Aust. Radiol. (1973, 19,356
The Narrow Lumbar Spinal Canal RHONDDA M. WILLIAMS, M.B., B.S., D.D.R. (Sydney) M.R.A.C.R. Sraf Radiologist, Department of Radiology, Prince Henry Hospital, Sydney, Australia
INTRODUCTION Narrowing of the cervical bony canal is an entity which has been recognised for many years, whilst the significance of a narrow lumbar spinal canal has been relatively neglected. Donath and Vogel (Wiener Achiv. Inn. Med. 1925, 10: 1-44) first described shortening of the pedicles and decreased interpedicular distance in achondroplastic dwarfs associated with a high incidence of spinal cord and nerve root compression. Later, Schlesinger and Taveras (Trans. Amer. Neurol. Ass. 1953, 78: 263-265) described a series of patients with narrow lumbar canals with reduction of the interpedicular distance. Verbiest (J. Bone and Joint Surg. 1954, 26B: 230-237) described narrowing of the lumbar canal in otherwise normal people with cauda equina claudication as a frequent presenting symptom. As the importance of the narrow lumbar spinal canal is now being recognised, this paper is to describe our experience with a simple method of assessing the approximate size of the lumbar canal.
METHOD There are two basic ways of measuring the lumbar spinal canal : (i) Direct measurement which will need correction for magnification, or (ii) Proportional measurement, which needs no correction. The method chosen for assessment of canal size is that of Jones and Thomson (Journl. Bone and Joint Surg. 1968,50B: 595-605) and is intended only as a guide to the relative size of the canal. The anteroposterior diameter of the canal and the intekdicular distance are measured and are related to the size of the vertebral body. These measurements can be performed on plain lumbar spine films and d o not need correction for magnification.
356
Using this technique, slight errors in estimating the posterior margin of the canal do not alter the ratio a great deal. The A.P. diameter of the spinal canal is the most difficult to measure as the posterior limit of the canal is hard to define (Figure 1 ). The measurement is taken from the middle of the posterior edge of the vertebral body to the base of the spinous process on the lateral film. The posterior limit of the canal is more easily defined in a patient with some residual Myodil from a previous myelogram. The A.P. canal measurement is multiplied by the interpedicular distance and is used as a ratio with A.P. x transverse diameters of the same vertebral body (Figure 2 ) : axb:cxd e.g.2x3:4x5 6 : 20 1 : 3.3 In this study one hundred consecutive myelograms from October 1973 to July 1974 were used and the measurements made on the plain films. The ratios were calculated for L3, L4 and LS on each patient and the mean value for each ratio, together with the standard deviation, were found.
RESULTS Jones and Thomson found their normal range to lie between I : 2.5 and I : 4.5. Their normal series used SO randomly selected patients attending an injury clinic without spinal fracture or injury. Our total range was Found to lie between I : 2.5 and 1 : 8.0. Using the mean 2 one standard deviation our normal range was: L3 and L4 1 to 3.0 to 1 to 6.0 L5 1 to 3.2 to I to 6.5 The higher values represent narrower lumbar spinal canals.
Auslralasian Rndiolq?.. Vol.
XIX. No. 4. Dcccmber. I975
THENARROW LUMBAR SPINAL CANAL
FIGURE I-Measuring points shown on a patient with a normal lumbar spinal canal.
Using the above figures a canal was taken to be significantly narrow if the ratio was above 1 to 6.0 for L3 and L4 and above 1 to 6.5 for L5.With these limitations three of our patients (3%) (Figures 3 and 4) were found to have significantly narrow canals at all three levels. There is an appreciable difference between our normal range and that of Jones and Thomson. Perhaps we have selected our patients by using only those who had back pain severe
enough to warrant myelography, or there may be some difference in the stature of our population in comparison with theirs.
DISCUSSION Primary narrowing of the lumbar canal is important, as any further slight decrease in the capacity of the canal will cause significant cauda equina compression. This may arise from disc
Australasian Radiology, Vol. X I X , No. 4, December, 1975
357
RHONDDA M. WILLIAMS
ment.
FIGURE3-Plain 358
films of a patient with a significantly narrow lumbar spinal canal. Australasian Radiology, Vol. XIX,No. 4,
December, 1975
THENARROW LUMBAR SPINALCANAL
FIGURELMyelogram of a patient with a significantly narrow canal. Note cauda equina nerve roots are easily visible and are shown to be stretched.
herniation or from mild degenerative processes which would not usually cause symptoms. With age there is often progressive loss of disc height, slight disc bulging plus an increase in the lumbar lordosis. This is enough to cause significant compression in an already narrow canal. Some patients may present with cauda equina claudication, which is parasthesiae or numbness occurring after walking a certain distance or after standing for a prolonged period. The suggested mechanism is that standing and walking cause an increase in the lumbar lordosis which is enough to embarrass the capacity of the spinal canal with traction on the nerve tissue and interference in its microscopic blood supply and consequent delay in
nerve conduction. These symptoms are relieved by sitting or flexion of the spine. It is important to recognise a narrow canal prior to myelography, as lumbar puncture and removal of contrast are usually quite difficult. A relatively large volume myelogram (9-12 ml. contrast) is more effective as it distends the dural sac completely, thus making a positive diagnosis more certain. Recognition of this condition is also important clinically, as conservative management is not rewarding in the long term. If surgery is contemplated, a more radical approach should be planned with multiple laminectomies, which are often difficult in themselves because of
Austrafasian Radiology, Vol. XIX,No. 4, December, 1975
359
RHONDDA M. WILLIAMS thickened laminae and encroachment of the posterior joints on the midline. CONCLUSION The ratio Of lumbar to body was studied in 100 patients and 3% of patients were found to have significantly narrow lumbar spinal canals. ACKNOWLEDGEMENT I would like to thank Dr. W. Sorby for his help in compiling this paper. REFERENCES ‘Donath, J., and Vogl, A. (1925) : “Untersuchungen uber den chondrodystrophischen Awergwuchs.” Wiener Archiv f u r inners Medizin und deren Greirzgebie, 10, 1-44. ‘Ehni, G., Clark, K., Wilson, C. B., and Alexander, E. ( 1969) : “Significanceof the Small Lumbar Spinal Canal: Cauda Equina Compression due to Spondytosis.” Jourit. Neurosurg., 31, 490-5 19.
%+stein, B. S., Epstein, 1. A., and Lavine, L. (1964): “The Effect of Anatomic Variations in the Lumbar Vertebrae and Spinal Canal in Cauda Equina and Nerve Root Syndromes.” Anterican Jourizu[ Of Ro~iitgeilology.91, 1055- 1063. ‘Jones, R. A. C., and Thomson, J. L. C. (1973) : Jour/lul of Bone urrd Joiitr Surgery, SOB, 506-512. : . ~ ~ M. l ~ A.~ (1973): ~ , ‘‘Lumbar spinal stenosis.~. Journal of Bone Joirit Surgery, SSB, 595-605. “Ruberson, G . H., Llewllyn, H. J., and Taveras, I. M. (1973): “The Narrow Lumbar Spinal Canal Syndrome.” Radiolog.v, 107, 89-97. ‘Schatzker, f., and Pennal, G. F. (1968): Journal of Boi;e and Joint Surgery, SSB, 606-618. “Schlesinger, E. B., and Taveras, J. M. (1953): “Factors in the Production of ‘Cauda Equina’ Syndromes in Lumbar Discs.” Transactions of the American Neurological Association, 78th annual meeting, 78, 263-265. “Verbiest, H. (1954): “A Radicular Syndrome from Developmental Narrowing of the Lumbar Vertebral Canal.” Journcil of Bone und Joint Surgery. 26B, 230-237.
The Royal Australasian College of Radiologists The following candidates were successful in the D.R.A.C.R. Examination held in August/ September, 1975: RADIODIAGNOSIS PART I: Dr. P. F-Y. Fung Dr. D. C. Y. Ho Dr. T. R. Ruut Dr. D. C. Sargeant Dr. M. E. B. Stewart Dr. P. Torkington Dr. P. C. Wilson Dr. R. S. Hooper Dr. D. B. Robertson Dr. W. J. Rogers Dr. E. Dauber Dr. K. R. J. White Dr. G. T. Fon Dr. B. J. Hockley Dr. P. J. Gleeson Dr. H. K-Y Ho Dr. K. Y . S . Li Dr. D; A. Lingard Dr. C. K. Lo Dr. E. Y. T. Ma Dr. P. M. Mok Dr. D. J. Shipp 360
New South Wales New South Wales New South Wales New South Wales New South Wales New South Wales New South Wales Victoria Victoria Victoria Queensland Queensland South Australia South Australia Western Australia New Zealand New Zealand New Zealand New Zealand New Zealand New Zealand New Zealand
RADIOTHERAPY & ONCOLOGY PART I: Dr. M. P. Berry New South Wales New South Wales Dr. E. G . Tan Victoria Dr. M. P. Bishop Dr. R. M. Drummond Victoria Victoria Dr. S. Leung Victoria Dr. K. H. Liew Victoria Dr. C. Yang RADIODIAGNOSIS PART 11: New South Wales Dr. A. A. S. Aho New South Wales Dr. V. R. G. Critoph Dr. N. A. Forster Victoria Victoria Dr. S. S. Merchant Victoria Dr. J . W. Pike Dr. B. D. Bachovzeff Queensland Dr. P. N. Davis Queensland Dr. P. B. Hopkins South Australia South Australia Dr. J. J. Mansfield Western Australia Dr. S . le P. Langlois Western Australia Dr. A. S. Patel New Zealand Dr. P. J. de Korte Dr. M. A. James New Zealand Dr. L. A. Warner New Zealand RADIOTHERAPY PART I1 : Dr. C. A. Bailey Victoria New South Wales Dr. M. J. Holecek New Zealand Dr. P. V. Bydder
Aur ;Ira/asian Radiology. Y o / . XIX. No. 4 . ~eCelJlhCr.1975
The Narrow Lumbar Spinal Canal RHONDDA M. WILLIAMS, M.B., B.S., D.D.R. (Sydney) M.R.A.C.R. Sraf Radiologist, Department of Radiology, Prince Henry Hospital, Sydney, Australia
INTRODUCTION Narrowing of the cervical bony canal is an entity which has been recognised for many years, whilst the significance of a narrow lumbar spinal canal has been relatively neglected. Donath and Vogel (Wiener Achiv. Inn. Med. 1925, 10: 1-44) first described shortening of the pedicles and decreased interpedicular distance in achondroplastic dwarfs associated with a high incidence of spinal cord and nerve root compression. Later, Schlesinger and Taveras (Trans. Amer. Neurol. Ass. 1953, 78: 263-265) described a series of patients with narrow lumbar canals with reduction of the interpedicular distance. Verbiest (J. Bone and Joint Surg. 1954, 26B: 230-237) described narrowing of the lumbar canal in otherwise normal people with cauda equina claudication as a frequent presenting symptom. As the importance of the narrow lumbar spinal canal is now being recognised, this paper is to describe our experience with a simple method of assessing the approximate size of the lumbar canal.
METHOD There are two basic ways of measuring the lumbar spinal canal : (i) Direct measurement which will need correction for magnification, or (ii) Proportional measurement, which needs no correction. The method chosen for assessment of canal size is that of Jones and Thomson (Journl. Bone and Joint Surg. 1968,50B: 595-605) and is intended only as a guide to the relative size of the canal. The anteroposterior diameter of the canal and the intekdicular distance are measured and are related to the size of the vertebral body. These measurements can be performed on plain lumbar spine films and d o not need correction for magnification.
356
Using this technique, slight errors in estimating the posterior margin of the canal do not alter the ratio a great deal. The A.P. diameter of the spinal canal is the most difficult to measure as the posterior limit of the canal is hard to define (Figure 1 ). The measurement is taken from the middle of the posterior edge of the vertebral body to the base of the spinous process on the lateral film. The posterior limit of the canal is more easily defined in a patient with some residual Myodil from a previous myelogram. The A.P. canal measurement is multiplied by the interpedicular distance and is used as a ratio with A.P. x transverse diameters of the same vertebral body (Figure 2 ) : axb:cxd e.g.2x3:4x5 6 : 20 1 : 3.3 In this study one hundred consecutive myelograms from October 1973 to July 1974 were used and the measurements made on the plain films. The ratios were calculated for L3, L4 and LS on each patient and the mean value for each ratio, together with the standard deviation, were found.
RESULTS Jones and Thomson found their normal range to lie between I : 2.5 and I : 4.5. Their normal series used SO randomly selected patients attending an injury clinic without spinal fracture or injury. Our total range was Found to lie between I : 2.5 and 1 : 8.0. Using the mean 2 one standard deviation our normal range was: L3 and L4 1 to 3.0 to 1 to 6.0 L5 1 to 3.2 to I to 6.5 The higher values represent narrower lumbar spinal canals.
Auslralasian Rndiolq?.. Vol.
XIX. No. 4. Dcccmber. I975
THENARROW LUMBAR SPINAL CANAL
FIGURE I-Measuring points shown on a patient with a normal lumbar spinal canal.
Using the above figures a canal was taken to be significantly narrow if the ratio was above 1 to 6.0 for L3 and L4 and above 1 to 6.5 for L5.With these limitations three of our patients (3%) (Figures 3 and 4) were found to have significantly narrow canals at all three levels. There is an appreciable difference between our normal range and that of Jones and Thomson. Perhaps we have selected our patients by using only those who had back pain severe
enough to warrant myelography, or there may be some difference in the stature of our population in comparison with theirs.
DISCUSSION Primary narrowing of the lumbar canal is important, as any further slight decrease in the capacity of the canal will cause significant cauda equina compression. This may arise from disc
Australasian Radiology, Vol. X I X , No. 4, December, 1975
357
RHONDDA M. WILLIAMS
ment.
FIGURE3-Plain 358
films of a patient with a significantly narrow lumbar spinal canal. Australasian Radiology, Vol. XIX,No. 4,
December, 1975
THENARROW LUMBAR SPINALCANAL
FIGURELMyelogram of a patient with a significantly narrow canal. Note cauda equina nerve roots are easily visible and are shown to be stretched.
herniation or from mild degenerative processes which would not usually cause symptoms. With age there is often progressive loss of disc height, slight disc bulging plus an increase in the lumbar lordosis. This is enough to cause significant compression in an already narrow canal. Some patients may present with cauda equina claudication, which is parasthesiae or numbness occurring after walking a certain distance or after standing for a prolonged period. The suggested mechanism is that standing and walking cause an increase in the lumbar lordosis which is enough to embarrass the capacity of the spinal canal with traction on the nerve tissue and interference in its microscopic blood supply and consequent delay in
nerve conduction. These symptoms are relieved by sitting or flexion of the spine. It is important to recognise a narrow canal prior to myelography, as lumbar puncture and removal of contrast are usually quite difficult. A relatively large volume myelogram (9-12 ml. contrast) is more effective as it distends the dural sac completely, thus making a positive diagnosis more certain. Recognition of this condition is also important clinically, as conservative management is not rewarding in the long term. If surgery is contemplated, a more radical approach should be planned with multiple laminectomies, which are often difficult in themselves because of
Austrafasian Radiology, Vol. XIX,No. 4, December, 1975
359
RHONDDA M. WILLIAMS thickened laminae and encroachment of the posterior joints on the midline. CONCLUSION The ratio Of lumbar to body was studied in 100 patients and 3% of patients were found to have significantly narrow lumbar spinal canals. ACKNOWLEDGEMENT I would like to thank Dr. W. Sorby for his help in compiling this paper. REFERENCES ‘Donath, J., and Vogl, A. (1925) : “Untersuchungen uber den chondrodystrophischen Awergwuchs.” Wiener Archiv f u r inners Medizin und deren Greirzgebie, 10, 1-44. ‘Ehni, G., Clark, K., Wilson, C. B., and Alexander, E. ( 1969) : “Significanceof the Small Lumbar Spinal Canal: Cauda Equina Compression due to Spondytosis.” Jourit. Neurosurg., 31, 490-5 19.
%+stein, B. S., Epstein, 1. A., and Lavine, L. (1964): “The Effect of Anatomic Variations in the Lumbar Vertebrae and Spinal Canal in Cauda Equina and Nerve Root Syndromes.” Anterican Jourizu[ Of Ro~iitgeilology.91, 1055- 1063. ‘Jones, R. A. C., and Thomson, J. L. C. (1973) : Jour/lul of Bone urrd Joiitr Surgery, SOB, 506-512. : . ~ ~ M. l ~ A.~ (1973): ~ , ‘‘Lumbar spinal stenosis.~. Journal of Bone Joirit Surgery, SSB, 595-605. “Ruberson, G . H., Llewllyn, H. J., and Taveras, I. M. (1973): “The Narrow Lumbar Spinal Canal Syndrome.” Radiolog.v, 107, 89-97. ‘Schatzker, f., and Pennal, G. F. (1968): Journal of Boi;e and Joint Surgery, SSB, 606-618. “Schlesinger, E. B., and Taveras, J. M. (1953): “Factors in the Production of ‘Cauda Equina’ Syndromes in Lumbar Discs.” Transactions of the American Neurological Association, 78th annual meeting, 78, 263-265. “Verbiest, H. (1954): “A Radicular Syndrome from Developmental Narrowing of the Lumbar Vertebral Canal.” Journcil of Bone und Joint Surgery. 26B, 230-237.
The Royal Australasian College of Radiologists The following candidates were successful in the D.R.A.C.R. Examination held in August/ September, 1975: RADIODIAGNOSIS PART I: Dr. P. F-Y. Fung Dr. D. C. Y. Ho Dr. T. R. Ruut Dr. D. C. Sargeant Dr. M. E. B. Stewart Dr. P. Torkington Dr. P. C. Wilson Dr. R. S. Hooper Dr. D. B. Robertson Dr. W. J. Rogers Dr. E. Dauber Dr. K. R. J. White Dr. G. T. Fon Dr. B. J. Hockley Dr. P. J. Gleeson Dr. H. K-Y Ho Dr. K. Y . S . Li Dr. D; A. Lingard Dr. C. K. Lo Dr. E. Y. T. Ma Dr. P. M. Mok Dr. D. J. Shipp 360
New South Wales New South Wales New South Wales New South Wales New South Wales New South Wales New South Wales Victoria Victoria Victoria Queensland Queensland South Australia South Australia Western Australia New Zealand New Zealand New Zealand New Zealand New Zealand New Zealand New Zealand
RADIOTHERAPY & ONCOLOGY PART I: Dr. M. P. Berry New South Wales New South Wales Dr. E. G . Tan Victoria Dr. M. P. Bishop Dr. R. M. Drummond Victoria Victoria Dr. S. Leung Victoria Dr. K. H. Liew Victoria Dr. C. Yang RADIODIAGNOSIS PART 11: New South Wales Dr. A. A. S. Aho New South Wales Dr. V. R. G. Critoph Dr. N. A. Forster Victoria Victoria Dr. S. S. Merchant Victoria Dr. J . W. Pike Dr. B. D. Bachovzeff Queensland Dr. P. N. Davis Queensland Dr. P. B. Hopkins South Australia South Australia Dr. J. J. Mansfield Western Australia Dr. S . le P. Langlois Western Australia Dr. A. S. Patel New Zealand Dr. P. J. de Korte Dr. M. A. James New Zealand Dr. L. A. Warner New Zealand RADIOTHERAPY PART I1 : Dr. C. A. Bailey Victoria New South Wales Dr. M. J. Holecek New Zealand Dr. P. V. Bydder
Aur ;Ira/asian Radiology. Y o / . XIX. No. 4 . ~eCelJlhCr.1975
