Prospective study of superior cluneal nerve disorder as a potential cause of low back pain and leg symptoms

Abstract

Background: Entrapment of the superior cluneal nerve (SCN) in an osteofibrous tunnel has been reported as a cause of low back pain (LBP). However, there are few reports on the prevalence of SCN disorder and there are several reports only on favorable outcomes of treatment of SCN disorder on LBP. The purposes of this prospective study were to investigate the prevalence of SCN disorder and to characterize clinical manifestations of this clinical entity.

Methods: A total of 834 patients suffering from LBP and/or leg symptoms were enrolled in this study. Diagnostic criteria for suspected SCN disorder were that the maximally tender point was on the posterior iliac crest 70 mm from the midline and that palpation of the tender point reproduced the chief complaint. When patients met both criteria, a nerve block injection was performed. At the initial evaluation, LBP and leg symptoms were assessed by visual analog scale (VAS) score. At 15 min and 1 week after the injection, VAS pain levels were recorded. If insufficient pain decrease or recurrence of pain was observed, injections were repeated weekly up to three times. Surgery was done under microscopy. Operative findings of the SCN and outcomes were recorded.

Results: Of the 834 patients, 113 (14%) met the criteria and were given nerve block injections. Of these, 54 (49%) had leg symptoms. Before injection, the mean VAS score was 68.6 ± 19.2 mm. At 1 week after injection, the mean VAS score significantly decreased to 45.2 ± 28.8 mm (p < 0.05). Ninety-six of the 113 patients (85%) experienced more than a 20 mm decrease of the VAS score following three injections and 77 patients (68%) experienced more than a 50% decrease in the VAS score. Surgery was performed in 19 patients who had intractable symptoms. Complete and almost complete relief of leg symptoms were obtained in five of these surgical patients.

Conclusions: SCN disorder is not a rare clinical entity and should be considered as a cause of chronic LBP or leg pain. Approximately 50% of SCN disorder patients had leg symptoms.

Figure 1

Photos during surgical superior cluneal nerve (SCN) release in case 9. Two branches of the SCN were identified within 5 cm above the iliac crest (dotted line) to be seen to emerge from beneath the lateral margin of the deep layer of fibro-thoraco-lumbar fascia. A blue tape has been used to lift and highlight a branch which remained compressed by the fascia (arrow). Curved arrow indicates another branch of SCN (A). Underneath these branches, the two other anastomosing branches were identified and a total of four branches were released (B).

Figure 2

Chief complaints of 113 subjects meeting the criteria for suspected superior cluneal nerve disorder. Of the 113 subjects meeting both criteria, 59 (52%) have only low back pain (LBP), 53 (47%) have LBP with leg symptoms, and 1 (1%) has only leg pain.

Figure 3

Distribution of vertebral fractures. Twenty-nine patients had multiple fractures.

Figure 4

X-ray in a 70-year-old SCN patient. A collapsed vertebral fracture at L1 is shown (arrow).

Figure 5

Changes in VAS scores of 113 subjects suspected with superior cluneal nerve disorder. The line graph shows the changes in VAS scores before, 15 min, and 1 week after nerve block injections of 113 patients meeting the both criteria for suspected superior cluneal nerve disorder. The mean VAS score is 68.6 ± 19.2 mm (25–100 mm) before injection. At 15 min after injection, the mean VAS score is 31.6 ± 27.0 mm (0–100 mm), a significant decrease (p < 0.05). At 1 week after injection, the VAS scores significantly decrease to 45.2 ± 28.8 mm (0–100 mm) (p < 0.05). If insufficient pain decrease or recurrence of pain was observed, injections were repeated every week up to three times, or until sufficient pain relief was obtained. Fifty-three (47%) patients required a second injection, and 28 (25%) patients required a third time injection.

Figure 6

Clinical manifestations in case 7. Image drawn by the patient showing leg pain remote from the iliac crest.

Figure 7

Pseudo limitation in lumbar flexion in case 16. Remarkable limitation in flexion had been very disruptive to her daily living and she is showing that she had been unable to pick up her stick from the floor (A). But, she could pick it up when the right hip was extended (B).