Spontaneous pneumomediastinum and Macklin effect: Overview and appearance on computed tomography

Abstract

Spontaneous pneumomediastinum (SPM) is described as free air or gas located within the mediastinum that is not associated with any noticeable cause such as chest trauma. SPM has been associated with many conditions and triggers, including bronchial asthma, diabetic ketoacidosis, forceful straining during exercise, inhalation of drugs, as well as other activities associated with the Valsalva maneuver. The Macklin effect appears on thoracic computed tomography (CT) as linear collections of air contiguous to the bronchovascular sheaths. With the recent availability of multidetector-row CT, the Macklin effect has been seen in the clinical setting more frequently than expected. The aim of this review article is to describe the CT imaging spectrum of the Macklin effect in patients with SPM, focusing on the common appearance of the Macklin effect, pneumorrhachis, and persistent SPM with pneumatocele.

Keywords: Computed tomography; Interstitial emphysema; Macklin effect; Pneumomediastinum; Spontaneous pneumomediastinum.

Figures

Figure 1

Chest computed tomography scan of an 82-year-old woman shows an injury to the posterior wall of the trachea, massive pneumomediastinum, and subcutaneous emphysema due to ruptured pars membranosa (arrow).

Figure 2

A 21-year-old woman with hypothyroidism and symptoms of cervical discomfort and tenderness. Multidetector-row computed tomography scan demonstrates air collection along the perivascular connective tissue, the Macklin effect (arrows), in the peripheral area (A) and in the perihilar area (B), and pneumomediastinum. Reprinted from ref. [5].

Figure 3

A 15-year-old girl with acute myeloid leukemia. Multidetector-row computed tomography scan demonstrates air collection along the perivascular connective tissue and the Macklin effect (arrow) in the perihilar area. A small pneumomediastinum is also noted.

Figure 4

A 15-year-old girl with cryptogenic organizing pneumonia associated with graft-vs-host disease. Multidetector-row computed tomography scan demonstrates air collection along the perivascular connective tissue, the Macklin effect (arrows) in the peripheral area (A) and in the perihilar area (B), and massive pneumomediastinum. This patient also has spinal pneumorrhachis (arrowhead). Reprinted from ref. [5].

Figure 5

A 16-year-old girl with persistent spontaneous pneumomediastinum and pneumatocele. Computed tomography shows massive pneumomediastinum and perihilar and peripheral Macklin effects (arrows). In the left lower lobe, a pneumatocele (arrowhead) is observed.