Correspondence: Dr Park, Indiana University School of Medicine, Department of Surgery, 9305 Calumet Ave, Suite 2-A, Munster, IN 46321 (email@example.com).
I am greatly honored to receive a letter regarding our article on the anatomy of the corrugator supercilii muscle. Dr Bernstein's clinical observation on some individuals with multiple corrugations, as evidenced by flattish vertical creases lateral to the distant glabellar crease, is an excellent point that could have been included in the article if we had thought of it at the time. I sincerely appreciate his bringing up this important observation that truly expands the value of the article. I have also noticed vertical lines extending almost to the lateral orbital rim on some elderly patients (Figure 1), which does not surprise me, because I have found the corrugator supercilii muscles, in some cadavers, extending almost to the level of lateral orbital rim (Figure 2). Although the motor innervation of the corrugator supercilii muscle as a branch of the frontal division of the facial nerve was not described in the article, I have found identifiable and distinctive branches to the corrugator supercilii muscle traveling along the supraorbital rim within about 1 cm of the orbital margin running from the temple almost parallel to the supraorbital rim until it reaches the lateral aspect of the bony attachment of the corrugator supercilii muscle (Figure 3). Although I have not studied the exact entry point of the particular nerve to the muscle itself, I was able to trace the main nerve right up to the supraorbital foramen, in some occasions passing the area above the foramen to enter the muscle close to its insertion. Since the anatomic study on the corrugator supercilii muscle, I have been dividing muscle in a fan-shaped fashion starting from the area medial to the supraorbital foramen. Lateral to the supraorbital foramen, I began to divide the muscle vertically at a right angle to the course of the muscle fibers (Figure 4). The decision as to the lateral extent of the muscle transection was based on the clinical observation of the extent of frowning during the preoperative examination. With the better understanding of the anatomy and the systematic resection of the muscle, I was able to eliminate muscle activities in its lateral aspect as well as the main segment medial to the supraorbital foramen. Following the muscle transection, any muscle fibers that remained attached to the dermis lateral to the actual wrinkle do not have the insertion to the bone. Therefore, those muscles simply hang loose without the ability to contract and cause wrinkles. If you still saw lateral vertical wrinkles, it just may be due to the pulling of the scar tissue by the residual lateralmost muscle fibers. The nerve entered the muscle fiber not only from beneath but also very close to its insertion. The nerve found was a single branch, which reached almost all the way to the corrugator supercilii muscle origin. I believe almost all the motor nerve branches to the corrugator supercilii muscle were divided in the process of slicing the muscles in a fan and vertical fashion up to its lateralmost insertion. Regarding Dr Bernstein's concern on possibly transecting the lower frontal facial nerve branch during the lateral muscle cut, I do not share the same concern for the following reasons. First, the frontalis muscle lies much higher than the corrugator muscle. Second, the nerve to the frontalis muscle enters the muscle at about the midsegment of the muscle bundle, not at its lowermost fibers. Third, although it is an unlikely event, severing the lowermost fibers of the frontalis muscle during the process of cutting the lateralmost fibers of the corrugator muscle would not damage the main trunk of the facial nerve because the facial nerve enters the lateral border of the frontalis muscle as multiple branches rather than as a single main trunk.
Park JI. Comments on Anatomy of the Corrugator Supercilii Muscle—Reply. Arch Facial Plast Surg. 2004;6(4):273-274. doi:10.1001/archfaci.6.4.273