Okajimas Folia Anat. Jpn., 82(4): 157–168, February, 2006

Clinical Anatomy in the Neck Region – The Position of Externaland Internal Carotid Arteries May be Reversed –

By

Hideshi ITO, Izumi MATAGA, *Ikuo KAGEYAMA and *Kan KOBAYASHI

The Nippon Dental University, School of Dentistry at Niigata, Department of Oral and Maxillofacial Surgery II,*Department of Anatomy

–Received for Publication, April 26, 2005 –

Key Words: Neck dissection, Common carotid artery, Hypoglossal nerve, External jugular vein, Cervical ansa, Vesselmeasurement

Summary: Knowledge of clinical anatomy in the neck region is useful for the diagnosis of primary tumors and metastaticlymph nodes. Arteries and nerves in the neck region of forty Japanese cadavers (80 cases), 18 males (36 cases) and 22females (44 sides) were studied by dissection. We obtained the following results. Reverse of the location of the externaland internal carotid arteries was found in 5 cases (6.3%). The course of the hypoglossal nerve made an acute curve andran anterior-inferior in the neck region. In regard to the height of bifurcation of the common carotid artery (CC), highbifurcation was seen in 25 (31.2%), standard bifurcation in 46 (57.5%), and low bifurcation in 9 (11.3%) in a total of 80cases. Furthermore, the facial artery had the largest inner diameter among the branches of the external carotid artery.Based on these findings, the facial artery will be one of the most beneficial arteries for transplantation as a recipientartery.

Knowledge of clinical anatomy in the neck re-gion is useful for the diagnosis of primary tumorsand metastatic lymph nodes1). Fundamental pro-cedures of neck dissections are classified by themethod of preservation of the internal jugular vein,the sternocleidomastoid muscle and the accessorynerve. The dissected region will be decided on ananatomical basis for the trapezius and omohyoidmuscles. Many variations regarding arteries andnerves in the neck area have been observed.Knowledge of the possible pattern of origin, course,and distribution of the vessels and nerves is neces-sary to obtain safe dissection of the neck. Althoughwe need more precise information regarding thestructure in the neck, we still have limited knowl-edge due to the many morphological variations foreach individual. Therefore, we tried to clarify thelimited anatomical knowledge regarding vessels andnerves in the neck.

Materials and Methods

1. MaterialsForty cadavers (80 cases), 18 males (36 cases)

and 22 females (44 cases) were studied by dissec-tion in the Nippon Dental University School ofDentistry at Niigata. The age of the cadaversranged from 44 to 102-years-old. The average ageof the cadavers was 75.7G 13.0 years (Table 1). Inall the cadavers, 10 of the following solution wasinjected into the femoral arteries: alcohol, 70%;formalin, 5%; phenols, 5%; and glycerin, 5%. Afterthe 1st fixation, the cadavers were preserved in atank for acute fixation.

2. MethodsAfter reflection of the skin toward the lateral

side in the neck portion, we dissected the platysmacarefully and made markers for fine nerves and

157

Corresponding Author: Hideshi Ito, D.D.S. Ph.D., Department of Oral and Maxillofacial Surgery II, The Nippon Dental UniversitySchool of Dentistry at Niigata, 1-8 Hamaura-cho, Niigata-city, 951-8580 Japan. e-mail: hidesan@ngt.ndu.ac.jp

vessels on the muscle with brightly colored threads.Then we reflected the platysma upwards to revealthe sternocleidomastoid muscle. We cut the sternaland clavicle parts of the muscle near the origin,then reflected the muscle toward the lateral side.After reflection, we carefully dissected the finetwigs of the vessels and arteries in the deep layer,and in particular we removed the connective tissueof the carotid sheath to dissect the common carotidartery, the internal jugular vein and the vagusnerve. Furthermore, we studied the relationshipbetween the cervical ansa and the infrahyoid mus-cles, namely, the sternohyoid, sternothyroid, thyro-hyoid and omohyoid muscles, the course of thenerve to the thyrohyoid, the branch of the hypo-glossal nerve and the distribution pattern of the ar-teries and veins in the neck region. Photographswe’re taken and amatomical sketches made at eachstep. We recorded the data and discussed our find-ings.

Observation Items

1. Location of the external and internal carotid ar-teries2. Height of bifurcation of the common carotid ar-tery (CC)3. Confluent part of the external jugular vein4. Course of the hypoglossal nerve5. Course of the cervical ansa6. Measurements of the inner diameters of themain arteries

1. Location of the external and internal carotidarteries

We classified the location of the external and in-ternal carotid arteries into two types. In the stan-dard type, the external carotid artery was locatedanterior to the internal carotid artery. In the re-versed type, the position of the external and in-

ternal carotid arteries was reversed, namely the in-ternal carotid artery was located anterior to theexternal carotid artery (Fig. 1).

2. Height of bifurcation of the common carotidartery

After dissection of the CC, the external and theinternal arteries, the height of CC bifurcation wasclassified into three types with the level of thetransverse process of the cervical vertebrae. Highbifurcation included division of the CC between thelevel of the second and third cervical vertebrae orabove the second vertebra. Standard bifurcationwas when the CC divided at the level of fourthvertebra, and low bifurcation meant that the CCdivided between the fourth and fifth vertebrae orbelow the fifth vertebra (Fig. 2). Furthermore, theorigin and course of the superior thyroid, lingualand facial arteries were observed.

3. Confluent part of the external jugular veinWe observed the confluent part of the external

jugular to the other veins. We classified it into threetypes. Type 1, in which the external jugular veinemptied directly into the subclavian vein; Type 2,

Table 1.

Age Male Female Total

40@49 years old 1 0 150@59 years old 3 0 360@69 years old 5 3 870@79 years old 5 9 1480@89 years old 4 5 990@99 years old 0 3 3over 100 years old 0 2 2

Total 18 22 40

Fig. 1. Reversed type.The position of the external and internal carotid arteriesare reversed. CC, Common carotid artery; ECA, Externalcarotid artery; ICA, Internal carotid artery; STA, Supe-rior thyroid artery; LA, Lingual artery; FA, Facial artery;OA, Occipital artery.

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in which the vein emptied into the venous angle(the influence between the internal jugular andsubclavian veins); and Type 3, in which the veinemptied into the internal jugular vein (Fig. 3).

4. Course of the hypoglossal nerveThe relationship between the course of the hy-

poglossal nerve and the bifurcation of the CC wasstudied (Fig. 4).

5. Course of the cervical ansaAccording to Kikuchi’s classification, basically

two types were observed. In the lateral type, thesuperior root and the inferior root made the cervi-

cal ansa superficial to the internal jugular vein. Inthe medial type, the two roots made the cervicalansa deep to the internal jugular vein (Fig. 5).

6. Measurements of the inner diameter of the mainarteries

Fifty-six sides were measured using a suitablyequipped stereomicroscope, because we had diffi-culties in measurement due to prior damage causedby a student dissection course. We chose four mainarteries; the external carotid, superior thyroid, lin-gual, and facial arteries (Fig. 6). We followed Shi-ma’s method2), which measured the inner diameterof arteries under the comparison between Japaneseand German specimens.

Fig. 2. Heigt of bifurcation of the common carotid artery.

Fig. 3. Confluent part of the external jugular vein.The external jugular vein is classified into three types: sv, Subclavian vein; ejv, External jugular vein; ijv, Internal jugular vein.

Clinical Anatomy in the Neck Region 159

Method of Measurements

In the superior thyroid, lingual and facial ar-teries, the arteries were cut lengthwise at 1 and3 cm distal to their origin. In the external carotidartery, the artery was cut lengthwise at 1 and 2 cm.All specimens were placed on a black corkboard.Each circumference was measured, and the in-ternal diameter was calculated (Fig. 7). Measure-ments were made with a stereoscopic microscope(STEREO PHOTO SMZ-10) and digital caliper.(DIGIMATIC CALIPER 500-110) To calculatethe average for each site, all samples were mea-

Fig. 4. Course of the hypoglossal nerve.XII: Hypoglossal nerve, CC: Common carotid artery.

Fig. 5. Course of the cervical ansa.ijv: Internal jugular vein, CC: Common carotid artery.

Fig. 6. Method of measurements for the blood vessel (insidediameter).

Fig. 7. Measuring parts.Points of transection of the arteries for measurement ofthe inside diameters. A, B, C, D: 1 cm distal. A 0, B 0, C 0:3 cm distal. D 0: 2 cm distal.

160 H. Ito et al.

sured three times. Differences in the internal diam-eter were tested by the Wilcoxon signed ranks test(p < 0.05). Differences between the right and leftsides were also tested by the Wilcoxon signed sumtest (p < 0.05).

Results

1. Location of the external and internal carotidarteries

Reversal of the location of the external and in-ternal carotid arteries was found in 5 cases (6.3%).In all cases, the superior thyroid, lingual and facialarteries arose from the posterior margin of the ex-ternal carotid artery, then ran forward superior tothe internal carotid artery (Fig. 8).

2. Height of bifurcation of the common carotidartery

In regard to the height of bifurcation of the CC,high bifurcation was seen in 25 (31.2%), standardbifurcation in 46 (57.5%), and low bifurcation in9 (11.3%) of a total of 80 cases (36 males, 44females). In males, high bifurcation was seen in 14(38.9%), standard and low bifurcation in 20(55.6%) and 2 (5.5%) respectively. In females, highbifurcation was seen in 11 (25.0%), standard andlow bifurcations in 26 (59.0%) and 7 (16.0%) re-spectively. The height of bifurcation tended to belower in males than in females (Table 2). Regardingside differences, a different bifurcation level in bothsides was seen in 15 cases (37.5%). There was onlyone case which had a high bifurcation on the leftside and a low bifurcation on the right side (Fig. 9).Frequent common stems in the superior thyroidartery, lingual, and facial arteries was observed in18 cases (22.5%). A common stem between thefacial and lingual arteries was found in 14 cases(17.5%), and between the lingual and the superiorthyroid arteries in 4 cases (5.0%). Although com-mon stems were found in 8 cases (44.4%) in thehigh bifurcation group and 10 cases (55.6%) in thestandard bifurcation group, no common stem wasobserved in the low bifurcation group.

Fig. 10 shows a typical case of a high bifurcationin the left neck and Fig. 11 indicates a typical caseof a low bifurcation.

3. Confluent part of the external jugular veinIn Type 1 the external jugular vein emptied di-

rectly into the subclavian vein, Type 2 into the ve-nous angle and Type 3 into the internal jugularvein. Forty cases (50.0%) were observed of Type 1,30 cases (37.5%) of Type 2, and 8 cases (10.0%) ofType 3. Observation was impossible in 2 cases due

to previous damage in this area from a student dis-section course.

4. Course of the hypoglossal nerveAlthough no relationship between the course of

the hypoglossal nerve and the bifurcation of the CCwas observed, the hypoglossal nerve made a gentlecurve in which the hypoglossal nerve crossed thesternocleidomastoid branch or a branch of the oc-cipital artery.

5. Course of the cervical ansaThe lateral type was seen in 39 cases (48.8%),

the medial type in 35 cases (43.7%), and 6 caseswere impossible to determine due to previousdamage.

6. Measurements of the inner diameter of mainarteries

The inner diameter of the superior thyroid arteryat 1 cm distal to the origin (point A) was 1.8 mm(max), 0.6 mm (min), and 1.1G 0.3 mm (mean).The inner diameter of the artery at 3 cm distal tothe origin (point A0) was 1.7 mm (max), 0.6 mm(min), and 1.0G 0.8 mm (mean). The inner diame-ter of the lingual artery at 1 cm distal to the origin(point B) was 2.8 mm (max), 0.7 mm (min), and1.3G 0.4 mm (mean). The inner diameter of theartery at 3 cm distal to the origin (point B 0) was2.2 mm (max), 0.6 mm (min), and 1.2G 0.3 mm(mean). The inner diameter of the facial artery at1 cm distal to the origin (point C) was 2.2 mm(max), 0.7 mm (min), and 1.5G 0.4 mm (mean).The inner diameter of the artery at 3 cm distal tothe origin (point C 0) was 2.2 mm (max), 0.7 mm(min), and 1.4G 0.3 mm (mean). The inner diame-ter of the external carotid artery at 1 cm distal tothe common carotid artery (point D) was 5.0 mm(max), 2.0 mm (min), and 3.5G 0.7 mm (mean).The inner diameter of the artery at 2 cm distal tothe origin (point D 0) was 4.8 mm (max); 1.2 mm(min), and 2.7G 0.8 mm (mean) (Table 3).

Discussion

The margins of the standard radical neck dissec-tion are decided as follows. The upper margin is theinferior margin of the mandible, the lower is thesupraclavicle, the posterior is the trapezius muscle,and the deep are the obliquus muscles. Fat tissue,fascia, interfascial lymph nodes and vessels andlymph nodes surrounding vessels were removed aswell as the internal jugular vein, sternocleidomas-toid muscle, and accessory nerve. According toMatsuura3) and Kamata4), a modified neck dissec-

Clinical Anatomy in the Neck Region 161

Fig. 8. The positions of reversed external and internal arteries.Upper left: Right side neck distant view, photographic findings.Upper right: Right side neck close-up view, photographic findings.Lower left: Right side neck distant view, anatomical sketch.Lower right: Right side neck close-up view, anatomical sketch.CC: Common carotid artery, ECA: External carotid artery, ICA: Internal carotid artery, LA: Lingual artery, SHA: Superiorthyroid artery, ijv: Internal jugular vein, SH: Sternohyoid muscle, OH: Omohyoid muscle, HB: Hyoid bone, GS: Sub-mandibular gland, ThG: Thyroid gland, X: Vagus nerve, XII: Hypoglossal nerve.

162 H. Ito et al.

tion is recommended due to the preservation offunction and morphology after an operation. Thismethod will preserve one of the following, namely,the internal jugular vein, sternocleidomastoid mus-cle, and accessory nerve. To these have also beenadded the supraomohyoid neck dissection in whichanatomical structures are removed above the omo-hyoid muscle. These procedures are quite similar tointernational classification5,6).

On the other hand, some structures must bepreserved due to post-operative function such likethe common carotid artery, vagus, especially therecurrent laryngeal nerve, hypoglossal and phrenicnerves. We need more precise knowledge regardingthese vessels and nerves.

The external and internal carotid arteries com-monly arise from the common carotid artery,

whereafter, the external carotid artery is locate an-teriorly to the internal carotid artery. Reversal ofthe location of the external and internal carotid ar-teries was found in 5 cases (6.3%). In all of thecases, the superior thyroid, lingual and facial ar-teries arose from the external carotid artery, thenran forward superiorly to the internal carotid ar-tery. The occipital artery arose from the anteriormargin of the external carotid artery, then randeeply to the external carotid artery and was dis-tributed to the occipital region. According to Ja-zuta7), the percentage of reversal of the locationbetween the external and internal carotid arterieswas 4.5% in adults. Our present data showed asimilar result. Although the reason why this rever-sal of the location of the two arteries is still notclear, operations should proceed carefully in thecase of the neck dissection and in the case of anemergency ligature of the external carotid artery tostop bleeding.

According to Adachi8), in 171 cases (80%) outof 214 cases, the height of bifurcation of the CCwas located between the transverse process of thethird and fourth cervical vertebrae. According toToyota9), the height of bifurcation of the CC was atthe level of the third vertebra in 240 arteries (147Japanese subjects) using cephaloangiography. Inour results, high bifurcation occurred in 25 (31.2%),standard bifurcation in 46 (57.5%), and low bifur-

Fig. 9. Difference of the bifurcation in the same individual.�: Bifurcation of the common carotid artery, CC: Common carotid artery.

Table 2.

Highbifurcationtype (%)

Standardbifurcationtype (%)

Lowbifurcationtype (%)

Male 14 (38.9) 20 (55.6) 2 (5.5)Female 11 (25.0) 26 (59.0) 7 (16.0)Total 25 (31.2) 46 (57.5) 9 (11.3)

Clinical Anatomy in the Neck Region 163

Fig. 10. A typical case of high bifurcation in the left neck.CC: Common carotid artery, ECA: External carotid artery, ICA: Internal carotid artery, TH: Thyrohyoid muscle, SH: Ster-nohyoid muscle, ST: Sternothyroid muscle, HB: Hyoid bone, XII: Hypoglossal nerve.

Fig. 11. A typical case of low bifurcation in the right neck.CC: Common carotid artery, ECA: External carotid artery, ICA: Internal carotid artery, ijv: Internal jugular vein, TH: Thy-rohyoid muscle, SH: Sternohyoid muscle, OH: Omohyoid muscle, HB: Hyoid bone, X: Vagus nerve.

164 H. Ito et al.

cation in 9 (11.3%) in a total of 80 cases. The per-centage of the standard type in our study is a littlesmaller than that of previous data.

A difference in bifurcation of the CC betweenthe right and left was not found, however, the leftside was little higher than the right. The height ofbifurcation tended to be lower in males than infemales. Regarding the side differences, a differentbifurcation at each side was seen in 15 cases(37.5%). There was only one case which had a highbifurcation on the left side and a low bifurcation onthe right. We suggest that a cause of these results isa morphogenetic difference between the externaland internal carotid arteries. According to Sa-dler10), embryologically, the external carotid arteryarises from the third aortic arch and unites parts ofthe first and second aortic arches. A part of originof the internal carotid artery arises from the thirdaortic arch and the remainders of the artery arisefrom the cranial part of the dorsal aorta. The levelof the bifurcation of the CC might be decided de-pending on how the internal carotid artery takes inthe segment of the third aortic arch. In our presentstudy, high bifurcation was when the common ca-rotid artery divided between the level of the secondand third cervical vertebrae or above the hyoidbone, and low bifurcation was when the CC dividedbetween the fourth and fifth vertebrae or near thethyroid cartilage.

Frequency of a common stem in the superiorthyroid artery, lingual, and facial arteries was ob-served in 18 cases out of 80 cases (22.5%). A com-mon stem between the facial and lingual arterieswas found in 14 cases (17.5%), and between thelingual and the superior thyroid arteries in 4 cases(5.0%). Although the common stem was found 8cases (44.4%) in the high bifurcation group and 10cases (55.6%) in the standard bifurcation group, nocommon stem was observed in the low bifurcationgroup. According to Adachi8), frequency of thecommon stem of superior thyroid, lingual and facialarteries increased in the high bifurcation group. We

obtained a similar result in our present study. In thecase of high bifurcation, branches of the externalcarotid artery tended to be a common stem due tothe limited space of the external artery, however, inthe case of low bifurcation, the branches of the ex-ternal carotid artery which are the superior thyroid,lingual and facial arteries tended to be independentarteries because the external carotid artery hasmore space.

According to Shima2) et al., a common stem be-tween the lingual and facial arteries was observedin 13 cases (21.7%) and the stem between the su-perior thyroid and lingual arteries was observed inone case (1.7%), namely in 14 cases out of 60 casescommon stems were observed using German ca-davers. The result of our present study was verysimilar to the result of the German study. Fre-quency of a common stem between the lingual andfacial arteries was greater than that of the lingualand superior arteries.

Furthermore, the superior thyroid artery tendsto be an independent branch in comparison withthe lingual and facial arteries. According to Ada-chi8), in 28 cases (13.3%) out of 214, the superiorthyroid artery arose from the common carotid ar-tery and in 58 cases (27.3%), the superior thyroidartery originated from near a bifurcation of thecommon carotid arteries. The reasons why thereare less common stem cases in the superior thyroidartery is enough space exists for the origin of thesuperior thyroid artery, because the superior thy-roid artery is the first branch of the external carotidartery after the bifurcation of the CC. However,according to Sato et al.11), the suggested reason wasthat each artery has a different course. Namely, thecourse of the lingual and facial arteries run superi-orly from the hyoid bone, and the course of the su-perior thyroid runs artery inferiorly from the hyoidbone.

According to Mochizuki12), the percentages ofthe external jugular vein which emptied directlyinto the subclavian vein (Type 1) was 49.9%, intothe venous angle (Type 2) was 36.6%, and into theinternal jugular vein (Type 3) was 12.5%, respec-tively. In our present study, we obtained a similarresult, forty cases (50.0%) were observed of Type1, 30 cases (37.5%) of Type 2, and 8 cases (10.0%)of Type 3. Two cases were difficult to observe dueto previous damage caused to the region by a stu-dent dissection course. On the base of the results, ifa ligature of the internal jugular vein is made at theupper clavicle margin, the blood stream of the ex-ternal carotid artery might be blocked.

The hypoglossal nerve is an important nervefor movement of the tongue. Although the inter-relationship between the course of the hypoglossal

Table 3.

Blood vessel diameter (mm)

Superiorthyroid artery

A A0

1.8@0.6 (1.1G 0.3) 1.7@0.6 (1.0G 0.8)Lingual artery B B 0

2.8@0.7 (1.3G 0.4) 2.2@0.6 (1.2G 0.3)Facial artery C C 0

2.2@0.7 (1.5G 0.4) 2.2@0.7 (1.4G 0.3)Externalcarotid artery

D D 0

5.0@2.0 (3.5G 0.7) 4.8@1.2 (2.7G 0.8)

Clinical Anatomy in the Neck Region 165

nerve and the level of bifurcation of the CC was notobserved clearly, the nerve tended to take a gentlecurve in the neck region and at the low bifurcationof the CC. The nerve looped round the inferiorsternocleidomastoid branch of the occipital arteryand having crossed the internal and external carotidarteries, it crossed the loop of the lingual artery alittle above the tip of the greater cornu of the hyoidbone, being itself crossed by the facial vein. Thesuperior and inferior branches of the occipital ar-tery ran to the sternocleidomastoid muscle. Wespeculated that the inferior branch might have aninfluence on the curved course of the hypoglossalnerve. According to Sato11), the location of the oc-cipital artery presumably decided the course of thehypoglossal nerve. Namely, the course of the occi-pital artery ran along the inferior margin of theposterior belly of the digastric muscle, and reachedmedial to the mastoid process. The artery thenpierced the propria dorsalis and trapezius muscles,and was distributed to the sternocleidomastoid andthe propria dorsalis muscles.

The lateral type was found in 39 cases (48.8%),the medial type in 35 cases (43.7%), and in 6 casesthe type was impossible to determine due to previ-ous damage. The cervical ansa is the nerve of thesuprahyoid muscles, and usually consists of the su-perior and inferior roots. The superior root consistsof the 1st, 2nd cervical and hypoglossal nerves, whilethe inferior root consists of the 2nd, 3rd and 4th

cervical nerves. There are two types: the medialand lateral types. In the lateral type, the superiorand inferior roots make a typical ansa superficial tothe internal jugular vein and in the medial type, thesuperior and inferior roots make an incompleteansa deep to the internal jugular vein. According toKazama13) and Kikuchi14), the percentages of thelateral type were 35.5%, 40.6% respectively. In thisstudy, our result indicated the percentage of thelateral type was 48.8% (39 cases).

For transplantations with vascular anastomosis,origin distribution and diameters of transplant andrecipient vessels should be selected as a morpho-logical condition. According to Lang et al.15–18), theorigin, course, distribution, and diameter of arteriesin the head and neck region were studied and thedata were applied clinically. According to Shima etal.19), the course, inner diameter, length and num-ber of venous valves were studied. These results areuseful for forearm transplantation. We made a de-cision to measure the inner diameter of arteries.

There are four methods to measure diameters ofarteries.1) Direct measurement of the outer diameter ofvessels using a sliding caliper20).2) Calculation of the inner diameter measurement

was made from an inner circumference after longi-tudinally opening a vessel21–24).3) Indirect measurement of the outer diameter25).4) Calculation of the inner diameter measurementwas made from an inner circumference after verti-cally cutting a vessel with 2 to 3 mm and longitudi-nally opening the vessel2,19,26).

In regard to the methods of Lang16), Imai25),measurement of true diameters was somewhat dif-ficult with these methods, because they measuredouter diameters. It was difficult to remove the con-nective tissue surrounding vessels and to maintainthe correct circum ference due to the flexibility ofthe vessels. Therefore, we selected the method ofYamashita23,24) and measured an inner diameter at1 cm and 3 cm from each origin of the branches ofthe external carotid artery. In accordance withShima et al.2), we measured the inner diameter ofthe external carotid artery at 1 cm and 2 cm fromthe bifurcation of the common carotid artery. Asignificant difference in the inner diameter of thesuperior thyroid artery between Japanese and Ger-man subjects was observed. The diameter of thesuperior thyroid artery was larger in Germans thanin Japanese (P < 0.05). A significant difference inthe diameter of the branches between the mesialand distal point was also found (P < 0.05). The di-ameters at the mesial point were larger than at thedistal point. However, in some cases of the diame-ter of the superior thyroid artery, the distal diame-ters were larger than the mesial diameters. Thereason why the distal diameter was larger than themesial was because there are many anastomosis inthe distal part of the superior thyroid artery. Thefacial artery had the largest inner diameter amongthe branches of the external carotid artery. Fromthis reason, the facial artery will be one of the mostbeneficial arteries for transplantation as a recipientartery.

Conclusions

Arteries and nerves in the neck region of fortycadavers (80 cases), 18 males (36 cases) and 22 fe-males (44 sides) were studied by dissection. Afterprecise dissection using a well-equipped stereo-microscope, photography and anatomical sketchingwas performed at each step. We obtained the fol-lowing results.1. Reversal of the location of the external and in-ternal carotid arteries was found in 5 cases (6.3%).2. In regard to the height of bifurcation of the CC,high bifurcation was seen in 25 (31.2%), standardbifurcation in 46 (57.5%), and low bifurcation in 9(11.3%) of totally 80 cases (36 males, 44 females).

166 H. Ito et al.

A frequency of a common stem in the superiorthyroid artery, lingual, and facial arteries was ob-served in 18 cases out of 80 cases (22.5%).3. Type 1 was where the external jugular vein di-rectly emptied into the subclavian vein, Type 2 intothe venous angle and Type 3 into the internaljugular vein. Forty cases (50.0%) were observed inType 1, 30 cases (37.5%) in Type 2, and 8 cases(10.0%) in Type 3.4. The course of the hypoglossal nerve made anacute curve and ran anterior-inferior in the neckregion in the case of no branches to the sternoclei-domastoid muscle, however, the nerve made a gen-tle curve when branches to the sternocleidomastoidmuscle existed.5. The lateral type of the cervical ansa was seen in39 cases (48.8%), while medial type was seen in 35cases (43.7%).6. The inner diameters of the superior thyroid ar-tery at 1 cm and 3 cm distal to the origin were1.1G 0.3 mm and 1.0G 0.8 mm, respectively. Theinner diameters of the lingual artery at 1 cm and3 cm distal to the origin were 1.3G 0.4 mm and1.2G 0.3 mm and the inner diameters of the facialartery at 1 cm and 3 cm distal to the origin were1.5G 0.4 mm and 1.4G 0.3 mm. The inner diame-ters of external carotid artery at 1 cm and 2 cmdistal to the origin were 3.5G 0.7 mm and2.7G 0.8 mm, respectively.

Acknowledgement

We acknowledge with thanks the assistance ofall staff of the Department of Maxillofacial SurgeryII and the Department of Anatomy, the NipponDental University School of Dentistry at Niigata.

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