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The oil myelogram after operation for lumbar disc lesions
Clin. Radio£ (1977) 28, 267-276 THE OIL MYELOGRAM AFTER OPERATION FOR LUMBAR DISC LESIONS IVAN MOSELEY
From the Lysholm Radiological Department, The National Hospital for Nervous Diseases, Queen Square, London WC1 3BG Post-operative myelograms in patients with renewed or persistent pain in the back or sciatica after lumbar disc surgery were reviewed in an attempt to differentiate between recurrent disc prolapse and other changes, particularly scarring and inflammation of the meninges. The most useful sign of recurrent disc prolapse was anterior indentation of the iophendytate (Myodil) column opposite a disc space. Inflammatory changes in the meninges were indicated by loculation of the subarachnoid space, matting or marked swelling of the nerve roots, irregularity of the theca, and by the absence of a posterior bulge of the subarachnoid space at the level of the operation. Waisting of the contrast medium column, non-filling of nerve root sheaths, complete myelographic block and posteriorly placed indentations were confirmatory evidence of the presence of disease, but not helpful in determining its nature. One of the most difficult clinical and radiological diagnostic problems in the often vexed field of low back pain and sciatica is that if the patient who, after an operation for lumbar intervertebral disc prolapse, complains of renewed or persistent pain. The diagnostic possibilities include recurrent disc prolapse, a second prolapse at a new level, and post-operative inflammation of the meninges. If the last mentioned obtains, further operation may sometimes be successful (Smolik and Nash, 1951), but often will cause a worsening of the disease (Silver et al. 1959). In discussing the advantages of Pantopaque myelography, Peacher and Robertson (1945) suggested that it should be helpful in determining the cause 'of post-operative symptoms such as multiple discs, adhesions, etc.', but this optimism has not been borne out by the experience of later workers, using eitheroily (Maltby and Prendergrass, 1946; Camp, 1950; Leader and Russell, 1953; Turnbull, 19 53; Borelti and Maglioni, 1956; Wright etal. 1971; Shapiro, 1975) or aqueous (Knutsson, 1949; Friberg and Hult, 1950) contrast media. These and other workers have found it difficult or impossible to differentiate between deformity due to disc protrusion and that due to meningeal scarring; indeed, in a number of centres, some deformity of the theca is assumed to be inevitable after disc surgery (Soule et al., 1945), although this has certainly not been universal experience (Lindblom, 1946; Knutsson, 1949; Silver et al., 1959). These discouraging and often contradictory reports have led to a situation in which the radiologist may equivocate, perhaps unnecessarily, when faced with the myelogram of a previously operated patient. This is patently unsatisfactory and it therefore seemed desirable to analyse the abnormalities which may be seen on the post-operative study in an attempt to increase the diagnostic accuracy.
MATERIAL AND METHODS Fifty-nine myelograms carried out, using Myodil, at the National Hospital for Nervous Diseases, Queen Square, since 1949 on 55 adult patients who had previously undergone lumbar disc surgery have been reviewed. The examinations were carried out for recurrent or persistent pain, at intervals of from 10 days to 22 years after the most recent operation. In 48 cases there had been only one previous surgical intervention, but nine patients had been operated upon twice, and two on three occasions each. As a result of the myelograms analysed in the present study, 27 patients were submitted to further operation. After an initial survey, which revealed a number of radiological abnormalities in the post-operative myelograms, each case was reviewed for the presence or absence of the signs listed in Table 1. These were graded as: + = definite or marked; -+ = minor or equivocal; - = absent. This scoring was carried out without prior knowledge of the previous interpretations, or the clinical or operative findings. Pre-operative myelograms were available for a number of the patients but it was thought more desirable to simulate the not uncommon and possibly 1 Myelographic abnormalities found in the post-operative s t u d i e s
Table
Anterior indentation of the contrast medium (Figs. 2, 3) WaNting of the contrast medium (Figs. 4, 5) Impaired filling of nerve root sheaths Complete block to the passage of contrast medium (Figs. 6, 7) Posterior indentation of the contrast medium (Fig. 8) Irregularity of the theca (Fig. 9) Matting, together, or unequivocal thickening of nerve roots (Fig. 6) Loculation of the subarachnoid space (Fig. 7) Posterior bulge of the theca (Fig. 10)
268
CLINICAL RADIOLOGY Table 2 - Incidence o f myelographic abnormalities
Sign Disc prolapse Anterior in dentation
Operative findings Scarring Other
Not operated
All
9 2 1
1 2 3
2" 2 5
6 6 20
18 12 29
Waisting
10 1 1
5 0 1
3 0 6
18 3 11
36 4 19
Root sleeve a m p u t a t i o n
11 l 0
5 0 1
3 5 1
18 5 9
37 11 11
3 1 8
1 0 5
2 2 5
3 1 28
4 46
Posterior i n d e n t a t i o n
3 0 9
2 0 4
4 0 5
9 0 23
18 0 41
Ragged theca
2 4 6
5 0 1
0 6 3
11 10 11
20 21
Matted roots
3 2 7
4 1 1
2 0 7
10 2 20
19 5 35
Loculation o f subarachnoid space
1 2 9
4 0 2
1 1 7
10 2 20
16 5 38
Block
xo
* This figure includes one case in which a loose bone chip was f o u n d lying alongside the theca; this was indistinguishable radiologically f r o m an e x t r u d e d disc fragment.
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Anterior indentation
Waisting
Root sheath Block Posterior Raggedness amputation indentation Fig. 1 - Percentage incidence o f myelographic abnormalities in all cases (D = recurrent disc prolapse; I = inflammation; N = no operative confirmation; A = all cases). A half-score only was allotted to cases in which any abnormality was slight or equivocal.
Matting of roots
Loculatioo
THE OIL MYELOGRAM
AFTER
OPERATION
FOR
LUMBAR
DISC
LESIONS
269
Fig. 2 - Recurrent pain 5 years after removal of large L4/5 disc. Myelogram: smooth anterior indentation opposite disc space. Recurrent disc prolapse confirmed at operatioru Fig. 3 - Recurrent pain 1 month after removal of L5/S1 disc. Myelogram: smooth antero-lateral defect at disc space (arrow). Thought to be a recurrent disc prolapse; operation showed a loose bone chip lying in this position.
more difficult situation encountered when a control examination is n o t to hand. In fact, a brief survey did not suggest that these pre-operative studies were of great value since the pathological changes were usually readily apparent on the post-operative radiographs; the diagnostic problem lay in their interpretation.
RESULTS
Fig. 4 - Unrelieved pain 6 months after removal of L4/5 disc. Myelogram: marked smooth waisting at L4/5; impaired root sheath filling L4/5 and L5/S1. (Lateral film - large anterior defect). Almost certainly a recurrent disc prolapse; no operation - original report equivocal.
The incidence of the radiological abnormalities in the surgically verified cases is shown in Table 2 and in all cases in Fig. 1. The apparently vague term 'meningeal inflammation' or 'scarring' has been used for two reasons (i) it was thought desirable to avoid the word 'arachnoiditis' with its emotional and possibly medico-legal overtones, which are such as to have led to a marked reluctance to use it even when appropriate: in one of the cases in the present series, the operative findings include 'thickening and loss of
270
CLINICAL RADIOLOGY
Fig. 5 - Pain for 7 years, 19 years after removal of large L4/5 disc. Myelogram: marked waisting at L4/5 (a) shown on oblique (b) to be circumferential, angular and irregular, the irregularity going down to L5/S1 disc space on the right; impaired root sheath filling. Presumed to be due to postoperative scarring; no operation.
translucency of the arachnoid' and 'reddening of the nerve roots', but there was 'no evidence of arachnoiditis', and (ii) the inflammatory changes may affect any of the meningeal layers, and even the extradural tissues, either singly or in combination, with similar resulting myelographic abnormalities. In more than one of the present cases exploration revealed considerable dural cicatrisation, with a lesser degree of scarring of the deeper layers of the meninges. In a few patients operation findings disclosed
either a disc prolapse with minor associated inflammatory changes, or alternatively, more severe inflammation with slight bulging of the discs. These have been classified according to the major pathology. It was clear at myelography that in some cases there was neither a recurrent disc protusion nor meningeal scarring. Thus, five cases showed respectively an arachnoid cyst, a neurofibroma, spondylolisthesis (all confirmed at operation), spondylosis, and a meningocoele (neither surgically explored), while eight cases were thought to be normal. Two of
THE OIL M Y E L O G R A M A F T E R O P E R A T I O N FOR LUMBAR DISC LESIONS
271
(Fig. 11). In 22 other myelograms a definite, though usually slight, backward bulge of the theca at the level of the laminectomy was noted (Fig, 10). This was much less common in the patients diagnosed radiologically as having meningeal inflammation, and was seen in none of the operatively proven cases of this condition. In was not, however, sufficiently common an observation in any of the diagnostic groups for its absence to be considered significant. No good clues were obtained as to the cause of the meningeal scarring; it was not, for example, more common in those cases in which the dura mater was known to have been opened at the original operation. At the time when most of the original pre-operative myelograms had been performed it was not common practice at this hospital, or indeed throughout Britain, to attempt to remove the Myodil at the conclusion of the examination, so that all groups had been similarly exposed. Proven inflammatory changes were found at intervals varying from 6 months to 9 years after operation.
DISCUSSION
Fig. 6 - Two laminectomies; recurrent pain for 6 months. Cisternal myelogram: subtotal block L2/3 (some Myodil had passed by 24 h); nerve roots prominent, matted and deviated to right; lateral film showed anterior indentation at L2/3. Operation showed L2/3 and 3/4 disc prolapses.
these eight were explored on clinical grounds, in one a nerve root was found to be adherent to a normal disc, while in the other a root was compressed, lateral to the theca, by an osteophyte. The meningocoele extended posteriorly from the intraspinal subarachnoid space at the operative level
Previous authors have suggested that certain myelographic observations may be helpful in the differentiation of recurrent disc disease from inflammatory changes, and from 'normal' postoperative appearances. (i) Recurrent Disc Prolapse. - The best description of the changes to be seen is that of Cronqvist (1959) who was working with the aqueous contrast medium Abrodil: 'a regular, rounded indentation opposite the disc involved, a varying degree of shortening of the dural sac of a nerve root, and in some cases definite thickening and medial displacement' of nerve roots, with 'a local decrease in the density of the contrast medium' to be seen in the antero-posterior projection (his technique did not apparently include lateral filming) with a central disc protrusion. These are, of course, much the same features as are to be found on the pre-operative study, and Bradford and Spurling (1945), working with iophendylate (Pantopaque), also described a 'typical filling defect'. Camp (1950) emphasised the sharpness and frequently elongated appearance of such a filling defect produced by a recurrent disc, while Epstein (1968) added that it could be either anteriorly or laterally placed. Soule et al. (1945) thought that the defect must be large and well defined to be significant, while Silver et al. (1959) considered 'any defect' good evidence of recurrent disc prolapse.
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CLINICAL RADIOLOGY
(ii) Meningeal Inflammatory Disease. - Factors which have been noted in this condition include: loculation (described by Smolik and Nash (1959) as 'string globulation') of the contrast medium within the subarachnoid space (Camp, 1950; Valentino, 1965; Epstein, 1968), frequently with a complete
block to its passage (French, 1946; Maltby and Prendergrass, 1946; Smolik and Nash, 1951), or with obliteration of the sacral sac (Malis et al., 1953); irregularity of the theca, often sharply defined and elongated (Camp, 1950), the deformities characteristically being dorsally located (Lindgren, 1951;
Fig. 7 - Two laminectomies, with spinal fluid leak and 'various abscesses'; persistent pain. Myelogram: (a) complete block at upper end of bone defect, with loculus to L4/5 disc space; fixed Myodil droplets from Tll to S1, (b) posterior defect. Operation: thickened dura mater with nerve roots matted to arachnoid mater and to each other.
THE OIL MYELOGRAM
AFTER OPERATION
Epstein, 1968); and deviation of the nerve roots (Cronqvist, 1959). Other workers have, however, sounded notes of caution: both Leader and Russell (1953) and Valentino (1965) encountered smooth, rounded defects with inflammatory disease, and Knutsson (1949) described three cases of large, smoothly rounded defects overlying the disc space, all found at operation to be the result of scarring. (iii) Normal. - For obvious reasons, few patients without symptoms are re-examined after operation. Four pain-free patients were studied, for unspecified indications, by Soule et al. (1945), who found 'slight but definite deformities at the operative level' in each case. Lindblom (1946) and Knuttsson (1949), on examining a total of five pain-free patients with Abrodil, found no abnormality, while of the 38 patients with recurrent pain examined by Silver et al. (1959), 22 were judged to be 'within normal limits'; these authors' criteria were not stated, but their aggressive diagnostic approach to any abnormality has been noted above. Thus, sharpness, large size and elongated nature of filling defects have been described with both disc and inflammatory disease, as has deviation of the nerve
Fig. 8 - Persistent pain 1 year after removal of L4 disc. Myelogxam: irregularity and possible septation o f posterior theca at operation site; minimal anterior defect at L4/5 disc space. Operation showed mass o f scar and adhesions only.
F O R L U M B A R DISC L E S I O N S
273
roots, this latter sign being described as typical of both conditions by the same author. Anterior location of filling defects is said to indicate disc prolapse, posterior location, scarring, while thecal irregularity and loculation also favour the latter. Although several writers have emphasised that complete block to the passage of contrast medium is common with inflammation, it is common knowledge that this may equally well occur with disc prolapse, especially when fragments of disc material have become extruded. With certain reservations, this synthesis of opinion would appear to be rather closely confirmed by the present study, in which three groups of signs have merged (Fig. 1). (1) Signs indicative of recurrent disc protrusion: only anterior indentation of the theca. (2) Non-discriminatory signs: (a) those which are common: waisting of the theca and loss of root sheaths; (b) those which are uncommon: complete block and posterior indentation of the theca. (3) Signs indicating meningeal inflammation: ragged theca, matted roots and loculation of the subarachnoid space. That anterior indentation is the only good sign of recurrent disc should not be surprising, since, when correctly interpreted, this is also the most reliable of signs on a pre-operative study. It is, however, of some interest to note that waisting of the theca, and obliteration of the nerve root sheaths, other useful observations before surgery, are of limited significance in the post-operative study; although present in the large majority of patients with disc prolapse, they are observed sufficiently frequently in the absence of disc disease as to be of little other than confirmatory value. Contrary to the suggestions of several groups of previous workers, and perhaps surprisingly, posteriorly situated deformity of the theca does not appear to be a good differential sign, unless it is also ragged. Conversely, the presence of a small bulge of the theca at the level of the operation (as attributed by Knutsson (1949) to excision of the ligamenta flava) would appear to be uncommon in the presence of scarring. (The demonstration of a frank meningocele in one of our cases and as described by Winckler and Powers (1950), clearly represents a pathological entity.) As might be anticipated, a complete block may be seen with either disc or inflammatory disease. Since of the eight cases judged finally to be normal, only three showed even equivocal abnormalities, it would appear that obvious deformity is not a necessary sequel to lumbar disc surgery. It should be noted that in the current study, the benefits of fluoroscopy and clinical discussion were not available as they had been at the time of the myelograms. If the diagnostic criteria suggested by
274
CLINICAL RADIOLOGY
the present study had been applied five patients w i t h scarring who were re-operated m i g h t have been spared further interference (e.g. those cases shown in Figs. 6 and 8), while at least one patient w o u l d have been ,re-explored for a virtually certain disc protrusion (Fig. '4).
Acknowledgement~ - I should like to thank Dr Fred Sondheimer, of San Francisco, whose comments stimulated this study, and Dr George du Boulay, who gave me helpful advice. My thanks are also due to the Department of Medical Illustration of the National Hospital, Queen Square, for the preparation of the illustrations, and to Miss P. Hampson, for secretarial assistance.
Fig. 9 (a and b) - Persistent pain after three explorations, the last 'normal'. Myelogram: extreme irregularity, mainly posterior, with matted nerve roots and obliterated root sheaths; small bulge at L4/5 disc space anteriorly. Presumably due to scarring; no operation.
THE OIL M Y E L O G R A M A F T E R O P E R A T I O N FOR L U M B A R DISC LESIONS
Fig. 10 - Persistent pain 6 years after removal of L5/S1 disc. Myelogram: posterior bulge of theca at level of laminectomy (arrows); the theca stands back from L5/S1 disc space. Thought to be normal. No operation, but L5/S1 level normal at discography. Fig. 11 - Pain for 3 months, 2 laminectomy. Myelogram: 5 × 4 × 7 cm municating through bone defect with supine film (a) erect, (b) head-down. No
years after L 4 - $ 2 meningocoete comsubarachnoid space; operation.
REFERENCES Borelli, F. J. & Maglione, A. A. (1956). The importance of myelography in spinal pathology. Analytical study of 150 cases. American JournalofRoentgenology, 76, 273-289. Bradford, F. K. & Spurling, R. G. (1945). Thelntervertebral
Disc. With special reference to rupture of the annulus fibrosus with herniation of the nucleus pulposus, 2nd edn. Thomas, Springfield. Camp, J. D. (1950). Contrast myelography past and present. Radiology, 54, 477-506. Cronqvist, S. (1959). The postoperative myelogram. Acta
radiologica, 52, 45- 51. 15
275
276
CLINICAL RADIOLOGY
Epstein, B. S. (1968). The Spine A Radiological Text and Atlas, 3rd edn. Lea and Febiger, Philadelphia. French, J. D. (1946). Clinical manifestations of lumbar spinal arachnoiditis. A report of 13 cases. Surgery, 20, 718-729. Friberg, S. & Hult, I. (1950). Comparative study of Abrodil myelogram and operative findings in low back pain and sciatica. Acta orthopaedica scandinavica, 20, 303- 314. Knutsson, K. (1949). The myelogram following operation for herniated disc. Acta radiologica, 31, 60-65. Leader, S. A. & Russell, M. J. (1953). The value of Pantopaque myelography in the diagnosis of herniation of the nucleus pulposus in the lumbosacral spine. American Journal o f Roentgenology, 69, 231-241. Lindblom, K. (1946). Lumbar myelography by AbrodiL Acta radiologiea, 27, 1-7. Lindgren, E. (1951). Myelographie. In Lehrbuch der R6ntgendiagnostik, Schinz, Baensch, Friedl & Uehlinger, Vol. 5. Thieme, Stuttgart. Malis, L., Newman, C. M. & Wolf, B. S. (1953). Full-column technic in lumbar disc myelography. Radiology, 60, 18-28. Maltby, G. L. & Prendergrass, R. C. (1946). Pantopaque myelography: diagnostic errors and review of cases. Radiology, 47, 35-46.
Peacher, W. G. & Robertson, C. L (1945). Pantopaque myelography: comparison of contrast media and spinal fluid reaction. Journal o f Neurosurgery, 2, 220-231. Shapiro, R. (1975). Myelography, 3rd edn. Year book Medical Publishers, Chicago. Silver, M. I., Field, F. A., Silver, C. M. & Simon, S. D. (1959). The postoperative lumbar myelogram. Radiology, 72, 344-347. Smolik, E. A. & Nash, F. P. (1951). Lumbar spinal arachnoiditis: a complication of intervertebral disc operation. Annals o f Surgery, 133, 490-495. Soule, A. B., Gross, S. W. & Irving, J. G. (1945). Myelog~aphy by the use of Pantopaque in the diagnosis of herniations of the intervertebral discs. American Journal o f Roentgenology, 53, 319-340. Turnbull, F. (1953). Postoperative inflammatory disease of Lumbar discs. Journal o f Neurosurgery, 10, 469-473. Valentino, V. (1965). Myelography. Thomas, Springfield. Winckler, H. & Powers, J. A. (1950). Meningocele following hemilaminectomy: two cases. North Carolina Medical Journal, 11, 292-294. Wright, F. W., Sanders, R. C., Steel, W. M. & O'Connor, B. T. (1971). Some observations in the value and techniques of myelography in lumbar disc lesions. Clinical Radiology, 22, 33-43.
From the Lysholm Radiological Department, The National Hospital for Nervous Diseases, Queen Square, London WC1 3BG Post-operative myelograms in patients with renewed or persistent pain in the back or sciatica after lumbar disc surgery were reviewed in an attempt to differentiate between recurrent disc prolapse and other changes, particularly scarring and inflammation of the meninges. The most useful sign of recurrent disc prolapse was anterior indentation of the iophendytate (Myodil) column opposite a disc space. Inflammatory changes in the meninges were indicated by loculation of the subarachnoid space, matting or marked swelling of the nerve roots, irregularity of the theca, and by the absence of a posterior bulge of the subarachnoid space at the level of the operation. Waisting of the contrast medium column, non-filling of nerve root sheaths, complete myelographic block and posteriorly placed indentations were confirmatory evidence of the presence of disease, but not helpful in determining its nature. One of the most difficult clinical and radiological diagnostic problems in the often vexed field of low back pain and sciatica is that if the patient who, after an operation for lumbar intervertebral disc prolapse, complains of renewed or persistent pain. The diagnostic possibilities include recurrent disc prolapse, a second prolapse at a new level, and post-operative inflammation of the meninges. If the last mentioned obtains, further operation may sometimes be successful (Smolik and Nash, 1951), but often will cause a worsening of the disease (Silver et al. 1959). In discussing the advantages of Pantopaque myelography, Peacher and Robertson (1945) suggested that it should be helpful in determining the cause 'of post-operative symptoms such as multiple discs, adhesions, etc.', but this optimism has not been borne out by the experience of later workers, using eitheroily (Maltby and Prendergrass, 1946; Camp, 1950; Leader and Russell, 1953; Turnbull, 19 53; Borelti and Maglioni, 1956; Wright etal. 1971; Shapiro, 1975) or aqueous (Knutsson, 1949; Friberg and Hult, 1950) contrast media. These and other workers have found it difficult or impossible to differentiate between deformity due to disc protrusion and that due to meningeal scarring; indeed, in a number of centres, some deformity of the theca is assumed to be inevitable after disc surgery (Soule et al., 1945), although this has certainly not been universal experience (Lindblom, 1946; Knutsson, 1949; Silver et al., 1959). These discouraging and often contradictory reports have led to a situation in which the radiologist may equivocate, perhaps unnecessarily, when faced with the myelogram of a previously operated patient. This is patently unsatisfactory and it therefore seemed desirable to analyse the abnormalities which may be seen on the post-operative study in an attempt to increase the diagnostic accuracy.
MATERIAL AND METHODS Fifty-nine myelograms carried out, using Myodil, at the National Hospital for Nervous Diseases, Queen Square, since 1949 on 55 adult patients who had previously undergone lumbar disc surgery have been reviewed. The examinations were carried out for recurrent or persistent pain, at intervals of from 10 days to 22 years after the most recent operation. In 48 cases there had been only one previous surgical intervention, but nine patients had been operated upon twice, and two on three occasions each. As a result of the myelograms analysed in the present study, 27 patients were submitted to further operation. After an initial survey, which revealed a number of radiological abnormalities in the post-operative myelograms, each case was reviewed for the presence or absence of the signs listed in Table 1. These were graded as: + = definite or marked; -+ = minor or equivocal; - = absent. This scoring was carried out without prior knowledge of the previous interpretations, or the clinical or operative findings. Pre-operative myelograms were available for a number of the patients but it was thought more desirable to simulate the not uncommon and possibly 1 Myelographic abnormalities found in the post-operative s t u d i e s
Table
Anterior indentation of the contrast medium (Figs. 2, 3) WaNting of the contrast medium (Figs. 4, 5) Impaired filling of nerve root sheaths Complete block to the passage of contrast medium (Figs. 6, 7) Posterior indentation of the contrast medium (Fig. 8) Irregularity of the theca (Fig. 9) Matting, together, or unequivocal thickening of nerve roots (Fig. 6) Loculation of the subarachnoid space (Fig. 7) Posterior bulge of the theca (Fig. 10)
268
CLINICAL RADIOLOGY Table 2 - Incidence o f myelographic abnormalities
Sign Disc prolapse Anterior in dentation
Operative findings Scarring Other
Not operated
All
9 2 1
1 2 3
2" 2 5
6 6 20
18 12 29
Waisting
10 1 1
5 0 1
3 0 6
18 3 11
36 4 19
Root sleeve a m p u t a t i o n
11 l 0
5 0 1
3 5 1
18 5 9
37 11 11
3 1 8
1 0 5
2 2 5
3 1 28
4 46
Posterior i n d e n t a t i o n
3 0 9
2 0 4
4 0 5
9 0 23
18 0 41
Ragged theca
2 4 6
5 0 1
0 6 3
11 10 11
20 21
Matted roots
3 2 7
4 1 1
2 0 7
10 2 20
19 5 35
Loculation o f subarachnoid space
1 2 9
4 0 2
1 1 7
10 2 20
16 5 38
Block
xo
* This figure includes one case in which a loose bone chip was f o u n d lying alongside the theca; this was indistinguishable radiologically f r o m an e x t r u d e d disc fragment.
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Anterior indentation
Waisting
Root sheath Block Posterior Raggedness amputation indentation Fig. 1 - Percentage incidence o f myelographic abnormalities in all cases (D = recurrent disc prolapse; I = inflammation; N = no operative confirmation; A = all cases). A half-score only was allotted to cases in which any abnormality was slight or equivocal.
Matting of roots
Loculatioo
THE OIL MYELOGRAM
AFTER
OPERATION
FOR
LUMBAR
DISC
LESIONS
269
Fig. 2 - Recurrent pain 5 years after removal of large L4/5 disc. Myelogram: smooth anterior indentation opposite disc space. Recurrent disc prolapse confirmed at operatioru Fig. 3 - Recurrent pain 1 month after removal of L5/S1 disc. Myelogram: smooth antero-lateral defect at disc space (arrow). Thought to be a recurrent disc prolapse; operation showed a loose bone chip lying in this position.
more difficult situation encountered when a control examination is n o t to hand. In fact, a brief survey did not suggest that these pre-operative studies were of great value since the pathological changes were usually readily apparent on the post-operative radiographs; the diagnostic problem lay in their interpretation.
RESULTS
Fig. 4 - Unrelieved pain 6 months after removal of L4/5 disc. Myelogram: marked smooth waisting at L4/5; impaired root sheath filling L4/5 and L5/S1. (Lateral film - large anterior defect). Almost certainly a recurrent disc prolapse; no operation - original report equivocal.
The incidence of the radiological abnormalities in the surgically verified cases is shown in Table 2 and in all cases in Fig. 1. The apparently vague term 'meningeal inflammation' or 'scarring' has been used for two reasons (i) it was thought desirable to avoid the word 'arachnoiditis' with its emotional and possibly medico-legal overtones, which are such as to have led to a marked reluctance to use it even when appropriate: in one of the cases in the present series, the operative findings include 'thickening and loss of
270
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Fig. 5 - Pain for 7 years, 19 years after removal of large L4/5 disc. Myelogram: marked waisting at L4/5 (a) shown on oblique (b) to be circumferential, angular and irregular, the irregularity going down to L5/S1 disc space on the right; impaired root sheath filling. Presumed to be due to postoperative scarring; no operation.
translucency of the arachnoid' and 'reddening of the nerve roots', but there was 'no evidence of arachnoiditis', and (ii) the inflammatory changes may affect any of the meningeal layers, and even the extradural tissues, either singly or in combination, with similar resulting myelographic abnormalities. In more than one of the present cases exploration revealed considerable dural cicatrisation, with a lesser degree of scarring of the deeper layers of the meninges. In a few patients operation findings disclosed
either a disc prolapse with minor associated inflammatory changes, or alternatively, more severe inflammation with slight bulging of the discs. These have been classified according to the major pathology. It was clear at myelography that in some cases there was neither a recurrent disc protusion nor meningeal scarring. Thus, five cases showed respectively an arachnoid cyst, a neurofibroma, spondylolisthesis (all confirmed at operation), spondylosis, and a meningocoele (neither surgically explored), while eight cases were thought to be normal. Two of
THE OIL M Y E L O G R A M A F T E R O P E R A T I O N FOR LUMBAR DISC LESIONS
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(Fig. 11). In 22 other myelograms a definite, though usually slight, backward bulge of the theca at the level of the laminectomy was noted (Fig, 10). This was much less common in the patients diagnosed radiologically as having meningeal inflammation, and was seen in none of the operatively proven cases of this condition. In was not, however, sufficiently common an observation in any of the diagnostic groups for its absence to be considered significant. No good clues were obtained as to the cause of the meningeal scarring; it was not, for example, more common in those cases in which the dura mater was known to have been opened at the original operation. At the time when most of the original pre-operative myelograms had been performed it was not common practice at this hospital, or indeed throughout Britain, to attempt to remove the Myodil at the conclusion of the examination, so that all groups had been similarly exposed. Proven inflammatory changes were found at intervals varying from 6 months to 9 years after operation.
DISCUSSION
Fig. 6 - Two laminectomies; recurrent pain for 6 months. Cisternal myelogram: subtotal block L2/3 (some Myodil had passed by 24 h); nerve roots prominent, matted and deviated to right; lateral film showed anterior indentation at L2/3. Operation showed L2/3 and 3/4 disc prolapses.
these eight were explored on clinical grounds, in one a nerve root was found to be adherent to a normal disc, while in the other a root was compressed, lateral to the theca, by an osteophyte. The meningocoele extended posteriorly from the intraspinal subarachnoid space at the operative level
Previous authors have suggested that certain myelographic observations may be helpful in the differentiation of recurrent disc disease from inflammatory changes, and from 'normal' postoperative appearances. (i) Recurrent Disc Prolapse. - The best description of the changes to be seen is that of Cronqvist (1959) who was working with the aqueous contrast medium Abrodil: 'a regular, rounded indentation opposite the disc involved, a varying degree of shortening of the dural sac of a nerve root, and in some cases definite thickening and medial displacement' of nerve roots, with 'a local decrease in the density of the contrast medium' to be seen in the antero-posterior projection (his technique did not apparently include lateral filming) with a central disc protrusion. These are, of course, much the same features as are to be found on the pre-operative study, and Bradford and Spurling (1945), working with iophendylate (Pantopaque), also described a 'typical filling defect'. Camp (1950) emphasised the sharpness and frequently elongated appearance of such a filling defect produced by a recurrent disc, while Epstein (1968) added that it could be either anteriorly or laterally placed. Soule et al. (1945) thought that the defect must be large and well defined to be significant, while Silver et al. (1959) considered 'any defect' good evidence of recurrent disc prolapse.
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(ii) Meningeal Inflammatory Disease. - Factors which have been noted in this condition include: loculation (described by Smolik and Nash (1959) as 'string globulation') of the contrast medium within the subarachnoid space (Camp, 1950; Valentino, 1965; Epstein, 1968), frequently with a complete
block to its passage (French, 1946; Maltby and Prendergrass, 1946; Smolik and Nash, 1951), or with obliteration of the sacral sac (Malis et al., 1953); irregularity of the theca, often sharply defined and elongated (Camp, 1950), the deformities characteristically being dorsally located (Lindgren, 1951;
Fig. 7 - Two laminectomies, with spinal fluid leak and 'various abscesses'; persistent pain. Myelogram: (a) complete block at upper end of bone defect, with loculus to L4/5 disc space; fixed Myodil droplets from Tll to S1, (b) posterior defect. Operation: thickened dura mater with nerve roots matted to arachnoid mater and to each other.
THE OIL MYELOGRAM
AFTER OPERATION
Epstein, 1968); and deviation of the nerve roots (Cronqvist, 1959). Other workers have, however, sounded notes of caution: both Leader and Russell (1953) and Valentino (1965) encountered smooth, rounded defects with inflammatory disease, and Knutsson (1949) described three cases of large, smoothly rounded defects overlying the disc space, all found at operation to be the result of scarring. (iii) Normal. - For obvious reasons, few patients without symptoms are re-examined after operation. Four pain-free patients were studied, for unspecified indications, by Soule et al. (1945), who found 'slight but definite deformities at the operative level' in each case. Lindblom (1946) and Knuttsson (1949), on examining a total of five pain-free patients with Abrodil, found no abnormality, while of the 38 patients with recurrent pain examined by Silver et al. (1959), 22 were judged to be 'within normal limits'; these authors' criteria were not stated, but their aggressive diagnostic approach to any abnormality has been noted above. Thus, sharpness, large size and elongated nature of filling defects have been described with both disc and inflammatory disease, as has deviation of the nerve
Fig. 8 - Persistent pain 1 year after removal of L4 disc. Myelogxam: irregularity and possible septation o f posterior theca at operation site; minimal anterior defect at L4/5 disc space. Operation showed mass o f scar and adhesions only.
F O R L U M B A R DISC L E S I O N S
273
roots, this latter sign being described as typical of both conditions by the same author. Anterior location of filling defects is said to indicate disc prolapse, posterior location, scarring, while thecal irregularity and loculation also favour the latter. Although several writers have emphasised that complete block to the passage of contrast medium is common with inflammation, it is common knowledge that this may equally well occur with disc prolapse, especially when fragments of disc material have become extruded. With certain reservations, this synthesis of opinion would appear to be rather closely confirmed by the present study, in which three groups of signs have merged (Fig. 1). (1) Signs indicative of recurrent disc protrusion: only anterior indentation of the theca. (2) Non-discriminatory signs: (a) those which are common: waisting of the theca and loss of root sheaths; (b) those which are uncommon: complete block and posterior indentation of the theca. (3) Signs indicating meningeal inflammation: ragged theca, matted roots and loculation of the subarachnoid space. That anterior indentation is the only good sign of recurrent disc should not be surprising, since, when correctly interpreted, this is also the most reliable of signs on a pre-operative study. It is, however, of some interest to note that waisting of the theca, and obliteration of the nerve root sheaths, other useful observations before surgery, are of limited significance in the post-operative study; although present in the large majority of patients with disc prolapse, they are observed sufficiently frequently in the absence of disc disease as to be of little other than confirmatory value. Contrary to the suggestions of several groups of previous workers, and perhaps surprisingly, posteriorly situated deformity of the theca does not appear to be a good differential sign, unless it is also ragged. Conversely, the presence of a small bulge of the theca at the level of the operation (as attributed by Knutsson (1949) to excision of the ligamenta flava) would appear to be uncommon in the presence of scarring. (The demonstration of a frank meningocele in one of our cases and as described by Winckler and Powers (1950), clearly represents a pathological entity.) As might be anticipated, a complete block may be seen with either disc or inflammatory disease. Since of the eight cases judged finally to be normal, only three showed even equivocal abnormalities, it would appear that obvious deformity is not a necessary sequel to lumbar disc surgery. It should be noted that in the current study, the benefits of fluoroscopy and clinical discussion were not available as they had been at the time of the myelograms. If the diagnostic criteria suggested by
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CLINICAL RADIOLOGY
the present study had been applied five patients w i t h scarring who were re-operated m i g h t have been spared further interference (e.g. those cases shown in Figs. 6 and 8), while at least one patient w o u l d have been ,re-explored for a virtually certain disc protrusion (Fig. '4).
Acknowledgement~ - I should like to thank Dr Fred Sondheimer, of San Francisco, whose comments stimulated this study, and Dr George du Boulay, who gave me helpful advice. My thanks are also due to the Department of Medical Illustration of the National Hospital, Queen Square, for the preparation of the illustrations, and to Miss P. Hampson, for secretarial assistance.
Fig. 9 (a and b) - Persistent pain after three explorations, the last 'normal'. Myelogram: extreme irregularity, mainly posterior, with matted nerve roots and obliterated root sheaths; small bulge at L4/5 disc space anteriorly. Presumably due to scarring; no operation.
THE OIL M Y E L O G R A M A F T E R O P E R A T I O N FOR L U M B A R DISC LESIONS
Fig. 10 - Persistent pain 6 years after removal of L5/S1 disc. Myelogram: posterior bulge of theca at level of laminectomy (arrows); the theca stands back from L5/S1 disc space. Thought to be normal. No operation, but L5/S1 level normal at discography. Fig. 11 - Pain for 3 months, 2 laminectomy. Myelogram: 5 × 4 × 7 cm municating through bone defect with supine film (a) erect, (b) head-down. No
years after L 4 - $ 2 meningocoete comsubarachnoid space; operation.
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Disc. With special reference to rupture of the annulus fibrosus with herniation of the nucleus pulposus, 2nd edn. Thomas, Springfield. Camp, J. D. (1950). Contrast myelography past and present. Radiology, 54, 477-506. Cronqvist, S. (1959). The postoperative myelogram. Acta
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Epstein, B. S. (1968). The Spine A Radiological Text and Atlas, 3rd edn. Lea and Febiger, Philadelphia. French, J. D. (1946). Clinical manifestations of lumbar spinal arachnoiditis. A report of 13 cases. Surgery, 20, 718-729. Friberg, S. & Hult, I. (1950). Comparative study of Abrodil myelogram and operative findings in low back pain and sciatica. Acta orthopaedica scandinavica, 20, 303- 314. Knutsson, K. (1949). The myelogram following operation for herniated disc. Acta radiologica, 31, 60-65. Leader, S. A. & Russell, M. J. (1953). The value of Pantopaque myelography in the diagnosis of herniation of the nucleus pulposus in the lumbosacral spine. American Journal o f Roentgenology, 69, 231-241. Lindblom, K. (1946). Lumbar myelography by AbrodiL Acta radiologiea, 27, 1-7. Lindgren, E. (1951). Myelographie. In Lehrbuch der R6ntgendiagnostik, Schinz, Baensch, Friedl & Uehlinger, Vol. 5. Thieme, Stuttgart. Malis, L., Newman, C. M. & Wolf, B. S. (1953). Full-column technic in lumbar disc myelography. Radiology, 60, 18-28. Maltby, G. L. & Prendergrass, R. C. (1946). Pantopaque myelography: diagnostic errors and review of cases. Radiology, 47, 35-46.
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