CT Cervical Spine

Normal anatomy, Variants and Trauma

1. CT Cervical Spine Dr. Yash Kumar Achantani OSR

2. Anatomy The cervical spine is the upper part of the spine extending from the skull base to the thorax. It normally consists of seven vertebrae. Its main function is to support the skull and maintain the relative positions of the brain and spinal cord. The normal cervical spine is curved - convex in front and concave at the back (cervical lordosis)

3. Of the seven cervical vertebrae, C1 (atlas) and C2 (axis) have very distinct anatomical features and are called atypical vertebra. C3 through C6 have typical anatomy (typical vertebra), while C7 looks very similar. Gross anatomy (typical vertebra) Small, oval-sized vertebral bodies Relatively wide vertebral arch with large vertebral foramen Relatively long, bifid (except for C7) inferiorly pointing spinous processes Transverse foramina protecting the vertebral arteries and veins

4. Anterior components of the typical cervical vertebra  : Body Pedicle Tranverse process Inferior articular process

5. Posterior components of the typical cervical vertebra  : Lamina Bifid spinous process Superior articular process Inferior articular process

6. First cervical vertebra C1- Atlas. It is an atypical cervical vertebra with unique features. It articulates with the dens of the axis and the occiput The atlas is composed of an anterior arch and a posterior arch, paired lateral masses, and paired transverse processes. It has the dens of the axis sit where a centrum (body) of a typical vertebra would be. The transverse ligament holds the dens of the axis against the anterior arch of the atlas and divides its vertebral canal into two parts. The anterior 1/3 is occupied by the dens. The posterior 2/3 contains the spinal cord

7. Second cervical vertebra C2- Axis It is an atypical cervical vertebra with unique features and important relations that make it easily recognisable. Its most prominent feature is the odontoid process, which is embryologically the body of the atlas (C1) . It plays an important role in rotation of the head with the majority of movement occurring around the dens and at the atlanto -axial joint.

8. Indications for CT cervical spine The most common indication for CT C-spine is suspicion of C-spine trauma in case of MVA. Other indications Persistent pain or radiculopathy, with > 6 weeks of conservative therapy and inadequate response to treatment New or progressive neurologic symptoms or deficits, e.g. motor or sensory loss attributable to cervical pathology. Fracture evaluation for suspected or known fracture

9. Injuries related to C1 vertebra Craniocervical Dissociation. Atlanto -occipital dissociation injuries Atlanto -axial subluxation Occipital Condyle Injuries. Fractures of the Atlas. Type I: isolated posterior arch fracture Type II: isolated anterior arch fracture Type III (Jefferson fracture): anterior and posterior arch fractures Type IV: comminuted lateral mass fracture

10. Atlanto -occipital dissociation injuries are severe and include both atlanto -occipital dislocations and atlanto -occipital subluxations. The key to the diagnosis, in addition to visualising gross disruption of the normal alignment of the atlanto -occipital joint, hinges on using a number of lines. 1. Basion -dens interval (BDI) >10 mm in adults 2. Basion -axial interval (BAI) >12 mm in adults 3. Powers ratio >1 (insensitive to a vertical distraction injury or posterior dissociation) 4. Atlantodental interval (ADI) >3 mm in adult males >2.5 mm in adult females

11. Normal intervals of the craniocervical junction. Midsagittal half-space volume-rendered CT image shows the Atlantodental interval (solid line), Basion -dens interval (double-headed arrow), Posterior axial line (dashed line), Basion -to – posterior axial line interval (dotted line), C1 – C2 spinolaminar distance (parallel lines).

12. Volume-rendered CT image shows the normal relationship of an occipital condyle and the lateral mass of C1, with close apposition, and the nearly equidistant intervals (solid lines) along all points in the midsagittal plane of the joint.

13. Volume-rendered CT image of a patient with atlanto -occipital dissociation after an MVC shows The “V sign” of cranially divergent predental lines (solid lines), A widened basion -dens interval (double-headed arrow), The posterior axial line (dashed line), A widened basion -to – posterior axial line interval (dotted line), And a widened C1 – C2 spinolaminar interval (parallel lines).

14. (c) Coronal volume-rendered CT image of a 26-year-old man with craniocervical distraction after a motorcycle collision shows bilateral widening of the atlanto -occipital joints (AO) and the atlantoaxial joints (AA) . (d) Volume-rendered CT image of a 23-year-old man with craniocervical distraction after a motorcycle collision shows the occipital condyles (OC) dissociated from the lateral masses of the atlas and shifted anteriorly.

15. Midsagittal volume-rendered CT image of a 23-year-old man shows a marked widening (solid lines) of the atlanto -occipital articulation, with anterior translation of the condyles and skull base.

16. Atlanto -axial subluxation is a disorder of C1-C2 causing impairment in rotation of the neck. It may be associated with dislocation of the lateral mass of C1 on C2. There are several ways in which a subluxation can occur: Anteroposterior subluxation Vertical subluxation Lateral subluxation  Rotatory subluxation

17. Rotatory subluxation , known as atlantoaxial rotatory fixation (AARF) is characterised into four different types :  Type I:  the atlas is rotated on the odontoid with no anterior displacement Type II:  the atlas is rotated on one lateral articular process with 3 to 5 mm of anterior displacement Type III:  comprises a rotation of the atlas on both lateral articular processes with anterior displacement greater than 5 mm Type IV:  characterised by rotation and posterior displacement of the atlas

18. Fielding and Hawkins classification of atlantoaxial rotatory subluxation

19. Volume-rendered CT image of a 45-year-old patient after an MVC shows a widened atlantodental interval (solid line) secondary to a transverse ligament injury.

20. McRae line is a radiographic line drawn on a lateral skull radiograph or midsagittal section of CT or MRI, joining the basion and opisthion . Normal position of the tip of dens is 5mm below this line. If the tip of the dens migrates above this line it indicates the presence of basilar invagination ( atlanto -axial impaction).

21. Chamberlain line is a line joining the back of hard palate with the opisthion on a lateral view of the craniocervical junction. It helps to recognise basilar invagination which is said to be present if the tip of the dens is >3 mm above this line.

22. The digastric (or biventer ) line has been described and used to evaluate basilar invagination on coronal recontructed CT image. The digastric line is drawn between right and left digastric grooves. The tip of the odontoid process and atlanto -occipital joint normally project 11 mm and 12 mm below this line respectively. Basilar invagination is present when atlanto -occipital joint projects at or above this line.

23. The bimastoid line has been described and used to evaluate basilar invagination on frontal skull plain film and coronal reconstructed CT image. The bimastoid line is drawn between the inferior tips of the of mastoid processes bilaterally. The tip of the odontoid process of C2 normally projects less than or equal to 10 mm above this line. Basilar invagination is present when the tip of the odontoid process projects above 10 mm.

24. Occipital Condyle Fractures Anderson and Montesano introduced the most widely used radiologic classification system for occipital condyle fractures, describing three different patterns of injury: Type I: comminution impaction injury resulting from axial loading with minimal or no fracture displacement- Stable Type II: skull base fracture extending through the occipital condyle- Stable Type III: alar ligament avulsion fracture- Unstable

25. Fractures may be unilateral with minimal distraction, may be bilateral, or may extend in a ring like configuration along the anterior foramen magnum, with bilaterality increasing the likelihood of instability. Approximately 75% of occipital condyle fractures are type III injuries.

26. Occipital condyle fractures in three patients. (a) Coronal multiplanar reformatted CT image of a 24-year-old man after a motorcycle collision shows a right type I condylar fracture (arrows) resulting from impaction of the condyle against the right lateral mass of C1.

27. (b) Off-axial MIP image of a 52-year-old man after an MVC shows a type II right occipital condyle fracture associated with a skull base fracture (arrows). (c) Coronal MIP image of an 18-year-old man with severe polytrauma after an MVC shows an avulsion fragment off the right occipital condyle (type III occipital condyle fracture).

28. Fractures of the Atlas Atlas fractures account for 25% of craniocervical injuries. As many as 44% of atlas fractures have associated fractures of the axis. Type I: Isolated posterior arches ---- Stable Type II: Isolated anterior arch ---- Stable

29. Type III: Bilateral posterior arch with bilateral or unilateral anterior arch (“Jefferson burst”)---- Stability Depends on integrity of transverse ligament. Type IV: Lateral mass ---- Stable Type V: Transversely oriented anterior arch fractures (avulsion of longus colli or atlantoaxial ligament)

30. Fractures of the atlas in three patients. (a) Off-axial MIP image of a 27-year-old woman after an MVC shows bilateral posterior arch fractures (TYPE 1) . Head rotation within the physiologic range results in asymmetry of the lateral atlantodental intervals.

31. (b) Off-axial MIP image of a 49-year-old woman after an MVC shows a three-part Jefferson fracture of the atlas (TYPE 3) . A congenital cleft (arrow) is incidentally depicted anteriorly at the foramen transversarium . The cleft is distinguished from a fracture by its smooth sclerotic appearance and because ring fractures should occur in at least two parts.

32. (c) Off-axial MIP image of a 50-year-old female pedestrian who was struck by a motor vehicle shows unilateral fractures of the left anterior and posterior arches, with separation of the lateral mass (TYPE 4).

33. Injuries related to C2 vertebra Hangman fracture Odontoid fracture

34. Hangman fracture , also known as traumatic spondylolisthesis of the axis, is a fracture which involves the pars interarticularis of C2 on both sides, and is a result of hyperextension and distraction. Levine and Edwards classification is used to classify hangman fractures of C2. Type I:  fracture with <3 mm antero -posterior deviation no angular deviation Type II:  fracture with >3 mm antero -posterior deviation significant angular deviation disruption of posterior longitudinal ligament Type IIa :  the fracture line is horizontal/oblique (instead of vertical) significant angular deviation without anterior translation Type III:  type I with bilateral facet joint dislocation

35. Hangman fracture (a) Off-axial MIP image of an 18-year-old patient after a fall from an all-terrain vehicle shows a type I hangman fracture with bilateral fractures of the pars interarticularis . (b) Sagittal half-space slab volume-rendered CT image of an 18-year-old patient (same patient as in a ) shows no translation or angulation of C2.

36. Hangman fracture (c) Sagittal volume-rendered CT image of a 27-year-old woman with a type II hangman fracture after an MVC shows anterior translation and angulation of C2. The patient also had bilateral posterior arch fractures from hyperextension. (d) Off-axial MIP image of a 62-year-old woman with an atypical type II hangman fracture after an MVC shows a pars fracture on the right and an oblique fracture through the posterolateral vertebral body.

37. (f) Sagittal volume-rendered CT image of a 26-year-old woman with a type IIa hangman fracture after an MVC shows a pars interarticularis fracture with anterior angulation of the body of C2 but no anterior translation.

38. Sagittal volume-rendered CT image of a 30-year-old woman with a type III hangman fracture after an MVC shows marked anterior translation of C2 with facet fracture-dislocation.

39. Nonodontoid nonhangman fracture. Coronal MIP image of a 73-year-old man after an MVC shows a nonodontoid nonhangman fracture involving the right lateral mass of C2.

40. Odontoid process fracture Also known as the peg or dens fracture, occurs where there is a fracture through the odontoid process of C2. The Anderson and D'Alonzo classification is the most commonly used classification of fractures of the odontoid process of C2. Type I Rare Fracture of the upper part of the odontoid peg Above the level of the transverse band of the cruciform ligament Usually considered stable

41. Type II Most common Fracture at the base of the odontoid Below the level of the transverse band of the cruciform ligament Unstable High risk of non-union Type III Through the odontoid and into the lateral masses of C2 Relatively stable if not excessively displaced Best prognosis for healing because of the larger surface area of the fracture

42. Coronal multiplanar reformatted CT image of a 51-year-old man after a motorcycle collision shows an oblique fracture of the odontoid tip ( type I odontoid fracture ). (b) Coronal volume-rendered CT image of a 24-year-old patient after a rollover MVC shows a type II odontoid fracture.

43. (c) Sagittal MIP image of an 86-year-old patient after a fall from standing shows a type IIa odontoid fracture with posterior displacement, posterior angulation, and comminution. (d) Coronal multiplanar reformatted CT image of a 78-year-old patient involved in an MVC shows a type III dens fracture (arrows).

44. Variants Os odontoideum Persistent ossiculum terminale

45. Os odontoideum is an anatomic variant of the odontoid process of C2 and needs to be differentiated from persistent ossiculum terminale and from a type 2 odontoid fracture. It can be associated with atlantoaxial instability. Although it was originally thought to be a congenital lesion due to a failure of the centre of ossification of the dens to fuse with the body of C2, it may actually represent an unremembered and/or unrecognised fracture through the dens growth plate before the age of 5 or 6. There may be associated instability and chronic symptoms.

46. Ossiculum terminale appears as a secondary ossification centre of the dens between 3-6 years and normally fuses by 12 years. Failure of fusion results in a persistent ossiculum terminale and is considered a normal anatomical variant of the axis. It lies above the transverse alar ligament and is therefore considered to be stable and it very rarely causes symptoms.

47. Coronal bone window CT image shows Ossiculum terminale

48. Injuries of the Subaxial Cervical Spine Subaxial injuries account for 65% of cervical spine fractures and 75% of dislocations . Two scoring systems have been developed that specifically incorporate multidetector CT for sub axial injuries: 1.The cervical spine Subaxial Injury Classification and Scoring (SLIC) system. 2.The cervical spine injury severity score. (SLIC system is more acceptable and easy)

49. The SLIC system, which was introduced in 2007 by Vaccaro et al The SLIC system is made up of three separately graded components, each representing major independent predictors of outcome. The three components of SLIC are Morphologic findings of bone spinal column disruption, (b) The integrity of the discoligamentous complex, and (c) Neurologic status. The three scores for these three components are summed to give the SLIC score (total score). Combined scores of 5 or more indicate the need for surgical intervention. Injuries with scores of 3 or less can be managed without surgery, and scores of 4 are indeterminate

50. SLIC Morphology Score The SLIC morphology score describes the structural integrity and relationships of vertebrae at an injured motion segment, with higher scores corresponding with worse outcomes and an increased need for surgery. Morphology can be characterized with CT alone, and complete discoligamentous injury can also usually be diagnosed with a high degree of specificity in more-severe cases.

51. Compression (Score of 1) and Burst (Score of 2).— Compression and burst fractures are characterized by loss of vertebral body height without evidence of distraction or translation, regardless of whether focal kyphosis is present.

52. Compression burst fracture. Sagittal half-space slab volume-rendered CT image of a 23-year-old man after an MVC shows a burst fracture of C7 without associated facet distraction.

53. Distraction (Score of 3) Distractive injuries of the subaxial cervical spine are characterized by dissociation in the vertical axis. Distraction may occur anteriorly as a result of hyperextension or posteriorly from hyperflexion. Hyperflexion injuries range from facet subluxation, with decreased apposition or diastasis of the articular surfaces. Facets are considered subluxated when there is less than 50% overlap of the articular surfaces or more than 2 mm of diastasis.

54. Associated findings include posterior disk space widening with angulation greater than 11° and (b) focal kyphotic deformity.

55. Flexion-distraction injuries in two patients. (a) Oblique volume-rendered CT image of a 39-year-old woman after an MVC shows bilateral C5-C6 facet distraction (arrows). (b) Sagittal volume-rendered CT image of a 39-year-old woman (same patient as in a ) shows C5-C6 kyphotic angulation and posterior disk space widening.

56. (c) Sagittal volume-rendered CT image of a 43-year-old woman who fell a short distance and landed on her head shows perched facets (arrow) at C5-C6, with focal kyphotic deformity. (d) Oblique volume-rendered CT image of a 43-year-old woman (same patient as in c ) shows interspinous widening ( * ) associated with the C5-C6 facet perch (arrow).

57. Hyperextension —Extension-type distraction injury is synonymous with the term hyperextension dislocation and results from disruption of the anterior longitudinal ligament and intervertebral disk. These injuries manifest with “extension teardrop” fracture, an avulsed fragment of the anterior inferior corner of the involved vertebral body, in 65% of cases, most commonly at C2. Extension teardrop fracture is characteristically a thin fracture fragment greater in the horizontal than the vertical dimension, is often associated with anterior disk space widening. Other stigmata of hyperextension injury such as facial trauma and compression fractures of the facets, laminae, and spinous processes may be seen

58. Extension-distraction injury. Sagittal multiplanar reformatted CT image of a 61-year-old patient after a fall from standing shows a “hyperextension teardrop” fracture (arrow) off the anterior inferior lip of C2, with associated posterior spinous process fractures of C6-T1.

59. Translation or Rotation (Score of 4)— Translation or rotation is demonstrated by vertebral offset in the horizontal axis and may occur with or without fracture. A pure translation of one vertebra relative to another may occur when discoligamentous structures are disrupted bilaterally, or rotation may occur when an intact facet serves as a pivot point. Translation or rotation injuries can result from unilateral or bilateral facet dislocations or fracture-dislocations. A horizontal distance of 3.5 mm between the posterior aspects of the rostral and caudal vertebral body at any given motion segment is used as a cutoff for translational injury .

60. Unilateral locked facets usually cause less than 50% anterior translation of the rostral vertebral body, whereas bilateral facet dislocations result in 50% or more translation.

61. Translation injuries. (a) Coronal posterior volume-rendered CT image of an 85-year-old patient after an MVC shows bilateral locked facets (arrows) at C5-C6.

62. (b) Sagittal volume-rendered CT image of a 24-year-old patient who was an unrestrained backseat passenger in an MVC shows locked facets at C5 (white arrow) on C6 (black arrow), with greater than 50% translation of the C5 vertebral body.

63. Translation injuries: Rotation-translation injury in a 61-year-old patient who was an unrestrained driver in an MVC. (a) Axial MIP image shows left C6 pedicle and laminar fractures (arrows), with separation of the lateral mass ( * ). (b) Multiplanar reformatted CT image through the midsagittal plane of the spine below the injured segment shows off-center spinous processes of C2 through C6 (arrow). (c) Sagittal half-space slab volume-rendered CT image shows less than 50% anterior translation of the C6 vertebral body, with rotated vertebral bodies at and above the injured level (arrow).

64. Translation injuries: flexion teardrop injury in a 27-year-old woman who was a victim of assault. (a) Sagittal half-space slab volume-rendered CT image shows the flexion teardrop injury pattern, with the classic findings of a triangular fragment (arrow) off the anterior inferior C6 vertebral body and posterior translation of the vertebral body and posterior elements, resulting in facet widening ( * ).

65. (b) Axial MIP image shows a sagittal fracture line (arrow) through the C6 vertebral body posterior to the teardrop fragment.

66. SLIC Discoligamentous Complex Score The term discoligamentous complex refers to The anterior longitudinal ligament, intervertebral disk, and posterior longitudinal ligament anteriorly and (b) The ligamentum flavum , facet capsules, interspinous ligament, and supraspinous ligament posteriorly. Abnormal bone relationships at CT are the primary way that discoligamentous complex injuries are diagnosed initially.

67. SLIC Neurology Score

68. Clay- shoveler fracture Clay- shoveler fractures  are fractures of the spinous process of a lower cervical vertebra. Often these injuries are unrecognised at the time and only found incidentally years later when the cervical spine is imaged for other reasons. Acutely they tend to be associated with : Motor vehicle accidents Sudden muscle contraction Direct blows to the spine

69. Sagittal CT image of a patient with neck pain after lifting a heavy object. Shows fracture of spinous process of C7 vertebra.

70. Vertebral Anomalies

71. Hemivertebra Hemivertebra is a type of vertebral anomaly and results from a lack of formation of one half of a vertebral body. It is a common cause of congenital scoliosis. It falls under the spectrum of segmentation anomalies and can involve one or multiple levels. A hemivertebra acts as a wedge within the vertebral column, resulting in curvature away from the side on which it is present.

72. Types of hemivertebra On the basis of attachment Fully segmental (free) not attached to either vertebra above or below most concerning Semi segmental: half segment is fused with vertebra above or below with no intervening intervertebral disc Non segemental not separated from (i.e. connected to) either level above or below causes less of a concern Incarcerated joined by pedicles to levels above and below causes less of a concern

73. On the basis of orientation Dorsal hemivertebra : classically results in kyphosis Lateral hemivertebra : classically results in scoliosis Ventral hemivertebra (extremely rare): results in lordosis

74. This case shows a semi-segmental left thoracic hemivertebra .

75. Block vertebra Block vertebra is a type of vertebral anomaly where there is a failure of separation of two or more adjacent vertebral bodies. Combined vertebrae may be of normal height, short, or tall Disc space is frequently rudimentary or absent The "wasp-waist sign" is seen in congenital block vertebra

76. CT scan revealed block vertebra on C5 and C6 vertebral level (arrowheads)

77. Butterfly vertebra Butterfly vertebra is a type of vertebral anomaly that results from the failure of fusion of the lateral halves of the vertebral body because of persistent notochordal tissue between them. There is widening of the affected vertebral body. The bodies above and below the butterfly vertebra adapt to the altered intervertebral discs on either side by showing concavities along the adjacent endplates. Some bone bridging may occur across the defect which usually happens in the thoracic or lumbar segments of the spine.

78. Arcuate foramen The arcuate foramen (foramen arcuale atlantis , ponticulus posticus or posterior ponticle , or Kimerle anomaly) is a frequently encountered normal variant of the atlas. It develops by calcification of the posterior atlanto -occipital membrane. The atlantic portion (V3) of the vertebral arteries pass through this foramen. Incidence is ~8% (range 1-15%) and it is more common in females. It has a variable morphology, can be complete or incomplete and may be unilateral or bilateral.

79. The arcuate foramen is contained within the circle annotation.

80. Other Conditions involving Cervical Spine

81. Ossification of the posterior longitudinal ligament Ossification of the posterior longitudinal ligament (OPLL) is typically an entity seen in patients of Asian descent, although it is seen in all ethnic groups. Location cervical: 75% thoracic: 15% lumbar: 10% Types of OPLL type 1  : continuous (ossification of several vertebral segments) type 2  : segmental (several segments are affected, ossification is disrupted) type 3  : mixed (mix of 1 and 2) type 4  : localised (circumscribed, only one or two segments)

82. Sagittal bone window CT showing OPLL

83. Diffuse idiopathic skeletal hyperostosis Diffuse idiopathic skeletal hyperostosis (DISH), also referred to as Forestier disease, is a common condition characterised by bony proliferation at sites of tendinous and ligamentous insertion of the spine affecting elderly individuals. On imaging, it is typically characterised by the flowing ossification of the anterior longitudinal ligament , The cervical and thoracic spines, in particular, are affected. DISH most commonly affects the elderly, especially 6 th  to 7 th  decades. Imaging:- Florid, flowing ossification is noted along the anterior or anterolateral aspects of at least four contiguous vertebrae, so-called flowing ossifications Disc spaces are usually well preserved Ankylosis is more commonly seen in the thoracic than in the cervical or lumbar spine.

84. There is calcification of anterior longitudinal ligament resulting in an irregular melting candle wax like calcified mass anterior to the C3 to T4 vertebrae, with normal appearing intervertebral disc spaces.

85. Rheumatoid arthritis Rheumatoid arthritis (RA) is a chronic autoimmune multisystemic inflammatory disease which affects many organs but predominantly attacks the synovial tissues and joints. The cervical spine is frequently involved in RA ( in approximately 50% of patients), whereas a thoracic and lumbar involvement are rare. Findings include: Erosion of the dens Atlantoaxial subluxation Atlantoaxial impaction (cranial settling): cephalad migration of C2 Erosion and fusion of uncovertebral ( apophyseal joints ) and facet joints Osteoporosis and osteoporotic fractures Erosion of spinous processes

86. Sagittal bone window CT image shows Severe degenerative change at the atlanto -dens articulation with erosions. 

87. Limitations of Multidetector CT Although multidetector CT is often sufficient for making the binary determination of whether surgery is necessary or not, important determinants of management, including disk herniations , ligamentum flavum infolding, cord swelling, contusion or hemorrhage , and epidural hematoma, are not well evaluated with CT but are clearly depicted at MR imaging.