Sternocleidomastoid muscle-splitting method for high cervical carotid endarterectomy: illustrative cases

Atsushi Sato Division of Neurosurgery, Ina Central Hospital, Ina, Nagano, Japan; and

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Tetsuo Sasaki Division of Neurosurgery, Ina Central Hospital, Ina, Nagano, Japan; and

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Toshihiro Ogiwara Division of Neurosurgery, Ina Central Hospital, Ina, Nagano, Japan; and

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Kazuhiro Hongo Division of Neurosurgery, Ina Central Hospital, Ina, Nagano, Japan; and

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Tetsuyoshi Horiuchi Department of Neurosurgery, Shinshu University School of Medicine, Matsumoto, Nagano, Japan

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BACKGROUND

The number of cervical carotid endarterectomies (CEAs) has decreased as carotid artery stenting (CAS) has increased. However, CEA and CAS both have advantages and disadvantages; therefore, appropriate procedures must be selected for individual patients. High-positioned carotid artery stenosis presents technical challenges for CEA and is occasionally managed by performing CAS. However, CAS is associated with a high risk of thrombosis in patients with soft plaques, suggesting a clinical need for a better procedure. Consequently, appropriate surgical treatment for patients requiring high-level CEAs is essential.

OBSERVATIONS

In this study, a novel and straightforward method was devised. The primary concept underlying this technique is separation of the sternocleidomastoid muscle (SCM) from other anatomical structures to ensure a wider surgical field. By anatomically separating the SCM into the sternal and clavicular head groups, the objective of the wider surgical field can be met. Herein, we report technical innovations in high-positioned carotid artery stenosis and evaluate their efficacy in two patients.

LESSONS

In conclusion, high CEA surgery using this new method is valuable and may eliminate barriers to more advanced approaches.

ABBREVIATIONS

3D = three-dimensional; CAS = carotid artery stenting; CEA = carotid endarterectomy; CTA = computed tomography angiography; MRA = magnetic resonance angiography; MRI = magnetic resonance imaging; SCM = sternocleidomastoid muscle; TOF = time of flight

BACKGROUND

The number of cervical carotid endarterectomies (CEAs) has decreased as carotid artery stenting (CAS) has increased. However, CEA and CAS both have advantages and disadvantages; therefore, appropriate procedures must be selected for individual patients. High-positioned carotid artery stenosis presents technical challenges for CEA and is occasionally managed by performing CAS. However, CAS is associated with a high risk of thrombosis in patients with soft plaques, suggesting a clinical need for a better procedure. Consequently, appropriate surgical treatment for patients requiring high-level CEAs is essential.

OBSERVATIONS

In this study, a novel and straightforward method was devised. The primary concept underlying this technique is separation of the sternocleidomastoid muscle (SCM) from other anatomical structures to ensure a wider surgical field. By anatomically separating the SCM into the sternal and clavicular head groups, the objective of the wider surgical field can be met. Herein, we report technical innovations in high-positioned carotid artery stenosis and evaluate their efficacy in two patients.

LESSONS

In conclusion, high CEA surgery using this new method is valuable and may eliminate barriers to more advanced approaches.

ABBREVIATIONS

3D = three-dimensional; CAS = carotid artery stenting; CEA = carotid endarterectomy; CTA = computed tomography angiography; MRA = magnetic resonance angiography; MRI = magnetic resonance imaging; SCM = sternocleidomastoid muscle; TOF = time of flight

In recent years, carotid artery stenting (CAS) has been increasingly used as a treatment for carotid artery stenosis instead of carotid endarterectomy (CEA). However, because CAS poses risks when treating vulnerable plaques, CEA remains a suitable procedure for such cases. Nonetheless, CAS is often selected for severe carotid artery stenosis because exposing the carotid artery to the high cervical region is challenging. If an appropriate technique could be developed for performing CEA in cases of high carotid artery stenosis, then CEA could be used to treat those cases effectively. A new technique would provide a feasible solution, particularly for unstable plaques that are located at high positions. Several treatment methods have been reported for high-neck CEA; however, in this case study, we propose a simpler and more innovative treatment method.

Illustrative Cases

Two patients were treated with the newly proposed sternocleidomastoid muscle (SCM) splitting method, which is described as follows. The patient was placed supine with the neck rotated to the contralateral side so that the mastoid was at the top of the horizontal plane. The lower jaw was elevated, the neck was fully extended, and the head was stabilized by fixation of the head frame. In principle, the temporal region should be approximately horizontal, and the line connecting the mastoid process and the anterior edge of the clavicle should be parallel to the direction of the trunk. A Z-shaped skin incision was made directly above the SCM. By cutting the platysma, the sternal and clavicular branches of the SCM were separated and moved forward and backward, respectively. At the upper end, we avoided cutting anteriorly or superiorly to the digastric muscle to preserve the mandibular branch of the facial nerve and expand the surgical field, until the digastric and hypoglossal nerves became visible. Because the jugular vein could be seen directly below the SCM, pulling it forward facilitated direct access to the carotid artery sheath. A wide, shallow surgical field was secured around the carotid artery if the SCM was sufficiently retracted anteroposteriorly. Incising and deploying this sheath fully exposed the common carotid artery bifurcation and the distal portion of the internal carotid artery.

Case 1

A 74-year-old male with a history of cerebral infarction developed a minor stroke and was hospitalized for treatment. A stenotic lesion was observed in the left internal carotid artery during the examination. A soft plaque was diagnosed based on fat-suppressed T1-weighted magnetic resonance imaging (MRI) and time-of-flight (TOF) magnetic resonance angiography (MRA; Fig. 1A and B). The walls were irregular and calcified. Three-dimensional computed tomography angiography (3D-CTA) of the left internal carotid artery stenosis revealed that the main site of stenosis was located at C2–3 (Fig. 1C). Consequently, performing CAS was considered high risk, and CEA was performed instead.

FIG. 1
FIG. 1

Case 1. Preoperative axial MRI and 3D-CTA and postoperative 3D-CTA are shown. A: Fat-suppressed T1-weighted MRI. B: TOF MRA. C: Preoperative 3D-CTA. D: Postoperative 3D-CTA. E: Postoperative axial CT. The white arrow demonstrates the surgical approach. F: Postoperative axial enhancement CT.

An oblique skin incision was made from the anterior to the posterior end of the SCM (Fig. 2A and B). Once the area between the sternal and clavicular heads of the SCM was visualized, the muscles were dissected by pulling back and forth with the forceps. The jugular vein was retracted anteriorly. Consequently, facial veins were not sacrificed. The digastric muscle was located in the front upper part of the surgical field and did not interfere with the surgery. To ensure sufficient intimal dissection at the upper edge of the plaque, the internal carotid artery was exposed 3 cm above the bifurcation. Sufficient space was secured even with a double-balloon shunt. After the intimal dissection, the vessels were approximated using 6–0 Gore-Tex sutures. No sutures were added to the avulsed area of the SCM, and the wound was closed by suturing the superficial layers, one layer at a time, until the surgery was completed. Postoperative 3D-CTA revealed an improvement in carotid stenosis (Fig. 1D), and axial CT images showed evidence of a split SCM (Fig. 1E). No major damage was observed in surrounding structures (Fig. 1F). Postoperatively, partial paresthesia was observed in the left mandible. We found no atrophy of the SCM, and no headaches or postoperative complications related to the surgery occurred. Sensory deficits eventually improved.

FIG. 2
FIG. 2

Case 1. A: The skin incision is indicated by the dotted line. B: Image showing the state of the wound after surgery with the neck extended. C: Image of the wound in normal head position.

Case 2

An 81-year-old male presented with cerebral infarction. He developed left-sided paresis and was admitted to our hospital for treatment. A stenotic lesion was observed in the right internal carotid artery. The patient subsequently developed chronic renal failure. Therefore, the use of contrast medium was contraindicated.

MRI revealed wall irregularities. A single angiography study of the right internal carotid artery showed that the main site of stenosis was C2–3. Based on these findings, CEA was performed. Subsequently, this patient achieved sufficient improvement in stenosis with the same technique used in Case 1. The patient presented with no neurological deficits and only mild swelling of the SCM for a few days. Postoperative 3D-CTA confirmed that the stenosis had improved because of good intimal ablation. To date, no surgery-related abnormalities or disorders have been reported.

Patient Informed Consent

The necessary patient informed consent was obtained in this

Discussion

Observations

CEA can be performed even in cases of high cervical stenosis by using the proposed SCM splitting method. Notably, the anatomy of the SCM must be fully understood to comprehend the basic principles of this method.

The SCM originates in the lateral superior marginal chain. It has an anterior component that extends from the entire surface to the mastoid process and a posterior component that originates from the medial end of the sternum and returns to the mastoid process through the entire lower surface (Fig. 3A). Because of the characteristics of this layered structure, by rotating the neck in the opposite direction to the side of the SCM, these two muscle groups are untwisted and run in parallel (Fig. 3B). Therefore, an exposed surface is revealed lengthwise between the two muscles. Detachment of the muscle surface after division does not impair the function of each muscle (Fig. 3C).

FIG. 3
FIG. 3

Diagram illustrating the relationship between positioning and the SCM. A: Standard CEA positioning. The dotted line indicates the SCM angle. B: The SCM is visible when the shoulders and temporal region are horizontal. The dotted line indicates the SCM angle. C: An image showing where the clavicular and sternal branches of the SCM are divided and the carotid artery bifurcation is exposed.

It should be noted that the auricular nerve runs across these two muscles. Considerable nerve damage can occur during cervical surgery even when approaching the leading edge of the SCM. The external jugular vein runs across both muscles, and they must be carefully moved upward or downward to obtain an unobstructed field of view when splitting the muscles. To confirm these anatomical structures, a Z-shaped skin incision was made below the anterior and posterior margins of the SCM (Fig. 2B and C), and the wound was fully expanded after the platysma muscle was dissected (Fig. 4B and C). Also, it was necessary to detach and move the nerves and blood vessel structures that obstructed the field of view (Fig. 4C). The upper border of the surgical field in a high-positioned CEA is primarily limited by the digastric muscle, although it is slightly displaced superiorly in this position. With close observation, the internal carotid artery and common carotid artery can be widely exposed in the shallow surgical field (Fig. 4E). The disadvantage of this method is that it can cause sensory disturbances around the wound due to damage of the greater auricular nerve. Also, if the cervical spine rotation is insufficient, the procedure can be difficult to perform.

FIG. 4
FIG. 4

Intraoperative images of the SCM-splitting method are shown. A: Exposed SCM. B: Splitting the SCM. C: Exposed jugular vein. D: The internal carotid artery is exposed, and the surrounding tissues are removed. E: Complete exposure of the intimal dissection area and secured carotid artery.

Reports on surgical techniques for high-positioned CEAs have used the posterior approach1–4; however, this approach3 requires the patient to be prone, and the surgical field behind the SCM must be slightly deeper. Studies have reported that aggressive surgery is possible with large backbends and positioning techniques,4 but positioning is difficult, and under those conditions the surgical field is viewed from a slightly angled direction. The method described in this report significantly facilitates surgery because it permits a shallow and wide surgical field through reasonable positioning.

The boundary between the sternal and clavicular head attachment muscles is usually visible, but the boundary becomes clearer at greater depths. Thus, if it is unclear, downward expansion of the surface exposure of the SCM is recommended.

One limitation of this method is that it requires a large degree of head rotation, which hinders its application in patients with limited rotation. Therefore, the neck rotation range should be assessed preoperatively. When splitting the SCM, surgeons should consider that damage to the greater auricular nerve can cause sensory disturbances around the mandible.

Lessons

The SCM-splitting method introduced herein is highly effective because it does not require extreme backward bending for high cervical surgery or prone positioning for posterior surgery and provides a wide and highly positioned surgical field. The surgery can proceed smoothly if sufficient preoperative lateral rotation is achieved. Temporal sensory disturbances occur mainly in the lower jaw as a complication. The period of muscle swelling can also be slightly prolonged.

Author Contributions

Conception and design: Sato. Acquisition of data: Sato, Ogiwara. Analysis and interpretation of data: Sato. Drafting the article: Sato. Critically revising the article: Sato, Hongo, Horiuchi. Reviewed submitted version of manuscript: Sato, Sasaki, Hongo. Approved the final version of the manuscript on behalf of all authors: Sato. Study supervision: Horiuchi.

Supplemental Information

Previous Presentations

Poster presentation at STROKE 2022, March 17, 2022, in Osaka, Japan.

References

  • 1

    Farhat-Sabet A, Aicher BO, Tolaymat B, et al. An alternative approach to carotid endarterectomy in the high carotid bifurcation. Ann Vasc Surg. 2020;65:240246.

  • 2

    Kondo T, Ota N, Göhre F, et al. High cervical carotid endarterectomy-outcome analysis. World Neurosurg. 2020;136:e108e118.

  • 3

    Sasaki T, Nakamura Y, Yomo S, et al. The posterior cervical triangle approach for high carotid artery exposure in carotid endarterectomy. J Neurosurg. 2012;116(3):680684.

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  • 4

    Takigawa T, Yanaka K, Yasuda M, Asakawa H, Matsumaru Y, Nose T Head and neck extension-fixation with a head frame for exposure of the distal internal carotid artery in carotid endarterectomy—technical note. Neurol Med Chir (Tokyo). 2003;43(5):271273.

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    • Export Citation
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  • FIG. 1

    Case 1. Preoperative axial MRI and 3D-CTA and postoperative 3D-CTA are shown. A: Fat-suppressed T1-weighted MRI. B: TOF MRA. C: Preoperative 3D-CTA. D: Postoperative 3D-CTA. E: Postoperative axial CT. The white arrow demonstrates the surgical approach. F: Postoperative axial enhancement CT.

  • FIG. 2

    Case 1. A: The skin incision is indicated by the dotted line. B: Image showing the state of the wound after surgery with the neck extended. C: Image of the wound in normal head position.

  • FIG. 3

    Diagram illustrating the relationship between positioning and the SCM. A: Standard CEA positioning. The dotted line indicates the SCM angle. B: The SCM is visible when the shoulders and temporal region are horizontal. The dotted line indicates the SCM angle. C: An image showing where the clavicular and sternal branches of the SCM are divided and the carotid artery bifurcation is exposed.

  • FIG. 4

    Intraoperative images of the SCM-splitting method are shown. A: Exposed SCM. B: Splitting the SCM. C: Exposed jugular vein. D: The internal carotid artery is exposed, and the surrounding tissues are removed. E: Complete exposure of the intimal dissection area and secured carotid artery.

  • 1

    Farhat-Sabet A, Aicher BO, Tolaymat B, et al. An alternative approach to carotid endarterectomy in the high carotid bifurcation. Ann Vasc Surg. 2020;65:240246.

  • 2

    Kondo T, Ota N, Göhre F, et al. High cervical carotid endarterectomy-outcome analysis. World Neurosurg. 2020;136:e108e118.

  • 3

    Sasaki T, Nakamura Y, Yomo S, et al. The posterior cervical triangle approach for high carotid artery exposure in carotid endarterectomy. J Neurosurg. 2012;116(3):680684.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Takigawa T, Yanaka K, Yasuda M, Asakawa H, Matsumaru Y, Nose T Head and neck extension-fixation with a head frame for exposure of the distal internal carotid artery in carotid endarterectomy—technical note. Neurol Med Chir (Tokyo). 2003;43(5):271273.

    • PubMed
    • Search Google Scholar
    • Export Citation

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