Study on the Occurrence of Double or Bifid Zygomaticus Major: A Muscle of Facial Expression

Background: Zygomaticus major is one of the muscles of facial expressions and is also known as musculus zygomaticus major, the greater zygomatic muscle, as well as musculus zygomaticus. There are so many variations in the insertion of this muscles and may leads to the formation of dimple in the cheek region. This particular property of this muscle is quiet interesting and became the background of this study. Materials and Methods: Present study was done among 10 cadaveric hemi faces belongs to the department of anatomy Tagore Medical College to find the occurrence of bifid zygomaticus major which is responsible for dimple formation in cheeks. Result: Among the 10 hemi faces we found only 2 faces with bifid zygomaticus major along its insertion. Conclusion: Even though bifid zygomaticus major is considered as a developmental defect, the dimple in cheek formed by it is always measured as a mark of beauty. So learning more about the muscle and its variation paved ways to produce artificial dimples in the face to beautify it.

Diagnosis of Zygomaticus Muscle Paralysis Using Needle Electromyography With Ultrasonography

A 22-year-old woman visited our clinic with a history of radiofrequency volumetric reduction for bilateral masseter muscles at a local medical clinic. Six days after the radiofrequency procedure, she noticed a facial asymmetry during smiling. Physical examination revealed immobility of the mouth drawing upward and laterally on the left. Routine nerve conduction studies and needle electromyography (EMG) in facial muscles did not suggest electrodiagnostic abnormalities. We assumed that the cause of facial asymmetry could be due to an injury of zygomaticus muscles, however, since defining the muscles through surface anatomy was difficult and it was not possible to identify the muscles with conventional electromyographic methods. Sono-guided needle EMG for zygomaticus muscle revealed spontaneous activities at rest and small amplitude motor unit potentials with reduced recruitment patterns on volition. Sono-guided needle EMG may be an optimal approach in focal facial nerve branch injury for the specific localization of the injury lesion.

Location of the Modiolous and the Morphologic Variations of the Risorius and Zygomaticus Major Muscle Related to the Facial Expression in Koreans / 체질인류학회지

Location of the modiolous and morphological variations of the risorius and zygomaticus major muscles are related to the facial expression. The zygomaticus major, levator labii superioris, depressor labii inferioris, depressor anguli oris, risorius, orbicularis oris, buccinator and levator anguli oris muscles insert on the lateral border of the lip, forming the modiolus and mutually associating each other for functioning. The knowledge of the location of the modiolus and surrounding structures are essential to anatomy, prosthodontics, linguistic, physiology and computer simulation based on facial expressions. The authors examined the location of the modiolus, the morphological variations and anatomical relationship of risorius and zygomaticus major muscle to understand the features of the smile of Korean by dissecting 39 cadavers. The location of the modiolus can be showed as three types, according to their height related to the intercheilion horizontal line. Type A that modiolus locate at the intercheilion line was shown in 20 sides (26.0%), type B that modiolus locate above the intercheilion line was shown in 12 sides (15.6%), then type C that modiolus locate under the intercheilion line was shown in 45 sides (58.4%). Most modioli located at 10 ~20 mm lateral to the mouth corner and 0 ~10 mm below the intercheilion line. The risorius muscle was classified into five types by directions of muscle fibers. The depressor anguli oris -risorius type (type I) was observed in 31 sides (40.2%), the platisma -risorius type (type II) was observed in 30 sides (39.0%). Previously, it has been known that zygomaticus major muscle attaches to the modiolus mainly as one bundle. However, the results were clearly shown that two bundles of the zygomaticus major muscle attaches to the modiolus and the position of the mouth edge in 18 sides (23.4%). To sum it up, facial expression is of fundamental importance concerning the morphological variations and these results also can be considered for the facial reconstruction surgery and computer animation department.