THE ACCURATE IDENTIFICATION OF MOTOR ROOTS AT THE LOWER END OF THE SPINAL CORD. I. B. MACDONALD, M.D., K. G. McKENZIE, M.D., A~D E. H. BOTTERELL, M.D.

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ANTERIOR RHIZOTOMY THE ACCURATE IDENTIFICATION OF MOTOR ROOTS AT THE LOWER END OF THE SPINAL CORD I. B. MACDONALD, M.D., K. G. McKENZIE, M.D., A~D E. H. BOTTERELL, M.D. Neurosurgical Division, Department of Surgery, and Department of Anatomy, University of Toronto, and Neurosurgical Service, Christie St.

1 ANTERIOR RHIZOTOMY THE ACCURATE IDENTIFICATION OF MOTOR ROOTS AT THE LOWER END OF THE SPINAL CORD I. B. MACDONALD, M.D., K. G. McKENZIE, M.D., A~D E. H. BOTTERELL, M.D. Neurosurgical Division, Department of Surgery, and Department of Anatomy, University of Toronto, and Neurosurgical Service, Christie St. Hospital, D.V.A., Toronto, Canada (Received for publication May 81, 1946) A THE meeting of the American Society of Neurological Surgeons held in Montreal on October ~0, 1944, Dr. Donald Munro 2 stimulated the members by a presentation on "Care of the Paraplegic." He showed movies of a number of patients completely paralyzed who were able to walk with the help of braces and crutches. The morale of these patients appeared to be excellent, and their general physical condition good. A number of them were earning their own livelihood. At this meeting, he stated that he had been unable to deal adequately with a certain group of patients who had marked spasticity and mass reflexes. These patients would not tolerate splinting. In a few of these he had converted the spastic paraplegia into a flaccid one, by cutting the anterior motor roots from thoracic ten to sacral one inclusive, and thus retaining the innervation of the bladder. This operation would seem to have a very definite place in the treatment of a certain group of cases and is a surgical procedure that will likely be carried out in many neurological centres. Experience with one case by one of us (K. G. McK.) demonstrated the difficulty of identification of the roots. The surgeon must have accurate anatomical knowledge and a definite plan to identify the root, otherwise the operation can be very confusing. Elsberg 1 stated that "the dentate ligament ends below, at the level of the first lumbar vertebra, in a fork-shaped extremity... The first lumbar posterior root rests upon this fork, so that the 'fork' may be used as an anatomical landmark for the identification of the first lumbar root." He recommended that other roots should be recognized by counting in either direction from this first lumbar sensory root. Anatomists agree that the highest process of the denticulate ligament is attached to the margin of the foramen magnum. There is disagreement, however, on the number of denticulations throughout the length of the ligament. A table of various opinions follows: Number of ligamentous processes About ~l s to ~ ~0 19 to ~$ About ~1 Authority Parsons. Gray's Anatomy. 26th ed. Picrsol. Human Anatomy. 9th ed. Cunningham. Text-book of Anatomy. 8th ed. A. Lee McGregor. A Synopsis of Surgical Anatomy. 4th ed. Emil Villiger. Brain and Spinal Cord. Tilney and Riley. The Form and Fnnctions of the Central Nervous System. Morris. Human Anatomy. 10th ed. 4~1

2 4~ I.B. MACDONALD, K. G. McKENZIE AND E. H. BOTTERELL Usually o-1 Werner Spalteholz. Hand Atlas of Human Anatomy. Vol. 3. O-0 to O-5 Sobotta and McMurrich. Atlas and Text-book of Human Anatomy. Vol. O-. About O-1 Quain's Elements of Anatomy. llth ed., vo]. 3, part 1. It is apparent from these observations that the lowest attachment of the denticulate ligament is at a variable vertebral level, and thus has not a constant relation to the first lumbar posterior root. From dissections of 10 cadavers, it is concluded that this anatomic landmark is inconstant. A table of results follows: Subject Root lying on lowest slip of the denticulate ligament Left Right A L-O- L-O- B L-1 L-1 C L-1 L-O- D L-I L-I E L-1 I,-1 F L -o. T-lo- G I,-O- L-1 H L-O- T-lo- I L-O- L-O- J l,-1 L-1 In 4 cases only, of the 10 cadavers dissected, were the posterior roots of the first lumbar nerves lying on the lowest slip of the denticulate ligament on both sides of the cadaver. It is important to note that in ~ cases, the twelfth thoracic root on the one side and the second lumbar root on the other side would have been identified as first lumbar roots by Elsberg's method of identification. Early in the dissections, it was apparent that counting the roots at the lower end of the spinal cord was extremely difficult and inaccurate, due to their close approximation to each other. It is important to realize, therefore, that if an upper lumbar root is definitely identified, the inaccurate procedure of counting other lower roots would still be necessary. THE ACCURATE IDENTIFICATION OF ROOTS AT THE LOWER END OF THE SPINAL CORD In an effort to eliminate the uncertain process of counting roots and because the lowest tooth of the denticulate ligament was not an accurate guide, a method was sought of identifying the lowest possible root of those to be divided. Observations on an additional 4 cadavers and a study of ~ cases at autopsy indicated that the first sacral motor root could be identified accurately because it is the lowest large root to leave the conus medullaris. The difference in size between the large first sacral root and the much smaller second sacral root is so striking that there is no special difficulty in distinguishing between them. In this second series of 6 dissections the first sacral root was identified at the lower end of the spinal cord by its size and position. The identification was found to be correct, bilaterally, in each case by following

ANTERIOR RHIZOTOMY 4~3 the root to its exit through the first sacral foramen. It is essential in making this identification to obtain a satisfactory view of the lower end of the cord.

3 ANTERIOR RHIZOTOMY 4~3 the root to its exit through the first sacral foramen. It is essential in making this identification to obtain a satisfactory view of the lower end of the cord. In actual operation it has been done in two ways: (a) A loose ligature is passed around the filum terminale avoiding trauma to the slender, friable, coccygeal roots. A blunt probe is passed downwards along the plane of the denticulate ligament and all the lower sensory roots on that side are hooked up en masse and held medially. The loose ligature is grasped and the filum terminale is pulled in a cranio-lateral direction between the bundles of anterior and posterior roots, into a position lateral to the medially retracted dorsal roots. The spinal cord is rotated to bring the anterior roots clearly into view by traction on the lowest process of the denticulate ligament and the filum terminale. Two or three contiguous roots may hinder this manoeuvre and can be cut without any deleterious results. The lowest big anterior root may then be definitely identified as the first sacral and cut, and all motor roots above sectioned up to the desired level. The procedure is repeated on the opposite side. (See Fig. 1.) (b) A second, and probably more simple method may be carried out by severing the lowest tooth of the denticulate ligament and retracting the posterior roots as above. If a few of these sensory roots, which are too taut for adequate retraction, are cut, a good view of file motor roots may be obtained. The main advantage of this latter procedure is that the laminectomy does not have to be carried down quite so far, as the ilium tcrminale does not have to be visualized as in (a). The only disadvantage of (b) is that the view of the lower roots is not as extensive as in (a) where the motor roots are put on the stretch which gives a clearer picture of the anatomy of this region. The identification of the highest root to be cut presents some difficulty; although accurate identification here is not as important as identification below where the supply of the bladder must be considered. It is suggested that accurate identification at this upper level should be made by placing a silver clip on what is judged to be a lower thoracic motor root at its exit from the dural canal. A portable x-ray plate will then accurately identify this clipped root in relation to the ribs and vertebrae. A pre-operative x-ray film to rule out vertebral or costal anomalies would be an additional precaution to insure accuracy. The necessary number of roots to be cut in the upper part of the exposure can then be counted, as the roots in this region are spaced sufficiently far apart to render this procedure easy. To gain adequate exposure for the sectioning of the tenth thoracic root to the first sacral, it is necessary to remove the spines and laminae from the tenth thoracic vertebra to the second lumbar vertebra. Through the cooperation of Professor J.C.B. Grant of the Department of Anatomy in the University of Toronto, one of us (I.B.M.), while a Demonstrator in Anatomy, was given the privilege of carrying out the series of dissections. CLINICAL NOTES In this centre, anterior rhizotomy has been performed on 6 patients because mass reflexes prevented adequate nursing care, the prevention of bedsores and efficient care of the genito-urinary tract. In all of these 6 patients,

4~4 I.B. MACDONALD, K. G. McKENZIE AND E. H. BOTTERELL mass reflexes have been abolished. In 5 instances identification of nerve roots was done by the method suggested above.

4 4~4 I.B. MACDONALD, K. G. McKENZIE AND E. H. BOTTERELL mass reflexes have been abolished. In 5 instances identification of nerve roots was done by the method suggested above. In contrast to Munro's experience, permanent disturbance of bladder function has followed the operation in ~ patients. Pre-operatively, these pa- FIG. 1. tients had bladders capable of good reflex contractions. Following operation, the bladder was completely flaccid and has remained so for three months or longer. Of the remaining 3 patients, reflex activity of the bladder was unchanged in two and in one patient cutaneous ureterostomies prevented assessment of bladder function after operation.

ANTERIOR RHIZOTOMY 435 At the moment, from this experience, it is our belief that: (a) There is the possibility, although in our opinion unlikely, that the roots were inadequately identified at

5 ANTERIOR RHIZOTOMY 435 At the moment, from this experience, it is our belief that: (a) There is the possibility, although in our opinion unlikely, that the roots were inadequately identified at operation. (b) In certain patients, the first sacral root may be necessary for adequate reflex activity of the bladder. (c) We believe that the most likely explanation for the abolishment of reflex activity of the bladder in these two, possibly three, patients is as follows: Section of a large number of anterior roots may cut off sufficient blood supply to the eonus medullaris to bring about loss of function in the sacral segments. At operation, it may be possible to save some of the arteries accompanying the anterior roots and every effort should be made to do so. (d) One of us (E.H.B.) has concluded that in future he will leave the first sacral root, for persisting spastieity about the ankle joints will unlikely interfere to a significant degree with the retraining program with braces and crutches. SUMMARY 1. The relation of the first posterior lumbar root to the lowest slip of the dentieulate ligament is inconstant. ~. A method of identifying the first sacral motor root is suggested. 3. It is advisable to preserve as many anterior root arteries as possible when performing an anterior rhizotomy. REFERENCES 1. ELSBI~RG, C.A. Some features of the gross anatomy of the spinal cord and nerve roots, and their bearing on the symptomatology and surgical treatment of spinal disease. Amer. J. Med. Sci., 1913, 144: MUNRO, D. The rehabilitation of patients totally paralyzed below the waist: with special reference to making them ambulatory and capable of earning their living. I. Anterior rhizotomy for spastic paraplegia. New Engl. J. Med., 1945, 233:

Sir William Asher ANATOMY

Sir William Asher ANATOMY SPINAL CORD INJURY BASICS RELATED TO LIFE CARE PLANNING Lesson 1 Sir William Asher Picture the pathetic patient lying long abed, the urine leaking from his distended bladder, the lime draining from his