Weaver M Libby, Hicks Caitlin W, Fritz Jan, Black James H, Lum Ying Wei
Division of Vascular Surgery and Endovascular Therapy, Johns Hopkins University School of Medicine, Baltimore, MD.
Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD.
Ann Vasc Surg. 2019 Aug;59:28-35. doi: 10.1016/j.avsg.2019.01.023. Epub 2019 Apr 19.
Local anesthetic (LA) blocks of the anterior scalene muscle are used to predict which patients with neurogenic thoracic outlet syndrome (TOS) may benefit from surgical decompression. The block is thought to work through both analgesic and muscle relaxation effects, but evidence of the latter is lacking. The aim of our study was to assess the effects of LA blocks on anterior scalene muscle anatomy as captured by magnetic resonance imaging (MRI).
Over a two-year period, a series of patients with neurogenic TOS underwent MRI-guided anterior scalene blocks with an LA. Patients underwent MRI both before injection and 30 minutes after injection. Anterior scalene muscle heights (measured from the superior border of the first rib to the top of C3 vertebrae) before and after injection were compared for the injected side and the noninjected (control) side, both overall and stratified by subjective patient response to injection.
A total of 54 patients with neurogenic TOS were included. The median age was 39 years (interquartile range, 27-45), 61% were women, and 46% had a history of neck trauma. Forty-five patients (83%) had a favorable response to injection. Overall, there was no significant change in scalene muscle height for either the injected side (preinjection: 90.0 ± 1.2 mm vs. postinjection: 90.7 ± 1.2; P = 0.12) or the control side (preinjection: 89.3 ± 1.4 mm vs. postinjection: 88.9 ± 1.3 mm; P = 0.83). However, when stratified by patient response, those with a positive response had a larger increase in muscle height for the injected side than for the control side (change in baseline: 0.65 ± 0.58 mm vs. -0.53 ± 0.48 mm; P = 0.05). In contrast, nonresponders had no significant change in scalene height for either the injected or control side (change in baseline: 0.59 ± 1.30 mm vs. 0.37 ± 1.07; P = 1.00). Notably, responders had significantly longer anterior scalene muscles at baseline than nonresponders (92.2 ± 1.1 mm vs. 79.5 ± 2.5; P < 0.001).
LA blocks of the anterior scalene muscle may provide symptomatic relief in patients with neurogenic TOS by increasing muscle height, although the clinical significance of this small change is unclear. Patients who do not have a response to the block tend to have significantly shorter anterior scalene muscle heights than patients who respond, suggesting an anatomic difference in responders versus nonresponders.
前斜角肌局部麻醉阻滞用于预测哪些神经源性胸廓出口综合征（TOS）患者可能从手术减压中获益。该阻滞被认为通过镇痛和肌肉松弛作用起效，但后者的证据尚缺乏。我们研究的目的是评估局部麻醉阻滞对磁共振成像（MRI）所显示的前斜角肌解剖结构的影响。
在两年时间里，一系列神经源性TOS患者接受了MRI引导下的前斜角肌局部麻醉阻滞。患者在注射前和注射后30分钟均接受了MRI检查。比较注射侧和未注射（对照）侧注射前后的前斜角肌高度（从第一肋上缘至C3椎体顶部测量），整体比较以及根据患者对注射的主观反应进行分层比较。
共纳入54例神经源性TOS患者。中位年龄为39岁（四分位间距，27 - 45岁），61%为女性，46%有颈部外伤史。45例患者（83%）对注射有良好反应。总体而言，注射侧（注射前：90.0±1.2mm vs.注射后：90.7±1.2mm；P = 0.12）和对照侧（注射前：89.3±1.4mm vs.注射后：88.9±1.3mm；P = 0.83）的斜角肌高度均无显著变化。然而，根据患者反应分层时，有阳性反应者注射侧肌肉高度的增加大于对照侧（基线变化：0.65±0.58mm vs. -0.53±0.48mm；P = 0.05）。相比之下，无反应者注射侧或对照侧的斜角肌高度均无显著变化（基线变化：0.59±1.30mm vs. 0.37±1.07mm；P = 1.00）。值得注意的是，有反应者基线时的前斜角肌明显比无反应者长（92.2±1.1mm vs. 79.5±2.5mm；P < 0.001）。
前斜角肌局部麻醉阻滞可能通过增加肌肉高度为神经源性TOS患者提供症状缓解，尽管这一微小变化的临床意义尚不清楚。对阻滞无反应的患者其前斜角肌高度往往比有反应的患者显著更短，提示有反应者与无反应者存在解剖学差异。
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