[An anomalous case of the thoracic cardiac nerve in the Japanese monkey]

A rare case of an anomalous right thoracic cardiac nerve that directly distributed to the left ventricle and left coronary artery was observed in a Japanese monkey. Its nerve arose from 4th and 5th thoracic ganglia on the right sympathetic trunk, descended obliquely along the thoracic vertebra toward the thoracic aorta at the level of the body of 7th thoracic vertebra. After reaching the aorta, it reflected upward and ascended along the medial-ventral surface of the aorta. Thereafter, it received a cardiac branch arising from the vagus nerve in the upper part of the thoracic aorta, and ran to the left-lateral aspect of the heart. Finally, it gave off main branches to the terminal part of the left coronary artery and the left ventricle, and small branches to the proximal part of the left coronary artery. In a human dissection, similar nerves (the thoracic splanchnic nerve or thoracic pulmonary nerve) originating at the thoracic ganglia and reaching to the lung, have also been observed. The superior, middle and inferior cervical cardiac nerves can easily reach the heart along the common carotid artery, the brachiocephalic artery and subclavian artery. But it is not easy for the thoracic cardiac nerve to reach the heart because of the topographical relationship of its thoracic origin and the peripheral distributions of the left side of the heart. Therefore, the thoracic cardiac nerve would have to run a complicated course.