Prevalence of neuropathic pain in cases with chronic pain related to spinal disorders
The incidence and characteristics of neuropathic pain associated with spinal disorders have not yet been fully clarified. The purpose of this study was to investigate the prevalence of neuropathic pain and the degree of deterioration of quality of life (QOL) in patients with chronic pain associated with spinal disorders who visited orthopedic outpatient clinics.
This cross-sectional study was conducted in 1,857 patients recruited from 137 medical institutions nationwide. Participants were men and women aged 20–79 years with a history of spine-related pain for at least 3 months and a visual analog scale (VAS) score of at least 30 in the previous week. Patients were screened using a neuropathic pain screening questionnaire. The degree of QOL deterioration and its correlation with the presence of neuropathic pain were assessed using the Short Form Health Survey with 36 questions (SF-36).
Overall prevalence of neuropathic pain was 53.3 %. It was relatively high in patients with cervical spondylotic myelopathy (77.3 %) and ligament ossification (75.7 %) and relatively low in those with low back pain (29.4 %) and spondylolysis (40.4 %). Only 56.9 % of patients with radiculopathy were diagnosed with neuropathic pain. Logistic regression analysis identified several risk factors, including advanced age, severe pain, disease duration of at least 6 months, and cervical lesions. In QOL assessment, physical functioning, role-physical, role-emotional, and social functioning were severely affected, and this trend was more pronounced in patients who were more likely to have neuropathic pain.
The frequency of neuropathic pain tended to be higher in patients with diseases associated with spinal cord damage and lower in patients with diseases that primarily manifested as somatic pain. A bias toward allodynia symptoms in the screening questionnaire may have resulted in the failure to diagnose neuropathic pain in some patients with radiculopathy. Poor QOL, primarily from the aspect of physical functioning, was demonstrated in patients with neuropathic pain associated with spinal disorders.
A significant number of people in the general population appear to suffer from chronic pain arising from the musculoskeletal system. According to a survey conducted by Nakamura et al. , 15.4 % of Japanese adults have chronic pain arising from the musculoskeletal system. The most commonly affected site (65 %) is the lumbar region, followed by neck and shoulder regions (55 % each), indicating a high incidence of chronic pain related to disorders of the spine.
Based on the mechanism of pain onset, chronic musculoskeletal pain has been classified into two types: (1) chronic nociceptive pain arising from deformation and inflammation of the bone(s), joint(s) and/or other spinal tissues; and (2) neuropathic pain caused by damage to nerve tissues per se. Spinal disorders often involve damage to nerve tissues, such as the spinal cord, nerve roots, and cauda equina, which gives rise to neuropathic pain. Neuropathic pain may also occur concurrently with nociceptive pain arising from involvement of intervertebral discs and paraspinal muscles. However, incidence and clinical features of neuropathic pain associated with spinal disorders have not yet been clearly elucidated.
Under the initiative of the Japanese Society for Spine Surgery and Related Research (JSSR), a study was conducted to determine the prevalence of neuropathic pain and the degree of quality of life (QOL) deterioration in patients with chronic pain associated with spinal disorders who visited orthopedic outpatient clinics in Japan. Results are reported herein.
Patients and methods
This was a cross-sectional study conducted on outpatients recruited from 137 Japanese medical institutions. Participant institutions were required to employ at least one board-certified spine surgeon approved by JSSR and to be an orthopedic hospital with at least 20 beds, a general hospital, or a university hospital. Participating institutions were selected from regions throughout the country: ten from Hokkaido, nine from Tohoku, ten from North Kanto, 35 from South Kanto, 11 from Tokai, seven from Hokuriku, 24 from Kansai, 13 from Chugoku-Shikoku, and 18 from Kyushu. The number of institutions was allocated according to the number of approved surgeons in each geographical area, with 10–20 patients recruited from each institution. The study was initiated in March 2010 and completed in November of the same year. The study protocol was approved by the institutional ethics committee of each participating institution.
The study participants were patients judged by spine surgeons to meet all of the following criteria:
1. Chronic pain persisting for at least 3 months
2. Spine-related pain (including in those who have undergone surgery)
3. Visual analogue scale (VAS) score of at least 30 during the previous 1 week
4. Age 20–79 years
5. Capable of filling out the questionnaire in Japanese without assistance
Patients meeting any of the following criteria were excluded from the study:
1. History of receiving nerve-block therapy in the previous 6 months
2. Pain arising from the spine, as well as from other tissues/organs
3. Being an inpatient
4. Severe paralysis
5. Incapable of giving consent due to the presence of complications
Patient background characteristics
Male gender (%)
63.4 ± 12.6
Body weight (kg)
60.4 ± 11.8
159.7 ± 9.1
Body mass index (kg/m2)
23.6 ± 3.6
Current pain (VAS; mm)
54.0 ± 25.0
Duration of pain (months)
47.4 ± 62.1
Level of the spinal disorder
324 (17.4 %)
108 (5.8 %)
1,537 (82.8 %)
7 (0.4 %)
1,442 (77.7 %)
70 (3.8 %)
174 (9.4 %)
167 (9.0 %)
42 (2.3 %)
148 (8.0 %)
200 (10.8 %)
553 (29.8 %)
325 (17.5 %)
14 (0.8 %)
Lumbar spinal stenosis
Intervertebral disc disorders
Cervical spondylotic myelopathy
Nerve root damage
Low back pain
Spine/spinal cord injury
Iatrogenic spinal disorder
Spine/spinal cord tumor
Infectious spondylitis/intervertebral discitis
Other types of spondylitis
Other types of neurological disorders
Questions on the nature of pain
There is a pinprick-like pain
There is an electric shock-like pain
There is a tingling burning pain
There is a pain with strong numbness
Only a light touch with clothing or cold wind causes a pain
Site of pain has decreased or increased sensation
Site of pain shows skin swelling and/or discoloration to red or purple
Logistic regression analysis was performed using factors with the potential to affect the result of judgment on the presence/absence of neuropathic pain in order to identify the risk factors for a ++ result. Variables were gender, age, severity of the current pain (VAS), duration of pain, and level of the spinal disorder.
The Short Form Health Survey with 36 items (SF-36) was used for health status. For each SF-36 subscale—physical functioning, role-physical, bodily pain, general health, vitality, social functioning, role-emotional, mental health—raw scores were calculated and converted to the 0–100 scoring system and then to the norm-based scoring [mean of the Japanese national standard is 50, with a standard deviation (SD) of 10] [3, 4, 5]. Possible correlations between assessment results for neuropathic pain and scores for individual subscales of tge SF-36 were assessed. Statistical analysis was performed using the software R 2.13.0 (R Foundation for Statistical Computing, Department of Statistics and Mathematics Wirtschafts Universitat, Wien, Austria).
Prevalence of neuropathic pain
Correlation between assessment of neuropathic pain and patient background factors
Correlation between assessment of neuropathic pain and type of medical treatment received
Factors affecting the of judgment on presence/absence of neuropathic pain
Risk factors for the presence of neuropathic pain identified by logistic regression
Not adjusted OR (95 % CI)
Adjusted OR (95 % CI)
Current pain score (VAS)a
10 to <50 mm
50 to <80 mm
80 to <100 mm
Level of spinal disordera,b
Gender had no effect on assessment results of neuropathic pain. Multiple regression analysis by age showed that the OR was 2.72 for the age group 41–69 years and 3.75 for those aged ≥70 years vs the age group ≤40 years; thus, the ratio increased with age. As for pain severity, OR for VAS scores 10 to <50 vs <10 was 2.33; furthermore, OR doubled for VAS scores 50 to <80 and doubled again for VAS scores ≥80. OR was 1.73 for pain duration ≥6 months vs <6 months. OR for cervical-level involvement vs lumbar/sacral-level involvement was 3.20.
Correlation between degree of QOL deterioration and neuropathic pain severity
According to the International Association for the Study of Pain, neuropathic pain is defined as pain caused by a lesion or disease of the somatosensory nervous system. A representative example of neuropathic pain associated with spinal disorders includes pain caused by compression or damage to the spinal cord or the nerve roots.
In their review, Sadosky et al.  reported the incidences of neuropathic pain in various diseases as follows: herpes zoster (postherpetic neuralgia) 7–27 %; diabetes (diabetic neuropathy) 9–22 %; cerebral stroke (poststroke pain); 8–11 %; spinal cord injury (postspinal cord injury pain) 10–80 %. Compared with their data, the incidence of neuropathic pain of 53.3 % in our survey of patients with spinal disorders is relatively high. However, our participants were limited to those who had chronic pain for at least 3 months, and the incidence may have been lower if we had also included spinal disorder patients who did not have a history of pain for such a long period of time.
Logistic regression analysis was carried out in this study to identify risk factors for the presence of neuropathic pain rated as ++. Specificity is important for a logistic analysis in order to identify factors predictive of neuropathic pain. Ogawa et al.  reported that when the screening score was ≥4 (i.e., corresponding to ratings of + or ++), specificity and sensitivity were 71.7 % and 87.7 %, respectively, which is appropriate for screening but insufficient for a logistic regression analysis. In contrast, the specificity of 89.1 % for a score ≥5 (i.e., corresponding to a rating of ++) is appropriate to conduct a logistic regression analysis. In our study, variables used in the logistic regression analysis were gender, age, severity of current pain (VAS), duration of pain, and level of the spinal disorder. The basic analysis showed no strong correlations among these variables. Logistic regression analysis identified the following risk factors for the presence of neuropathic pain: advanced age, severe pain, disease duration of at least 6 months, and a cervical-level lesion. These results indicate that the more severe the damage to the nerve tissue, the higher the incidence of neuropathic pain.
In the survey of medical treatments, NSAIDs were by far the most frequently used medications overall (~77 %). NSAIDs are effective for relieving nociceptive pain but are considered to be ineffective, in principle, for treating neuropathic pain. Anticonvulsants, which are effective in treating neuropathic pain, were used slightly more often in the ++ group than in the other groups, but the proportion was still only about 16 %. In October 2010, when our study was about to be completed, the anticonvulsant drug pregabalin was approved in Japan for insurance-covered treatment of peripheral neuropathic pain. Therefore, its may have increased after this study in the patients who were evaluated as having neuropathic pain.
When data were summarized by disease, the incidence of neuropathic pain was low in conditions such as low back pain and spondylolysis, which, as the names themselves indicate, represent spinal-tissue-related pain, i.e., somatic pain. The incidence was high in diseases such as cervical spondylotic myelopathy and spine/spinal cord injury, the names of which suggest neuropathic conditions. However, only 57 % of patients with nerve root damage were diagnosed as having neuropathic pain. According to the above-mentioned definition by the International Association for the Study of Pain, patients with nerve root damage (radiculopathy) should always be diagnosed as having neuropathic pain, because the name of the disease itself suggests it. This discrepancy between disease name and diagnosis results can be attributed to the characteristics of the neuropathic pain screening questionnaire we used in the survey. The questionnaire comprised seven components that were biased toward allodynia symptoms, such as “Only a light touch with clothing or cold wind causes a pain,” and “There is a tingling, burning pain.” However, in actual clinical situations, allodynia symptoms are less frequently seen in cases of nerve root damage associated with intervertebral disc herniation, etc. In the future, we anticipate the development of a diagnostic tool that can be applied for neuropathic pain both with and without allodynia.
On the other hand, approximately 30 % of patients with low back pain were diagnosed as having neuropathic pain, although low back pain manifests primarily as somatic pain via nociceptive mechanisms. Therefore, this result also indicates a limitation of this screening tool in that patients with nociceptive pain may receive a diagnosis of neuropathic pain if allodynia-like symptoms are present. However, low back pain may be associated with neuropathic pain in some cases when some kind of damage to the peripheral nervous tissues in the lumbar spine and surrounding areas is present or neuroplastic changes have developed in the synapses of the dorsal horn of the spinal cord as a result of prolonged afferent nociceptive signals (central sensitization). Freynhagen et al.  reported that 37 % of patients with chronic low back pain had some factor suggestive of neuropathic pain. Because our study assessed only 17 patients with low back pain, additional studies with a larger sample size of participants with low back pain are warranted.
The study was conducted with the collaboration of the following executive committee members in regional blocks nationwide. Manabu Ito (Hokkaido), Yushin Ishii, Shin-ichi Konno (Tohoku), Atsushi Seichi (North Kanto), Yasuaki Tokuhashi, Kazuhiro Chiba (South Kanto), Yukihiro Matsuyama, Hideo Hosoe (Tokai), Norio Kawahara, Yoshiharu Kawaguchi (Hokuriku), Hiroaki Nakamura, Motoki Iwasaki (Kinki), Toshihiko Taguchi, Toru Hasegawa, Shinichiro Taniguchi (Chugoku-Shikoku), Hiroaki Konishi (North Kyushu), and Kazunori Yone (South Kyushu). This study was sponsored and funded by the Pfizer Japan Inc.
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