Department of Orthopaedic Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
J Neurosurg. 2012 Nov;117(5):890-6. doi: 10.3171/2012.8.JNS111734. Epub 2012 Sep 7.
The diaphragmatic height index (DHI) was developed to measure the difference in diaphragm levels. The purpose of this study was to set definite DHI values and test the accuracy of these values for use as a new diagnostic test for phrenic nerve dysfunction.
All data for this study were obtained from medical charts and retrospectively reviewed.
One hundred sixty-five patients with brachial plexus injury who had undergone nerve transfers between 2005 and 2008 were divided into Groups A and B. Group A consisted of 40 patients (mean age 28.0 years) who had sustained concomitant injury of the brachial plexus and phrenic nerves. Patients in Group A1 had right phrenic nerve injury and those in Group A2 had left phrenic nerve injury. Intraoperative direct electrical stimulation of the phrenic nerve was considered the gold standard in assessing nerve function in all patients with brachial plexus injury. Group B consisted of 125 patients (mean age 28.7 years) with brachial plexus injury and normal phrenic nerve function. Group C, the control group, consisted of 80 patients with nonbrachial plexus injury (mean age 34.0 years) who had undergone other kinds of orthopedic operations between April and June 2009. Standard posteroanterior chest radiographs were blindly interpreted using the Siriraj inhouse picture archiving and communication system in all 245 patients in the study. First, a reference line (R line) was drawn along the inferior endplate of T-10. Then, 2 lines (lines A and B) were drawn through the highest point of each diaphragm and parallel to the R line. The difference between these 2 lines divided by the height of T-10 was defined as the DHI. The cutoff points of the DHI for diagnosing right and left phrenic nerve dysfunction were analyzed with a receiver operating characteristic curve. The accuracy of these DHI values was then evaluated. The DHI in Group C was 0.64 ± 0.44, slightly higher than the DHI in Group B, with no significant difference. Diaphragmatic height indexes in Groups A1 and A2 were 2.0 ± 0.99 and -1.04 ± 0.83, respectively, which were significantly different from those in Groups B and C (p < 0.05). The cutoff point of the DHI for diagnosing right phrenic nerve dysfunction was > 1.1, and that for left phrenic nerve dysfunction was < 0.2. The sensitivity and specificity of right and left DHI values were 90.5% and 86.3%, and 94.7 and 88.3%, respectively.
Data in this study show that diaphragm paralysis can be simply and reliably predicted by the DHI. Diaphragmatic height index values > 1.1 and < 0.2 are proposed as the new diagnostic test for right and left phrenic nerve dysfunction with a high degree of accuracy. This index is applicable in diagnosing phrenic nerve dysfunction that occurs concomitantly with brachial plexus injury or from other etiologies.
膈肌高度指数（DHI）用于测量膈肌水平的差异。本研究的目的是设定明确的 DHI 值，并测试这些值作为一种新的膈神经功能障碍诊断测试的准确性。
本研究所有数据均来自病历，并进行回顾性分析。
2005 年至 2008 年间接受神经转移术的 165 例臂丛损伤患者分为 A 组和 B 组。A 组包括 40 例患者（平均年龄 28.0 岁），伴有臂丛和膈神经同时损伤。A1 组患者右侧膈神经损伤，A2 组患者左侧膈神经损伤。所有臂丛损伤患者均采用术中膈神经直接电刺激作为评估神经功能的金标准。B 组包括 125 例（平均年龄 28.7 岁）臂丛损伤且膈神经功能正常的患者。C 组为对照组，包括 80 例（平均年龄 34.0 岁）非臂丛损伤患者，他们于 2009 年 4 月至 6 月间接受了其他类型的骨科手术。在研究的 245 例患者中，均使用 Siriraj 内部图像存档和通信系统进行盲法解读标准后前位胸部 X 线片。首先，沿 T-10 下终板绘制参考线（R 线）。然后，通过每个膈肌的最高点绘制两条线（线 A 和线 B），并与 R 线平行。这两条线之间的差值除以 T-10 的高度定义为 DHI。使用受试者工作特征曲线分析 DHI 诊断右侧和左侧膈神经功能障碍的截断值。然后评估这些 DHI 值的准确性。C 组的 DHI 为 0.64 ± 0.44，略高于 B 组，但无显著差异。A1 组和 A2 组的膈肌高度指数分别为 2.0 ± 0.99 和-1.04 ± 0.83，与 B 组和 C 组有显著差异（p < 0.05）。诊断右侧膈神经功能障碍的 DHI 截断值为> 1.1，诊断左侧膈神经功能障碍的 DHI 截断值为< 0.2。右侧和左侧 DHI 值的灵敏度和特异性分别为 90.5%和 86.3%，94.7%和 88.3%。
本研究数据表明，膈肌麻痹可以通过 DHI 简单可靠地预测。建议 DHI 值> 1.1 和< 0.2 作为诊断右侧和左侧膈神经功能障碍的新诊断测试，具有较高的准确性。该指数适用于诊断同时伴有臂丛损伤或其他病因的膈神经功能障碍。
