Compression of the cervical internal carotid artery by the stylopharyngeus muscle: an anatomical study with potential clinical significance. Laboratory investigation.

OBJECT: Occasionally, the internal carotid artery (ICA) may be symptomatically compressed in the neck by an elongated styloid process. The authors are unaware, however, of any study to date in which the aim was to describe the compression of this part of the ICA by surrounding muscles extending from the styloid process.

METHODS

In 20 adult cadavers (40 sides), dissection of the cervical ICA was performed, with special attention given to the relationship between this artery and the stylopharyngeus muscle. In addition, rotation of the head was performed while observing for any compression of the ICA by this muscle. Last, the segment of the ICA immediately adjacent to the stylopharyngeus was excised and evaluated for signs of gross compression.

RESULTS

Five sides (12.5%) were found to have an ICA that was grossly compressed by the neighboring stylopharyngeus muscle, and this was confirmed on excised ICA specimens. Moreover, such compression was increased with ipsilateral rotation of the head. Effacement of the lumen of the ICA by the stylopharyngeus ranged from approximately 30 to 50%. Such compression was increased by approximately 25% with ipsilateral rotation of the head.

CONCLUSIONS

To the authors' knowledge, compression of the cervical ICA by the stylopharyngeus muscle has not been previously described. Such a relationship should be appreciated by the clinician who treats patients with symptoms of ICA stenosis or occlusion as a potential extracranial site of compression. Based on this study, a subset of patients with occlusion of the cervical ICA but without elongation of the styloid process should be included within the definition of Eagle syndrome.