The sphincter, also known as the testicular sheath, is a continuation of the male peritoneum and is divided into a mural and a visceral layer. The mural layer is lined with the inner fascia of the spermatic cord, while the visceral layer covers the surface of the testis and epididymis, and the visceral layer and the mural layer migrate away from each other at the posterior border of the testis. The lumen between the visceral and mural layers, the sphincter lumen, contains a small amount of fluid. When plasma collects and increases in the syringomyelia cavity, syringomyelia occurs and is the most common lesion causing scrotal enlargement. In infants, syringomyelia often resolves on its own without treatment. Smaller asymptomatic syringomyelia in adults usually do not require treatment. Larger syringomyelia require puncture and aspiration or surgery.