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Naissance inhabituelle de l’anse cervicale observée au cours d’une endartériectomie carotidienne
Cas cliniques Naissance inhabituelle de l’anse cervicale observee au cours d’une endart eriectomie carotidienne Ryan E. Accord, Phillipe Reyntjens, Martine Samyn, Johannes Reuwer, Venlo, Pays Bas
re carotide pour endarte riectomie exige la connaissance de l’anaL’abord chirurgical de l’arte riectomie carotidienne, une tomie normale et des variantes anatomiques. Pendant une endarte rieure de l’anse cervicale a e te trouve e. variante anatomique rare d’origine de la racine supe l’anatomie habituelle, aucune racine supe rieure de l’anse cervicale provenant Contrairement a te trouve e. Au lieu de cela, ce qui semblait e ^tre l’anse cervicale du nerf hypoglosse n’a e provenait du nerf vague et passait au-dessus de la bifurcation carotide, gagnant les muscles sous-hyoı¨diens. La section de cette anse cervicale, pour une bonne exposition, n’a eu aucune quence fonctionnelle ou cosme tique. conse
The surgical approach of the carotid artery for carotid endarterectomy demands knowledge of normal anatomy and anatomic variation. This knowledge not only prevents iatrogenic damage to essential vessels and nerves, but can also facilitate the procedure because some structures can be ligated or transacted without clinical consequences. The ansa cervicalis is frequently encountered during dissection of the carotid bifurcation. In some cases, sacrificing the ansa cervicalis might be necessary to obtain adequate exposure for safe arterial reconstruction. This article describes a rare anatomic variant of the origin of the upper root of the ansa cervicalis found during carotid endarterectomy and discusses the previously reported morphological variants.
DOI of original article: 10.1016/j.avsg.2010.02.010. Department of Surgery, Subdivision Vascular Surgery, VieCuri Medical Center, Venlo, Pays Bas. Correspondence : Ryan E. Accord, Department of Surgery, VieCuri Medical Centre, Tegelseweg 210, 5912 BL Venlo, Pays Bas, E-mail: [email protected] Ann Vasc Surg 2010; 24: 692.e17-692.e19 DOI: 10.1016/j.acvfr.2010.12.048 Ó Annals of Vascular Surgery Inc. e par ELSEVIER MASSON SAS Edit
CASE DESCRIPTION A 79-year-old male patient was referred to us by the neurologist after a recent transient ischemic attack, with clinical signs matching embolization to the left middle cerebral artery territory. Duplex and CT-scan of the carotid arteries revealed a more then 70% stenosis of the left internal carotid artery, making the patient a good candidate for carotid endarterectomy. One year previously, the patient had already undergone an uncomplicated right-sided carotid endarterectomy. Through a longitudinal skin incision, dissection was carried out following the medial border of the left sternocleidomastoid muscle until exposition of the common carotid artery. After opening the carotid sheath, the vagus nerve was identified running parallel and lateral to the common and internal carotid artery. Dissection of the cranial part op the carotid arteries revealed the hypoglossal nerve approximately 1 cm cranially to the bifurcation, passing transversely over the external and internal carotid arteries. However, contrary to the commonly found anatomy (Figs. 1A, 1B), no upper root of the ansa cervicalis originating from the hypoglossal nerve was found. Instead what seemed to be the ansa cervicalis originated from the vagus nerve and passed over the carotid bifurcation, branching to the infrahyoid muscles (Fig. 1C). Great effort was undertaken to preserve what was thought to be an atypical ansa cervicalis; nevertheless, sacrificing the nerve was needed to facilitate exposure for a safe endarterectomy. The endarterectomy itself was performed in a
756.e17
756.e18 Cas cliniques
Fig. 1. A Photograph of normal anatomy during leftsided carotid endarterectomy. B Corresponding schematic drawing of the cervical loop. The upper root of the ansa cervicalis (1), the descendens hypoglossi, branching from the hypoglossal nerve (n.XII) and giving of branches that will innervate the infrahyoid muscles (2-5). The upper root of the ansa cervicalis derives from C1. The inferior root (6) is formed from C2 or C3, and is also
Annales de chirurgie vasculaire
known as the descendens cervicalis. C A schematic drawing of the anatomic variant found in the presented case. The superior root of the ansa cervicalis originates from the nervus vagus (n.X) and not from the hypoglossal nerve (n.XII). CCA, common carotid artery; ICA, internal carotid artery; ECA, external carotid artery; IJV, internal jugular vein.
Vol. 24, No. 5, 2010
conventional way with primary closure of the arteriotomy. The patient made an uncomplicated postoperative recovery. Immediate postoperative evaluation and outpatient follow-up at 1 and 6 months revealed no signs of dysphagia and dysphonia or palsy of the homolateral hemi-tongue.
DISCUSSION The ansa cervicalis (formally known as the ansa hypoglossi) is formed by two roots, the superior root and the inferior root. The superior root normally derives from a branch of the hypoglossal nerve and is also known as the descendens hypoglossi (see Figs. 1A and B). The superior root contains fibers from C1 to C2, whereas the inferior root of the ansa cervicalis is formed from C2 or C3, and is also known as the descendens cervicalis. The upper and lower roots join to form a loop, which gives branches to all but one of the four infrahyoid muscles, specifically the sternothyroid, sternohyoid, and the omohyoid muscles. The infrahyoid muscles depress the hyoid bone and larynx during swallowing and speaking. Transection of the ansa cervicalis has no serious functional or cosmetic consequences.1 However, late changes in phonation have been described, but are not fully understood.2 The course, location, and function of the ansa cervicalis are well studied and described in otolaryngology literature, mainly because the ansa cervicalis is considered prime choice in laryngeal reinnervation surgery.3 Most frequently encountered variation involves the lower root of the ansa cervicalis,4 whereas upper root variation is less commonly observed. The published data revealed three reports describing an anatomic variant similar to our findings, but in human cadavers. Vollala et al. describe an upper root of the ansa cervicalis derived from the vagus.2 Muscular branches from this ansa cervicalis showed normal innervations of the infrahyoid muscles. Abu-Hijleh describes a bilateral absent ansa cervicalis replaced by a plexus formed by vagus nerves from C1 and C2 supplying the strap muscles.5 They named this plexus the vagocervical plexus.
Cas cliniques 756.e19
Rath and Anand found one ansa cervicalis replaced by a vagocervical complex during bilateral dissection of the neck in 200 human cadavers.6 The description of an alternative ansa cervicalis and replaced ansa cervicalis found in the cadaver studies strongly resembles our intraoperative findings. Interestingly, the operative report of the right-sided endarterectomy that our patient underwent 1 year prior, made notice of an absent ansa cervicalis and a very anterior course of the vagus nerve. Even though the operative report lacks details, we do suspect that this patient had a bilateral morphological variation of ansa cervicalis. What was labeled as a notable anteriorly located vagus nerve might very well have been alternative ansa cervicalis. The presented case illustrates the clinical significance of good anatomic knowledge of even rare anatomic variants. The unusual origin of the ansa cervicalis and its course made it necessary for the surgeon to sacrifice it to improve exposure of the carotid bifurcation. Follow-up revealed that this was without any clinical consequences.
The authors thank Xiomara Accord-Frijmersum for producing the illustrations used in this report.
REFERENCES 1. Loukas M, Thorsell A, Tubbs RS, et al. The ansa cervicalis revisited. Folia Morphol (Warsz) 2007;66:120-125. 2. Vollala VR, Bhat SM, Nayak S, et al. A rare origin of upper root of ansa cervicalis from vagus nerve: case report. Neuroanatomy 2005;4:8-9. 3. Chhetri DK, Berke GS. Ansa cervicalis nerve: review of the topographic anatomy and morphology. Laryngoscope 1997;107:1366-1372. 4. Khaki AA, Shokouhi G, Shoja MM, et al. Ansa cervicalis as a variant of spinal accessory nerve plexus: a case report. Clin Anat 2006;19:540-543. 5. Abu-Hijleh MF. Bilateral absence of ansa cervicalis replaced by vagocervical plexus: case report and literature review. Ann Anat 2005;187:121-125. 6. Rath G, Anand C. Vagocervical complex replacing an absent ansa cervicalis. Surg Radiol Anat 1994;16:441-443.
re carotide pour endarte riectomie exige la connaissance de l’anaL’abord chirurgical de l’arte riectomie carotidienne, une tomie normale et des variantes anatomiques. Pendant une endarte rieure de l’anse cervicale a e te trouve e. variante anatomique rare d’origine de la racine supe l’anatomie habituelle, aucune racine supe rieure de l’anse cervicale provenant Contrairement a te trouve e. Au lieu de cela, ce qui semblait e ^tre l’anse cervicale du nerf hypoglosse n’a e provenait du nerf vague et passait au-dessus de la bifurcation carotide, gagnant les muscles sous-hyoı¨diens. La section de cette anse cervicale, pour une bonne exposition, n’a eu aucune quence fonctionnelle ou cosme tique. conse
The surgical approach of the carotid artery for carotid endarterectomy demands knowledge of normal anatomy and anatomic variation. This knowledge not only prevents iatrogenic damage to essential vessels and nerves, but can also facilitate the procedure because some structures can be ligated or transacted without clinical consequences. The ansa cervicalis is frequently encountered during dissection of the carotid bifurcation. In some cases, sacrificing the ansa cervicalis might be necessary to obtain adequate exposure for safe arterial reconstruction. This article describes a rare anatomic variant of the origin of the upper root of the ansa cervicalis found during carotid endarterectomy and discusses the previously reported morphological variants.
DOI of original article: 10.1016/j.avsg.2010.02.010. Department of Surgery, Subdivision Vascular Surgery, VieCuri Medical Center, Venlo, Pays Bas. Correspondence : Ryan E. Accord, Department of Surgery, VieCuri Medical Centre, Tegelseweg 210, 5912 BL Venlo, Pays Bas, E-mail: [email protected] Ann Vasc Surg 2010; 24: 692.e17-692.e19 DOI: 10.1016/j.acvfr.2010.12.048 Ó Annals of Vascular Surgery Inc. e par ELSEVIER MASSON SAS Edit
CASE DESCRIPTION A 79-year-old male patient was referred to us by the neurologist after a recent transient ischemic attack, with clinical signs matching embolization to the left middle cerebral artery territory. Duplex and CT-scan of the carotid arteries revealed a more then 70% stenosis of the left internal carotid artery, making the patient a good candidate for carotid endarterectomy. One year previously, the patient had already undergone an uncomplicated right-sided carotid endarterectomy. Through a longitudinal skin incision, dissection was carried out following the medial border of the left sternocleidomastoid muscle until exposition of the common carotid artery. After opening the carotid sheath, the vagus nerve was identified running parallel and lateral to the common and internal carotid artery. Dissection of the cranial part op the carotid arteries revealed the hypoglossal nerve approximately 1 cm cranially to the bifurcation, passing transversely over the external and internal carotid arteries. However, contrary to the commonly found anatomy (Figs. 1A, 1B), no upper root of the ansa cervicalis originating from the hypoglossal nerve was found. Instead what seemed to be the ansa cervicalis originated from the vagus nerve and passed over the carotid bifurcation, branching to the infrahyoid muscles (Fig. 1C). Great effort was undertaken to preserve what was thought to be an atypical ansa cervicalis; nevertheless, sacrificing the nerve was needed to facilitate exposure for a safe endarterectomy. The endarterectomy itself was performed in a
756.e17
756.e18 Cas cliniques
Fig. 1. A Photograph of normal anatomy during leftsided carotid endarterectomy. B Corresponding schematic drawing of the cervical loop. The upper root of the ansa cervicalis (1), the descendens hypoglossi, branching from the hypoglossal nerve (n.XII) and giving of branches that will innervate the infrahyoid muscles (2-5). The upper root of the ansa cervicalis derives from C1. The inferior root (6) is formed from C2 or C3, and is also
Annales de chirurgie vasculaire
known as the descendens cervicalis. C A schematic drawing of the anatomic variant found in the presented case. The superior root of the ansa cervicalis originates from the nervus vagus (n.X) and not from the hypoglossal nerve (n.XII). CCA, common carotid artery; ICA, internal carotid artery; ECA, external carotid artery; IJV, internal jugular vein.
Vol. 24, No. 5, 2010
conventional way with primary closure of the arteriotomy. The patient made an uncomplicated postoperative recovery. Immediate postoperative evaluation and outpatient follow-up at 1 and 6 months revealed no signs of dysphagia and dysphonia or palsy of the homolateral hemi-tongue.
DISCUSSION The ansa cervicalis (formally known as the ansa hypoglossi) is formed by two roots, the superior root and the inferior root. The superior root normally derives from a branch of the hypoglossal nerve and is also known as the descendens hypoglossi (see Figs. 1A and B). The superior root contains fibers from C1 to C2, whereas the inferior root of the ansa cervicalis is formed from C2 or C3, and is also known as the descendens cervicalis. The upper and lower roots join to form a loop, which gives branches to all but one of the four infrahyoid muscles, specifically the sternothyroid, sternohyoid, and the omohyoid muscles. The infrahyoid muscles depress the hyoid bone and larynx during swallowing and speaking. Transection of the ansa cervicalis has no serious functional or cosmetic consequences.1 However, late changes in phonation have been described, but are not fully understood.2 The course, location, and function of the ansa cervicalis are well studied and described in otolaryngology literature, mainly because the ansa cervicalis is considered prime choice in laryngeal reinnervation surgery.3 Most frequently encountered variation involves the lower root of the ansa cervicalis,4 whereas upper root variation is less commonly observed. The published data revealed three reports describing an anatomic variant similar to our findings, but in human cadavers. Vollala et al. describe an upper root of the ansa cervicalis derived from the vagus.2 Muscular branches from this ansa cervicalis showed normal innervations of the infrahyoid muscles. Abu-Hijleh describes a bilateral absent ansa cervicalis replaced by a plexus formed by vagus nerves from C1 and C2 supplying the strap muscles.5 They named this plexus the vagocervical plexus.
Cas cliniques 756.e19
Rath and Anand found one ansa cervicalis replaced by a vagocervical complex during bilateral dissection of the neck in 200 human cadavers.6 The description of an alternative ansa cervicalis and replaced ansa cervicalis found in the cadaver studies strongly resembles our intraoperative findings. Interestingly, the operative report of the right-sided endarterectomy that our patient underwent 1 year prior, made notice of an absent ansa cervicalis and a very anterior course of the vagus nerve. Even though the operative report lacks details, we do suspect that this patient had a bilateral morphological variation of ansa cervicalis. What was labeled as a notable anteriorly located vagus nerve might very well have been alternative ansa cervicalis. The presented case illustrates the clinical significance of good anatomic knowledge of even rare anatomic variants. The unusual origin of the ansa cervicalis and its course made it necessary for the surgeon to sacrifice it to improve exposure of the carotid bifurcation. Follow-up revealed that this was without any clinical consequences.
The authors thank Xiomara Accord-Frijmersum for producing the illustrations used in this report.
REFERENCES 1. Loukas M, Thorsell A, Tubbs RS, et al. The ansa cervicalis revisited. Folia Morphol (Warsz) 2007;66:120-125. 2. Vollala VR, Bhat SM, Nayak S, et al. A rare origin of upper root of ansa cervicalis from vagus nerve: case report. Neuroanatomy 2005;4:8-9. 3. Chhetri DK, Berke GS. Ansa cervicalis nerve: review of the topographic anatomy and morphology. Laryngoscope 1997;107:1366-1372. 4. Khaki AA, Shokouhi G, Shoja MM, et al. Ansa cervicalis as a variant of spinal accessory nerve plexus: a case report. Clin Anat 2006;19:540-543. 5. Abu-Hijleh MF. Bilateral absence of ansa cervicalis replaced by vagocervical plexus: case report and literature review. Ann Anat 2005;187:121-125. 6. Rath G, Anand C. Vagocervical complex replacing an absent ansa cervicalis. Surg Radiol Anat 1994;16:441-443.