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Styloid ProcessAnd AUas TransverseProcess Relationship

By Roy W. Sweat, D.C.

T he temporal bones take partin the formation of the sidesand base of the skull. Eachconsists of four parts which

are morphologicallydistinctelementsthat have become fused with one an-other. The styloid process is one ofthe four basic parts of the temporalbone.

The styloid process is developedfrom the cranialend ofthe cartilageofthe second visceral or hyoid arch bytwo centers: one forthe proximalpartof the process, termed the tympanoh-yal, appears before birth; the other,for the distal part of the process,termed the stylohyal,does not appearuntil after birth.

The styloid process is a slender,pointed bone averaging about 2.5 cmin length. It projects anterior and in-ferior from the under surface of thetemporal bone. Its proximal part (thetympanohyal)issurrounded by a bonysheath, derived from the tympanicplate and best marked on its antero-lateral aspect, while its distalpart (thestylohyaQgivesattachment to certainmuscles and ligaments.

The stylohyoidligament isa fibrouscord, attached to the tip of the styloidprocess and the lesser cornu of thehyoid bone. This ligament is derivedfrom the cartilage of the second vis-ceralarchand maybe partiallyossified;in many mammals it forms a distinctbone, the epihyal (Figure1).

The Doctors of Chiropracticshould study and examine therelationship of the styloid pro-cess on the x-rays and be awareof any aberrancy before begin-ning care of the patient.

Today's Chiropractic/January-February, 1986 93

UnUateral and BUateralAberrancies

In normal anatomical formation,the styloid process is anterior andmedial to the atlas transverse process(Figures 2 and 3). In aberrant forma-tions the styloid process can be lateraland posterior and can superimposeor articulate with the atlas transverseprocess (Figures 4 and 5).

When the styloid is aberrant unila-terally on the side of atlas laterality,adjusting forces must be minimal orlight The adjusting force may be trans-mitted through the styloid to the atlastransverse process for movement ofthe atlas (Figure 6). This aberrancycan make it difficult or impossible tomove the atlas.

When the styloid aberrancy is onthe opposite side ofthe atlas laterality, itcan make moving the atlas lateralitydifficult or impossible. When the aber-rancy is bilateral and the styloid pro-cesses superimpose or articulate withthe atlas transverse processes on eachside, it can make movement of theatlas impossible (Figure 7).Conclusion

The Doctor of Chiropractic shouldstudy and examine the relationship ofthe styloid process with the atlas trans-verse process on the x-rays and beaware of any aberrancy before begin-ning care of the patient

The doctor'satlasadjustingprogrammay be highly efficient, but due toaberrancies of the styloidprocess andthe atlas transverse process, subluxa-tion reductions and results may beless than desired..

About the author: Roy W. Sweat,D.C., a regular contributor to Today'sChiropractic, is a Palmer Collegegraduate. An assistant professor atLife Chiropractic College, Dr. Sweathas designed a chiropractic adjusting

instrument and a series of attach-ments.for x-ray machines and theorth'bgonal adjusting tables.

References1. Gray'sAnatomy .35th BritishEdition,W.B.Saunder Co. Pages 121, 266, 295.2.Atlas of RadiologicalAnatomy: 3rd Edition.Lothar Wicke.Pages 2, 16,46.3.Sobota Atlas of Human Anatomy I: Urbanand Schwarzenberg. Page 104. Sweat ChiropracticClinic: Case Studies.5. DissectionClass. MaconWeaver,Ufe Chiro-practic College. 1985.