The understanding of the basic anatomy of the occipital artery (OA) is crucial, and computed tomography angiography is an effective tool for this purpose. In the present study, a comparison between healthy subjects and patients with internal carotid artery (ICA) stenosis and occlusion was made. The following parameters were measured: Age, sex, diameters and lengths of the OA in different locations, distance from the edge of the foramen magnum to the OA and the distance from the midline to the OA at the level of the superior nuchal line. A total of 205 participants who met the inclusion criteria were selected for further investigation. In addition, 50 healthy subjects (100 sides, left and/or right) were selected as the control group. A total of 155 patients (180 sides, left and/or right) were selected as the stenosis and occlusion groups, including the mild and moderate ICA stenosis group (50 sides, left and/or right), severe ICA stenosis group (80 sides, left and/or right) and the ICA occlusion group (50 sides, left and right). General information, measured parameters and statistical analysis results are provided for these groups. No significant differences were observed in the anatomical parameters of the OA among these groups. Thus, in addition to providing anatomical data, the present study demonstrates that stenosis and the occlusion of the ICA do not significantly alter the anatomy of the OA.
The occipital artery (OA) is a main artery that originates from the external carotid artery (ECA) and may be involved in a number of diseases, such as moyamoya disease, dural arteriovenous fistula (DAVF), aneurysm, etc. (
Previous studies on the OA have been mostly based on cadavers and catheter-based angiography procedures (
In addition to providing OA parameters, most importantly, in the present study, the OA anatomy was compared between healthy subjects and patients with internal carotid artery (ICA) stenosis and occlusion to determine whether the OA parameters differed. This was performed as the OA can become dilated or thicker than normal in the presence of a DAVF (
An imaging study was performed on Han Chinese candidates, including healthy subjects and patients with ICA stenosis and occlusion, who underwent cervical CTA examinations between January, 2020 and September, 2021 at the First Hospital of Jilin University, Changchun, China. The healthy subjects underwent a cervical CTA examination during routine physical examinations.
Prior to the CTA, the following exclusion criteria were used: A history of severe or anaphylactic reaction to iodinated contrast, an inability to cooperate with scanning protocols, hemodynamic instability, diabetes, the administration of any anticoagulant medication, renal impairment.
The present study was approved by the Ethics Committee of the First Hospital of Jilin University (approval no. 2021-533). Written informed consent was obtained from all participants. The original CTA data were further processed on a GE Workstation (version 4.7) (GE Healthcare; Cytiva).
CTA examinations were performed on 256-multidetector CT scanners (GE Healthcare; Cytiva) at the First Hospital of Jilin University, utilizing THE test bolus injection technique to acquire the optimal trigger time (
First, contrast-enhanced imaging upon CTA of the participants was clear, and the ECA and OA could be clearly seen and measured. For the healthy subjects, no ECA or ICA abnormities were observed. For patients with ICA stenosis and occlusion, the history of ICA stenosis and occlusion was chronic and progressive due to arteriosclerosis; in these patients, the ECA was normal and had no stenosis at the origin. No tumor or vascular diseases, such as scalp or intramuscular hemangioma (
Accordingly, the patients were divided into a mild and moderate ICA stenosis (ICA stenosis <70%) group, a severe ICA stenosis (ICA stenosis 70-99%) group and an ICA occlusion group (
The raw CTA data were post-processed using the GE Workstation (version 4.7; GE Healthcare; Cytiva). The raw CTA data were primarily reconstructed using volume rendering. Structures that affected the measurements were removed using the cutting tool. The diameter of the vessel and the distances between structures were obtained using the ‘measure distance’ tool. The curved length of a vessel was measured using the two-click AVA tool, and the curved three-dimensional length could be measured accurately. All the parameters were measured three times, and the average value was used for analysis.
The vessel diameters included the ECA diameter at the OA origin, the OA diameter at its origin, the OA diameter at the superior nuchal line, the OA diameter 2 cm above the superior nuchal line and the OA diameter at the midline of the foramen magnum. When measuring the OA diameter at the superior nuchal line and OA diameter 2 cm above the superior nuchal line, if the OA was branched, the thickest portion of the main trunk was measured.
A number of variations were recorded, including the common origin with other ECA branches arising from the ICA and OA-vertebral artery anastomosis (
Statistical assessments were performed using GraphPad Prism (version 8.02) software (GraphPad Software, Inc.). Continuous variables are expressed as the mean ± standard deviation. A paired t-test was used for the comparison of two continuous variables. Ordinary one-way ANOVA followed by Tukey's multiple comparisons test was used for the comparison of multiple continuous variables. The Chi-squared test was used to compare count data among multiple groups. A P-value <0.05 was considered to indicate a statistically significant difference.
A total of 205 Han Chinese participants who met the inclusion criteria were selected for further investigation. A total of 50 healthy subjects (100 sides, left and/or right) were selected as the control group. In total, 155 patients (180 sides) were selected as the stenosis and occlusion groups, including the mild and moderate ICA stenosis group (50 sides, left and/or right), severe ICA stenosis group (80 sides, left and/or right) and ICA occlusion group (50 sides, left and/or right).
In the control group (50 subjects), the average age was 60.14±11.56 years (range, 33-88 years), and the ratio of males to females was 1.94:1 (33/17). In the mild and moderate ICA stenosis group (38 patients), the average age was 64.26±9.38 years (range, 37-80), and the ratio of males to females was 2.8:1 (28/10). In the severe ICA stenosis group (71 patients), the average age was 64.73±8.31 years (range, 33-79 years), and the ratio of males to females was 1.54:1 (43/28). In the ICA occlusion group (46 patients), the average age was 62.04±9.361 years (range, 41-80 years), and the ratio of males to females was 1.54:1 (30/16). The age and sex data, and their comparisons are summarized in
It should be noted that for the participants, their weight, height and body mass index should be included. However, as some data were from the out-patient department, these data could not be provided.
Among the healthy subjects, the ECA diameter at the OA origin was 4.37±0.93 mm (range, 2.5-8.7 mm). The OA diameter at its origin was 1.94±0.33 mm (range, 1.3-2.8 mm). The length of the OA from its origin to the superior nuchal line was 142.2±19.39 mm (range, 104.9-185.9 mm). The OA diameter at the superior nuchal line was 1.68±0.35 mm (range, 0.8-3.0 mm). The OA diameter 2 cm above the superior nuchal line was 1.14±0.39 mm (range, 0.4-2.3 mm). The length of the OA between the superior nuchal line and 2 cm above the superior nuchal line was 39.34±9.1 mm (range, 22.6-71.2 mm). The OA diameter at the midline of the foramen magnum was 2.07±0.39 mm (range, 1.5-3.1 mm). The distance from the edge of the foramen magnum to the OA was 29.88±3.47 mm (range, 24.1-42.1 mm). The length of the OA from the midline level of the foramen magnum to the superior nuchal line was 89.82±14.89 mm (range, 56.9-129.5 mm). The distance from the midline to the OA at the level of the superior nuchal line was 36.09±4.42 mm (range, 25.6-48.7 mm). The overall data and their comparisons are summarized in detail in
A common origin of the OA and the ascending pharyngeal artery was found on 15.4% of sides (43/280). A common origin of the OA and the posterior auricular artery was observed on 3.6% of sides (10/280). The OA-vertebral artery was found in 2.1% of sides (6/280). The OA arising from the ICA was not observed.
There were no significant differences in age, sex, or anatomical parameters of the OA among the control, mild and moderate ICA stenosis group, severe ICA stenosis group and ICA occlusion groups (P>0.05) (
The OA is a crucial structure (
In the present study, CTA data were collected from a control group with a normal ICA and patients with stenosis and occlusion of the ICA. The analysis of the OA diameter did not reveal any differences among the different locations and OA lengths among all groups, indicating that the redistribution of blood flow due to severe stenosis or occlusion of the ICA was insufficient in changing the anatomic characteristics of the OA. In addition, these OA data are valuable, as there are no previous studies that have provided CTA data on the OA in Han Chinese population, at least to the best of our knowledge.
The OA is a large artery that has been reported to provide a mean blood flow of 15 to 80 ml/min when used for posterior fossa bypass (
In the present study, in healthy subjects, the OA diameter at its origin was 1.94 mm, which is smaller than that in the study by Alvernia
The OA branches from the ECA; in rare cases, the OA can arise from the ICA (
After leaving the ECA, the OA then runs in the occipital groove of the temporal bone, medial to the digastric groove (
For a bypass between the OA and intracranial artery, the OA should be dissected from its distal end, and the dissection should extend to the level of the mastoid process after the digastric groove (
The OA crossed upwards over the superior nuchal line; however, its diameter did not decrease significantly at this point. In the study by Kawashima
For surgical purposes, it is important to consider that the diameter of the main trunk of the OA remains >1.0 mm. In the study by Alvernia
In conclusion, the presents study reported data on the OA diameter in Han Chinese patients. In addition, it was demonstrated that the stenosis and occlusion of the ICA did not significantly alter the anatomy of the OA.
Not applicable.
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
JY designed the study and drafted the manuscript. TL collected the data. TL and JY confirm the authenticity of all the raw data. JY and TL revised the manuscript. Both authors have read and approved the final manuscript.
The present study was approved by the Ethics Committee of the First Hospital of Jilin University (Approval no. 2021-533). Written informed consent was obtained from the participants.
The participants or their parents/guardians provided consent and agreed to have their data (shown in the figures) published.
The authors declare that they have no competing interests.
CTA of the ICA in different groups. (A) CTA illustrating mild ICA stenosis (arrow). (B) CTA illustrating moderate ICA stenosis (arrow). (C) CTA illustrating severe ICA stenosis (arrow). (D) CTA illustrating an ICA occlusion (arrow). CCA, common carotid artery; CTA, computed tomography angiography; ECA, external carotid artery; ICA, internal carotid artery; OA, occipital artery.
Parameters measured on computed tomography angiography. (A) The number 1 indicates the diameter of the ECA at the OA origin, and the number 2 indicates the diameter of the OA at its origin. (B) Number 3 indicates the length of the OA from its origin to the superior nuchal line. (C) Number 4 indicates the diameter of the OA at the middle of the superior nuchal line, number 5 indicates the diameter of the OA 2 cm above the middle of the superior nuchal line, and number 6 indicates the length of the OA between the superior nuchal line and 2 cm above the superior nuchal line. (D) Number 7 indicates the OA diameter at the midline of the foramen magnum, and number 8 indicates the distance from the edge of the foramen magnum to the OA. (E) Number 9 indicates the length of the OA from the midline level of the foramen magnum to the superior nuchal line. (F) Number 10 indicates the distance from the midline to the OA at the level of the superior nuchal line. CCA, common carotid artery; ECA, external carotid artery; ICA, internal carotid artery; OA, occipital artery; VA, vertebral artery.
OA variations on CTA. (A) CTA illustrating the normal order of the APA, OA and PAA. (B) CTA illustrating the common trunk of the OA and APA. (C) CTA illustrating the common trunk of the OA and PAA. (D) CTA illustrating the anastomosis of the OA and VA (arrowhead). CCA, common carotid artery; CTA, computed tomography angiography; ECA, external carotid artery; ICA, internal carotid artery; OA, occipital artery; VA, vertebral artery; APA, ascending pharyngeal artery; PAA, posterior auricular artery.
Dilated OA in DAVF as a feeding artery. Lateral digital subtracted angiography of the external carotid artery illustrating that the OA (asterisk) was dilated and was the feeding artery of a DAVF (circle); the MMA also served as a feeding artery. The image presented was from a case with DAVF that was not included in the present study. Patient consent for publication and written informed consent were acquired. DAVF, dural arteriovenous fistula; MMA, middle meningeal artery; OA, occipital artery; STA, superficial temporal artery.
Computed tomography angiography of the course of the OA in the occipital groove. (A and B) The images presented were from the same case. The digastric groove and occipital groove are shown; (B) the OA runs in the occipital groove. (C and D) The images presented were from the same case. The bilateral OAs are shown; (D) the right OA (single asterisk) was close to the occipital groove and the left OA (double asterisks) was away from the occipital groove. OA, occipital artery.
Age data of the study participants.
Group | Range (years) | Mean (years) | P-value |
---|---|---|---|
Control (50 subjects) | 33-88 | 60.14±11.56 | 0.0527 |
Mild and moderate ICA stenosis (38 subjects) | 37-80 | 64.26±9.38 | |
Severe ICA stenosis (71 subjects) | 33-79 | 64.73±8.31 | |
ICA occlusion (46 subjects) | 41-80 | 62.04±9.36 |
aThe data were analyzed using ordinary one-way ANOVA; due to the P-value >0.05, one-way ANOVA indicated that the degree of ICA stenosis had no significant effect on patient age. The P-values from multiple comparisons between groups are presented in
Sex data of the study participants.
Group | Male (no. of participants) | Female (no. of participants) | P-value |
---|---|---|---|
Control (50 subjects) | 33 | 17 | 0.5947 |
Mild and moderate ICA stenosis (38 subjects) | 28 | 10 | |
Severe ICA stenosis (71 subjects) | 43 | 28 | |
ICA occlusion (46 subjects) | 30 | 16 |
aData were analyzed using the Chi-squared test; due to the P-value >0.05, the Chi-squared test indicated that the degree of ICA stenosis had no significant effect on the sex of patients. P-values of all the comparisons made are presented in
Multiple comparisons of the age and sex data in
P-value | ||
---|---|---|
Comparison between groups | Age | Sex |
Control vs. mild and moderate ICA stenosis | 0.1942 | 0.4388 |
Control vs. severe ICA stenosis group | 0.0505 | 0.5423 |
Control vs. ICA occlusion group | 0.7672 | 0.9357 |
Mild and moderate ICA stenosis vs. severe ICA stenosis group | 0.9950 | 0.1707 |
Mild and moderate ICA stenosis vs. ICA occlusion group | 0.7184 | 0.4035 |
Severe ICA stenosis group vs. ICA occlusion group | 0.4530 | 0.6117 |
For age data, Tukey's multiple comparisons test was used. For sex data, the Chi-squared test was used. ICA, internal carotid artery.
Measured parameters in the different groups.
No. | Parameter | Groups | Range (mm) | Mean (mm) | P-value |
---|---|---|---|---|---|
1 | ECA diameter at the OA origin | Control | 2.5-8.7 | 4.37±0.93 | 0.0888 |
Mild and moderate stenosis | 3.0-5.9 | 4.14±0.61 | |||
Severe stenosis | 2.9-5.7 | 4.09±0.66 | |||
Occlusion | 2.1-6 | 4.3±0.86 | |||
2 | OA diameter at its origin | Control | 1.3-2.8 | 1.94±0.33 | 0.1260 |
Mild and moderate stenosis | 1.3-2.5 | 1.89±0.26 | |||
Severe stenosis | 0.8-2.8 | 2.02±0.34 | |||
Occlusion | 1.4-3.1 | 2.0±0.31 | |||
3 | Length of the OA from its origin to the superior nuchal line | Control | 104.9-185.9 | 142.2±19.39 | 0.1467 |
Mild and moderate stenosis | 97-211.1 | 147.1±22.3 | |||
Severe stenosis | 89.8-198.6 | 143.1±22.15 | |||
Occlusion | 109.1-200.3 | 149.6±19.92 | |||
4 | OA diameter at the superior nuchal line | Control | 0.8-3 | 1.68±0.35 | 0.5392 |
Mild and moderate stenosis | 0.7-2.3 | 1.59±0.39 | |||
Severe stenosis | 0.7-2.7 | 1.63±0.45 | |||
Occlusion | 0.9-2.7 | 1.68±0.41 | |||
5 | OA diameter 2 cm above the superior nuchal line | Control | 0.4-2.3 | 1.14±0.39 | 0.6269 |
Mild and moderate stenosis | 0.4-2.2 | 1.07±0.45 | |||
Severe stenosis | 0.4-2.0 | 1.08±0.38 | |||
Occlusion | 0.5-2.2 | 1.06±0.39 | |||
6 | Length of the OA between the superior nuchal line and 2 cm above the superior nuchal line | Control | 22.6-71.2 | 39.34±9.10 | 0.0782 |
Mild and moderate stenosis | 23.9-64.1 | 36.71±7.74 | |||
Severe stenosis | 20.4-61.1 | 36.25±8.55 | |||
Occlusion | 22.4-59.1 | 36.83±7.93 | |||
7 | OA diameter at the midline of the foramen magnum | Control | 1.5-3.1 | 2.07±0.39 | 0.3562 |
Mild and moderate stenosis | 1.5-2.8 | 1.97±0.24 | |||
Severe stenosis | 1.4-3.4 | 2.04±0.37 | |||
Occlusion | 1.4-2.8 | 2.08±0.36 | |||
8 | Distance from the edge of the foramen magnum to the OA | Control | 24.1-42.1 | 29.88±3.47 | 0.8757 |
Mild and moderate stenosis | 24.6-38.4 | 29.54±3.20 | |||
Severe stenosis | 24.3-36.2 | 29.72±2.64 | |||
Occlusion | 23.2-35.9 | 29.49±2.98 | |||
9 | Length of the OA from the midline level of the foramen magnum to the superior nuchal line | Control | 56.9-129.5 | 89.82±14.89 | 0.8427 |
Mild and moderate stenosis | 54.9-129.9 | 92.25±15.56 | |||
Severe stenosis | 41.3-153.5 | 91.08±19.36 | |||
Occlusion | 51.4-136.7 | 91.44±15.33 | |||
10 | Distance from the midline to the OA at the level of the superior nuchal line | Control | 25.6-48.7 | 36.09±4.42 | 0.0723 |
Mild and moderate stenosis | 27.7-45.2 | 35.96±4.16 | |||
Severe stenosis | 19.3-48.3 | 37.75±5.15 | |||
Occlusion | 26.1-45.5 | 36.34±4.72 |
In the table, the control group included 100 sides (left and/or right), the mild and moderate ICA stenosis group included 50 sides (left and/or right), the severe ICA stenosis group included 80 sides (left and/or right), and the ICA occlusion group included 50 sides (left and/or right).
aThe data were analyzed using ordinary one-way ANOVA; due to the P-value >0.05, one-way ANOVA indicated that the degree of ICA stenosis had no significant effect on these parameters. The P-values from multiple comparisons between groups are presented in
Multiple comparisons of the parameters in the different groups shown in
P-value | |||||||
---|---|---|---|---|---|---|---|
No. | Parameter | Control vs. mild and moderate ICA stenosis | Control vs. severe ICA stenosis group | Control vs. ICA occlusion group | Mild and moderate ICA stenosis vs. severe ICA stenosis group | Mild and moderate ICA stenosis vs. ICA occlusion group | Severe ICA stenosis group vs. ICA occlusion group |
1 | ECA diameter at the OA origin | 0.3497 | 0.0906 | 0.9637 | 0.9839 | 0.7388 | 0.4445 |
2 | OA diameter at its origin | 0.8024 | 0.4240 | 0.6987 | 0.1438 | 0.3135 | 0.9959 |
3 | Length of the OA from its origin to the superior nuchal line | 0.5281 | 0.9915 | 0.1656 | 0.7133 | 0.9262 | 0.3013 |
4 | OA diameter at the superior nuchal line | 0.5571 | 0.8511 | >0.9999 | 0.9358 | 0.6683 | 0.9078 |
5 | OA diameter 2 cm above the superior nuchal line | 0.7506 | 0.7821 | 0.6997 | 0.9981 | 0.9998 | 0.9940 |
6 | Length of the OA between the superior nuchal line and 2 cm above the superio nuchal line | 0.2906 | 0.0811 | 0.3340 | 0.9905 | 0.9999 | 0.9809 |
7 | OA diameter at the midline of the foramen magnum | 0.3476 | 0.9360 | 0.9997 | 0.6864 | 0.4262 | 0.9374 |
8 | Distance from the edge of the foramen magnum to the OA | 0.9223 | 0.9877 | 0.8910 | 0.9874 | 0.9999 | 0.9760 |
9 | Length of the OA from the midline level of the foramen magnum to the superior nuchal line | 0.8301 | 0.9562 | 0.9416 | 0.9796 | 0.9948 | 0.9994 |
10 | Distance from the midline to the OA at the level of the superior nuchal line | 0.9985 | 0.0928 | 0.9909 | 0.1476 | 0.9784 | 0.3350 |
Tukey's multiple comparisons test was used to analyze the data. ECA, external carotid artery; ICA, internal carotid artery; OA, occipital artery.
Measured parameters in the control group.
No. | Parameter | Side | Range (mm) | Mean (mm) | P-value |
---|---|---|---|---|---|
1 | ECA diameter at the OA origin | L | 2.8-8.7 | 4.35±0.97 | 0.8079 |
R | 2.5-7.4 | 4.38±0.89 | |||
2 | OA diameter at its origin | L | 1.4-2.8 | 1.93±0.34 | 0.5843 |
R | 1.3-2.6 | 1.95±0.32 | |||
3 | Length of the OA from its origin to the superior nuchal line | L | 106.9-185.9 | 143.6±18.06 | 0.3137 |
R | 104.9-178.5 | 140.8±20.73 | |||
4 | OA diameter at the superior nuchal line | L | 0.8-3.0 | 1.69±0.37 | 0.7572 |
R | 0.9-2.5 | 1.67±0.33 | |||
5 | OA diameter 2 cm above the superior nuchal line | L | 0.5-2.3 | 1.16±0.38 | 0.3075 |
R | 0.4-2.2 | 1.12±0.40 | |||
6 | Length of the OA between the superior nuchal line and 2 cm above the superior nuchal line | L | 22.6-64.4 | 40.09±9.32 | 0.4840 |
R | 22.8-71.2 | 38.62±8.91 | |||
7 | OA diameter at the midline of the foramen magnum | L | 1.5-3.0 | 2.06±0.38 | 0.8261 |
R | 1.6-3.1 | 2.08±0.40 | |||
8 | Distance from the edge of the foramen magnum to the OA | L | 24.1-42.1 | 30.29±3.69 | 0.1594 |
R | 24.7-40.0 | 29.46±3.22 | |||
9 | Length of the OA from the midline level of the foramen magnum to the superior nuchal line | L | 56.9-126.5 | 89.28±16.21 | 0.5473 |
R | 65.0-129.5 | 90.36±13.59 | |||
10 | Distance from the midline to the OA at the level of the superior nuchal line | L | 27.6-47 | 36.78±4.24 | 0.0957 |
R | 25.6-48.7 | 35.44±4.54 |
In the table, the control group included 100 sides (50 left sides and right sides). Data were analyzed using a paired t-test. L, left; R, right; ECA, external carotid artery; ICA, internal carotid artery; OA, occipital artery.