Evaluation of the Longus Colli Muscle in Relation to Stellate Ganglion Block

Background and Objectives: The longus colli (LC) muscle is an important structure of the anterior cervical spine and has a critical role in stellate ganglion block. This technique involves withdrawing the needle to locate its port for injection above the anterior surface of the LC muscle; however, its exact thickness at the C5, C6, and C7 levels has not been measured. The aim of this anatomic and magnetic resonance-supported study was to evaluate the thickness of the LC muscle at these levels from the anterior tubercle of each vertebra toward the vertebral body at 5-, 10-, and 15-mm distances to provide precise anatomic data for stellate ganglion block. Methods: Ten cadavers, 60 vertebral body specimens, and cervical magnetic resonance imaging (MRI) scans of 40 adult patients were used for measurements. Results: The main findings of this study are that the thickness of the LC muscle varies between 5.0 and 10.0 mm at C6 and C7 in cadavers and between 8.0 and 10.0 mm in MRI scans. Sex has an important role; MRI scans revealed that male patients have a considerably thicker LC muscle at each vertebral level. Conclusion: We found a highly variable thickness of the LC muscle in anatomic and imaging studies, which may lead to negative block results.