The cricothyroid artery typically originates as a branch of the superior thyroid
artery and courses medially to reach the median cricothyroid ligament. Anatomical
variations of this pattern are not well documented in the literature. We
present a case in which the left cricothyroid artery originated from the left superior
thyroid artery near the superior border of the thyroid cartilage and coursed
medially to pierce the thyroid lamina. This variation was found during a routine
anatomy dissection at the American University of the Caribbean School of Medicine.
The possible clinical implications and their relevance to emergency airway
management procedures are discussed

Cruz, GS

Louis, RG

Loukas, M

English

Via Medica Journals

Folia Morphol. Vol. 63, No. 3, pp. 359–362Copyright © 2004 Via MedicaISSN 0015–5659www.fm.viamedica.plC A S E  R E P O R T359Address for correspondence: Dr. Marios Loukas MD, PhD, Assistant Professor, Department of Anatomy, American University of theCaribbean, Jordan Road, Cupecoy, Lowlands, Sint Maarten, Netherlands Antilles, tel: 0599 545 2298 ext 224, fax: 0599 545 2440,e-mail: edsg2000@yahoo.comA case of an anomalous cricothyroid arteryMarios Loukas1, Robert G. Louis Jr.1, Giovanna Santoni Cruz11Department of Anatomy, American University of the Caribbean, Sint Maarten, Nederland Antilles[Received 6 April 2004; Accepted 14 May 2004]The cricothyroid artery typically originates as a branch of the superior thyroidartery and courses medially to reach the median cricothyroid ligament. Anatom-ical variations of this pattern are not well documented in the literature. Wepresent a case in which the left cricothyroid artery originated from the left supe-rior thyroid artery near the superior border of the thyroid cartilage and coursedmedially to pierce the thyroid lamina. This variation was found during a routineanatomy dissection at the American University of the Caribbean School of Med-icine. The possible clinical implications and their relevance to emergency airwaymanagement procedures are discussed.Key words: cricothyroid artery, thyroid lamina, cricothyroidmembrane, median cricothyroid ligament, cricothyroidostomy,cricothyrodectomyINTRODUCTIONThe cricothyroid artery is, at most, briefly men-tioned in anatomical literature. Most sources agreethat the cricothyroid artery usually arises from thesuperior thyroid artery and commonly has rich anas-tomoses with the superior laryngeal artery deep tothe lamina of the thyroid cartilage [1, 9, 19]. In ap-proximately 93% of cases, a transverse cricothyroidartery can be found to originate from the superiorthyroid artery [5]. In 1996, Dover et al. [5] foundthat in patients where a transverse cricothyroid ar-tery was present, 93% of these were seen coursingacross the upper one third of the cricothyroid mem-brane, while the remaining 7% cross the lower por-tion of the membrane. This study also identified col-lateral anastamoses between the transverse cricothy-roid arteries at the level of the cricothyroid membrane. The elective use of cricothyroidotomy for emer-gency airway management has been a topic of de-bate since Chevalier Jackson’s [8] paper on high tra-cheotomies. Jackson condemned the procedurestating that “no end of cases of laryngeal stenosis isthe result of these operations.”. However, Brantiganand Grow’s [3] study of 655 patients revived the useof this procedure by recommending routine use ofcricothyroidotomy in patients whose managementrequires tracheotomy. Since then numerous studieshave been published advocating cricothyroidotomiesas a safe and effective option for emergency airwaymanagement. The position of the cricothyroid ar-tery should be remembered as it is prone to injuryand haemorrhage during surgical procedures in thisregion. Knowledge of the anatomy of the region isinvaluable for the safe execution of emergency cri-cothyroidotomy. We present a case in which the lefttransverse cricothyroid artery arises from the leftsuperior thyroid artery and pierces the lamina of thethyroid cartilage.CASE REPORTDiscovery of the case presented here was madeduring a routine anatomical dissection of the anteri-or cervical triangle at the American University of theCaribbean School of Medicine in Sint Maarten, N.A.The specimen was found in a 75-year-old femalecadaver who had died of metastatic lung cancer.360Folia Morphol., 2004, Vol. 63, No. 3No other vascular anomalies were found within thearea in question. The dissection involved reflectionof the skin and superficial fascia with a midline inci-sion extending from the mental protuberance to thelevel of the jugular notch. After isolation of the ca-rotid sheath, the branches of the external carotidwere traced distally. The left superior thyroid arteryoriginated as the first anterior branch of the left ex-ternal carotid artery, slightly superior to the bifurca-tion of the common carotid artery. After curving in-feromedially, the superior thyroid artery immediate-ly gave rise to 3 branches. The infra-hyoid artery wasfound coursing superomedially along the inferiorborder of the hyoid bone. The superior laryngeal ar-tery was found coursing anteriorly to join with theinternal laryngeal nerve before piercing the thyrohy-oid membrane. The artery to the sternocleidomas-toid (superficial descending) was found coursing pos-teroinferiorly across the carotid sheath to supply theanterior border of the sternocleidomastoid muscle.After giving rise to these branches, the superior thy-roid artery continued its descent along the lateralborder of the left thyroid lamina. The artery presentedwas found at approximately one third of the dis-tance between the superior and inferior borders ofthe thyroid cartilage (Fig. 1, 2). No other brancheswere found before the terminating branches localisedto the superior pole of the thyroid gland. The localmusculature was then carefully reflected to reveal thecourse of the artery. After reflection of the sternohy-oid, omohyoid and thyrohyoid muscles, it was foundthat the artery continued medially for approximately1 cm, where it then pierced the thyroid cartilage. Anorifice of approximately 5 mm was found in the thy-roid lamina, which transmitted this artery to the in-ternal surface. A vertical incision was made down themidline of the thyroid cartilage to allow inspection ofthe distribution of the artery from the interior surfaceof the thyroid lamina. The artery was found to giveseveral small branches which continued on to supplythe underlying tissue. Similar inspection of the con-tralateral superior thyroid artery revealed that theanomaly was unilateral and typical branching patternswere observed on the right side of the specimen.Figure 1. The cricothyroid artery is penetrating the thyroid lamina instead of the thyroid membrane.361Marios Loukas et al., Cricothyroid arteryDISCUSSIONTo the best of our knowledge, this is the firstcase of an artery which pierces the thyroid cartilage.On the basis of accepted standards of nomencla-ture, an artery is named according to its termina-tion. Following these guidelines, we decided to namethis a transverse cricothyroid artery, despite its anom-alous origin and course.The embryological development of the head andneck is marked by the emergence of 6 paired pha-ryngeal arches, which appear as condensations ofmesenchyme during the Week 5 of development. Thelaryngeal cartilage, which includes the thyroid, cri-coid, arytenoid, corniculate and cuneiform cartilag-es, arises from a fusion of the cartilaginous compo-nents of the 4th and 6th pharyngeal arches [12]. Bloodvessel formation begins during Week 3 in the em-bryo.  Early vessels form from the coalescence of iso-lated cavities of condensed mesenchyme, which arelined internally by angioblasts. These cells are even-tually differentiated into the endothelial cells whichline the vasculature [14]. The pharyngeal arch arter-ies are derivatives of the paired ventral aorta whicharise as distal extensions of the truncus arteriosus[6]. The precise timing and co-ordination of theseevents is still a topic of much investigation, makingthe origin of this variation difficult to discern. It ispossible that in this patient the arterial developmentprogressed prior to the fusion of the 4th and 6th pha-ryngeal arches, leaving an ostium in the thyroid lam-ina, through which the transverse cricothryoid ar-tery could travel. Another possibility is that this ar-tery arose as a nutrient branch to the thyroid carti-lage during development and subsequently becameenlarged and replaced the typical cricothyroid artery.Since the discovery of this variation was madepost mortem, it is unknown whether the existenceof this branching pattern had any clinical conse-quences. However, the existence of this branchingpattern, in addition to its aberrant course, uncoversseveral possible surgical implications. The use of cri-cothyroidotomy for emergency airway managementhas been the topic of much investigation and con-troversy. The major controversy has generally focusedon the development of subglottic stenosis [2, 7, 11,16–18]. Other complications include local haemor-rhage caused by injury to the transverse cricothy-roid artery. Insertion of the tracheotomy tube be-fore ligation of the damaged vessels could lead toaspiration of blood by the patient and resulting suf-focation [15]. Despite these possible complications,there are many studies which advocate cricothy-roidotomy as a viable option for establishing an air-way in patients for whom oral or nasotracheal intu-bation is contraindicated.  Indications for cricothy-roidotomy include facial, neck or potential cervicalspine injury combined with airway compromise [10].In addition, cricothyroidotomy can be performedmore quickly and easily than tracheotomy becausethe cricothyroid membrane is located immediatelybeneath the skin and its landmarks are more easilylocalised [13]. Methods are described using bothhorizontal and vertical incision techniques [4]. Ad-vantages and disadvantages exist for both methods.A vertical incision will facilitate subsequent exten-sion of the incision caudally for classic tracheotomy.The disadvantages of this technique include an in-creased risk of damage to the cricoid cartilage aswell as haemorrhage from the cricothyroid artery [4].A horizontal incision along the lower portion of thecricothryoid membrane decreases the risk of vascu-lar injury but may cause the cannula to tilt and scrapeagainst the tracheal wall. Execution of this proce-dure using either technique requires knowledge oflocal anatomy in order to minimise the chance ofcomplications.During the course of routine dissections in themedical anatomy laboratory, students are not typi-cally instructed to observe or document anatomicalvariations. The purpose of these dissections is to pro-vide the students with detailed instruction of typicalanatomical structures along with any common vari-ations. It has not escaped our attention that thisFigure 2. Schematic representation of the neck area with theanomalous cricothyroid artery.Common carotid arterySuperiorthryroid arteryAbnormal transversecricothyroid artery362Folia Morphol., 2004, Vol. 63, No. 3variation could have been overlooked due to the in-structive rather than investigative nature of mostclassroom dissections. An anatomical study involv-ing many cadavers which systematically documentsthe origin and course of the cricothyroid artery wouldbe needed in order to determine the prevalence ofthis anomaly. Such a study would serve to clarify thepatterns of anatomical variation in the superior thy-roid and cricothyroid arteries and provide a moreaccurate base of knowledge for the guidelines foremergency airway management procedures.REFERENCES1. Bergmann RA, Thompson SA, Afifi AK, Saadeh FA(1988) Compendium of human anatomic variation.Urban and Schwarzenberg, Baltimore, pp. 353–367.2. Boyd AD, Romita MC, Conlan AA, Fink SD, Spencer FC(1979) A clinical evaluation of cricothyroidotomy. SurgGynecol Obstet, 149: 365–368.3. Brantigan CO, Grow Sr JB (1978) Cricothyroidotomy:Elective use in respiratory problems requiring trache-otomy. J Thor Card Surg, 71: 72–80.4. Cole RR, Aguilar EA (1988) Cricothyroidotomy versustracheotomy: an otolaryngologists perspective. Laryn-goscope, 98: 131–135.5. Dover K, Howdieshell, TR, Colborn GL (1996) The di-mensions and vascular anatomy of the cricothyroidmembrane: relevance to emergent surgical airwayaccess. Clin Anat, 9: 291–295.6. Drews U (1995) Color atlas of embryology. ThiemeMedical. New York, pp. 174–175.7. Esses BA, Jafek BW (1987) Cricothyroidotomy: a de-cade of experience in Denver. Ann Otol Rhinol Laryn-gol, 96: 519–524.8. Jackson C (1921) High tracheostomy and other errorsthe chief causes of chronic laryngeal stenosis. Surg Gy-necol Obstet, 32: 392–398.9. Lippert H, Pabst R (1985) Arterial variations in man:classification and frequency. JF Bergman. Munich,pp. 83–84.10. McGill J, Clinton JE, Ruiz E, (1982) Cricothyroidotomyin the Emergency Department. Ann Emerg Med, 11:361–364.11. O’Connor JV, Reddy K, Ergin MA, Griepp RB (1985)Cricothyroidotomy for prolonged ventilatory supportafter cardiac operations. Ann Thorac Surg, 39: 353–354.12. Sadler TW (1995) Langman’s Medical Embryology.Williams and Wilkins. Chapel Hill N.C., p. 317.13. Safar P, Penninckx J (1967) Cricothyroid membranepuncture with special cannula. Anesthesiology, 28:943–948.14. Sweeney LJ (1998) Basic concepts in embryology.Mcgraw-Hill. Pennsylvania, pp. 270–271.15. Unger KM, Moser KM (1973) Fatal complication of tran-stracheal aspiration. Arch Intern Med, 132: 437–439.16. van Hasselt EJ, Bruining HA, Hoeve LJ (1985) Electivecricothyroidotomy. Intensive Care Med, 11: 207–209.17. Walls RM (1988) Cricothyroidotomy. Emer Med Clinof North Am, 6: 725–736.18. Weymuller EA (1982) Cricothyroidotomy controversy.Ann Otol Rhinol Laryngol, 9: 670.19. Williams PL, Warrick M, Dyson M, Bannister LH (eds.).(1989) Gray’s anatomy. Churchill Livingstone. NewYork, pp. 1253–1254.

A case of an anomalous cricothyroid artery

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A case of an anomalous cricothyroid artery

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