The pineal gland is innervated by postganglionic sympathetic nerves from the superior cervical ganglion. As the axons enter the gland, they synapse with the pinealocytes. In this report, we describe a case in which the conarii nerve was observed crossing the distal portion of the ascending branch of the venous sinus, thus penetrating the capsule of the pineal gland. The nerve observed consisted of a bundle of unmyelinated axons and collagen fibers which are surrounded by endothelial cells. This is the first report of a completely engulfed and detached conarii nerve within a venous sinus.