What sort of imaging
- In awake, symptomatic patients (neck pain and/or neurology) CT of the cervical spine should be the initial imaging study.
- Extremely sensitive for bony injuries,
- Not adequate for assessing
- Soft tissues
- Traumatic disc herniation
- Spinal cord contusion
- Ligamentous injuries
- May require flexion-extension X-rays (see below) and/or MRI.
- Three-view radiographs (anteroposterior, lateral and open-mouth odontoid view) should be obtained only if it is not possible to obtain a high-quality CT scan,
- Should be supplemented with CT as soon as it becomes available if there is high suspicion of injury or poor visualization on plain X-ray.
How to clear C spine
- If the CT scan is normal and the patient continues to have neck pain
- Continue cervical immobilization until asymptomatic
- Discontinue cervical immobilization after normal MRI (< 48 h post-injury) and/or adequate dynamic flexion/extension radiographs,
- MRI STIR
- Identify damaged ligaments that indirectly suggests potential laxity in the joints and vertebrae (i.e. potential instability),
- Which could cause a subluxation and narrow the spinal canal.
- True cervical spinal instability can only be directly confirmed with cervical flexion-extension lateral radiographs.
- Condition for x-rays
- Patient does not move his/her neck past the point of worsening pain or symptoms,
- Lateral views must include the C7-T1 disc space to ensure the entire cervical spine can be imaged.
- Discontinue immobilization at the discretion of the treating physician.
- If CT, MRI and dynamic flexion/extension views are normal in a symptomatic patient (i.e. most likely muscle spasm or soft tissue trauma) one can either
- Remove the collar or
- Continue immobilization until the patient is reviewed in a few weeks, at which point
- The collar can be removed without further imaging if the patient has a stable and normal neurological examination or
- Repeat dynamic X-rays if still symptomatic.
- In obtunded or comatose patients
- A high-quality CT scan of the entire spinal axis is recommended initially (as there is a risk of non-contiguous injury that would otherwise remain occult).
- If the CT scan is normal, MR imaging within 48 h may identify subtle signs of cervical spine injury.
- If the MR scan is normal or performed after 48 h, the clinician must determine whether to continue cervical collar immobilization on an individual patient basis.
Imaging modalities
X-rays
- Soft tissues
- Retropharyngeal space > 7 mm, or retrotracheal space > 14 mm (adult) or 22 mm (paeds).
- Displaced prevertebral fat stripe.
- Tracheal deviation & laryngeal dislocation.
- Vertebral alignment
- Loss of lordosis.
- Acute kyphotic angulation.
- Torticollis.
- Widened interspinous space (flaring).
- Axial rotation of vertebra.
- Discontinuity in contour lines.
- Abnormal joints
- ADI: > 3 mm (adult) or > 4 mm (paeds).
- Narrowed or widened disc space.
- Widening of apophyseal joints.
Cervical spine
- Must be cleared radiographically from the cranio-cervical junction down through and including the C7–1 junction
- Incidence of pathology at C7–1 junction may be as high as 9%)
- Lateral portable C-spine X-ray while in rigid collar
- This study by itself will miss ≈ 15% of injuries
- If all 7 cervical vertebrae AND the C7–1 junction are adequately visualized and are normal + if the patient has no neck pain or tenderness + is neurologically intact (neurologically intact implies patient is alert, not drugged/intoxicated, & able to report pain reliably) → then remove the cervical collar and complete the remainder of the cervical spine series (AP and open-mouth odontoid (OMO) view).
- Lateral, AP, and OMO views together detect essentially all unstable fractures in neurologically intact patients (although the AP view rarely provides unique information).
- In a severely injured patient, limitation to an AP and lateral view usually suffices for the acute (but not complete) evaluation
- If the above studies are normal, but there is neck pain, tenderness or neurologic findings (there may be a spinal cord injury even with normal plain films), or if the patient is unable to reliably verbalize neck pain or cannot be examined for neurologic deficit, then further studies are indicated, which may include any of the following
- Oblique views
- Demonstrates the neural foramina (may be blocked with a unilateral locked facet), shows a different projection of the uncinate processes than the AP view, and helps assess the integrity of the articular masses and lamina
- The lamina should align like shingles on a roof
- Flexion-extension views
- Purpose: to disclose occult ligamentous instability.
- Rationale: It is possible to have a purely ligamentous injury involving the posterior ligamentous complex without any bony fracture.
- Lateral flexion-extension views help detect these injuries, and also evaluate other injuries (e.g. compression fracture) for stability.
- If have limited flexion due to paraspinal muscle spasm (sometimes resulting from pain), a rigid collar should be prescribed, and if the pain persists 2–3 weeks later the flexion-extension films should be repeated.
- Options
- A cervical MRI done within 48–72 hours of the trauma (may be more sensitive with STIR sequences or equivalent) may identify ligamentous or other soft-tissue injury, especially in patients who cannot cooperate for flexion-extension X-rays.
- ❌ Contraindications
- The patient must be cooperative and free of mental impairment (i.e., no head injury, street or prescription drugs, alcohol…)
- There should not be any subluxation > 3.5mm at any level on cross-table C-spine X-rays, which is a marker for possible instability
- Patient must be neurologically intact (if there is any degree of spinal cord injury, proceed instead first with imaging studies, e.g. MRI)
- F/E X-rays are no longer recommended in obtunded patients due to a low yield, poor cost-effectiveness, and they may be dangerous
- Technique
- The patient should be sitting, and is instructed to flex the head slowly, and to stop if it becomes painful.
- Serial X-rays are taken at 5–10° increments (or followed under fluoro with spot films at the end of movement), and if normal, the patient may be encouraged to flex further.
- This is repeated until evidence of instability is seen, or the patient cannot flex further because of pain or limitation of motion.
- The process is then repeated for extension.
- Findings
- Normal flexion-extension views demonstrate slight anterior subluxation distributed over all cervical levels with preservation of the normal contour lines
- Abnormal findings include: “flaring” of the spinous processes, see exaggerated widening
- Pillar views
- Aim to demonstrate the cervical articular masses en face (reserved for cases suspected of having articular mass fracture)
- Method
- The head is rotated to one side (requires that the upper cervical spine injury has been excluded by previous radiographs), the X-ray tube is off centred 2 cm from midline in the opposite direction and the beam is angled 25° caudad, centred at the superior margin of the thyroid cartilage
- If subluxation is present at any level and is ≤ 3.5mm and the patient is neurologically intact (neurologically intact implies patient is alert, not drugged/intoxicated, and able to report pain reliably), then obtain flexion-extension films (see below)
- If no pathologic movement, may discontinue cervical collar
- Even if no instability is demonstrated, may need delayed films once pain and muscle spasms have resolved to reveal instability
- If lower C-spine (and/or cervical-thoracic junction) are not well visualized
- Repeat lateral C-spine X-ray with caudal traction on the arms (if not contraindicated based on other injuries, e.g. to shoulders)
- If still not visualized, then obtain a “swimmer’s” (Twining) view
- The X-ray tube is positioned above the shoulder furthest from the film, and aimed towards the axilla closest to the film with the tube angled 10–15° toward the head while the arm is elevated above the head
- If still not visualized: CT scan through non-visualized levels (CT is poor for evaluating alignment and for fractures in the horizontal plane, thin cuts with reconstructions ameliorates this shortcoming)
- See questions regarding stability of the subaxial spine
- Patients with C-spine fractures or dislocations should have daily C-spine X-rays during initial traction or immobilization
- Thoracic and lumbosacral LS-spine
- AP and lateral X-rays for all trauma patients who
- Were thrown from a vehicle, or fell ≥ 6 feet to the ground
- Complain of back pain
- Are unconscious
- Are unable to reliably describe back pain or have altered mental status preventing adequate exam (including inability to verbalize regarding back pain/tenderness)
- Have an unknown mechanism of injury, or other injuries that cast suspicion of spine injury
- Reminder
- When abnormalities of questionable vintage are identified, a bone scan may be helpful to distinguish an old injury from an acute one
- In an adult, a bone scan will become “hot” within 24–48 hrs of injury, and will remain hot for up to a year
- In the elderly
- Less useful
- The scan may not become hot for 2–3 weeks and can remain so for over a year
- If a bony abnormality is identified or if there is a level of neurologic deficit ascribable to a specific spinal level, either a CT or MRI scan through that area should be done if possible
MRI
- If there are neurological signs and symptoms suggesting injury to the cervical spine.
- Consider MRI for assessing ligamentous and disc injuries suggested by CT or clinical findings.
- Utility is limited to specific situation and the accuracy has not been determined
- Emergent MRI (or myelogram)
- Myelogram
- Caution: cervical myelogram in patients with cervical spine injuries usually requires C1–2 puncture to achieve adequate dye concentration in the cervical region without dangerous extension of the neck or tilting of the patient as required when dye is injected via LP. Furthermore, pressure shifts from LP exacerbates deficit in 14% of cases with complete block.
- Indications
- Incomplete SCI
- To check for soft tissue compressing cord
- Neurologic deterioration (worsening deficit or rising level) including after closed reduction
- Neurologic deficit not explained by radiographic findings, including
- Fracture level different from level of deficit
- No bony injury identified: further imaging is done to R/O soft tissue compression (disc herniation, hematoma…) that would require surgery
- Always keep in mind the possibility of arterial dissection in this setting.
- MRI (non-emergent)
- MRI may be used to identify potentially unstable occult ligamentous or soft tissue injury.
- Note: abnormal signal on MRI is not always associated with instability on flexion-extension X-rays.
- It has been recommended that this MRI should be done within 48 hours or 72 hours of injury.
- MRI is not reliable for identifying osseous injury.
- Indications
- Inconclusive cervical spine radiography, including questionable fractures
- Significant midline paraspinal tenderness and patient unable to have flexion-extension X-rays
- Obtunded or comatose patients
- Significant abnormal findings: (T2WI and STIR are the most helpful sequences. )
- Ventral signal abnormalities with prevertebral swelling
- Dorsal signal abnormalities. Abnormal signal limited to the interspinous is probably not as unstable as when it extends into the ligamentum flavum.
- Disc disruption indicated by abnormal signal intensity within the disc, increased disc height, or frank disc protrusions
MRA/CTA
- Vertebral malalignment
- A high-risk fracture (that is, a high-grade or complex facial fracture or a base of skull fracture likely to involve the internal carotid artery or vertebral artery)
- Posterior circulation syndrome.
CT scan
- Helpful in identifying bony injuries, especially in areas difficult to visualize on plain radiographs.
- Cannot exclude significant soft-tissue or ligamentous injury