Synopsis
Use mediastinal compartments, pleural reflections, lung-root relations, great vessels, nerves and lymphatic pathways to solve clinically applied thoracic anatomy problems.
- The mediastinum is divided by the transverse thoracic plane from the sternal angle to the T4–T5 disc into superior and inferior regions; the inferior region is further anterior, middle and posterior.
- At the lung root the phrenic nerve passes anteriorly and the vagus passes posteriorly, a relation that predicts which nerve is endangered by dissection on either surface.
- The left recurrent laryngeal nerve loops beneath the aortic arch near the ligamentum arteriosum, linking hoarseness to disease or intervention at the aortopulmonary window.
Reasoning priorities
Assign a mass or structure to a mediastinal compartment at a defined vertebral level.
Use sternum, pericardium, trachea, oesophagus and vertebral body as anchors, then trace the lesion on adjacent slices before attaching a compartment label.
Worked reasoning
A supplied contrast CT description places a mass beneath the left aortic arch beside the ligamentum arteriosum; the patient has new hoarseness but preserved diaphragmatic movement.
- Fix the level at the aortopulmonary window and identify the aortic arch, left pulmonary artery and ligamentum region as the spatial inputs.
- Trace the left vagus down the thorax and its recurrent laryngeal branch looping under the arch before ascending in the tracheoesophageal groove.
- Use preserved diaphragm movement to reduce support for phrenic dysfunction while recognising that this does not define mass histology.
- Conclude that left recurrent laryngeal involvement is anatomically plausible and predicts impaired laryngeal motor function requiring direct assessment.
- Verify by checking vocal-fold movement and the full imaging extent; do not infer malignant invasion merely from adjacency and hoarseness.