Anatomical description of the ventral and dorsal cervical rootlets in rats: A microsurgical study

Abstract

Purpose: To describe the anatomical aspects of the cervical rootlets and to quantify the number of rootlets that compose C1 to T1. Methods: Twenty male rats were used in this study. The dorsal rootlets from C1 to T1 were analyzed. To study the ventral rootlets, the posterior root avulsion was performed using a microhook, allowing exposure of the ventral roots through manipulation of the denticulate ligament and arachnoid mater. The parameters analyzed were the number of ventral and dorsal rootlets by side and level. Results: The formation of the respective spinal nerve was observed in the spinal roots the union of the ventral and dorsal roots. In four animals the C1 spinal root had no dorsal and/or ventral contribution. There is no normal pattern of numerical normality of the dorsal and ventral rootlets. The average number of fascicles per root was 4.08, with a slight superiority on the left side. There was a slight superiority of the dorsal rootlets compared to the ventral rootlets. Conclusions: This investigation was the first to study cervical rootlets in rats. In 20% of the sample studied, the dorsal root of C1 was absent mainly on the left side. There is a nonlinear numerical increase from C1 to T1 in the rootlets. There is a numerical predominance of cervical fascicles on the left side, confronting several studies related to the functional predominance of right laterality, requiring new studies that correlate these variables.

Anatomical description of the extratemporal facial nerve under high-definition system: a microsurgical study in rats

“…Although this experimental model is used in several studies on facial nerves, few of them consider microsurgical anatomy and possible anatomical variations, which may lead to significant biases in interpretation due to the different neural arrangements present in the model in question. Specific studies on the anatomy of the facial nerve of rats are old and lacked the technology to microdissect the terminal branches of the nerve and understand their anatomical distribution 20,21 . For this, the extended video microsurgery system was used, which allows greater comfort for the surgeon and better access to the surgical field, making dissection less time-consuming 19 .…”

“…This makes it difficult to dissect it without damaging part of it, due to its intrinsic relationship with the adjacent tissue. Some authors report the need to remove part of the temporal bone to facilitate surgical access [20][21][22] , but in this study the cranial bones were preserved. It is noteworthy that rats do not have an internal jugular vein; thus, all cranial drainage occurs through tributary veins of the external jugular vein, which has a clear path laterally to almost all branches that make up the facial nerve 26,27 .…”

“…This anatomical variation is in line with what has already been described in the literature, justifying why these two branches are not used in experimental studies. Moreover, they have a complex pattern of distribution with variation in the pattern of ramifications, making it difficult to perform surgical procedures, especially in the zygomatic branch of the facial nerve 20,21 .…”

“…In this study, the temporal and posterior cervical branches of the facial nerve had the smallest diameter and their lengths were not measured because of the anatomical variation of their subdivisions. Some studies state that the posterior cervical nerve constitutes the shortest length 20,21 .…”

“…The buccal nerve, follows between the masseter and temporalis muscles, passing inferiorly to the eyes in the nasal direction. A study reports that the final divisions of the mandibular branch in Wistar rats innervate both muscle fibers of the lower and upper lip 20 . They also mention that the infratemporal portion of the facial nerve in rats is purely motor, resembling other peripheral nerves 23,28,29 .…”