With its ability to directly evaluate all of the soft tissues of the spine, MRI plays a critical role in the evaluation of the trauma patient with ligamentous injury and possible instability. This article discusses the use of MRI in acute spinal trauma. The recognition of soft tissue injuries impacts patient management, aids in surgical planning, and influences patient outcome.
is a Neuroradiology Fellow and
is a Professor, Department of Radiology, University of North
Carolina, Chapel Hill, NC.
Some of this article was originally presented as an electronic
exhibit at RSNA 2006: Hollingshead MC, Castellano F, Pulnik J,
Castillo M. MRI of ligamentous and soft tissue injury in the
cervical spine. Electronic exhibit at the RSNA 92nd Scientific
Assembly and Annual Meeting, November 2006; Chicago, IL.
Magnetic resonance imaging (MRI) allows the radiologist to
directly evaluate all of the soft tissues of the spine, including
the ligaments, cord, disks, and vasculature. Thus, it can be
crucial in the evaluation of the trauma patient with ligamentous
injury and possible instability. While radiographs and computed
tomography (CT) may suggest soft tissue injury, MRI allows for
direct visualization and confirmation. This article will review the
use of MRI in acute spinal trauma. Recognition of soft tissue
injuries helps guide patient management and surgery, results in
changes in management, and influences prognosis.
At our institution, patients with significant trauma undergo
evaluation of the cervical spine with screening CT using
reconstructed 2-mm axial images (acquired at 0.6 mm) with coronal
and sagittal reformations. MRI is obtained in patients whose CT
scans show a potentially unstable injury, obtunded patients who
cannot localize symptoms, and those with neurologic symptoms. Our
protocol includes sagittal T1-weighted (T1W), T2-weighted (T2W),
and short-tau inversion-recovery (STIR) sequences (3 mm thick), as
well as an axial T2*-weighted (T2*W) sequence (3 mm thick) without
contrast. For the evaluation of thoracic or lumbar spinal trauma,
an evaluation begins with plain films. CT imaging consists of 2-mm
axial reconstructed images with coronal and sagittal reformations,
often all obtained from the raw data acquired during an evaluation
of the thorax and/or abdomen. Our MRI protocol includes sagittal
T1W, T2W, and STIR sequences (4 mm thick), as well as axial T1W,
T2W, and T2*W sequences (4 mm thick) without contrast.
Normal ligaments and identification of injury
MRI allows direct visualization of some of the ligaments that
support the craniocervical junction. Ligaments are generally
linear, low-signal-intensity structures. The anterior atlantoaxial
membrane extends from the axis, C2, to the atlas, C1.
The anterior atlanto-occipital membrane extends from C1 to the
The apical dental ligament extends from the superior tip of the
dens to the clivus.
Posteriorly, the tectorial membrane originates on C2 and extends to
the clivus. Deep to the tectorial membrane is the transverse
ligament, which inserts on the internal surface of the lateral
masses of C1. The alar ligaments are also deep to the tectorial
The major subaxial ligaments include the anterior and posterior
longitudinal ligaments and the posterior ligamentous complex (PLC).
The anterior longitudinal ligament (ALL) is a low-signal, linear
structure along the anterior portion of the vertebral body cortex
and disks. The ALL adheres to the midportion of the vertebral body
and blends with the annulus over the disks.
The posterior longitudinal ligament (PLL) is a low-signal, linear
structure along the posterior portion of the vertebral body and the
disks. It is best seen on T2W images because of adjacent bright
cerebrospinal fluid of the spinal canal.
The PLC, which includes the interspinous ligaments, ligamentum
flavum, and facet joint capsular ligaments, is not as well defined
on MRI as the ALL or PLL.
An advantage of MRI is its ability to accurately identify a
An area of discontinuity indicates a disruption (Figure 1).
However, the ligament can also be "stripped" away from its
underlying structure, which is indicated by separation from those
structures. This is exhibited as increased T2 and STIR signal deep
to the ligament. "Thinning" or "stretching" of the ligament may
indicate injury as well (Figure 2). Because the PLC is not as well
defined as other ligaments, one can identify injury as increased T2
or STIR signal within the complex (Figure 3).
Ligamentous injury and instability
The definition of spinal instability remains controversial.
Broadly speaking, an injury should be considered unstable when
there is the possibility of further skeletal or neurologic injury
The clinician needs to identify unstable injuries in order to
perform appropriate, timely intervention.
MRI can contribute by directly visualizing injured ligaments.
However, because of a lack of large studies with surgical or
pathological correlation, it is not known to what degree MRI may
overestimate the degree of damage.
Traditionally, in the subaxial cervical spine, one can attempt
to identify unstable injuries by using specific measurements on
plain films. Daffner et al
described 5 radiographic signs that are suggestive of instability:
displacement of a vertebral body by 2 mm, widening between the
spinal laminae by 2 mm, abnormalities involving the facets, injury
involving the posterior portion of the vertebral body, and an
increased interpediculate width of 2 mm.
Denis developed the "3-column model of the spine" for evaluation
for thoracolumbar spine instability.
The anterior column of the spine consists of the ALL and anterior
two thirds of the disks and vertebral bodies. The middle column
includes the PLL and posterior one third of the disks and vertebral
bodies. The posterior column includes everything dorsal to the
middle column. Instability is indicated by injury to the middle
column and one other column. This model has also been applied to
the subaxial cervical spine.
"Clearance" of the cervical spine
The role of MRI in the "clearance" of the cervical spine,
particularly in obtunded patients, continues to be debated.
The goal is to identify an isolated ligamentous injury of the
cervical spine that is not suspected on plain film or CT. Chiu et
evaluated 14,577 patients who experienced blunt trauma. There was
an overall incidence of ligamentous injury without evidence of
fracture of 0.6%. Of the "unreliable patients," a total of 14 of
2605 patients (0.5%) had a ligamentous injury without associated
fracture. MRI was not used in this study.
Studies have shown that cervical spine CT may be effective in
excluding significant ligamentous injuries. Hogan et al
examined 366 obtunded trauma patients. CT had a negative predictive
value for ligamentous injury of 98.9% and a negative predictive
value of 100% for unstable injuries. Schuster et al
reported their experience with 12 obtunded patients who could move
all 4 extremities and had a negative CT. Cervical spine MRI was
negative in all of these patients. However, another study examined
150 patients admitted to the intensive care unit after blunt
trauma. Of 108 patients with normal radiographs, MRI showed an
extradural soft tissue injury or ligamentous injury in 27.
In a recent comprehensive review, Ackland et al
evaluated the literature on this topic, including some of the
studies above. They suggest that MRI should be used in screening
obtunded patients who are at high risk of cervical spine injury but
temper that recommendation with a comment on the lack of and need
for prospective studies.
Spinal cord injury
MRI allows the evaluation of the spinal cord. The cord may be
directly damaged by a traumatic event or by impingement because of
an associated injury, such as a herniated disk (Figures 4 and 5).
MRI can identify the level of cord injury and the associated soft
tissue injuries. Because of this, it can assist in operative
Injury to the cord is revealed by the presence of high T2
signal, which indicates edema or contusion, as well as by signal
changes that are indicative of hemorrhage or cord infarct (Figures
6 and 7). The presence of intramedullary hemorrhage and longer
segments of edema are more often associated with complete spinal
cord injuries and a worse prognosis.
In 1999, Shepard et al
found that MR results did not add much in terms of prognostic
implications when compared with clinical predictors, but confirmed
that the presence of hemorrhage was associated with a worse
prognosis. An earlier study had concluded that MRI complemented and
improved the ability to predict outcome after spinal cord injury.
Spinal cord injury without radiographic abnormality (SCIWORA)
has been seen in approximately 34.8% of pediatric patients with
spinal cord injury, though the reported incidence varies widely.
These patients have persistent neurologic complaints despite
negative radiographs or CT.
Until about age 9, a child's spine is hyper-mobile when compared
with the adult spine, which allows for cord damage at the time of
injury without residual radiographic evidence.
MRI allows visualization of the cord injury and can aid in
Vertebral artery injury
Vertebral artery injury is associated with cervical spine
injury, particularly when the trauma is severe.
Although angiography remains the gold standard, evaluation with
magnetic resonance angiography (MRA) has been advocated as a
In a study of 319 patients with significant cervical spine trauma
(including 261 fractures, 24 bilateral facet dislocations, 22
unilateral facet dislocation, and 12 cases of SCIWORA), 52 patients
had a vertebral artery injury diagnosed by MRA.
In another study, 83 of 632 patients with fracture, dislocation, or
neurologic symptoms related to a cervical cord injury had an acute
vertebral artery injury identified with MRA.
One study identified 4 cases of vertebral artery injury in 12
patients with a fracture involving the foramen transversarium.
Types of injuries associated with vertebral artery injury are
fracture-dislocations, fractures of the foramen transversarium,
interfacetal dislocations, and injuries involving sites of exit and
entry of the vertebral artery into the foramen transversarium in
the upper and lower portions of the cervical spine (Figure 8).
Vertebral artery injuries may be diagnosed on initial routine
sequences, but additional MRA sequences can be performed for
further or initial evaluation. In particular, an axial T1W sequence
is useful for evaluating dissection.
While patients may present with posterior circulation symptoms,
most patients are asymptomatic. The risk of stroke is increased
with bilateral injury.
Extramedullary hemorrhage can be identified with MRI (Figure 9).
Posttraumatic epidural hematomas, which are thought to be venous in
origin, most often involve the cervical or thoracic spine.
Usually, they are dorsal to the thecal sac, as the PLL is firmly
adherent to the dura anteriorly.
Subdural hematomas are most often ventral to the cord.
These collections can be clinically significant if there is cord
MRI can provide an early diagnosis, which would lead to prompt
treatment; however, depending on the signal characteristics of the
hemorrhage, a diagnosis can sometimes be difficult (Figure 10).
Specific types of cervical spine injury
Discussion of injuries to the cervical spine can be divided into
the craniocervical junction and the subaxial cervical spine.
Atlantooccipital dislocation can be obvious on plain film or CT,
but dissociation can be more difficult to identify (Figure 2).
The mechanism of injury involves distraction and may involve
flexion or extension.
These injuries are severe and unstable; the diagnosis must be made
Though most often fatal, patients now survive more frequently.
This may be because of more rapid emergency response, improved
life-support measures at the scene, and earlier diagnosis because
of improvements in imaging.
Identification of atlanto-occipital dislocation can be difficult in
children because of their lack of complete ossification, but MRI
can reveal the ligamentous injuries directly.
Signs of brain- stem injury should alert the clinician to consider
A similar mechanism of injury leads to atlantoaxial distraction.
(Figure 7) MRI can show injuries that involve the articular
capsules, tectorial membrane, and other atlantoaxial ligaments.
Injuries of the subaxial spine are classified based on the
mechanism of injury. Hyperextension injuries usually involve either
a rear impact motor vehicle collision or a direct blow to the face.
Usually, the lower cervical spine is involved.
These injuries can be ligamentous rather than osseous and can be
difficult to diagnose on plain films.
The prevertebral soft tissues and ALL are initially injured with
progression of injury posteriorly, with increasing severity leading
Disk injuries include avulsion from the endplate or herniation.
With more severe injury, particularly in patients with
hyperextension dislocation, cord injury may manifest as central
cord syndrome (Figure 1).
This involves weakness of the upper limbs greater than the lower
limbs in conjunction with bladder dysfunction and sensory deficits.
In two thirds of patients, an avulsion fragment, longer in
transverse dimension, is identified along the anterior-inferior
Flexion injuries of the cervical spine range from mild strains
to fracture dislocation injuries. The posterior ligaments are
usually injured (Figure 3). Bilateral interfacetal dislocation is
due to an extensive injury to the musculature and ligaments from
flexion and distraction (Figure 11).
The anterior and middle columns are usually involved.
While the PLL was traditionally thought to be completely disrupted,
Carrino et al
reported that the PLL was intact in 60% (18 of 30) of patients with
bilateral interfacetal dislocation. However, they acknowledge that
despite the fibers being visibly intact on MRI, the ligaments are
most likely injured and thinned as well as mechanically weakened,
possibly because of partial tears from stretching.
These injuries are unstable and surgery is required, but the
urgency and approach are based on the degree of neurological injury
and associated factors such as disk herniation.
Unilateral interfacetal dislocation involves flexion, rotation, and
Progressive flexion forces can cause a large fracture of the
anterior portion of the cervical vertebral body with retropulsion
of the posterior portion of the vertebral body into the spinal
canal leading to the "flexion teardrop injury" (Figure 5).
The radiographic appearance can be deceptive, as only the fracture
may be recognized.
However, this is an unstable injury with a high incidence of spinal
cord injury. Surgical intervention is required, but the best
approach is controversial.
The thoracic spine is stabilized by the ribs, leading to less
frequent injury unless the trauma is severe.
The lower thoracic and lumbar spine is more mobile, which leads to
an increased risk of injury.
Types of thoracolumbar injury include wedge compression, burst,
fracture dislocation, and flexion-distraction (Figure 6).
MRI allows visualization of the associated ligamentous and spinal
Vaccaro et al
have recently developed a new classification system for
thoracolumbar injuries. The classification is based on 3
components: radiographic appearance of injury, status of the PLC,
and neurologic symptoms.
Many factors are involved in surgical planning, but the status of
the PLC and neurologic symptoms are key.
Since MRI provides information regarding the status of the soft
tissues, it is useful in operative planning and in identifying
stability via this classification. The morphologic types of injury
include compression, translational/rotational, and distraction. A
grading system is applied to determine the severity of the injury.
One type of flexion-distraction injury in the thoracolumbar
spine is the Chance fracture. Classically, there is a horizontal
fracture involving the pedicles that may extend into the vertebral
body, but variants of this injury can be purely ligamentous,
involving only the facets and disk.
Burst fractures can have a similar appearance on plain film, but
MRI allows for the examination of the posterior column and PLC to
appropriately diagnose the injury (Figure 12).
MRI allows the radiologist to directly evaluate the soft tissues
of the spine and is, therefore, crucial in the evaluation of the
patient with ligamentous injury and, thus, instability. Recognition
of soft tissue injuries impacts patient management and outcome.