舌骨に関連した頚部内頚動脈狭窄症について—舌骨は急性脳血管症候群の危険因子となり得るか？

Internal Carotid Artery Stenosis Associated with Hyoid Bone:Can Hyoid Bone be a Risk Factor for Acute Cerebrovascular Syndrome?

Ⅰ．はじめに

　過長した茎状突起が内頚動脈やその周囲の交感神経叢を刺激することによって顔面や頚部の痛みを生じる過長茎状突起症（Eagle症候群）はよく知られた病態であり²⁾，急性脳血管症候群（acute cerebrovascular syndrome：ACVS）を引き起こすことでも知られている¹⁰⁾．一方，stylohyoid complexの一部である舌骨の機械的刺激によるACVS発症の認知度は極めて低く，報告例もほとんどない^{1,3-5,7-9,11-13,15,17)}．

　そこで今回われわれは，比較的馴染みの薄い舌骨においても茎状突起同様にACVS発症の危険性があるのか解明することを目的とし，本研究を行った．

　Eagle syndrome is a well-known disease caused by elongation of the styloid process and/or calcification of the stylohyoid ligament, which interferes with adjacent anatomical structures, giving rise to acute cerebrovascular syndrome（ACVS）and/or pain. Although hyoid bone is also a stylohyoid complex, its association with ACVS is not well known. Thus, we investigated the anatomical relationship between the internal carotid artery（ICA）and the hyoid bone.

　Between January 2014 and December 2015, three-dimensional computed tomographic angiography（3D-CTA）of the neck was performed for 218 patients. Of the patients, an abnormal anatomical relationship was noted in 10（4.6%）cases. In 5 cases, the ICA was entrapped by the hyoid bone. In 3 cases, the ICA was in contact with or adjusted to the hyoid bone. In 2 cases, the ICA was compressed by the hyoid bone, causing ACVS. In 7 cases, the position and course of the ICA were inward. In 4 of these cases, the hyoid bone was repositioned back to its normal location. Moreover, in 1 case, the course of the ICA was repositioned back to its normal location beside the hyoid bone.

　The anatomical position of the hyoid bone may vary more than expected and can be a risk factor for ACVS. In particular, in cases of ACVS where the ICA has an inward course, the relationship between the ICA and the hyoid bone should be proactively examined.