Successful Identification and Assessment of the Superior Cluneal Nerves with High-Resolution Sonography

Background: Low back pain is a disabling and common condition, whose etiology often remains unknown. A suggested, however rarely considered, cause is neuropathy of the medial branch of the superior cluneal nerves (mSCN)-either at the level of the originating roots or at the point where it crosses the iliac crest, where it is ensheathed by an osseo-ligamentous tunnel. Diagnosis and treatment have, to date, been restricted to clinical assessment and blind infiltration with local anesthetics. Objective: To determine whether visualization and assessment of the mSCN with high-resolution ultrasound (HRUS) is feasible. Study Design: Interventional cadaver study and case series. Methods: Visualization of the mSCN was assessed in 7 anatomic specimens, and findings were confirmed by HRUS-guided ink marking of the nerve and consecutive dissection. Further, a patient chart and image review was performed of patients assessed at our department with the diagnosis of mSCN neuropathy. Results: The mSCN could be visualized in 12 of 14 cases in anatomical specimens, as confirmed by dissection. Nine patients were diagnosed with mSCN syndrome of idiopathic or traumatic origin. Diagnosis was confirmed in all of them, with complete resolution of symptoms after HRUSguided selective nerve block. Limitations: These findings are first results that need to be evaluated in a systematic, prospective and controlled manner. Conclusion: We hereby confirm that it is possible to visualize the mSCN in the majority of anatomical specimens. The patients described may indicate a higher incidence of mSCN syndrome than has been recognized. mSCN syndrome should be considered in patients with low back pain of unknown origin, and HRUS may be able to facilitate nerve detection and US-guided nerve block.