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Background <p>The phrenic nerve provides the sole motor innervation to the diaphragm, and terminal injury can lead to respiratory dysfunction. Although its proximal anatomy is well described, side-specific information on terminal branching at the diaphragm remains limited. This study aimed to characterize the phrenic nerve’s terminal course, branching pattern, and spatial relationships at the diaphragm.</p> Methods <p>Thirty-six hemidiaphragms from 18 fresh human anatomical specimens were examined. The number and orientation of visible terminal branches before diaphragmatic penetration, the shortest distance from the initial terminal branching point to the diaphragm, the thickness of the terminal diaphragmatic segment of the phrenic nerve before visible branching, and relationships to the central tendon, pericardium, and inferior vena cava were recorded. Branching orientation was described primarily by anatomical direction and secondarily by a clock-face model for each hemidiaphragm.</p> Results <p>The right phrenic nerve gave rise to 3.5 ± 0.6 branches (range, 3–5), and the left to 3.0 ± 1.49 branches (range, 1–7). Direct diaphragmatic entry without visible branching before diaphragmatic penetration was observed in three left-sided specimens. The shortest distance from the initial terminal branching point to the diaphragm was greater on the right than on the left (21.01 ± 7.00&#xa0;mm versus 10.74 ± 3.81&#xa0;mm; <i>p</i> &lt; 0.001). The thickness of the terminal diaphragmatic segment before visible branching did not differ significantly between sides (right: 2.64 ± 0.75&#xa0;mm; left: 2.36 ± 0.70&#xa0;mm; <i>p</i> = 0.111). The most frequent branching direction was anterolateral bilaterally, and no branch was observed exactly along the 9 o’clock axis in either hemidiaphragm.</p> Conclusion <p>The terminal anatomy of the phrenic nerve showed side-specific asymmetry at the diaphragm. The clock-face model provided a standardized method for mapping the orientation of visible terminal branches. These macroscopic findings should be interpreted as anatomical observations and may guide future histological, functional, and surgical studies.</p>

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Terminal Anatomy of the Phrenic Nerve: Branching Patterns and Spatial Relationships at the Diaphragm

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Mehmet Aydin,
  • Tulin Sen Esmer,
  • Mehmet Yilmaz,
  • Zekiye Gozde Kara,
  • Sait Ozsoy,
  • Yasin Baris Seven,
  • Halil Ibrahim Acar

摘要

Background

The phrenic nerve provides the sole motor innervation to the diaphragm, and terminal injury can lead to respiratory dysfunction. Although its proximal anatomy is well described, side-specific information on terminal branching at the diaphragm remains limited. This study aimed to characterize the phrenic nerve’s terminal course, branching pattern, and spatial relationships at the diaphragm.

Methods

Thirty-six hemidiaphragms from 18 fresh human anatomical specimens were examined. The number and orientation of visible terminal branches before diaphragmatic penetration, the shortest distance from the initial terminal branching point to the diaphragm, the thickness of the terminal diaphragmatic segment of the phrenic nerve before visible branching, and relationships to the central tendon, pericardium, and inferior vena cava were recorded. Branching orientation was described primarily by anatomical direction and secondarily by a clock-face model for each hemidiaphragm.

Results

The right phrenic nerve gave rise to 3.5 ± 0.6 branches (range, 3–5), and the left to 3.0 ± 1.49 branches (range, 1–7). Direct diaphragmatic entry without visible branching before diaphragmatic penetration was observed in three left-sided specimens. The shortest distance from the initial terminal branching point to the diaphragm was greater on the right than on the left (21.01 ± 7.00 mm versus 10.74 ± 3.81 mm; p < 0.001). The thickness of the terminal diaphragmatic segment before visible branching did not differ significantly between sides (right: 2.64 ± 0.75 mm; left: 2.36 ± 0.70 mm; p = 0.111). The most frequent branching direction was anterolateral bilaterally, and no branch was observed exactly along the 9 o’clock axis in either hemidiaphragm.

Conclusion

The terminal anatomy of the phrenic nerve showed side-specific asymmetry at the diaphragm. The clock-face model provided a standardized method for mapping the orientation of visible terminal branches. These macroscopic findings should be interpreted as anatomical observations and may guide future histological, functional, and surgical studies.