The vertebral transverse process contains two additional processes of its own. The more superior (and larger) of the two is called the mammillary process, which connects posteriorly to the superior articular facet, and is in the same plane as the transverse process.
There is normal variation in the size of this process, but occasionally, a large mammillary process in a sufficiently obliqued radiograph will give the appearance of the "two-eyed scotty dog," with one eye being the usual pedicle and the other eye being the mammillary process.
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| Oblique view showing the "two-eyed Scotty dog" appearance at L3. The anterior ring-shaped opacity represent the pedicle (large arrow); the more posterior ring-shaped opacity represents a prominent mammillary process (small arrow). |
1. Patel NP, Kumar R, Kinkhabwala M, Wengrover S. "Radiology of lumbar vertebral pedicles: variants, anomalies, and pathologic conditions" Radiographics. Vol 7:1 (Jan 1987) pp. 101-137.