Variations in the spatial relationship between the hyoid bone and the carotid arteries and their clinical significance

Table 2 A summary of the observed types, classification, comparison with the previous study and comments about the clinical significance

Topographical types	Anatomical relationship	Current study	Manta et al[2]	Comments
Type 0	Carotid arteries posterior to the tip of the GHHB	46.9%	57.14%	Null type
Type I	ECA medial to GHHB	0.4%	0.34%	Low clinical penetrance, hemodynamically not significant carotid artery compression
Type II	ICA medial to GHHB	0%	0.34%	Low clinical penetrance, associated with reported cases of TIAs in systemic prothrombotic conditions or repetitive mechanical neck stress situations
Type III	Both ICA and ECA medial to GHHB	0%	1.02%	Low clinical penetrance, hemodynamically not significant carotid artery compression
Type IV	CCA medial to GHHB	0.2%	1.02%	Low clinical penetrance, associated with neurological deficits contralateral to the affected vessel in elderly patients
Type V	CB medial to GHHB	0%	0.34%	Low clinical penetrance, hemodynamically not significant carotid artery compression
Type VI	ECA lateral to GHHB	23.9%	20.41%	High anatomical prevalence, not implicated in any reported cases of TIA or stroke
Type VII	ICA lateral to GHHB	0.2%	0%	Low clinical penetrance, hemodynamically not significant carotid artery compression
Type VIII	Both ICA and ECA lateral to GHHB	13.2%	3.74%	High clinical penetrance, associated with significant neurological symptomatology, including hemiparesis, hemiplegia, aphasia, cervical pain, and loss of somatosensory function
Type IX	CCA lateral to GHHB	10%	8.5%	Low clinical penetrance, associated with the formation of a carotid pseudoaneurysm
Type X	CB lateral to GHHB	3.6%	6.46%	Low clinical penetrance, associated with the dissection of a carotid pseudoaneurysm
Type XI	ICA medial and ECA lateral to GHHB	1.1%	0.34%	High clinical penetrance, involving cases of cryptogenic strokes or unexplained TIAs in younger patients
Type XII	ECA medial and ICA lateral to GHHB	0.4%	0.34%	Low clinical penetrance, associated with neurological deficits contralateral to the affected vessel in elderly patients

ECA: External carotid artery; ICA: Internal carotid artery; CCA: Common carotid artery; GHHB: Greater horn of the hyoid bone; CB: Carotid bifurcation; TIAs: Transient ischemic attack.