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Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: S: Stylohyoideus

Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: S

Stylohyoideus

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD

Peer Review Status: Internally Peer Reviewed


A close relationship exists between the stylohyoid and the posterior belly of the digastric; one or the other occasionally fails to separate from a common muscle mass. These two muscles develop from the deep aspect of the premuscle mass located at the base of the hyoid arch. Stylohyoideus arises from the lateral and dorsal part of the styloid process (processus styloideus ossis temporalis) by a round tendon, and attaches to the ventral surface of the body of the hyoid bone near its junction with the greater cornu.

Mori has reported three forms of variation for this muscle:

1) the stylohyoideus may pass the medial side of the intermediate tendon of the digastricus muscle (70.1% of 254 sides or 127 cadavers).
2) the stylohyoid may pass to the lateral side of the intermediate tendon of digastricus (1.9% of 254 sides), and
3) The end tendon of stylohyoideus is divided into two parts to allow the intermediate tendon of digastricus to pass through, the two parts rejoin and inserts onto the ventral surface of the body of the hyoid bone (27.9% of 254 sides).

Right and left side variations are:

1) On both sides the tendon divides to allow passage of the digastric tendon in 15.7% of 127 cadavers,
2) On both sides the tendon of stylohyoideus passes medial to the intermediate tendon of diagastricus in 66.1% of 127 cadavers,
3) On both sides the tendon passes the lateral side of the tendon of digastricus in 0.7% of 127 cadavers.

A bundle of muscle fibers sometimes passes from the tip of the styloid process to the angle of the mandible, forming what may be termed stylomandibularis. The stylohyoid may be absent uni- or bilaterally; duplication of the stylohyoid has also been observed. Another slip, stylohyoideus profundus, varies in its insertion, sometimes accompanying the styloidhyoid proper, sometimes inserting into the lesser horn of the hyoid, and in some cases replacing the stylohyoid ligament. Accessory slips may join the muscle from the digastric, from the stylomandibular ligament , or the angle of the mandible.

Another muscular slip is occasionally found, stylochondrohyoideus (Douglass) or stylohyoideus novus (Santorini) or stylohyoideus profundus (Sappey), passing from the styloid process to the lesser horn (cornu) of the hyoid bone, accompanying or replacing the stylohyoid ligament. The lessor cornu is the most common insertion site but others are also seen.

If the stylohyoid fails to divide near its insertion (which typically permits passage of the intermediate tendon of the digastric), the insertion may be a single head passing in front or behind the digastric tendon.

Syn.: m. Griffelzungenbeinmuskel.


References

Anson, B.J., Ed. (1966) Morris' Human Anatomy, 12th ed. The Blakiston Division, McGraw-Hill Book Company, New York.

Hashimoto, I. (1959) The relation of the situation between the M. stylohyoideus and the digastricus mandibulae. Kaibogaku Zasshi 34:333-339. In Japanese.

Henle, J. (1871) Handbuch der Muskellehre des Menschen, in Handbuch der systematischen Anatomie des Menschen. Verlag von Friedrich Vieweg und Sohn, Braunschweig.

Jordan, J. (1963) On the deep stylohyoid muscle in man. Folia Morphol. (Warsaw) 22:7-10.

Kirino, T. and I. Hashimoto. (1954). The relationship between the M. stylohyoideus and the venter posterior m. digastrici. Kokubyori Gakkai Zasshi 21:172. In Japanese.

Koike, C. and Y. Takayama. (1958) The muscles inserted into the processus styloideus. Tokyo Shikadaigaku Kaibogakukyoshitsu Gyosekishu 8:1-4. In Japanese.

Macalister, A. (1871) The varieties of the styloid muscles. J. Anat. Physiol. 5:28-31.

Macalister, A. (1875) Observations on the muscular anomalies in the human anatomy. Third series with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-130.

Mori, M. (1964) Statistics on the musculature of the Japanese. Okajimas Fol. Anat. Jap. 40:195-300.

Schaefer, E.A., Symington, J. and T.H. Bryce., Eds. (1923) Quain's Elements of Anatomy, 11th ed. Longmans, Green and Co., London.

Tsukamoto, T. and S.Tanaka. (1958) On the M. digastricus, M. stylohyoideus. Tokyo Shikadaigaku Kaibogakukyoshitsu Gyosekishu 8:1-4. In Japanese.

Weber, A. (1918) Signification du muscle stylo-hyoidien profound. Soc. Biol., Comptes Rendus Hebdomadiares des Séances et Mémoires 81:816-817.

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