J Orthop Sci (2014) 19:22–25 DOI 10.1007/s00776-013-0491-1
ORIGINAL ARTICLE
Overactive bladder in cervical spondylotic myelopathy Zhuo Wang • Toshihiko Sakakibara Yuichi Kasai
•
Received: 7 April 2013 / Accepted: 20 October 2013 / Published online: 12 November 2013 Ó The Japanese Orthopaedic Association 2013
Abstract Background Overactive bladder (OAB) is a new disease concept defined by the International Continence Society in 2002. There have been no reports of OAB among patients with cervical spondylotic myelopathy assessed on the basis of symptom questionnaires. Methods One-hundred-and-six patients diagnosed with cervical spondylotic myelopathy and treated by use of laminoplasty were examined. The patients were classified into two groups, those identified as having OAB (OAB group) and those identified as not having OAB (non-OAB group), by use of the Overactive Bladder Symptom Score collected before and 1 year after surgery. The clinical results for the two groups were assessed. OAB symptom prevalence and post-operative symptom improvement were investigated 1 year postoperatively. Results Of the 106 patients, 50 were identified as having OAB (symptom prevalence 47.2 %). Of these 50 patients, symptom improvement was observed for only 14 (28 %) 1 year after surgery. For both groups good improvement on the basis of the Japanese Orthopedic Association score was observed 1 year postoperatively, but there were no significant differences between them. Conclusions Post-operative improvement of OAB symptoms in cervical spondylotic myelopathy patients was low, which indicated that OAB was most frequently attributable to non-neurogenic and idiopathic, but not neurogenic, causes. It is considered necessary to tell patients with cervical spondylotic myelopathy that the
Z. Wang T. Sakakibara Y. Kasai (&) Department of Spinal Surgery and Medical Engineering, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507, Japan e-mail: [email protected]
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possibility of post-operative OAB symptom improvement is not high when the explanation for informed consent is given before the operation.
Introduction Cervical spondylotic myelopathy is a disease with nerve symptoms, for example numbness of limbs and reduced muscle strength [1]. Sometimes, the disease is accompanied by urinary disturbance, referred to as neurogenic bladder [2]. The symptoms of neurogenic bladder include the inability to defer urination, pollakiuria (frequent daytime urination), and urinary incontinence, most of which are attributable to overactive bladder (OAB) caused by involuntary contraction of the detrusor muscle of the bladder [3–5]. OAB is a new disease concept defined by the International Continence Society in 2002. It is a symptom syndrome always accompanied by pollakiuria and urinary urgency as the essential symptoms, irrespective of the presence or absence of urinary incontinence [6]. Since this definition was established, easy determination of OAB on the basis of a symptom questionnaire is currently accepted as a standard procedure without requiring such complicated urological tests as a urodynamic study [7, 8]. Examples of symptom questionnaires include the Overactive Bladder Questionnaire (OAB-q) [9], the International Prostate Symptom Score (IPSS) [10], and the Overactive Bladder Symptom Score (OABSS) [11]. There have been no reports of OAB among patients with cervical spondylotic myelopathy assessed on the basis of basis of these symptom questionnaires. In this regard, we investigated the prevalence of symptoms of OAB and its post-operative improvement among
OAB in cervical spondylotic myelopathy
patients with cervical spondylotic myelopathy, on the basis of the OABSS. Compared with the rather complicated IPSS and OAB-q methods, the OABSS system proposed in Japan is simpler [11, 12].
Materials and methods Of the 125 patients who were given a diagnosis of cervical spondylotic myelopathy and who underwent laminoplasty at our department-affiliated hospitals during the 3 years from September 2006 to August 2009, 19 patients who were under treatment at the urology department were excluded, because they may have poor urinary function, and the remaining 106 patients whose OABSS was collected 1 year after surgery were enrolled as the subjects of the study. All study protocols were approved by the ethics committee at our university (approval no. 1306). We certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during the course of this study. Preoperative myelography was performed on all the patients, and no patients were observed with distinct lumbar spinal canal stenosis. The mean age of patients at the time of surgery was 69.2 years (range 46–82 years). There were 62 men and 44 women. The operation was performed in all of these cases by the same surgeon. Double-door spinous processsplitting laminoplasty was performed in 85 cases and single-door spinous process-splitting laminoplasty in 21 cases. The OABSS system (Table 1) prepared in 2006 was used as the method of OAB determination, and any patient whose score for question 3 was C2 points and whose total score for questions 1, 2, and 4 was C3 points was identified as having OAB [13, 14]. Any patient whose score for question 3 was lower and whose total score for the four questions decreased after 1 year from the time of surgery in comparison with the pre-operation level was assessed as showing post-operative symptom improvement. OAB symptom prevalence and post-operative symptom improvement were investigated. The patients were classified into two groups, those who were identified as having OAB (OAB group) and those who were identified as not having OAB (non-OAB group), and the age, sex, preoperative Japanese Orthopaedic Association (JOA) score (Cervical Spondylotic Myelopathy Treatment Result Assessment Criteria established by the Japanese Orthopaedic Association; full score: 17 points), post-operative JOA score improvement (by Hirabayashi’s method), and the preoperative MRI cumulative score [15] to assess the compression condition of the cervical cord were compared between the two groups. With regard to the preoperative MRI cumulative score, one radiologist who was not involved in this study assessed the T1 and T2-weighted
23 Table 1 Overactive bladder symptom score (OABSS) Question
Frequency
Q1. How many times do you typically urinate from waking in the morning until sleeping at night?
B7
0
8*14
1
C15
2
Q2. How many times do you typically wake up to urinate from sleeping at night until waking in the morning?
0
0
1
1
2
2
C3
3
Q3. How often do you have a sudden desire to urinate, which is difficult to defer?
Q4. How often do you leak urine because you cannot defer the sudden desire to urinate
Score
Not at all
0
Less than once a week
1
Once a week or more
2
About once a day
3
2–4 times a day
4
5 times a day or more
5
Not at all
0
Less than once a week
1
Once a week or more
2
About once a day
3
2–4 times a day
4
5 times a day or more
5
Patients were instructed to circle the score that best applied to their urinary condition during the past week; the overall score was the sum of the four scores
sagittal planes of MRI by scoring each intervertebral compression extent in the dural duct and spinal cord from 0 to 5 points, after which the total score of intervertebral compressions was obtained. The Student t test or v2 test was used for statistic analysis, and P \ 0.05 was considered to indicate a significant difference.
Results Of the 106 patients, 50 were identified as having OAB, so symptom prevalence was 47.2 %. Of these 50 patients, symptom improvement was observed for 14 (28 %), only, 1 year after surgery. When the 50 patients in the OAB group were compared with the 56 patients in the non-OAB group, there was no significant difference between the two groups with regard to age and sex. Preoperative mean OABSS score was 7.1 ± 2.6 points in the OAB group and
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2.7 ± 1.6 points in the non-OAB group. Mean OABSS score 1 year after surgery was 5.8 ± 2.9 points in the OAB group and 2.9 ± 1.5 points in the non-OAB group (Table 2). Mean OABSS scores in the OAB group were significantly higher than that in the non-OAB group both preoperatively and postoperatively (P \ 0.01), but there were no significant differences between pre and postoperative data in both groups (P [ 0.05). Mean scores of each domain of OABSS in both groups are shown in Table 3. With regard to the clinical results, the mean JOA score 1 year after surgery was 13.5 ± 3.7 points versus 8.9 ± 3.4 points before surgery, indicating improvement of 56.8 ± 21.2 %. The pre-operative JOA score and postoperative JOA improvement tended to be somewhat lower in the OAB group than in the non-OAB group, but there were no significant differences between the two groups. Preoperative mean evaluation points of bladder function (perfect score: 3 points) in JOA score was 1.6 ± 1.2 points in the OAB group and 1.8 ± 0.7 points in the non-OAB group, whereas mean scores 1 year after surgery were 1.7 ± 0.8 points in the OAB group and 1.8 ± 0.9 points in Table 2 Summarized results. Comparison of the OAB and non-OAB groups OAB group
Non-OAB group
P value
Number of patients
50
56
Mean age at surgery (years)
71.3 (54–82)
68.9 (46–79)
[0.05
Male
32
30
[0.05
Female
18
26
7.1 ± 2.6
2.7 ± 1.6
\0.01
Postoperation Mean preoperative JOA score
5.8 ± 2.9 8.8 ± 3.1
2.9 ± 1.5 9.1 ± 2.9
\0.01 [0.05
Improvement of JOA score
54.9 ± 23.5 %
57.2 ± 20.9 % [0.05
Preoperative MRI cumulative score
14.9 (5–21)
12.1 (6–19)
Gender
Mean OAB Score Preoperation
[0.05
Table 3 Mean scores of each domain of the OABSS for the OAB and non-OAB groups OAB group
Q1
Non-OAB group
Preoperation
Postoperation
Preoperation
Postoperation
1.4 ± 0.7
1.3 ± 0.6
0.7 ± 0.6
0.7 ± 0.9
Q2
1.7 ± 0.8
1.4 ± 0.6
0.9 ± 0.6
0.8 ± 0.5
Q3 Q4
2.5 ± 0.7 1.5 ± 1.3
1.8 ± 0.9 1.2 ± 0.8
0.6 ± 0.5 0.8 ± 0.6
0.7 ± 0.6 0.9 ± 0.8
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the non-OAB group. There were no significant differences between the two groups and no correlations between JOA bladder function score and OABSS score in either group pre and postoperatively. The preoperative MRI cumulative score was somewhat higher in the OAB group but there was no significant difference between the two groups (Table 2).
Discussion In 2003, the Neurogenic Bladder Society in Japan conducted an OABSS survey with regard to OAB among Japanese people 40 years old or older. As a result, it was estimated that approximately 7 % of the Japanese population (approx. 8,100,000 people) had OAB symptoms. With regard to the prevalence of OAB symptoms by age stratum, the proportions of people with the corresponding symptoms were 12.1 % among those in their 60s, 22.6 % among those in their 70s, and 36.8 % among those 80 years old or older, indicating an increase in symptom prevalence with aging [16]. The causes of OAB are approximately classified into three types: neurogenic, non-neurogenic, and idiopathic [17]. Neurogenic OAB includes the diseases attributable to disorders in the brain, pons, and spinal cord, whereas nonneurogenic OAB is caused by prostate hypertrophy in males and reduced pelvic muscle strength in females after giving birth [17, 18]. OAB whose cause is unknown is classified as idiopathic. It is reported that the prevalence of idiopathic OAB is the highest among these three causes [17, 19]. According to the results of this study, the appearance of OAB was not clearly reflected in the clinical results and image findings, suggesting that many OAB cases are attributable to an idiopathic rather than neurogenic cause. Mochida et al. [20] observed neurogenic bladder in 22 (36.7 %) of 60 patients with cervical spondylotic myelopathy and reported that OAB was detected in 13 (21.7 %) patients on the basis of results from cystometry. However, the diagnostic criteria for OAB were not clear and idiopathic or non-neurogenic patients were inevitably excluded from their study. Although it is believed the OABSS has high sensitivity and low specificity, it was recommended as the diagnosis guideline in 2009 and has become a standard diagnosis tool for OAB [13, 14]. When subjects with a mean age of 69.2 years were investigated by use of the OABSS system in this study, OAB incidence was 47.2 % (nearly half) among patients with cervical spondylotic myelopathy, which is higher than the 22.6 % among the Japanese population in their 70 s reported by Japanese Neurogenic Bladder Society [16]. In this study we thus assumed that approximately half of our
OAB in cervical spondylotic myelopathy
OAB patients had cervical spondylotic myelopathy, which caused neurogenic bladder as a result of cervical cord compression, and that the other cases were non-neurogenic or idiopathic. In general, orthopedic surgeons tend to consider overactive bladder is equivalent to neurogenic bladder. However, post-operative improvement was observed in only 14 (28 %) of 50 patients in this study. The possibility that irreversible change had already occurred in the spinal cord of patients may be a reason for such poor post-operative OAB improvement. It is more likely that OAB was most frequently attributable to non-neurogenic and idiopathic causes. The authors suggest it is necessary for orthopedic surgeons to explain sufficiently to cervical spondylotic myelopathy patients with possible neurogenic bladder, when obtaining informed consent, that the possibility of improvement of OAB is low even if cervical laminoplasty is performed. Because this study is the first in the world to use the OABSS system to investigate OAB symptom prevalence and post-operative improvement among patients with cervical spondylotic myelopathy, the results obtained may be regarded as valuable. However, there are several limitations to this study. First, a possibility cannot be denied that the excluded patients with urinary cancer may have neurogenic bladder. Second, there was no control group comprising healthy volunteers. Third, much of the pathology of OAB remains unknown because urological X-ray tests, MRI, scintigraphy, echography, urological endoscopy, and urodynamics tests were not performed as part of this study. The authors intend to continue research in this direction by, as far as possible, conducting urological tests for patients determined to have OAB and investigating cervical MRI and myelo-CT images in detail to elucidate OAB pathology among patients with cervical spondylotic myelopathy. Conflict of interest This manuscript does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly to the subject of this manuscript.
References 1. Epstein NE. Laminectomy for cervical myelopathy. Spinal Cord. 2003;41:317–27. 2. Misawa T, Kamimura M, Kinoshita T, Itoh H, Yuzawa Y, Kitahara J. Neurogenic bladder in patients with cervical compressive myelopathy. J Spine Disord Tech. 2005;18:315–20.
25 3. Reitz A, Schurch B. Intravesical therapy options for neurogenic detrusor overactivity. Spinal cord. 2004;42:267–72. 4. Abrams P. Describing bladder storage function: overactive bladder syndrome and detrusor overactivity. Urology. 2003;62(5 Suppl 2):28–37. 5. de Groat WC, Yoshimura N. Changes in afferent activity after spinal cord injury. Neurourol Urodyn. 2010;29:63–76. 6. Abrams P, Cardozo L, Fall M, Griffiths D, Rosier P, UImsten U, Van Kerrebroeck P, Victor A, Wein A, Standardisation SubCommittee of the International Continence Society. The standardisation of terminology of lower urinary tract function: report from the standardization Sub-Committee of the International Continence Society. Neurourol Urodyn. 2002;21:167–78. 7. Digesu GA, Khullar V, Cardozo L, Salvatore S. Overactive bladder symptoms: do we need urodynamics? Neurourol Urodyn. 2003;22:105–8. 8. Malone-Lee JG, Al-Buheissi S. Does urodynamic verification of overactive bladder determine treatment success? Result from a randomized placebo-controlled study. BJU Int. 2009;103:931–7. 9. Coyne K, Revicki D, Hunt T, Corey R, Stewart W, Bentkover J, Kurth H, Abrams P. Psychometric validation of an overactive bladder symptom and health-related quality of life questionnaire: the OAB-q. Qual Life Res. 2002;11:563–74. 10. Kaplan SA, Roehrborn CG, Chancellor M, Carisson M, Bavendam T, Guan Z. Extended-release tolterodine with or without tamsulosin in men with lower urinary tract symptoms and overactive bladder: effects on urinary symptoms assessed by the international prostate symptom score. BJU Int. 2008;102:1133–9. 11. Homma Y, Yoshida M, Seki N, Okoyama O, Kakizaki H, Gotoh M, Yamanishi T, Yamaguchi O, Takeda M, Nishizawa O. Symptom assessment tool for overactive bladder syndrome: overactive bladder symptom score. Urology. 2006;68:318–23. 12. Homma Y, Gotoh M. Symptom severity and patient perceptions in overactive bladder: how are they related? BJU Int. 2009;104: 968–72. 13. Yamaguchi O, Nishizawa O, Takeda M, Yokoyama O, Homma Y, Kakizaki H, Obara K, Gotoh M, Igawa Y, Seki N, Yoshida M, Neurogenic Bladder Society. Clinical guidelines for overactive bladder. Int J Urol. 2009;16:126–42. 14. Homma Y, Kakizaki H, Yamaguchi O, Yamanishi T, Nishizawa O, Yokoyama O, Takeda M, Seki N, Yoshida M. Assessment of overactive bladder symptoms: comparison of 3-day bladder diary and the overactive bladder symptoms score. Urology. 2011;77: 60–4. 15. Kasai Y, Uchida A. New evaluation method using preoperative magnetic resonance imaging for cervical spondylotic myelopathy. Arvh Orthop Trauma Surg. 2001;121:508–10. 16. Homma Y, Yamaguchi O, Hayashi K. An epidemiological survey of overactive bladder symptoms in Japan. BJU Int. 2005;96: 1314–8. 17. Ouslander JG. Management of overactive bladder. N Engl J Med. 2004;350:786–99. 18. Wagg A, Majumdar A, Toozs-Hobson P, Patel AK, Chapple CR, Hill S. Current and future trends in the management of overactive bladder. Int Urogynecol J Pelvic Floor Dysfunct. 2007;18:81–94. 19. Gulur DM, Drake MJ. Management of overactive bladder. Nat Rev Urol. 2010;7:572–82. 20. Mochida K, Shinomiya K, Andou M. Urodynamic and electrophysiologic study of the urinary disturbances caused by cervical myelopathy. J Spinal Disord. 1996;9:141–5.
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ORIGINAL ARTICLE
Overactive bladder in cervical spondylotic myelopathy Zhuo Wang • Toshihiko Sakakibara Yuichi Kasai
•
Received: 7 April 2013 / Accepted: 20 October 2013 / Published online: 12 November 2013 Ó The Japanese Orthopaedic Association 2013
Abstract Background Overactive bladder (OAB) is a new disease concept defined by the International Continence Society in 2002. There have been no reports of OAB among patients with cervical spondylotic myelopathy assessed on the basis of symptom questionnaires. Methods One-hundred-and-six patients diagnosed with cervical spondylotic myelopathy and treated by use of laminoplasty were examined. The patients were classified into two groups, those identified as having OAB (OAB group) and those identified as not having OAB (non-OAB group), by use of the Overactive Bladder Symptom Score collected before and 1 year after surgery. The clinical results for the two groups were assessed. OAB symptom prevalence and post-operative symptom improvement were investigated 1 year postoperatively. Results Of the 106 patients, 50 were identified as having OAB (symptom prevalence 47.2 %). Of these 50 patients, symptom improvement was observed for only 14 (28 %) 1 year after surgery. For both groups good improvement on the basis of the Japanese Orthopedic Association score was observed 1 year postoperatively, but there were no significant differences between them. Conclusions Post-operative improvement of OAB symptoms in cervical spondylotic myelopathy patients was low, which indicated that OAB was most frequently attributable to non-neurogenic and idiopathic, but not neurogenic, causes. It is considered necessary to tell patients with cervical spondylotic myelopathy that the
Z. Wang T. Sakakibara Y. Kasai (&) Department of Spinal Surgery and Medical Engineering, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie 514-8507, Japan e-mail: [email protected]
123
possibility of post-operative OAB symptom improvement is not high when the explanation for informed consent is given before the operation.
Introduction Cervical spondylotic myelopathy is a disease with nerve symptoms, for example numbness of limbs and reduced muscle strength [1]. Sometimes, the disease is accompanied by urinary disturbance, referred to as neurogenic bladder [2]. The symptoms of neurogenic bladder include the inability to defer urination, pollakiuria (frequent daytime urination), and urinary incontinence, most of which are attributable to overactive bladder (OAB) caused by involuntary contraction of the detrusor muscle of the bladder [3–5]. OAB is a new disease concept defined by the International Continence Society in 2002. It is a symptom syndrome always accompanied by pollakiuria and urinary urgency as the essential symptoms, irrespective of the presence or absence of urinary incontinence [6]. Since this definition was established, easy determination of OAB on the basis of a symptom questionnaire is currently accepted as a standard procedure without requiring such complicated urological tests as a urodynamic study [7, 8]. Examples of symptom questionnaires include the Overactive Bladder Questionnaire (OAB-q) [9], the International Prostate Symptom Score (IPSS) [10], and the Overactive Bladder Symptom Score (OABSS) [11]. There have been no reports of OAB among patients with cervical spondylotic myelopathy assessed on the basis of basis of these symptom questionnaires. In this regard, we investigated the prevalence of symptoms of OAB and its post-operative improvement among
OAB in cervical spondylotic myelopathy
patients with cervical spondylotic myelopathy, on the basis of the OABSS. Compared with the rather complicated IPSS and OAB-q methods, the OABSS system proposed in Japan is simpler [11, 12].
Materials and methods Of the 125 patients who were given a diagnosis of cervical spondylotic myelopathy and who underwent laminoplasty at our department-affiliated hospitals during the 3 years from September 2006 to August 2009, 19 patients who were under treatment at the urology department were excluded, because they may have poor urinary function, and the remaining 106 patients whose OABSS was collected 1 year after surgery were enrolled as the subjects of the study. All study protocols were approved by the ethics committee at our university (approval no. 1306). We certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during the course of this study. Preoperative myelography was performed on all the patients, and no patients were observed with distinct lumbar spinal canal stenosis. The mean age of patients at the time of surgery was 69.2 years (range 46–82 years). There were 62 men and 44 women. The operation was performed in all of these cases by the same surgeon. Double-door spinous processsplitting laminoplasty was performed in 85 cases and single-door spinous process-splitting laminoplasty in 21 cases. The OABSS system (Table 1) prepared in 2006 was used as the method of OAB determination, and any patient whose score for question 3 was C2 points and whose total score for questions 1, 2, and 4 was C3 points was identified as having OAB [13, 14]. Any patient whose score for question 3 was lower and whose total score for the four questions decreased after 1 year from the time of surgery in comparison with the pre-operation level was assessed as showing post-operative symptom improvement. OAB symptom prevalence and post-operative symptom improvement were investigated. The patients were classified into two groups, those who were identified as having OAB (OAB group) and those who were identified as not having OAB (non-OAB group), and the age, sex, preoperative Japanese Orthopaedic Association (JOA) score (Cervical Spondylotic Myelopathy Treatment Result Assessment Criteria established by the Japanese Orthopaedic Association; full score: 17 points), post-operative JOA score improvement (by Hirabayashi’s method), and the preoperative MRI cumulative score [15] to assess the compression condition of the cervical cord were compared between the two groups. With regard to the preoperative MRI cumulative score, one radiologist who was not involved in this study assessed the T1 and T2-weighted
23 Table 1 Overactive bladder symptom score (OABSS) Question
Frequency
Q1. How many times do you typically urinate from waking in the morning until sleeping at night?
B7
0
8*14
1
C15
2
Q2. How many times do you typically wake up to urinate from sleeping at night until waking in the morning?
0
0
1
1
2
2
C3
3
Q3. How often do you have a sudden desire to urinate, which is difficult to defer?
Q4. How often do you leak urine because you cannot defer the sudden desire to urinate
Score
Not at all
0
Less than once a week
1
Once a week or more
2
About once a day
3
2–4 times a day
4
5 times a day or more
5
Not at all
0
Less than once a week
1
Once a week or more
2
About once a day
3
2–4 times a day
4
5 times a day or more
5
Patients were instructed to circle the score that best applied to their urinary condition during the past week; the overall score was the sum of the four scores
sagittal planes of MRI by scoring each intervertebral compression extent in the dural duct and spinal cord from 0 to 5 points, after which the total score of intervertebral compressions was obtained. The Student t test or v2 test was used for statistic analysis, and P \ 0.05 was considered to indicate a significant difference.
Results Of the 106 patients, 50 were identified as having OAB, so symptom prevalence was 47.2 %. Of these 50 patients, symptom improvement was observed for 14 (28 %), only, 1 year after surgery. When the 50 patients in the OAB group were compared with the 56 patients in the non-OAB group, there was no significant difference between the two groups with regard to age and sex. Preoperative mean OABSS score was 7.1 ± 2.6 points in the OAB group and
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2.7 ± 1.6 points in the non-OAB group. Mean OABSS score 1 year after surgery was 5.8 ± 2.9 points in the OAB group and 2.9 ± 1.5 points in the non-OAB group (Table 2). Mean OABSS scores in the OAB group were significantly higher than that in the non-OAB group both preoperatively and postoperatively (P \ 0.01), but there were no significant differences between pre and postoperative data in both groups (P [ 0.05). Mean scores of each domain of OABSS in both groups are shown in Table 3. With regard to the clinical results, the mean JOA score 1 year after surgery was 13.5 ± 3.7 points versus 8.9 ± 3.4 points before surgery, indicating improvement of 56.8 ± 21.2 %. The pre-operative JOA score and postoperative JOA improvement tended to be somewhat lower in the OAB group than in the non-OAB group, but there were no significant differences between the two groups. Preoperative mean evaluation points of bladder function (perfect score: 3 points) in JOA score was 1.6 ± 1.2 points in the OAB group and 1.8 ± 0.7 points in the non-OAB group, whereas mean scores 1 year after surgery were 1.7 ± 0.8 points in the OAB group and 1.8 ± 0.9 points in Table 2 Summarized results. Comparison of the OAB and non-OAB groups OAB group
Non-OAB group
P value
Number of patients
50
56
Mean age at surgery (years)
71.3 (54–82)
68.9 (46–79)
[0.05
Male
32
30
[0.05
Female
18
26
7.1 ± 2.6
2.7 ± 1.6
\0.01
Postoperation Mean preoperative JOA score
5.8 ± 2.9 8.8 ± 3.1
2.9 ± 1.5 9.1 ± 2.9
\0.01 [0.05
Improvement of JOA score
54.9 ± 23.5 %
57.2 ± 20.9 % [0.05
Preoperative MRI cumulative score
14.9 (5–21)
12.1 (6–19)
Gender
Mean OAB Score Preoperation
[0.05
Table 3 Mean scores of each domain of the OABSS for the OAB and non-OAB groups OAB group
Q1
Non-OAB group
Preoperation
Postoperation
Preoperation
Postoperation
1.4 ± 0.7
1.3 ± 0.6
0.7 ± 0.6
0.7 ± 0.9
Q2
1.7 ± 0.8
1.4 ± 0.6
0.9 ± 0.6
0.8 ± 0.5
Q3 Q4
2.5 ± 0.7 1.5 ± 1.3
1.8 ± 0.9 1.2 ± 0.8
0.6 ± 0.5 0.8 ± 0.6
0.7 ± 0.6 0.9 ± 0.8
123
the non-OAB group. There were no significant differences between the two groups and no correlations between JOA bladder function score and OABSS score in either group pre and postoperatively. The preoperative MRI cumulative score was somewhat higher in the OAB group but there was no significant difference between the two groups (Table 2).
Discussion In 2003, the Neurogenic Bladder Society in Japan conducted an OABSS survey with regard to OAB among Japanese people 40 years old or older. As a result, it was estimated that approximately 7 % of the Japanese population (approx. 8,100,000 people) had OAB symptoms. With regard to the prevalence of OAB symptoms by age stratum, the proportions of people with the corresponding symptoms were 12.1 % among those in their 60s, 22.6 % among those in their 70s, and 36.8 % among those 80 years old or older, indicating an increase in symptom prevalence with aging [16]. The causes of OAB are approximately classified into three types: neurogenic, non-neurogenic, and idiopathic [17]. Neurogenic OAB includes the diseases attributable to disorders in the brain, pons, and spinal cord, whereas nonneurogenic OAB is caused by prostate hypertrophy in males and reduced pelvic muscle strength in females after giving birth [17, 18]. OAB whose cause is unknown is classified as idiopathic. It is reported that the prevalence of idiopathic OAB is the highest among these three causes [17, 19]. According to the results of this study, the appearance of OAB was not clearly reflected in the clinical results and image findings, suggesting that many OAB cases are attributable to an idiopathic rather than neurogenic cause. Mochida et al. [20] observed neurogenic bladder in 22 (36.7 %) of 60 patients with cervical spondylotic myelopathy and reported that OAB was detected in 13 (21.7 %) patients on the basis of results from cystometry. However, the diagnostic criteria for OAB were not clear and idiopathic or non-neurogenic patients were inevitably excluded from their study. Although it is believed the OABSS has high sensitivity and low specificity, it was recommended as the diagnosis guideline in 2009 and has become a standard diagnosis tool for OAB [13, 14]. When subjects with a mean age of 69.2 years were investigated by use of the OABSS system in this study, OAB incidence was 47.2 % (nearly half) among patients with cervical spondylotic myelopathy, which is higher than the 22.6 % among the Japanese population in their 70 s reported by Japanese Neurogenic Bladder Society [16]. In this study we thus assumed that approximately half of our
OAB in cervical spondylotic myelopathy
OAB patients had cervical spondylotic myelopathy, which caused neurogenic bladder as a result of cervical cord compression, and that the other cases were non-neurogenic or idiopathic. In general, orthopedic surgeons tend to consider overactive bladder is equivalent to neurogenic bladder. However, post-operative improvement was observed in only 14 (28 %) of 50 patients in this study. The possibility that irreversible change had already occurred in the spinal cord of patients may be a reason for such poor post-operative OAB improvement. It is more likely that OAB was most frequently attributable to non-neurogenic and idiopathic causes. The authors suggest it is necessary for orthopedic surgeons to explain sufficiently to cervical spondylotic myelopathy patients with possible neurogenic bladder, when obtaining informed consent, that the possibility of improvement of OAB is low even if cervical laminoplasty is performed. Because this study is the first in the world to use the OABSS system to investigate OAB symptom prevalence and post-operative improvement among patients with cervical spondylotic myelopathy, the results obtained may be regarded as valuable. However, there are several limitations to this study. First, a possibility cannot be denied that the excluded patients with urinary cancer may have neurogenic bladder. Second, there was no control group comprising healthy volunteers. Third, much of the pathology of OAB remains unknown because urological X-ray tests, MRI, scintigraphy, echography, urological endoscopy, and urodynamics tests were not performed as part of this study. The authors intend to continue research in this direction by, as far as possible, conducting urological tests for patients determined to have OAB and investigating cervical MRI and myelo-CT images in detail to elucidate OAB pathology among patients with cervical spondylotic myelopathy. Conflict of interest This manuscript does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly to the subject of this manuscript.
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