Neuro-radiology

Neuroradiology (1992) 34:267-270

9 Springer-Verlag 1992

Changes seen on magnetic resonance imaging in the intervertebral disc space after chemonucleolysis: a hypothesis concerning regeneration of the disc after chemonucleolysis E Kato, K. Mimatsu, N. Kawakami, and T. Miura Department of Orthopaedic Surgery, School of Medicine, Nagoya University, Nagoya City, Japan Received: 16 May 1991

Summary. M e a s u r e m e n t s of the intervertebral disc space were m a d e by magnetic resonance imaging and plain film examinations over a period of 2 years in 26 patients w h o had u n d e r g o n e chemonucleolysis. T h e height of the posterior p o r t i o n of the disc decreased after 3 m o n t h s and never recovered; the height of the a n t e r i o r p o r t i o n also decreased but r e c o v e r e d slightly o v e r the same period. T h e angle of lordosis and the range of m o t i o n in the treated s e g m e n t were decreased, but recovered. M a r k e d decrease in signal f r o m the disc was o b s e r v e d after 2 weeks which did not recover till 2 years after chemonucleolysis. We suspect that the disc d e g e n e r a t e d m a r k e d l y after chemonucleolysis and

c h a n g e d into a type of scar tissue, m a t u r a t i o n of which could stabilize the affected segment.

Key words: L u m b a r disc herniation - Disc height - Chym o p a p a i n - Chemonucleolysis - Magnetic r e s o n a n c e imaging

Chemonucleolysis with c h y m o p a p a i n has r e c e n t l y b e c o m e established as a t r e a t m e n t for l u m b a r disc herniation [1,2]. C h y m o p a p a i n hydrolyses p r o t e o g l y c a n s and decreases pressure within the disc, with dissolution of its c o m p o n e n t s .

Table 1. Japanese Orthopaedic Association low back pain scores following chemonucleolysis (J Jpn Orthop Assoc 60: 391-394,1986) I. Subjective Symptoms (9 points) A. Low~-backPain a. None b. Occasional mild pain c. Frequent mild or occasional severe pain d. Frequent or continuous severe pain B. Leg Pain and/or Tingling a. None b. Occasional slight symptoms c. Frequent slight or occasional severe symptoms d. Frequent or continuous severe symptoms C. Gait a. Normal b. Able to walk farther than 500 meters, although it results in pain, tingling, and/or muscle weakness c. Unable to walk farther than 500 meters because of leg pain, and/or muscle weakness d. Unable to walk farther than 100 meters because of leg pain, and/or muscle weakness II. Clinical Signs (6 points) A. Straight-leg Raising Test (including tight hamstrings) a. Normal b. 30~ ~ c. 2.79), at 2 weeks and 4 weeks (t = 6.35 > 2.79), at 4 weeks and 3 months (t = 4.13 > 2.79), at 3 and 6months (t=3.00>2.79), and at 1 and 2years (t = 3.12 > 2.79) N=26

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Twenty-six patients with lumbar disc herniation sufficient to cause sciatica underwent chemonucleolysis with Chymopapain between November 1986 and August 1988, the diagnosis being confirmed by myelography, discography, and MRI in all cases. There were 22 men and 4 women with ages ranging from 17 to 58 years (mean 28 years). The straight-leg raising (SLR) test was positive in all, ranging from 20 ~to 60~(mean 35~ their Japanese Orthopaedic Association (JOA) scores for low back pain ranged from 4 to 21 (mean 14.4) (Table 1). The L4-5 disc was incriminated in 21 patients, and the L5-S, disc in 5. Prior to chemonucleolysis, all patients underwent conservative treatment consisting of lumbar traction, epidural block, and inj ection of steroids into the discs, as inpatients. As they had either no therapeutic effect or only slight improvement of their symptoms and signs, it was decided that further treatment was warranted. Chemonucleolysis was performed through a lateral approach under local anaesthesia. Twelve patients received 5nKat units of Discase (Travenol Laboratories, Deerfield, Ill.), and t4 were given 4nKat units of Chymodiactin (Flint Laboratories, Deerfield, Ill.). MRI was performed with a 0.5 T superconductive magnet using a standard body coil, as surface coils were not available. Sagittal images, 1 cm thick were obtained. T1- (spin echo TR 500 ms/TE 40 ms) and T2-weighted images (spin echo TR 1500 ms/TE 80 ms) were obtained. All patients were imaged prior to chemonucleolysis and serially afterwards at 2 and 4 weeks, 3 and 6 months, and at 1 and 2 years. In addition, standard lateral radiographs in the neutral position were taken prior to chemonucleolysis and serially afterwards, at the same time as MRI. Films in flexion and extension were also taken before treatment and 3 and 6 months and i and 2 years later. The height of the anterior and posterior portions of the disc, and the maximum height of the body of L5 were measured on each sagittal MR image and lateral radiographs in the neutral position. From these data anterior and posterior disc indexes were calculated by Brandner's method [15]. The angle of lordosis at the treated segment was also measured on each saggital MRI and all three lateral radiographs by Wiltse's method [16] (Fig. 1). The values from the MRI were compared with those from the neutral position plain films taken at the same time. From the angle of lordosis in flexion and extension, the range of motion in the treated segment was calculated.

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A l l p a t i e n t s h a d e x c e l l e n t o r g o o d results, so t h a t no o p e r ative s u r g e r y was n e e d e d . T h e S L R test, in p a r t i c u l a r , b e c a m e n e g a t i v e e a r l y a f t e r c h e m o n u c l e o l y s i s (in 8 cases w i t h i n 2 w e e k s , 10 w i t h i n 4 weeks, 4 within 3 m o n t h s , a n d 4 within 6 m o n t h s ) . A l t h o u g h t h e s y m p t o m o f low b a c k p a i n i m p r o v e d , this was r e l a t i v e l y p r o l o n g e d , it finally disa p p e a r i n g o v e r a 3 - m o n t h p e r i o d in m o s t cases [8]. T h e

269

Fig.5 a-c. TR 500 ms/TE 40 ms sagittal MR images in a 27-year-old man with right sciatica a Initial study showing a large hernia at IA-5. Anterior disc index is 0.28 and posterior 0.11; angle of lordosis 15~ b Two weeks after chemonucleolysis. Decrease in height of disc: anterior index 0.14, posterior 0.08; angle of lordosis 12~ c Three months after chemonucleolysis. More decrease in height; anterior index 0.11, posterior 0.06; angle of lordosis 10~ Fig. 6 a-c. Same patient as Fig. 7. Anterior disc index and angle of lordosis gradually recovered, but posterior disc index did not a Six months after chemonucleolysis: anterior disc index 0.14, posterior 0.06, angle of lordosis 11~ b A year after chemonucleolysis: anterior disc index 0.t7, posterior, angle of lordosis 12~ c Two years after chemonucleolysis: anterior disc index 0.18, posterior 0.06, angle of lordosis 15"

J O A scores gradually i m p r o v e d over the 2 years of the study (Fig. 2). T h r e e m o n t h s after chemonucleolysis, the average disc index posterior, as shown by M R I , h a d decreased significantly to 57% (P < 0.01, t = 11.07 > 2.79) and by plain films to 63% (P < 0.01, t = 14.36 > 2.79) c o m p a r e d with p r e t r e a t m e n t values, and no re-expansion was observed until 2 years after chemonucleolysis (P < 0.01, t = 2.10 < 2.79 and t = 1.77 < 2.79) (Figs. 3-6). T h e average disc index anteriorly also decreased significantly, to 41% by M R I (P < 0.01, t = 15.41 > 2.79) and to 56% by plain films P < 0.01, t = 9.89 > 2.79) 3 m o n t h s after c h e m o n u c l e olysis, but h a d increased again significantly to 67% by M R I (P < 0.01, t = 7.49 > 2.79) and 71% by plain films (P