No abstract

Communications between the ansa cervicalis and the vagus nerve, although described only as variations in many textbooks, can be observed frequently in the dissection room. Following macroscopic observation, some of such cases were subsequently dissected under surgical microscope to determine the nature of such communications. As a result, two broad categories of communications between the ansa cervicalis complex and the vagus nerve could be recognized: (i) false (pseudo) communications, where the two nerves were attached only by the connective tissue with no fiber exchange; and (ii) true communications, with nerve fiber involvement. Fiber analysis showed that the majority of the ansa-vagal communications observed during gross dissection were of the first category. True communications, when present, were only scanty contributions and always directed towards the side of the vagus. In addition, the vagus (region of the inferior ganglion) and hypoglossal nerves were found to be in close contact at the base of the skull and usually could not be separated by gross dissection. But such attachments, too, were shown to be almost entirely of false nature except for the possible presence of a few fine nerve filaments. It seems that the ansa-vagal communications are merely a result of the close physical relationship between the two structures and serve no significant functional purpose, but at the same time may hinder the prospects of using ansa cervicalis in surgical procedures such as re-innervation of laryngeal and facial muscles, following damage to recurrent laryngeal and facial nerves, respectively.

Characteristics of the nerve to the pyramidalis muscle (NPy), including its origin, course and distribution, were observed (macroscopically) in detail in the present study. The spinal segments that give rise to the nerve vary considerably and involve Th12-L2. The course and distribution of the nerve also vary widely. The NPy is given off from one of the following: (i) the anterior cutaneus branch (Rca) of the intercostals nerve; (ii) the ilioinguinal (li) nerve; or (iii) the genital branch (Rg) of the genitofemoral nerve. The NPy can be classified into nine types according to features of the course and branching pattern of the Rca and li. In three of 67 cases, the pyramidalis muscle had two nerves. Double-innervated pyramidalis muscles received one nerve from a transitional-type Rca (Rcat) and a second nerve derived from one of the superficial Rca (Rcas), li or Rg. The NPy derived from the deep Rca (Rcap; Type 1), Rcat (Type 2) and containing their features as well as the Type 9 (Rcat + li + Rg) reach the muscle from behind. Types 3-8 (not containing features of the Rcap and Rcat) enter the muscle from its surface. The branch that gives off the NPy is determined by the level of segmental origin, with the segmental origin of branches from the Rca (Types 1-4), li (Types 5-6) and Rg (Types 7-9) getting lower in that order. The level of segmental origin of the NPy derived from different Rca becomes lower in the following order: Rcap (Type 1), Rcat (Type 2), Rcas (Type 3), Rcas' (Rcas entering the inguinal canal; Type 4). When the origin of the NPy is from a lower segment, the origin of the boundary nerve (Rcap/Rcas) is also deviated downward. The changes in the NPy are related to the deviation of the entire lumbar plexus.

The authors encountered a very rare human autopsy case in which the supernumerary branch of the glossopharyngeal nerve and a nerve branch arising from the external carotid plexus communicated with the superficial cervical ansa. This anomaly was observed on the left side of a 71-year-old male cadaver during the gross anatomical seminar at Niigata University in 2004. The nerve fascicle and fiber analyses indicated that the supernumerary branch of the glossopharyngeal nerve separated cranial to the branches to the pharyngeal constrictor muscles, carotid sinus and stylopharyngeal muscle and sent the nerve fibers to the muscular branches to the platysma and the cutaneous branches to the cervical region. Additionally, it was shown that the branch arising from the external carotid plexus sent the nerve fibers to the cutaneous branch to the cervical region. Although the external carotid plexus is primarily postganglionic sympathetic fibers originating from the superior cervical ganglion, the vagus and glossopharyngeal nerves gave off branches connecting to the plexus, and therefore it was not possible to determine the origins of this branch of the external carotid plexus. The present nerve fascicle analysis demonstrates that the supernumerary branch of the glossopharyngeal nerve, which innervated the platysma, did not share any nerve components with the branches to the pharyngeal constrictor muscles, carotid sinus and stylopharyngeal muscle, suggesting that this supernumerary branch may be categorized into the different group from these well-known branches.

A middle thymothyroid artery, arising from the anterior aspect of the right common carotid as an anomalous branch was observed in a 71-year-old Japanese male cadaver. It soon divided into a thyroidea ima artery, a branch supplying the sternoclavicular joints, and a thymic branch. In addition, twigs from these three main branches supplied the sternohyoid and sternothyroid muscles, right inferior parathyroid gland and also some deep cervical lymph nodes. Anatomical features, clinical implications and a brief account of the developmental aspects of this rare variation are included in this report.