Neuro-radiology
Neuroradiology (1992) 35:55-56
9 Springer-Verlag 1992
Bilateral aberrant cervical internal carotid arteries D. J. Shanley Department of Radiology, Tripler Army Medical Center, Honolulu, Hawaii, USA Received: 12 February 1992
Summary. A patient with symptomatic bilateral aberrant cervical internal carotid arteries, demonstrated on CT and MRI, is described.
Key words: Internal carotid artery - Computed tomography - Magnetic resonance imaging - Magnetic resonance angiography
The aberrant internal carotid artery is an uncommon anomaly which poses a significant risk for the unsuspecting otolaryngologist or head and neck surgeon.
Case note A 65-year-old women complained of intermittent hoarseness and foreign body sensation in her throat for 7 years. She had no history of hypertension or other significant medical problem. Visual inspection of the oropharynx and indirect laryngoscopy revealed mild hyperemia of the posterior pharynx and a slight bulge bilaterally in the soft tissues of the posterior pharyngeal wall. Contrast-enhanced CT of the neck and head demonstrated a vascular structure extending from the level of the hyoid bone to the base of the skull on each side of the midline in the retropharyngeal space (Fig. 1). By tracing their course proximally and distally it was possible to identify these structures as the internal carotid arteries. MRI of the neck again demonstrated the medially-lying internal carotid arteries in the posterior pharyngeal area (Fig.2). MR angiography (MRA) clearly demonstrated the aberrant course of the internal carotid arteries (Fig.3).
Discussion Frequently asymptomatic, the anomalous cervical internal carotid artery is typically found on the right of the pharynx during routine physical examination or as an incidental finding on CT or MRI of the neck. Thorough inspection and palpation of the pharynx, as well as awareness of the anomaly, are essential to avoid accidental injury to the vessel during surgery [1-3].
The common carotid artery normally bifurcates at the C3--4 or C4--5 level, giving rise to the external and internal carotid arteries. The internal carotid artery courses cephalad within the carotid sheath, accompanied by the internal jugular vein and vagus nerve and lying deep to the sternocleidomastoid muscle. Initially, the internal carotid artery is usually posterolateral to the external carotid artery, assuming a more medial location as it approaches the skull base. The cervical segment of the internal carotid artery can be further subdivided into a lower, sternomastoid, portion and an upper, retrostyloid, portion as it courses through the parapharyngeal space [4]. The sternomastoid internal carotid artery is normally lateral to the pharyngeal wall and the middle and inferior constrictor muscles, anterior to the prevertebral muscles, and posterior and slightly medial to the external carotid artery. The internal carotid artery enters the retrostyloid region after coursing above the inferior border of the posterior belly of the digastric muscle, and normally lies lateral to the pharyngeal wall. Embryologically, the internal carotid artery originates from the third aortic arch and the dorsal aorta [5-7]. A sharp angulation is found at the junction of these vessels. The glossopharyngeal nerve crosses the developing carotid artery at this bend. Normally, the dorsal aortic root descends into the chest by the 8th week of development, straightening the course of the internal carotid artery. Kelly [7] postulated that incomplete straightening of the vessel enables the embryonic angulation to persist, resulting in a congenitally tortuous internal carotid artery. Pronounced growth of the dorsal aortic arch component decreases the traction on the embryonic bend as the heart descends into the chest. Marked asymmetry in the relative growth of the dorsal aortic arch component will significantly influence the degree and level of tortuosity. Anatomic descriptions of tortuous internal carotid arteries in the otolaryngology literature range from mild kinking to the formation of complete circular loops. Congenital tortuosity of the artery may become more pronounced during adult life due to atherosclerotic or hypertensive changes in the wall of the vessel. CT, conven-
56
Fig.1. Contrast enhanced CTimages of the neck (a-e from below upward) demonstrate the near-midline course of the aberrant internal carotid arteries (arrowheads) in the retropharyngeal space Ng.2. Coronal Tl-weighted (SE 700/18) MRI of the neck shows the medial course of the internal carotid arteries (arrows) Fig. 3. Anterior view of MR angiogram demonstrates the aberrant course of the internal carotid arteries
(arrows)
tional angiography, and M R I are useful modalities for d e m o n s t r a t i n g the a b e r r a n t position and course of the artery, but the multiplanar capability of M R I provides greater a n a t o m i c detail of the pharynx. M R A provides a noninvasive technique for imaging the carotid system, c o m p l e m e n t i n g the information o b t a i n e d f r o m the routine spin-echo study without significantly prolonging the examination time.
3. Frokjer GM, Carter JB, Knibbe MA (1988) Soft tissue mass of posterior pharyngeal wall. J Oral Maxillofac Surg 46:48-51 4. Newton T, Potts D (eds) (1974) Radiology of the skull and brain. Angiography. Mosby, St. Louis, pp 1202-1207 5. Bergovist B (1946) Anomalies in the course of arteria carotis interna in the upper region of the pharynx. Acta Otolaryngol (Stockh) 34:246255 6. Ricciardelli E, Hillel AD, Schwartz AN (1989) Aberrant carotid artery. Arch Otolaryngol Head Neck Surg 115:519-522 7. Kelly AB (1925) Tortuosity of the internal carotid in relation to the pharynx. J Laryngol Oto140:15-23
References 1. McKenzie W, Woolf CI (1959) Carotid abnormalities and adenoid surgery. J Laryngol Oto173:596~602 2. Skillern PG (1913) Anomalous internal carotid artery and its clinical significance in operations on tonsils. JAMA 60:172-173
Dean J. Shanley, D. O. Department of Radiology Tripler Army Medical Center Honolulu, HI 96859, USA
Neuroradiology (1992) 35:55-56
9 Springer-Verlag 1992
Bilateral aberrant cervical internal carotid arteries D. J. Shanley Department of Radiology, Tripler Army Medical Center, Honolulu, Hawaii, USA Received: 12 February 1992
Summary. A patient with symptomatic bilateral aberrant cervical internal carotid arteries, demonstrated on CT and MRI, is described.
Key words: Internal carotid artery - Computed tomography - Magnetic resonance imaging - Magnetic resonance angiography
The aberrant internal carotid artery is an uncommon anomaly which poses a significant risk for the unsuspecting otolaryngologist or head and neck surgeon.
Case note A 65-year-old women complained of intermittent hoarseness and foreign body sensation in her throat for 7 years. She had no history of hypertension or other significant medical problem. Visual inspection of the oropharynx and indirect laryngoscopy revealed mild hyperemia of the posterior pharynx and a slight bulge bilaterally in the soft tissues of the posterior pharyngeal wall. Contrast-enhanced CT of the neck and head demonstrated a vascular structure extending from the level of the hyoid bone to the base of the skull on each side of the midline in the retropharyngeal space (Fig. 1). By tracing their course proximally and distally it was possible to identify these structures as the internal carotid arteries. MRI of the neck again demonstrated the medially-lying internal carotid arteries in the posterior pharyngeal area (Fig.2). MR angiography (MRA) clearly demonstrated the aberrant course of the internal carotid arteries (Fig.3).
Discussion Frequently asymptomatic, the anomalous cervical internal carotid artery is typically found on the right of the pharynx during routine physical examination or as an incidental finding on CT or MRI of the neck. Thorough inspection and palpation of the pharynx, as well as awareness of the anomaly, are essential to avoid accidental injury to the vessel during surgery [1-3].
The common carotid artery normally bifurcates at the C3--4 or C4--5 level, giving rise to the external and internal carotid arteries. The internal carotid artery courses cephalad within the carotid sheath, accompanied by the internal jugular vein and vagus nerve and lying deep to the sternocleidomastoid muscle. Initially, the internal carotid artery is usually posterolateral to the external carotid artery, assuming a more medial location as it approaches the skull base. The cervical segment of the internal carotid artery can be further subdivided into a lower, sternomastoid, portion and an upper, retrostyloid, portion as it courses through the parapharyngeal space [4]. The sternomastoid internal carotid artery is normally lateral to the pharyngeal wall and the middle and inferior constrictor muscles, anterior to the prevertebral muscles, and posterior and slightly medial to the external carotid artery. The internal carotid artery enters the retrostyloid region after coursing above the inferior border of the posterior belly of the digastric muscle, and normally lies lateral to the pharyngeal wall. Embryologically, the internal carotid artery originates from the third aortic arch and the dorsal aorta [5-7]. A sharp angulation is found at the junction of these vessels. The glossopharyngeal nerve crosses the developing carotid artery at this bend. Normally, the dorsal aortic root descends into the chest by the 8th week of development, straightening the course of the internal carotid artery. Kelly [7] postulated that incomplete straightening of the vessel enables the embryonic angulation to persist, resulting in a congenitally tortuous internal carotid artery. Pronounced growth of the dorsal aortic arch component decreases the traction on the embryonic bend as the heart descends into the chest. Marked asymmetry in the relative growth of the dorsal aortic arch component will significantly influence the degree and level of tortuosity. Anatomic descriptions of tortuous internal carotid arteries in the otolaryngology literature range from mild kinking to the formation of complete circular loops. Congenital tortuosity of the artery may become more pronounced during adult life due to atherosclerotic or hypertensive changes in the wall of the vessel. CT, conven-
56
Fig.1. Contrast enhanced CTimages of the neck (a-e from below upward) demonstrate the near-midline course of the aberrant internal carotid arteries (arrowheads) in the retropharyngeal space Ng.2. Coronal Tl-weighted (SE 700/18) MRI of the neck shows the medial course of the internal carotid arteries (arrows) Fig. 3. Anterior view of MR angiogram demonstrates the aberrant course of the internal carotid arteries
(arrows)
tional angiography, and M R I are useful modalities for d e m o n s t r a t i n g the a b e r r a n t position and course of the artery, but the multiplanar capability of M R I provides greater a n a t o m i c detail of the pharynx. M R A provides a noninvasive technique for imaging the carotid system, c o m p l e m e n t i n g the information o b t a i n e d f r o m the routine spin-echo study without significantly prolonging the examination time.
3. Frokjer GM, Carter JB, Knibbe MA (1988) Soft tissue mass of posterior pharyngeal wall. J Oral Maxillofac Surg 46:48-51 4. Newton T, Potts D (eds) (1974) Radiology of the skull and brain. Angiography. Mosby, St. Louis, pp 1202-1207 5. Bergovist B (1946) Anomalies in the course of arteria carotis interna in the upper region of the pharynx. Acta Otolaryngol (Stockh) 34:246255 6. Ricciardelli E, Hillel AD, Schwartz AN (1989) Aberrant carotid artery. Arch Otolaryngol Head Neck Surg 115:519-522 7. Kelly AB (1925) Tortuosity of the internal carotid in relation to the pharynx. J Laryngol Oto140:15-23
References 1. McKenzie W, Woolf CI (1959) Carotid abnormalities and adenoid surgery. J Laryngol Oto173:596~602 2. Skillern PG (1913) Anomalous internal carotid artery and its clinical significance in operations on tonsils. JAMA 60:172-173
Dean J. Shanley, D. O. Department of Radiology Tripler Army Medical Center Honolulu, HI 96859, USA
