RESUMEN
The three-dimensional structure of thoracic and lumbar nerves was investigated in rats using Sihler's staining method. It was observed that the dorsal and lateral cutaneous nerves pierced the surface muscles to enter the subcutaneous tissue at a point 1-2 segments caudal to the base of the spinal nerve, while the ventral cutaneous nerves pierced the surface muscles 7 segments caudal to the base. The dorsal and lateral cutaneous nerves also ran more caudally, 2-3 and 2-4 segments, respectively, in the subcutaneous tissue. In addition, the tilt angles of spinal nerve rami lying against the transverse plane of the body trunk increased caudally, and the ventral rami showed a drastic increase in their tilt angle. Combined with our previous studies on dermatomes and sclerotomes, the present results imply that the innervation territory of the spinal nerve is shaped like a “deformed cone”, with the apex at the base of the spinal nerve and the lateral aspect expanding caudally. The stereoscopic structure of spinal nerve innervation territories may provide novel viewpoints for use in the diagnosis and treatment of disorders of the spine and spinal cord.