagnoses of cervi- cal cord tumors or neural diseases such as amyotrophic lateral sclerosis, multiple sclerosis, syringomyelia, and subacute com- bined degeneration of the cord are frequently made. Proper ther- apy has resulted in improvement in a large number of these pa- tients, and even more significantly, the earlier the diagnosis is madeif$ proper therapy is instituted, the better is the prog- nosis. 2
There are many conditions that may narrow the subarachnoid space. The thrust of this monograph is the abnormal narrowing (stenosis) caused by insufficient bony growth of the posterior ele- ments. This is referred to as developmental or congenital steno- sis. Degenerative bony changes may contribute to the narrowing (Table 1).
EMBRYOLOGY
The vertebral column begins forming at approximately the third week of gestation. At this time a crude membranous ver- tebral column forms from sclerotomes that rapidly proliferate to surround the primitive notochord. The membranous vertebral column is succeeded by a cartilaginous vertebral column arising
TABLE L-CLASSIFICATION OF SPINAL STENOSIS
DEVELOPMENTAL(COI~E~~AL)STENOSIS Idiopathic
Cervical Thoracic Lumbar
Achondroplasia Hypochondroplasia Other (Klippel-Feil syndrome, etc.)
ACQUIREDSTENOSIS Degenerative
With developmental stenosis Without developmental stenosis
from pairs of cartilaginous centers on either side of the noto- chord, which form the bodies, and pairs of centers arising in the lateral portions of the arch, which form the cartilaginous arch. This occurs at approximately the fourth week of fetal develop- ment. Shortly thereafter, early centers of ossification appear in the dorsal and ventral aspects of the vertebral bodies, beginning in the lower thoracic and upper lumbar regions and spreading cranially and caudally. At approximately the eighth week of fe- tal development, ossification centers appear in the vertebral arches of the upper cervical vertebrae and extend inferiorly gradually. By the end of the first year of life, the two ossification centers in the laminae fuse in the lumbar spine, followed by fu- sion in the thoracic and cervical regions. In about the third year of life, the arches of the cervical region unite with their respec- tive bodies. Fusion continues until. the lower lumbar vertebrae fuse in about the sixth year of life.lgV 2o
The development of C-l and C-2 is much more complex and will not be expounded here since these levels appear not to be involved in the development of myelopathy due to simple devel- opmental stenosis.
Kessler concluded from his studies of the normal spine in chil- dren and adolescents that the vast majority of growth in the size of the spine occurs before age 3 years. He therefore concluded that the etiological onset of a congenitally narrow canal must be between the ages of 8 weeks’ gestation and the third year of life.6
In 1972 Godlewski suggested premature closure of ossification centers secondary to excess growth hormone as the etiology of
8
congenital spinal stenosis.6 Both and associates in 1975 sug- gested that the formation of the bony spinal canal was inti- mately associated with the development of the neural ele- ments.‘i Furthermore, they suggested that this association is mediated via a neurohormone that acts on chrondroblasts in a negative chemotactic manner. This hypothesis, which has some experimental support, is thought to fit quite well with the em- bryologic findings in the cervical and thoracic regions. In the lumbar region the same theory is workable but more difficult to comprehend because it is the cauda equina that is contained therein. According to this theory, the bony canal and foramina are affected by the additive effects of the multiple nerve fibers and their neurotactic zones.21 The exact mechanism of congeni- tal stenosis, however, has never been proved.
CONGENITAL CERVICAL SPINAL STENOSIS
Stenosis of the cervical spinal canal as a cause of neurologic symptomatology has only recently been stressed in the litera- ture. Even less has been written concerning congenital cervical canal stenosis.
The earliest articles suggesting the importance of the size of the cervical canal were written by Camp, Adson, and Shugrue (1933) and by Elsberg and Dyke (1934). Both these papers, how- ever, focused on measurement of the interpediculate distances as an estimate of canal size and stressed the lack of reliability of these measurements due to poor visualization of the pedicles in the upper three or four vertebrae. Nevertheless, Elsberg and Dyke demonstrated the interpediculate distances to be in the range of 30 mm.22 Lindgren in 1937 suggested focusing on the sagittal diameter of the cord, but the thrust of his report was evaluation of enlargement of the canal due to tumor involve- ment. Later, Boijsen in 1954 further stressed the importance of the sagittal diameter in evaluating cord size.23 He showed that the interpediculate distance was not only difficult to measure consistently, but furthermore that it did not even anatomically represent the narrowest dimension of the canal. His studies il- lustrated that the sagittal diameter of the canal as measured from the dorsal surface of the midportion of the vertebral body to the union of the arches dorsally represented the smallest di- ameter throughout the cervical vertebrae. At C-l the posterior margin of the odontoid was used in measuring. In thoracic and lumb;; sections the sagittal and frontal diameters were the same.
In the same report Boijsen published a fine study of the nor- mal sagittal dimensions of the cervical canal in 200 normal in- dividuals (100 males and 100 females).23 In 1956 Wolf et al. per- formed a similar study on 200 normal adults using a 72-inch
9
focus-film distance and found a continuous slight decrease in the sagittal dimensions from the foramen magnum to C-3.l’ The av- erage AP diameter from C-3 through C-7 was found to be nearly constant at approximately 17 mm in adults.17 Burrows con- firmed these findings in 1963 (Fig U7
In 1954 Pallis, Jones, and Spillane initially suggested that the cervical canal was smaller in cases of cervical spondylosis.24 Further work along this line by Payne and Spillane, reported in 1957, tended to confirm this initial finding.5 Although their study dealt primarily with the effects of spondylosis, they did suggest that the initial sagittal diameter of the canal was closely related to the likelihood of developing myelopathy. They also found that in extension the canal size was reduced and that the maximal canal size was achieved in slight flexion. They hy- pothesized that relaxation and bulging of the ligamenta flava into the canal in hyperextension was responsible.5 Penning, however, suggests that one must also take into account degen- eration of the posterior articulations, which allows mild retro- listhesis of the superior vertebrae upon their inferior partners in hyperextension, resulting in a l- to 2-mm decrease in the sagit- tal diameter of the canal at the site of overlap.25 These two mechanisms are believed to account for the rare instances of se-
26 _
24-
22-
20 -
P s E la- H E
16-
Id-
12 -
10 I I I I I I I
C-l c-2 c-3 c-4 C-5 C-6 c-7
Fig l.-Average sagittal diameter at each cervical level using 724nch focus-grid distance. Shaded area indicates 2 2 SD. (Modified from Table 2 in Burrows,7 by permission.)
10
vere myelopathies in patients who have sustained hyperexten- sion injuries without fractures or dislocations.” ’
The contributions of osteophytic overgrowth at the posterolat- era1 margins of the bodies, posterior protrusion of disc material, hypertrophy of the ligamenta flava, and dorsal intrusions into the canal by osteophytes secondary to apophyseal arthrotic changes have been expounded by multiple authors.7y “7 llp 17, 26
Payne and Spillane evaluated 90 patients (30 normal, 30 with spondylosis but asymptomatic, and 30 with spondylosis and myelopathy). While the average AP diameter in the normal group was 17 mm, that in the symptomatic group was 14 mm.5 Multiple studies have determined the AP dimension of the cord to average 10 mm in the cervical spine, although there may be variation above and below this value in select cases. The dural sheath contributes an additional 2-3 mm. It is easy to surmise, therefore, that the smaller the dimensions of the canal origi- nally, the less encroachment is needed to result in cord compres- sion and symptoms.7, 25, 27 This was aptly demonstrated by Ed- wards and LaRocca, who showed that patients with large canals had larger osteophytes as compared to patients with small ca- nals when the patients had similar symptomatology.27
Hinck et al. in 1962 were the first specifically to address the question of developmental stenosis of the cervical canal and its possible significance.28 In articles published in 1962, 1964, and again in 1966, Hinck and colleagues addressed the establish- ment of normal values for sagittal diameters in the pediatric age group and also stressed the uniform nature of the curves in any one individual. Thus, even though a patient’s sagittal measure- ments might fall within the normal range, a variance from the normal curve for that individual probably indicates an abnor- mality.12, 13,28
There has been an ongoing debate as to the exact mechanism of the symptom complex found in this entity. Kahn in 1947 sug- gested that symptoms were caused by direct pressure effects on the cord.2g However, subsequent pathologic correlation studies have discounted this theory. The most plausible explanations at present suggest the primary insult is compression of the anterior spinal artery and its branches or compression of the end vessels within the cord itself.6’ lo, 2g
CLINICAL FEATURES
AGE.-A majority of patients diagnosed with congenital cer- vical spinal stenosis have sought medical attention for the prob- lem between ages 40 and 70. It is thought that this age at pre- sentation reflects the development of degenerative spurs in middle-aged persons which results in symptomatology. A second
11
group of younger patients has also been noted (Table 2). These patients present primarily with a history of acute trauma.6P s-169 3o
%x.-There has been an uncanny and unexplained male pre- dominance in this entity. After reviewing the literature, and in- cluding our three cases, we found 79 males out of 93 reported patients with developmental sagittal diameters of 12 mm or less 68-14, 30
PRECIPITATING EVENTS.-A large number of patients give a history of hyperextension injuries. This is particularly true of patients who present at a younger age. Five of six patients pre- senting at age 20 or younger had such a history. Others reported less specific types of trauma such as simple falls. Older patients were much less likely to present with a definite trauma his- tory. S-11,13, 14
SIGNS AND SYMPTOMS.-CeIItIXl cord symptoms predominate. These include spasticity, sensory deficits (especially decreased proprioception), low-threshold micturition reflex, small bladder capacity, incontinence, lower and upper extremity weakness, wasting with fasciculations in the u reflexia in the lower extremities.‘-1
zger extremities, and hyper- ’
LABORATORY FINDINGS.-The CSF protein level may be slightly elevated in some patients.15
PLAIN RADIOGRAPHIC FINDINGS.-Plain films show either dif- fuse or focal decreases in the cervical sagittal diameters. Spon- dylotic spurring, uncal spurring, and retrolisthesis may be pres- ent. Associated spinal anomalies are uncommon, aside from
TABLE 2.-AGE AT PRESENTATION OF PATENTS WITH SYMPTOMATIC
*Based on previously published re- ports in which ages were given, and our own patient data.
12
Fig 2.-Plain radiographic findings in spinal stenosis. A, focal congenital stenosis at C-4. Note minimal spurring at C4-5 (arrow). Sagittal measurements were as fol- lows: C-3, 16 mm; C-4, 14 mm; C-5, 16 mm. 8, generalized congenital spinal ste- nosis with sagittal dimensions ranging from 10.5 to 12 mm from C-3 through C-7. Note short laminae (single arrows) and minimal degenerative bony spurring at C5-6 (double arrow). C, marked degenerative spurring (arrows) arising secondary to disc disease in a patient with focal congenital stenosis from C-3 through C-5.
lumbar spine stenosis in 10%-S% of cases. Congenital block vertebra, turricephaly, and s
P ina bifida occulta have been noted
in a few patients (Fig 2).8-13, 5, 26
CT AND MYELOGFUPHY CHANGES.-CT demonstrates marked encroachment on the spinal cord in an AP direction by bony spurs, bars, or disc material. Myelography demonstrates an ap- parent increase in the transverse size of the cord in the PA view, suggesting an intramedullary tumor. In the lateral view, how- ever, compression of the cord anteriorly secondary to spurs and bars and posteriorly secondary to hypertrophied ligamenta flava is seen. High-grade blocks may be seen, with im 5 rovement in flow in the slightly flexed position (Figs 3 and 41gm1 ’ 26
DIAGNOSIS
Any patient presenting with myelopathy of the cervical spine should be evaluated for congenital stenosis. Unfortunately, many patients have been misdiagnosed as having entities such as amyotrophic lateral sclerosis, multiple sclerosis, cord tumors, syringomyelia, and subacute combined degeneration of the cord. A rapid, correct diagnosis is important, since studies have shown that the response to therapy decreases with increasing duration of symptoms.15, 3o
13
Fig 3.-Myelographic findings in spinal stenosis. A, high-grade obstruction at C3-4 with apparent cord widening and with cutoff of nerve root sheaths at C4-5 (R) and C5-6 bilaterally. B, same patient as in Figure 28. There is a marked apparent widening of cord in PA projection with nerve root cutoff at C4-5 through C6-7 bilat- erally. C, note high-grade obstruction of contrast column at C4-5 disc level second- ary to encroaching bony spurs anteriorly (black arrow) and posteriorly (white arrow). D, both anterior and posterior encroachment on contrast column secondary to bony spurs (sing/e arrows) and ligamenta flava (double arrows).
Fig 4.-CT findings in spinal stenosis. A, CT scan demonstrates flattening of cord in sagittal dimension secondary to soft disc. Measurement, 5.9 mm. B, same patient as in Figures 2,B and 3,B. Sagittal reconstruction CT scan demonstrates generalized stenosis with sagittal compression of cord, which measures 6.2 mm at its smallest dimension. C, marked bony encroachment on canal resulting in sagittal dimension of 5.1 mm at its narrowest point.
14
TREATMENT
The preferred form of treatment for patients with congenital stenosis is wide and extensive posterior laminectomies and, at times, discectomy. Anterior discectomies and fusions give good results only when one or two levels are involved, and even then the underlying problem of a tight bony canal must be consid- ered. The usual course following proper therapy is a slow pro- gressive improvement in neurologic function over as much as a year (Fig 5).31-33
OTHER CAUSES
Multiple additional entities can cause spinal stenosis acutely or chronically, but their discussion was thought to be outside the limits of this report. Acutely, fractures and fracture-dislocations can cause stenosis. Likewise, foreign bodies and missile injuries such as gunshot wounds may encroach on the bony canal. More chronic causes such as other arthritides, bacterial osteomyelitis, tuberculosis, fungal diseases, Paget’s disease, tumors, chondro- dysplasias, Klippel-Feil syndrome, and various congenital mal- formations of the craniovertebral junction are not discussed.26
THORACIC CANAL STENOSIS
The relative smallness of the dorsal cord in relation to the area of the dorsal canal means that there must be a marked decrease in the area in order to produce compressive symptoms of the cord. A review of the literature revealed only a single case of developmental stenosis of a thoracic vertebra leading to a myelographic block requiring decompression. At surgery, mark-
Fig B.-Same patient as Figure 3,C. Postoperative myelogram following extensive posterior laminectomies from C-3 through C-6, with marked relief of compressive changes.
15
edly thickened laminae of the ninth thoracic vertebra were iden- tified and removed. The patient recovered nearly complete nor- mal function of the lower extremities.34
We recently treated a similar patient, a 53-year-old man who presented with a l-year history of progressive weakness in his legs (Fig 6). He had been ambulatory with the aid of crutches until 3 weeks prior to admission, at which time he became un- able to ambulate at all. On neurologic examination he was found to have hyperactive deep tendon reflexes in the lower extremi- ties and positive Babinski signs bilaterally. A loss of sensory perception was noted below T-10. A metrizamide myelogram from the lumbar approach revealed a block at the T-10 level. Dorsal compression of the sac was noted and an extradural le- sion was suspected. A second myelogram was carried out from the Cl-2 approach and the upper extent of the lesion was iden- tified at the T-9 level. The following day lateral tomography without contrast revealed thickened laminae partially compro- mising the AP diameter of the thoracic canal. At surgery wide decompression laminectomies were carried out from T-8 through T-11, and laterally to the pedicles. Once this bone had been re- moved, dural pulsations below the involved area, which had been absent, returned to normal. The patient improved rapidly following surgery and within a year returned to normal activi- ties.
ACHONDROPLASIA
Achondroplasia is the most common type of short limb dwarf- ism. It is an inherited condition of the autosomal dominant type
Fig 6.-A, complete block at TlO-11 level by what appears to be a dorsal mass (arrow). B, myelography from the Cl-2 approach demonstrating a partial block at the T9-10 level (arrow). C, hypertrophied laminae (WKIWS) on .a lateral midline to- mogram made without metrizamide.
16
of transmission. If an achondroplastic mates with a normal per- son, the chances are 50% that the offspring will be achondro- plastic. Most achondroplasts, however, are born to normal par- ents and are spontaneous mutants. The chances of normal parents having a second achondroplastic child are not greater than for the general population.
Achondroplasia is one of the oldest disease conditions known to man. In ancient Egypt archeological findings indicate that achondroplastics were valued to the point of being considered godlike. Similar social status is suggested by stone figures found in Ohio dating back to ancient American Indians. Records from the Boman Empire show that achondroplasts held positions of honor, though they were not on the level of gods. Emperors re- tained them as counselors, while the wealthy used them as jest- ers. By the Middle Ages, achondroplast dwarfs had lost their uniqueness. They were no longer retained by royalty as advi- sors, but more commonly were used as “pets” in wealth house- holds and were kept for their entertainment value only. By the & 19th and 20th centuries achondroplasts were considered normal except for their physical appearance. It was not uncommon for them to become paraplegic in their middle and later years. In the early 1900s the etiolog of their paraplegia was recognized as a narrow lumbar canal.
Achondroplasia should be considered the archetype of congen- ital spinal stenosis. The entire spine is involved, with most of the symptoms developing in craniocervical and lumbar areas. The spinal cord itself is normal. The lumbar area has been most extensively studied, and several clinical syndromes have been described. These include nerve root compression either from disc herniations or from osteophyte formation. A syndrome not un- like that of aortoiliac arterial obstruction which is associated with intermittent sensory symptoms following exercise is thought to be due to pressure ischemia of the cauda equina.37
Rapid or slowly developing transverse myelopathies have dif- ferent etiologies. The chronic form is usually associated with an- gular kyphosis in the thoracic region (often of a marked degree) or gibbus formation, while the acute form is more commonly as- sociated with intervertebral disc herniation (Fig 7).
The following factors appear to be responsible for the lumbar canal stenosis:
1. Decreased interpediculate distance. In normal *individuals the interpediculate distance increases from L-l to L-5, while in achondroplasts it decreases.
2. Pedicles and inferior facets. Both the pedicles and inferior facets are thickened and shortened. The inferior facets con- sistently encroach on the nerve roots. Both the pedicles and the inferior facets push the dura medially.
3. AP dimension. There is a marked decrease in the AP di- 17
Fig 7.-Achondroplasia. A, note AP orientation of the facets and interpediculate distances, which decrease from L-l to L-5. B, lateral view in a patient with angular kyphosis. Note the short pedicles (single arrow) and hypertrophied facets (double arrows).
ameter, as evidenced by compression of the contents with little fat in evidence in the epidural space.
4. Cross-sectional area. The cross-sectional area of the achon- droplastic lumbar spine has been shown to be 27%-50% of the normal cross-sectional area. The lower values occur in the lower lumbar spine.
4. Nerve root canal size. There is consistent stenosis of the root canals, the canals being 0.1-0.28 cm smaller in diam- eter than norma1.38
Other spinal deformities common to achondroplasts range from flattening of the back to extreme kyphosis. Gibbus forma- tion may be present secondary to wedging of vertebral bodies.
Four clinical syndromes have been described with achondro- plasia,37 as follows:
1. Nerve root compression. The syndrome is caused by her- niated discs and osteophyte formation.
2. Transverse myelopathy. This condition may develop over many years and is usually associated with severe kyphosis.
3. Acute transverse myelopathy. Sudden paraplegia may be seen following trauma or sudden motion.
4. Intermittent claudication of the cauda equina. This syn- 18
drome is suggestive of vascular disease of the lower ex- tremities in that it is related to activity. Patients experi- ence coldness and numbness. It may be due to pressure ischemia of the cauda equina.
Treatment consists of first ruling out all other causes of symp- toms such as vascular disease. The minimum operation as an initial procedure appears to be a laminectomy from T-11 to L-5. The laminectomy should be wide and should include removal of the medial portion of the inferior facets (Fig 8).37* 38 With con- comitant radicular compression, root canal decompression will require superior facet resection.
Hypochondroplasia, a condition related to achondroplasia, was first described in 1969.3g Patients with hypochondroplasia have some of the features of achondroplasia, but usually in less severe form. Both conditions are of the autosomal dominant inheritance type, with most cases being spontaneous mutations. Spinal ste- nosis is less marked in hypochondroplasia, while kyphosis is nonexistent.40
Figure 9 shows a 57-year-old male hypochondroplastic dwarf, 5 feet 2 inches tall. When first seen in 1980 he complained of tiring easily, frequent falls, and back pain that dated back for 12 years. The pain was dull and aching, nonradiating, and cen- tered in the lumbar area. He reported that he received some relief by assuming the squatting position. Besides being short- statured, he was quite muscular. His family history revealed several relatives of similar description. Water-soluble contrast myelography followed by CT revealed generalized spinal steno- sis. The patient was treated with lumbar laminectomy from L-2
Fig 8.-Achondroplasia. A, extensive laminectomies have been carried out from L-l through L-5 in a 26-year-old woman. B, in the same patient, a Cl-2 puncture myelogram shows a tight canal and bulging C4-5 disk (arrow).
19
Fig 9.-Hypochondroplasia. A, note marked hypertrophy of the facets and lami- nae. B, lateral lumbar myelogram obtained following difficult needle placement. Note the complete block over the body of L-3 CarfowL C, note decreased AP diameter (IO mm) of the spinal canal in this lateral cervical spine. D, cervical myelogram demon- strating a bar at the C3-4 level. E, CT scan at the C3-4 level shows the spinal canal to measure 6 mm.
through L-5, with good results. One year later he was seen fol- lowing a fall, at which time he complained of weakness of both lower extremities as well as of the left arm. In addition to cer- vical canal stenosis, extensive cervical bar formation was found. Good results with return of normal function followed C-3 through C-6 laminectomies.
CONVENTIONAL RADIOGRAPHIC FINDINGS IN LUMBAR CANAL STENOSIS
AP VIEW
The interpediculate distances increase from L-l to L-5 in nor- mal people, while in achondroplasts the interpediculate dis- tances actually decrease. This may be why some of the early reports on spinal stenosis as an isolated anomaly stated that the
20
Fig 10.-A, intetfacetal spaces are seen at multiple levels. Note also thickened laminae. B, normal AP lumbar spine. Compare with A.
interpediculate measurement was abnormally small. It is now generally accepted that nearly all patients with spinal stenosis have normal interpediculate measurements (e.g., > 19 mm). Any measurement of 1’7 mm or less should be considered abnor- mally small. The pedicles themselves may appear abnormally large, either in the horizontal or vertical direction, or both. The interfacetal spaces at multiple levels may be visualized on the AP view, whereas they are seen only occasionally in normal spines. This is thought to be due to a shortening of the laminae (Fig 10).
The interlaminar spaces are decreased from normal or may even be absent due to thickened and more vertically oriented laminae.
Articular facets may be large and hypertrophic, extending into the canal. The medial intraspinal borders of the articular processes may be situated close to each other.
OBLIQUE VIEWS
Oblique views confirm the abnormally thickened laminae and pedicles but add little to the diagnosis of spinal stenosis. They are more valuable in the study of spondylolysis.
21
LATERAL VIEW
The vertebral body is normal in spinal stenosis. There may be slight dorsal scalloping, which is normal.
The pedicles may be thick. Shortening results in a decreased diameter of the lateral recess of the spinal canal. This dimension may be decreased to as little as 2 mm from a normal of 5-7 mm.*l This is best seen on CT scans, the axial view providing a look at the morphology as well as providing accurate measure- ments. On plain films, the intervertebral foramina appear small in the AP direction. An abnormally thick superior articular facet may decrease the vertical dimension of the intervertebral foramen (Fig 11).
The laminae may be so short and oriented in a vertical direc- tion as to appear as a more or less solid mass of bone.
The AP measurement of the lumbar canal, which is the most important measurement, cannot be determined accurately from the plain film. Complex motion tomography using magnification correction has been extensively used to determine canal size. Verbiest considers the lower limits of normal to be 15 mm, lo-12 mm for relative stenosis, and 10 mm or less for severe or absolute stenosis.42 The ready availability of CT scanners makes
Fig Il.-A, short thick pedicles and hypertrophied superior facets encroaching on the intervertebral foramen (arrow). 6, normal lateral lumbar spine for comparison with A.
22
the measurements easier to determine. AP stenosis may be me- dian or lateral in location, depending on the size and location of the articular facets.
A decreased AP diameter is the most common finding of de- velopmental stenosis. Any of the other above-mentioned features may be present to a greater or lesser degree.
CONGENITAL LUMBAR SPINAL STENOSIS
The original description of congenital lumbar canal stenosis giving rise to the syndrome was reported by Schlesinger and Taveras in 1953.43 They pointed out that some patients with bulging lumbar discs present clinically with unusual symptoms. These include multiple instead of single level involvement, as well as symptoms of cauda equina compression. In these patients myelography revealed a complete or nearly complete block. This block, together with an elevated CSF protein level, led to the suspicion of expanding tumors. An analysis of the lumbar spine films of these patients led to the conclusion that there were de- creased interpediculate distances at the levels of disc bulging. In addition, there was a decreased capacity (volume) of the spinal canal, which Schlesinger and Taveras believed was more impor- tant in producing symptoms than the size of the disc bulging. Usually, vertically oriented laminae as opposed to laterally flared ones were noted, as were medially placed facets. At sur- gery, exposure of the dural sac was technically more difficult, and engorged epidural veins were noted. In conclusion, they stated that the unusual structure of the spinal canal, as indi- cated by interpediculate measurements at the low end of the normal range, was the rincipal cause of multiple nerve root involvement and block. 4P
Probably the earliest reference to congenital lumbar stenosis came from Turkey. In his 1947 paper, “Spina bifida aperta and congenital stricture of the spinal canal,” Sarpyener described bony strictures in the lumbar canal at one or more levels.44 Most of the patients also had spina bifida occulta. Some of the patients had a block at myelography. The films in the article appear to show what we would now refer to as myelodysplasia. These pa- tients had various problems, such as enuresis, club-foot, and spastic paralysis. Sarpyener reported curing several of these with laminectomy.44
In 1954 Verbiest described seven male patients who presented with weakness of the lower extremities, anesthesia, numbness of the sacral dermatomes, and bilateral sciatica. These symp- toms occurred only on walking and were relieved with sitting or bed rest. In several patients it was necessary to rule out vascu- lar disease of the lower extremities. Myelography was carried out via suboccipital puncture, or lumbar puncture, using Lipio-
23
dol, and in each case demonstrated a complete block. With change in position it was possible to maneuver some contrast material past the block in a few patients. The Lipiodol was close to the posterior margins of the vertebral bodies at the levels of the blocks, thus ruling out large disc herniations. Two of the patients had blocks over the vertebral bodies, not at the level of the discs. (Figure 12 depicts a similar circumstance in one of our patients.) At surgery Verbiest found extensive bony compression of the dural sac without disc her-Cation. Laminectomies were performed, and in several cases the medial portions of the artic- ular processes were removed, giving good clinical results. Ver- biest attempted to measure the AP diameter of the lumbar ca- nals on x-ray films but concluded that this method was inaccurate. He wrongly concluded that this condition was lim- ited to the lumbar spine.
That report concluded that bony spinal stenosis alone could produce symptoms without disc herniation being present.45 In a follow-up report in 1955 Verbiest reported the development of an instrument for the direct measurement of the AP diameter of the lumbar canal at surgery. Reporting six cases, he found the AP diameter of the lumbar spines at the site of surgery to be at or below the low end of the normal range. The interpediculate
A
Fig 12.-Congenital lumbar stenosis. A, the complelte block is over a vertebral body, and metrizamide is close to the posterior surface of the vertebral body. B, CT at the level of the blockshovwthe subarachnoid space to measure 10 mm, indica- tive of severe stenosis:
24
flg 13.-Congenital lumbar stenosis with posterior disc bulging. A, a nearly com- plete block is present at the L4-5 level and disc bulging is present. B, midline CT with sagittal reconstruction showing hypertrophied lamina and an AP measurement of 7 mm.
Fig 14.-Congenital lumbar stenosis with posterior lipping. A, typical lumbar ste- nosis with abnormally oriented facets and thickened laminae-a difficult myelogram. B, note indentation of the metrizamide anteriorly by lipping, and posteriorly by ab- normal laminae. AP measurement is 8 mm.
25
distances of these patients were in the normal to high-normal range. The ligamenturn flavum was examined in each of the cases and was found to be normal. Verbiest concluded that de- velopmental narrowing of the lumbar canal was due to the ab- normally short AP diameter of the bony canal. Symptoms could be exaggerated in a narrow canal when posterior lipping or when disc bulging was present.46 (Figures 13 and 14 are exam- ples of degenerative changes further compromising the AP di- ameter of the spinal canals of patients with congenital lumbar canal stenosis.
Lumbar spinal stenosis has been defined by Bower as “any type of narrowing of the central spinal canal, nerve canals, and/ or lateral recesses.” The “nerve canal” extends from the point where the nerve root leaves the dura to the lateral extent of the intervertebral foramen. Stenosis may be localized or general- ized.
The incidence of spinal stenosis is difficult to ascertain since most cases have been reported in small groups or in single in- dividuals. Eisenstein carried out a rather elaborate study on 2,166 lumbar vertebrae from 433 skeletons. The age at death ranged from 16 to 96 years, and skeletons were from both cau- casian and negroid populations. The spinal canals were mea- sured in both the AP and transverse diameters. The AP diame- ters were measured at the midpoint of the vertebral body so that osteoarthritic spurring would not be a factor. The conclusion was reached that any AP diameter less than 15 mm and any trans- verse diameter less than 20 mm should be considered stenotic. Some 1.3% of the vertebrae were found to be stenotic in 6.3% of the skeletons. If one vertebra was found to be stenotic, the chances were 60% that an additional stenotic vertebra would be present in the same skeleton. Eisenstein found spinal canal di- mensions to be similar in males and females, and detected only minimal racial differences.4g* 5o Verbiest estimates absolute ste- nosis (510 mm) to occur in one in 500 in the population, or 4% of those patients presenting with nerve root compression. This group also had a 5% incidence of cervical canal bony stenosis.42
In a 1976 article Verbiest stated that 12 mm or less was the AP dimension for the diagnosis of lumbar canal stenosis.3 Rob- erson and Taveras gave the AP measurement of 13 mm or less as abnormally sma11.47 Bower pointed out also that the AP mea- surement is the essential measurement. He defines mild stenosis as an AP diameter of less than 14 mm and severe stenosis as an AP diameter of less than 10 mm.48
The trefoil configuration of the lumbar spinal canal has been considered to be part of the pathologic anatomy of spinal steno- sis (see Fig 15). This is due to the thickened and vertically ori- ented lamina and thickened articular facets which encroach on the lumbar canal. Eisenstein found the trefoil configuration in
26
Fig 15.-Lumbar spinal stenosis. A, normal; 6, sagittal flattening; C, concentric stenosis; D, trefoil configuration with disc herniation; E, sagittal flattening with a bulging disk; F, trefoil configuration with a bulging disk.
15% of lumbar vertebrae. While the trefoil configuration was more commonly associated with an abnormally short AP diam- eter (15%, as opposed to 6.3% for the group as a whole), most vertebrae with the trefoil configuration had normal AP diame- ters.4g
Nelson describes the clinical presentation of these patients as being of two types: claudicant and sciatic. In the claudicant type the patient, usually male, is in his third or fourth decade of life. At rest the patient is asymptomatic, but with walking, paresthe- sias develop and lead to numbness. With increasing gait and balance problems, the patient quickly learns that dramatic symptomatic relief is obtained by sitting down or sometimes crouching. Lying on a flat surface gives the most dramatic relief. Peripheral pulses are equal and normal. Straight-leg raising is also normal. Patients with advanced cases may show muscle wasting. The patient with the sciatic type of symptoms will give a long history of lower back pain with the more recent onset of leg pain. Again, as with the claudicant type, there will be dra- matic relief of symptoms when activity is stopped and a sitting or lying position is assumed. Physical examination may show no abnormality. The reason why these patients prefer the sitting position has been worked out by Brieg. He has shown that when the spine goes from the extension mode to the flexion mode there
27
is an increase in the AP diameter of the spinal canal as well as a straightening of the ligamenturn flavum. In addition, the nor- mal slight posterior protrusion of the discs will disappear.51
Treatment of lumbar spinal stenosis begins with a thorough understanding of the underlying pathology. Lee et al. divide the pathology into three different types, the treatment for each being different. Concentric stenosis is secondary to a generalized growth error in the posterior elements not unlike that seen in achondroplasia. The myelogram shows a decreased AP diameter as well as transverse measurement. Sugittd flattening repre- sents a developmental error which results in a decreased sagit- tal diameter. The myelogram shows a normal AP view, but a decreased AP diameter on the lateral view (Fig 16). Abnormal articulur processes are usually enlarged and bilateral. They may be accompanied by degenerative changes (Fig 17). Any of these abnormalities may be seen with the others. Treatment should at first be conservative in nature, involving rest, local heat, anal- gesics, and perhaps job counseling. Surgical intervention should be considered under the following situations:
1. Intolerable pain during daily activity while the patient is undergoing conservative treatment.
2. Significant progressive muscle weakness. 3. Sphincter dysfunctions. While uncommon in lumbar spinal
stenosis, these represent surgical emergencies.52 Since symptom-producing lumbar spinal stenosis is frequently
accompanied by disc herniation or degenerative arthritis, these conditions must be taken into consideration when planning treatment. The number of levels involved should be carefully determined and the anatomy studied with plain films, myelog- raphy, and CT.
Fig l&-Moderately severe congenital lumbar stenosis, sagittal flattening type. A, AP myelogram is essentially normal except for a small disc herniation at the L4-5 level. B, note the decreased AP diameter, which measured 12 mm, and the disc hemiation (arrow). C, CT of another case of sagittal flattening. Little metrizamide is seen due to the crowded roots.
28
Fig 17.-Abnormally large articular processes with superimposed degenerative changes. Note the trefoil configuration.
Treatment consists of bilateral laminectomy for sagittal flat- tening. The other types of stenosis require more extensive resec- tions involving not only the laminae but also the superior and inferior articukr processes. Following such extensive decom- pressive procedure, spinal stability has not been a problem.52P 63
Results following surgery depend on several factors, not the least of which is the surgeon’s understanding of the problem, related conditions, and the “solution.” Verbiest reports that two thirds of his patients were symptom free following surgery.54 One report on the outcome in 81 patients noted that 91% or more were cured.55 Delfini et al. reported 80% satisfactory re- sults, slightly less than with other causes of the lumbar syn- drome.53
LATERAL RECESS STENOSIS
Bon2 narrowing lateral to the dura was first described in 1957. The anatomy from the point where the nerve root exits the dura to its exit from the bony spine has been referred to as
29
intervertebral foramen, nerve root canal, and lateral recess. This mixed terminology has led to some confusion. Lateral re- cess is now generally accepted to indicate a funnel-shaped struc- ture extending laterally from the dura and bounded posteriorly by the superior articular facet, anteriorly by the vertebral body and disc, and laterally by the medial surface of the pedicle. The nerve root then goes under the pedicle and exits the spinal canal at the intervertebral foramen. This area should be referred to as the intervertebral cana1.57
Clinically, patients with stenosis of either of these areas pre- sent with severe unilateral radicular pain brought on by walk- ing or standing for several minutes, and relieved by sitting or squatting. The myelogram is normal or may show only flatten- ing or cutoff of the nerve root. CT has proved its worth in mak- ing this diagnosis and therefore leading to the appropriate treat- ment (Fig 18). A lateral recess that is encroached on by a thickened or hypertrophied articular facet and measures 3 mm or less in the AP direction should be considered abnormally sma11.58 That portion of the canal under the pedicle may be ab- normally small in developmental stenosis and should be consid- ered abnormal if it measures less than 3 mm.56
Fig l&-Lateral recess stenosis. Note enlarged articular process encroaching on the lateral recess (arrows).
30
DISCUSSION
The search for the etiology of back (and neck) pain can occupy a significant proportion of the radiologist’s time. It includes not only radiographic film reading (interpretations) but also myelo- graphic procedures as well. This has led to a preoccupation with the search for disc herniations, and we have tended to overlook the “bony envelope.”
Cervical and lumbar spinal stenoses are highly treatable syn- dromes caused by abnormally small bony envelopes which pre- dispose to compressive changes in the cord and cauda equina. The condition may or may not be associated with disc hernia- tion. A rather minimal disc protrusion may be the first manifes- tation causing the patient to seek medical help. The symptoms may be those of cervical myelopathy, cauda equina compression, or radiculopathies. They may suggest disc herniation or may be attributed to a psychiatric condition. The AP dimension of the canal is primarily affected either centrally or laterally in the lateral recesses. Myelography is usually required for diagnosis, while CT is also helpful. Successful treatment involves adequate decompression, which may need to extend to the lateral recesses and multiple levels.
The concept that symptomatic degenerative spinal changes oc- cur primarily in patients with some degree of spinal stenosis is becoming popular. Several authors think that all symptomatic patients have spinal stenosis.3, 4
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
REFERENCES
Mixter W.J., Barr J.S.: Rupture of the intervertebral disc into the spinal canal. N. Engl. J. Med. 211:210, 1934. Semmes R., Murphy F.: The syndrome of unilateral rupture of the sixth cer- vical intervertebral disc, with compression of the seventh cervical nerve root. JAMA 121:1209, 1943. Verbiest H.: Fallacies of the present definition, nomenclature, and classifi- cation of the stenoses of the lumbar vertebral canal. Spine 1:219, 1976. Schatzker J., Pennal G.: Spinal stenosis, a cause of cauda equina compres- sion. J. Bone Joint Surg. 50B:606, 1968. Payne E., Spillane J.: The cervical spine: An anatomico-pathological study of 70 specimens (using a special technique) with particular reference to the problem of cervical spondylosis. Bruin 80571, 1957. Kessler J.T.: Congenital narrowing of the cervical spinal canal. J. Neural. Neurosurg. Psychiatry 38:1218, 1975. Burrows E.H.: The sagittal diameter of the spinal canal in cervical spondy- losis. Clin. Radiol. 14:77, 1963. Grant T.T., Puffer J.: Cervical stenosis: A developmental anomaly with quadriparesis during football. Am. J. Sports Med. 4:219, 1976. Moiel R.H., Raso E.: Waltz T.A.: Central cord syndrome resulting from con- genital narrowness of the cervical sninal canal. J. Trauma 101502. 1970. Mair W.G.P., Druckman R.: The pathology of spinal cord lesions’and their relation to the clinical features in protrusion of cervical intervertebral discs (a report of four cases). Brain 76:70, 1953. Epstein J.A., Epstein B.S., Lavine L.S.: Cervical myeloradiculopathy caused by arthrotic hypertrophy of the posterior facets and laminae. J. Neurosurg. 49:387, 1978.
31
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
Hinck V.C., Gordy P.D., Storino H.E.: Developmental stenosis of the cervical spinal canal: Radiological considerations. Neurology 14864, 1964. Hinck V.C., Sachdev N.S.: Developmental stenosis of the cervical spinal canal. Bruin 89:27, 1966. Ogino H., et al.: Canal diameter, anteroposterior compression ratio, and spondylotic myelopathy of the cervical spine. Spine 81, 1983. Countee R.W., Vijayanathan T.: Congenital stenosis of the cervical spine: Diagnosis and management. J. Natl. Med. Assoc. 71:257, 1979. Enstein J.A., Carros R.: Cervical myelopathy caused by developmental ste- nosis of the spinal canal J. Neurosu~g. 51:362, 1979. Wolf B.S., et al.: The sagittal diameter of the bony cervical spinal canal and its significance in cervical spondylosis. J. Mount Sinai Hosp. 23:283, 1956. Markuske H.: Sagittal diameter measurement of the bony cervical spinal canal in children. Pediatr. Radiol. 6:129, 1977. Epstein B.S.: The Spine: A Radiologic& Text and Atlas. Philadelphia, Lea & Febiger, 1976, pp. 13-23. Bailey D.K.: The normal cervical spine in infants and children. Radiology 59:712, 1952. Roth M., et al.: Morphogenesis of the spinal canal: Normal and stenotic. Neuroradiology 10:277, 1976. Elsberg C.A., Dyke C.G.: The diagnosis and localization of tumors of the spinal cord by means of measurements made on the x-ray films of the ver- tebrae, and correlations of clinical and x-ray findings. Bull. Neurol. Inst. NY 3:359, 1934. Boijsen E.: The cervical spinal canal in introspinal expansive processes. A& Radiol. 42:101, 1954. Pallis C., Jones A., Spillane J.: Cervical spondylosis: Incidence and implica- tions. Brain 77~274, 1954. Penning L.: Some aspects of plain radiography of the cervical spine in chronic myelopathy. Neurology 12:513, 1962. Epstein B.S., Epstein, J.A., Jones M.D.: Anatomicoradiological correlations in the cervical spine: Discal disease and stenosis. Clin. Neurosurg. 25:148, 1978. Edwards WC., LaRocca H.: The developmental segmental sagittal diameter of the cervical spinal canal in patients with cervical spondylosis. Spine 8:20, 1983. Hinck V.C., Hopkins C.E., Savara B.S.: Sag&al diameter of the cervical spinal canal in children. Radiology 79:97, 1962. Kahn E.A.: The role of the dentate ligaments in spinal cord compression and the syndrome of lateral sclerosis. J. Neurosurg. 4:191, 1947. Veidlenger O.F., Colwell J.C., et al.: Cervical myelopathy and its relation- ship to cervical stenosis. Spine 6:550, 1981. Galera R. Tovi D.: Anterior disc excision with interbody fusion in cervical spondylotic myelopathy and rhizopathy. J. Neurosurg. 28:305, 1968. Guidetti B., Fortuna A.: Long-term results of surgical treatment of myelo- pathy due to cervical spondylosis. J. Neurosurg. 30:714, 1969. Phillips D.G.: Surgical treatment of myelopathy with cervical spondylosis. J. Neurol. Neurosurg. Psychiatry 36879, 1973. Govoni A.F.: Developmental stenosis of a thoracic vertebra resulting in nar- rowing of the spinal canal. AJR 112:401, 1971. Johnston F.E.: Some observations on the roles of achondroplastic dwarfs through history. Clin. Pediatr. 2:703,1963. Sumita M.: Beitrage zur Lehre von der Chondrodystrophia foetalis (Kauf- mann) und Osteogenesis imperfecta (Vrolik) mit besonderer Berucksichti- auna der anatomischen und klinischen Differential-dia9nose. Dtsch. 2. Chir. i7:1:110, 1910. Galanski M., Herrmann R., Knoche V.: Neurological complications and mye- lographic features of achondroplasia. Neuroradiology 17:59, 1978.
32
38. Lutter L.D., Longstein J.E., Winter R.B., et al.: Anatomy of the achondro- plastic lumbar canal. Clin. Orthop. 126:139, 1977.
39. Beals R.K.: Hypoachondroplasia: Report of five kindreds. J. Bone Joint Surg. 51A:728, 1969.
40. Wynne-Davies R., Walsh W.K., Gormley J.: Achondroplasia and hypoach- ondroplasia. J. Bone Joint Surg. 63B:508, 1981.
41. Epstein J.A., Epstein B., Lavine L.: Nerve root compression associated with narrowing of the lumbar spinal curve. J. Neural. Neurosurg. Psychiatry 36:584, 1962.
42. Verbiest H.: Stenosis of the bony lumbar vertebral canal, in Wackenheim A.. Babin E. (eds.): The Narrow Lumbar Canal. Berlin, Springer-Verlaa, 1980, pp. 115-139.
._ I -.
43. Schlesinger E.B., Taveras J.M.: Factors in the production of “cauda equina” syndromes in lumbar discs. Trans. Am. Neural. Assoc. 78:263, 1953.
44. &upyener M.A.: Spina bifida aperta and congenital stricture of the spinal canal. J. Bone Joint Surg. 29:817, 1947.
45. Verbiest H.: A radicular syndrome from developmental narrowing of the lumbar canal. J. Bone Joint Surg. 36B:230, 1954.
46. Verbiest H.: Further experiences on the pathological influence of a develop- mental narrowness of the bony lumbar vertebral canal. J. Bone Joint Surg. 37B:576, 1955.
48. Bower V.: Lumbar spinal stenosis. Childs Brain 4:257, 1978. 49. Eisenstein S.: The morphometry and pathological anatomy of the lumbar
spine in south african negroes and caucasoids with specific reference to spinal stenosis. J. Bone Joint Surg. 59B,2,173, 1977.
50. Eisenstein S.: Measurements of the lumbar spinal canal in two racial groups. Clin. Orthop. 11542, 1976.
51. Nelson M.A.: Lumbar spinal stenosis. J. Bone Joint Surg. 55B:506, 1973. 52. Lee C.K., Hansen H.T., Weiss A.B.: Developmental lumbar spinal stenosis:
Pathology and surgical treatment. Spine 3:246, 1978. 53. Delfini F.R., Gambacorta D., Cantore G.P.: Congenital stenosis of lumbar
spinal canal: Comparison of results of surgical treatment for this and other causes of lumbar syndrome. Acta Neurochir. 42:199, 1978.
54. Verbiest H.: Results of surgical treatment of idiopathic developmental ste- nosis of the lumbar vertebral canal. J. Bone Joint Surg. 59B:181-188, 1977.
55. Weir B., DeLeo R.: Lumbar stenosis: Analysis of factors affecting outcome in 81 surgical cases. Can. J. Neural. Sci. 8:295, 1981.
56. Schlesinger P.: Low lumbar nerve-root compression and adequate operative exposure. J. Bone Joint Surg. 39A:541, 1957.
