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The Cervicocranium: Its Radiographic Assessment¹

¹ From the Department of Radiology, University of Texas Medical School, 6431 Fannin, MSB 2.100, Houston, TX 77030. Received October 26, 1999; revision requested December 7; revision received December 20; accepted February 1, 2000. Address correspondence to the author (e-mail: john.h.harris@uth.tmc.edu).

View larger version (121K): [in a new window]   Figure 1a. (a) Typical adequate open-mouth radiographic projection. The principal shortcoming of this particular open-mouth view is complete obscuration of the occipital condyles by the maxillary premolar and molar teeth (*). Obscuration of the tip of the dens is of secondary importance because of the rarity of a type I dens fracture. The lateral atlantodental asymmetry (arrows) is positional. The limitations of this open-mouth view are negated by (b) the normal cervicocranial prevertebral soft-tissue contour (arrowheads) as seen in this lateral projection, and the cervicocranium can be declared radiographically normal.

View larger version (133K): [in a new window]   Figure 1b. (a) Typical adequate open-mouth radiographic projection. The principal shortcoming of this particular open-mouth view is complete obscuration of the occipital condyles by the maxillary premolar and molar teeth (*). Obscuration of the tip of the dens is of secondary importance because of the rarity of a type I dens fracture. The lateral atlantodental asymmetry (arrows) is positional. The limitations of this open-mouth view are negated by (b) the normal cervicocranial prevertebral soft-tissue contour (arrowheads) as seen in this lateral projection, and the cervicocranium can be declared radiographically normal.

View larger version (0K): [in a new window]   Figure 2. Permission to reprint this figure electronically was denied by the publisher. Please see print version.

View larger version (58K): [in a new window]   Figure 3a. (a) Schematic representation shows an anterior view of the anterior ligaments of the cervicocranium. (Reprinted, with permission, from reference 3.) (b) Midsagittal schematic representation of the anterior soft-tissue anatomy of the cervicocranium. Arrowheads = retropharyngeal fascial space, AA = atlantoaxial ligament, AOM = anterior atlanto-occipital membrane, B = basion, C1 = anterior tubercle of the atlas, C2 = axis including its odontoid process, SC = superior constrictor muscle. (Adapted and reprinted, with permission, from reference 4.)

View larger version (88K): [in a new window]   Figure 3b. (a) Schematic representation shows an anterior view of the anterior ligaments of the cervicocranium. (Reprinted, with permission, from reference 3.) (b) Midsagittal schematic representation of the anterior soft-tissue anatomy of the cervicocranium. Arrowheads = retropharyngeal fascial space, AA = atlantoaxial ligament, AOM = anterior atlanto-occipital membrane, B = basion, C1 = anterior tubercle of the atlas, C2 = axis including its odontoid process, SC = superior constrictor muscle. (Adapted and reprinted, with permission, from reference 4.)

View larger version (158K): [in a new window]   Figure 4. Midsagittal cadaveric section shows the normal cervicocranial prevertebral soft-tissue contour (arrowheads), which is concave above and below the anterior tubercle (T) and convex anterior to the tubercle. (Reprinted, with permission, from reference 5.)

View larger version (88K): [in a new window]   Figure 5. Optimal open-mouth radiographic projection shows the intact occipital condyles (oc) and lateral masses (LM) of C1, the entire dens (D), and the axis body (AB). The right articular lateral mass of C1 is congenitally smaller than the left, which explains why the lateral atlantodental intervals are symmetric, while the lateral corner of the right lateral mass of C1 is not on the same vertical plane (line) as its C2 counterpart.

View larger version (160K): [in a new window]   Figure 6a. (a, b) Contact lateral radiographs show normal cervicocranial prevertebral soft-tissue contour (arrowheads) in two adults. Residual adenoidal tissue (*) can be seen in both.

View larger version (161K): [in a new window]   Figure 6b. (a, b) Contact lateral radiographs show normal cervicocranial prevertebral soft-tissue contour (arrowheads) in two adults. Residual adenoidal tissue (*) can be seen in both.

View larger version (111K): [in a new window]   Figure 7. Contact lateral radiograph in a 150-lb (68.2-kg) adult shows a normal cervicocranial prevertebral soft-tissue contour (arrowheads) partially obscured by the ascending mandibular rami (arrows).

View larger version (99K): [in a new window]   Figure 8. Contact lateral radiograph shows a normal cervicocranial prevertebral soft-tissue contour (arrowheads) in a large adult. Although it is obvious that the thickness of the cervicocranial prevertebral soft-tissue shadow is greater than that in 150-lb (68.2-kg) adults (as in Fig 7), the contour remains the same and is normal.

View larger version (142K): [in a new window]   Figure 9a. The effect of pharyngeal distention on the cervicocranial prevertebral soft-tissue contour in infants and young children. (a) On the initial contact lateral radiograph in an infant, the contour of the cervicocranial prevertebral soft tissue is diffusely abnormally convex (arrowheads). (b) On the repeat contact lateral radiograph obtained minutes later during inspiration, the cervicocranial prevertebral soft-tissue contour inferior to the C1 tubercle is concave (arrowheads) and, therefore, normal. The cervical spine was also declared clinically normal.

View larger version (140K): [in a new window]   Figure 9b. The effect of pharyngeal distention on the cervicocranial prevertebral soft-tissue contour in infants and young children. (a) On the initial contact lateral radiograph in an infant, the contour of the cervicocranial prevertebral soft tissue is diffusely abnormally convex (arrowheads). (b) On the repeat contact lateral radiograph obtained minutes later during inspiration, the cervicocranial prevertebral soft-tissue contour inferior to the C1 tubercle is concave (arrowheads) and, therefore, normal. The cervical spine was also declared clinically normal.

View larger version (116K): [in a new window]   Figure 10. Lateral cervical spine radiograph shows a normal cervicocranial prevertebral soft-tissue contour in a 3-year-old child. While not as precisely defined as in adults, the cervicocranial prevertebral soft-tissue contour (arrowheads) is concave above and below the atlas tubercle and convex anterior to the tubercle.

View larger version (114K): [in a new window]   Figure 11. Contact lateral radiograph of the cervical spine shows a normal cervicocranial prevertebral soft-tissue contour (arrowheads) in a 9-year-old child.

View larger version (82K): [in a new window]   Figure 12a. Comparison of (a) routine and (b) contact lateral radiographs obtained minutes apart in the same patient. (a) On a routine lateral radiograph, the cervicocranial prevertebral soft-tissue contour (arrowheads) is ill-defined and appears abnormal above (*) the C1 tubercle. Caudal to the tubercle, the contour is ambiguous. (b) Contact lateral radiograph shows the cervicocranial prevertebral soft-tissue contour (arrowheads) to be normal.

View larger version (78K): [in a new window]   Figure 12b. Comparison of (a) routine and (b) contact lateral radiographs obtained minutes apart in the same patient. (a) On a routine lateral radiograph, the cervicocranial prevertebral soft-tissue contour (arrowheads) is ill-defined and appears abnormal above (*) the C1 tubercle. Caudal to the tubercle, the contour is ambiguous. (b) Contact lateral radiograph shows the cervicocranial prevertebral soft-tissue contour (arrowheads) to be normal.

View larger version (114K): [in a new window]   Figure 13. Contact lateral radiograph of the cervicocranium shows a normal cervicocranial prevertebral soft-tissue contour (arrowheads) in the presence of a nasogastric tube. * = adenoidal tissue.

View larger version (25K): [in a new window]   Figure 14. Schematic shows the comparison of the average width of the cervicocranial prevertebral soft-tissue shadow anterior to the anterior tubercle of C1 (Y) between healthy individuals and patients with subtle fracture. The reader is urged to ignore the measurements per fracture type and instead compare the "Normal" width with the "All" width. The latter represents the average thickness in all patients in the fracture group. HD = high dens fracture (type II), JBF = Jefferson bursting fracture, LD = low dens fracture (type III).

View larger version (24K): [in a new window]   Figure 15. Schematic shows the comparison of the average area (stippled) between healthy individuals (Normal) and patients with subtle cervicocranial fracture (All). The reader is urged to compare only the averages to recognize the statistically significant difference between the healthy subjects and the fracture group. HD = high dens fracture (type II), JBF = Jefferson bursting fracture, LD = low dens fracture (type III).

View larger version (139K): [in a new window]   Figure 16a. (a) Contact lateral radiograph shows diffusely abnormal cervicocranial prevertebral soft-tissue contour (arrowheads) in a patient with bilateral C1 anterior arch fractures. (b) Transverse CT images show the bilateral C1 anterior arch fractures (solid arrows). On the left, the fracture extends into the left lateral mass of C1 (open arrow).

View larger version (156K): [in a new window]   Figure 16b. (a) Contact lateral radiograph shows diffusely abnormal cervicocranial prevertebral soft-tissue contour (arrowheads) in a patient with bilateral C1 anterior arch fractures. (b) Transverse CT images show the bilateral C1 anterior arch fractures (solid arrows). On the left, the fracture extends into the left lateral mass of C1 (open arrow).

View larger version (133K): [in a new window]   Figure 17a. Focally abnormal cervicocranial prevertebral soft-tissue contour. (a) On the contact lateral radiograph, the cervicocranial prevertebral soft-tissue shadow is convex (arrowheads) inferior to the anterior tubercle of C1 in a patient with a minimally displaced Jefferson bursting fracture (arrow). (b) Transverse and (c) sagittal CT images show the Jefferson bursting fracture (solid arrow in b) and a minimally displaced low (type III) dens fracture (open arrows in b and c).

View larger version (125K): [in a new window]   Figure 17b. Focally abnormal cervicocranial prevertebral soft-tissue contour. (a) On the contact lateral radiograph, the cervicocranial prevertebral soft-tissue shadow is convex (arrowheads) inferior to the anterior tubercle of C1 in a patient with a minimally displaced Jefferson bursting fracture (arrow). (b) Transverse and (c) sagittal CT images show the Jefferson bursting fracture (solid arrow in b) and a minimally displaced low (type III) dens fracture (open arrows in b and c).

View larger version (100K): [in a new window]   Figure 17c. Focally abnormal cervicocranial prevertebral soft-tissue contour. (a) On the contact lateral radiograph, the cervicocranial prevertebral soft-tissue shadow is convex (arrowheads) inferior to the anterior tubercle of C1 in a patient with a minimally displaced Jefferson bursting fracture (arrow). (b) Transverse and (c) sagittal CT images show the Jefferson bursting fracture (solid arrow in b) and a minimally displaced low (type III) dens fracture (open arrows in b and c).

View larger version (135K): [in a new window]   Figure 18a. (a) Contact lateral radiograph shows an anterosuperiorly oblique abnormal cervicocranial prevertebral soft-tissue contour (arrowheads). (b) Transverse CT images show that this patient has a type III right occipital condylar fracture (arrows).

View larger version (181K): [in a new window]   Figure 18b. (a) Contact lateral radiograph shows an anterosuperiorly oblique abnormal cervicocranial prevertebral soft-tissue contour (arrowheads). (b) Transverse CT images show that this patient has a type III right occipital condylar fracture (arrows).

View larger version (161K): [in a new window]   Figure 19a. The importance of pharyngeal distention relative to assessment of the cervicocranial prevertebral soft-tissue contour. (a) On the initial lateral cervical spine radiograph obtained with the patient recumbent, the soft palate (sp) and the uvula (u) are in contact with the posterior pharyngeal wall, thereby making assessment of the cervicocranial prevertebral soft-tissue shadow impossible. (b) On a contact lateral radiograph obtained during inspiration, a few minutes after a, the pharynx is well distended with air, revealing a normal cervicocranial prevertebral soft-tissue contour (arrowheads); therefore, the cervicocranium is negative.

View larger version (154K): [in a new window]   Figure 19b. The importance of pharyngeal distention relative to assessment of the cervicocranial prevertebral soft-tissue contour. (a) On the initial lateral cervical spine radiograph obtained with the patient recumbent, the soft palate (sp) and the uvula (u) are in contact with the posterior pharyngeal wall, thereby making assessment of the cervicocranial prevertebral soft-tissue shadow impossible. (b) On a contact lateral radiograph obtained during inspiration, a few minutes after a, the pharynx is well distended with air, revealing a normal cervicocranial prevertebral soft-tissue contour (arrowheads); therefore, the cervicocranium is negative.

View larger version (134K): [in a new window]   Figure 20a. Change in the cervicocranial prevertebral soft-tissue contour secondary to flexion. (a) On the neutral contact lateral radiograph, the cervicocranial prevertebral softtissue is concave (arrowhead) caudal to the atlantal tubercle. (b) On the flexed contact lateral radiograph, however, it becomes convex (arrowhead).

View larger version (138K): [in a new window]   Figure 20b. Change in the cervicocranial prevertebral soft-tissue contour secondary to flexion. (a) On the neutral contact lateral radiograph, the cervicocranial prevertebral softtissue is concave (arrowhead) caudal to the atlantal tubercle. (b) On the flexed contact lateral radiograph, however, it becomes convex (arrowhead).

View larger version (65K): [in a new window]   Figure 21. Obliteration of the cervicocranial prevertebral soft-tissue contour by fluid. Contact lateral radiograph of the cervicocranium with the patient supine shows the long air-fluid level (arrows) in the pharynx and nasopharynx interrupted by the uvula (u); this represents saliva or blood in the posterior recess of the pharynx.

View larger version (145K): [in a new window]   Figure 22. Lateral cervical spine radiograph shows a large nasopharyngeal hematoma (*) associated with a LeFort type III midfacial fracture that has completely obliterated the nasooropharyngeal airway and, consequently, impaired the ability to assess the cervicocranial prevertebral soft-tissue contour rostral and anterior to the anterior tubercle of the atlas. Therefore, this patient requires CT for evaluation of the cervicocranium.

View larger version (111K): [in a new window]   Figure 23. Lateral radiograph shows obliteration of the cervicocranial prevertebral soft-tissue contour by means of prevertebral soft-tissue swelling (arrows) associated with hyperextension dislocation of the lower cervical spine.

View larger version (123K): [in a new window]   Figure 24. Lateral radiograph shows abnormal cervicocranial prevertebral soft-tissue contour (arrows) secondary to retropharyngeal cellulitis in which the air-soft-tissue interface is irregular and ill defined, which is characteristic of retropharyngeal inflammation.

View larger version (157K): [in a new window]   Figure 25. Lateral radiograph shows abnormal cervicocranial prevertebral soft-tissue contour (black arrows) secondary to retropharyngeal cellulitis associated with massive adenoidal (*) and pharyngeal tonsillar hypertrophy (white arrows).

View larger version (150K): [in a new window]   Figure 26. Contact lateral radiograph shows a radiographically obvious type II traumatic spondylolisthesis (arrow). Although not necessary for diagnostic purposes, the cervicocranial prevertebral soft-tissue contour is abnormally convex (arrowheads) throughout its extent.

View larger version (114K): [in a new window]   Figure 27. Normal basion-axial interval (curly brace) and basion-dental interval (curved line). On the contact lateral radiograph of the cervicocranium, the basion-axial interval is the distance between the basion (arrowhead) and the posterior axial line (straight line). The basion-dental interval is the distance between the basion and the superior cortical margin of the dens (arrow). Normally, neither the basion-axial interval nor the basion-dental interval should exceed 12 mm.

View larger version (108K): [in a new window]   Figure 28. Lateral radiograph shows a grossly abnormal convex cervicocranial prevertebral soft-tissue shadow (arrowheads) associated with anterior-distracted occipitoatlantal subluxation in which the basion (arrow) is more than 12 mm anterior to the posterior axial line (line).

View larger version (106K): [in a new window]   Figure 29. Contact lateral radiograph shows the normal short angle (arrow) at the junction of the adenoidal tissue (*) and the cervicocranial prevertebral soft-tissue shadow (arrowheads).

View larger version (122K): [in a new window]   Figure 30a. Occipital condylar fracture with ipsilateral fracture of the mass of C1. (a) On the contact lateral radiograph, the cervicocranial prevertebral soft-tissue contour is abnormally convex (arrowheads) rostral to the anterior tubercle of C1. (b) Transverse CT image at the occipitoatlantal level shows the occipital condylar fracture (arrowhead) and fracture of the ipsilateral articular mass and transverse process of C1 (arrow).

View larger version (129K): [in a new window]   Figure 30b. Occipital condylar fracture with ipsilateral fracture of the mass of C1. (a) On the contact lateral radiograph, the cervicocranial prevertebral soft-tissue contour is abnormally convex (arrowheads) rostral to the anterior tubercle of C1. (b) Transverse CT image at the occipitoatlantal level shows the occipital condylar fracture (arrowhead) and fracture of the ipsilateral articular mass and transverse process of C1 (arrow).

View larger version (120K): [in a new window]   Figure 31a. Fracture of the lateral mass of C1. (a) The only abnormality seen on the contact lateral radiograph is the abnormal convex cervicocranial prevertebral soft-tissue contour (arrowheads). (b) Transverse CT images shows a minimally displaced fracture of the right lateral mass of C1 (arrows). Fractures of the lateral mass of C1 are rarely, if ever, visible on the lateral cervical spine radiograph.

View larger version (55K): [in a new window]   Figure 31b. Fracture of the lateral mass of C1. (a) The only abnormality seen on the contact lateral radiograph is the abnormal convex cervicocranial prevertebral soft-tissue contour (arrowheads). (b) Transverse CT images shows a minimally displaced fracture of the right lateral mass of C1 (arrows). Fractures of the lateral mass of C1 are rarely, if ever, visible on the lateral cervical spine radiograph.

View larger version (144K): [in a new window]   Figure 32a. Fracture of the anterior arch of C1 in a 2-year-old child. (a) The cervicocranial skeleton is negative on the contact lateral radiograph, but the cervicocranial prevertebral soft-tissue contour (arrowheads) is abnormally convex. The small soft-tissue mass (*) extending anterior to the cervicocranial prevertebral soft-tissue-air interface represents posterior pharyngeal lymphoid tissue. (b) Transverse CT images show that the abnormal convex contour in a is secondary to acute fracture of the right side of the anterior arch of C1 (arrow).

View larger version (85K): [in a new window]   Figure 32b. Fracture of the anterior arch of C1 in a 2-year-old child. (a) The cervicocranial skeleton is negative on the contact lateral radiograph, but the cervicocranial prevertebral soft-tissue contour (arrowheads) is abnormally convex. The small soft-tissue mass (*) extending anterior to the cervicocranial prevertebral soft-tissue-air interface represents posterior pharyngeal lymphoid tissue. (b) Transverse CT images show that the abnormal convex contour in a is secondary to acute fracture of the right side of the anterior arch of C1 (arrow).

View larger version (137K): [in a new window]   Figure 33a. Jefferson bursting fracture of C1. (a) The only abnormality on the contact lateral radiograph in this patient, who was in a major motor vehicle collision, is a grossly abnormal cervicocranial prevertebral soft-tissue contour (arrowheads). Specifically, all of the visualized cervicocranial skeleton is intact and in normal alignment. The abnormal cervicocranial prevertebral soft-tissue contour was the indication for (b) transverse cervicocranial CT, which demonstrated bilateral anterior arch of C1 fractures (solid arrows) and a subtle fracture at the junction of the lateral mass and the posterior arch of C1 on the right (open arrow).

View larger version (111K): [in a new window]   Figure 33b. Jefferson bursting fracture of C1. (a) The only abnormality on the contact lateral radiograph in this patient, who was in a major motor vehicle collision, is a grossly abnormal cervicocranial prevertebral soft-tissue contour (arrowheads). Specifically, all of the visualized cervicocranial skeleton is intact and in normal alignment. The abnormal cervicocranial prevertebral soft-tissue contour was the indication for (b) transverse cervicocranial CT, which demonstrated bilateral anterior arch of C1 fractures (solid arrows) and a subtle fracture at the junction of the lateral mass and the posterior arch of C1 on the right (open arrow).

View larger version (130K): [in a new window]   Figure 34. Abnormal cervicocranial prevertebral soft-tissue shadow associated with acute traumatic rupture of the transverse atlantal ligament. With this relatively underexposed contact lateral radiograph of the cervicocranium, it is difficult to assess the width of the anterior atlantodental interval. However, anterior displacement of the spinolaminar line of C1 (black arrow) with respect to that of C2 (white arrow) and the abnormal cervicocranial prevertebral soft-tissue contour (arrowheads) should create a high level of suspicion for this injury, which must then be confirmed with CT or MR imaging.

View larger version (159K): [in a new window]   Figure 35a. Subtle type II dens fracture with abnormal cervicocranial prevertebral soft-tissue contour. (a) Contact lateral radiograph shows an abnormally convex cervicocranial prevertebral soft-tissue contour (arrowheads) extending inferior to the anterior tubercle of C1. The axis ring is intact, and the base of the dens is obscured. (b) Sagittal and (c) coronal CT images confirm the minimally displaced type II dens fracture (arrows). The vertical hypoattenuating line of the superior facet of the right lateral mass of C1 (arrowhead in c) represents the superior margin of the tubercle for attachment of the transverse atlantal ligament and should not be mistaken for a fracture.

View larger version (97K): [in a new window]   Figure 35b. Subtle type II dens fracture with abnormal cervicocranial prevertebral soft-tissue contour. (a) Contact lateral radiograph shows an abnormally convex cervicocranial prevertebral soft-tissue contour (arrowheads) extending inferior to the anterior tubercle of C1. The axis ring is intact, and the base of the dens is obscured. (b) Sagittal and (c) coronal CT images confirm the minimally displaced type II dens fracture (arrows). The vertical hypoattenuating line of the superior facet of the right lateral mass of C1 (arrowhead in c) represents the superior margin of the tubercle for attachment of the transverse atlantal ligament and should not be mistaken for a fracture.

View larger version (110K): [in a new window]   Figure 35c. Subtle type II dens fracture with abnormal cervicocranial prevertebral soft-tissue contour. (a) Contact lateral radiograph shows an abnormally convex cervicocranial prevertebral soft-tissue contour (arrowheads) extending inferior to the anterior tubercle of C1. The axis ring is intact, and the base of the dens is obscured. (b) Sagittal and (c) coronal CT images confirm the minimally displaced type II dens fracture (arrows). The vertical hypoattenuating line of the superior facet of the right lateral mass of C1 (arrowhead in c) represents the superior margin of the tubercle for attachment of the transverse atlantal ligament and should not be mistaken for a fracture.

View larger version (142K): [in a new window]   Figure 36a. Type I atypical traumatic spondylolisthesis heralded by an abnormal cervicocranial prevertebral soft-tissue contour. (a) Contact lateral radiograph of the cervicocranium shows the abnormally convex cervicocranial prevertebral soft-tissue contour (arrowheads), even in the presence of a nasogastric tube. A pars interarticularis fracture line is not visible. (b) Transverse CT images show the atypical fracture line on the right (open arrows) and the pars interarticularis fracture on the left (solid arrows).

View larger version (61K): [in a new window]   Figure 36b. Type I atypical traumatic spondylolisthesis heralded by an abnormal cervicocranial prevertebral soft-tissue contour. (a) Contact lateral radiograph of the cervicocranium shows the abnormally convex cervicocranial prevertebral soft-tissue contour (arrowheads), even in the presence of a nasogastric tube. A pars interarticularis fracture line is not visible. (b) Transverse CT images show the atypical fracture line on the right (open arrows) and the pars interarticularis fracture on the left (solid arrows).

View larger version (148K): [in a new window]   Figure 37. Contact lateral radiograph demonstrates objective confirmation of an equivocal concavity of the cervicocranial prevertebral soft tissue (arrowheads) below the anterior atlantal tubercle. The thin column of air posterior to the line from the soft tissue anterior to the atlantal tubercle to the soft tissues anterior to the anterior-most cortex of the axis body demarcates the cervicocranial prevertebral soft-tissue concavity.

View larger version (139K): [in a new window]   Figure 38. False-positive cervicocranial prevertebral soft-tissue contour. On this contact lateral radiograph in a patient clinically suspected of having an acute cervical spine injury, the cervicocranial prevertebral soft-tissue contour is abnormally convex (arrowheads). A CT image of the cervicocranium (not shown), obtained because of the abnormal contour, was negative. Occipitoatlantal subluxation is excluded owing to the normal (<12-mm) distance between the posterior axial line and the basion (black arrow; basion-axial interval). The calcified dentate ligament (solid white arrow) indicates a normal basion-dental interval, which also is less than 12 mm. Rupture of the transverse atlantal ligament is excluded because of the normal anterior atlantodental interval (open white arrow).

View larger version (136K): [in a new window]   Figure 39a. False-negative cervicocranial prevertebral soft-tissue contour. (a) Lateral radiograph shows a normal cervicocranial prevertebral soft-tissue contour (arrowheads). (b) However, transverse CT images obtained because of severe cervicocranial pain and painful limitation of motion demonstrate a minimally displaced fracture of the right anterior arch of C1 (arrows).

View larger version (180K): [in a new window]   Figure 39b. False-negative cervicocranial prevertebral soft-tissue contour. (a) Lateral radiograph shows a normal cervicocranial prevertebral soft-tissue contour (arrowheads). (b) However, transverse CT images obtained because of severe cervicocranial pain and painful limitation of motion demonstrate a minimally displaced fracture of the right anterior arch of C1 (arrows).