Alleged H/O road traffic accident followed by paraplegia.
1. Retroplacement of the D11 vertebral body with disruption of
the D10-D11 facet joints and rupture of the anterior and posterior longitudinal
ligaments.
2. Altered signal in the spinal cord over the D9-D10 to the D11-D12 levels may
represent cord edema/contusion.
3. Compression fracture of the D11 vertebral body with altered signal that may
represent bone bruise/edema.
4. Severe cord compression by the postero-superior margin of the D11 vertebral
body.
Fractures and dislocations involving the thoracic spine are most
common at the thoracolumbar junction, as it is a relatively mobile portion of
the spine. They are usually a result of flexion and compression forces. The
spine may be divided into three columns as follows:
Anterior column:
disk, vertebral body and anterior longitudinal ligament
Middle column:
corresponds to an osteoligamentous complex that includes the posterior vertebral
body, posterior annulus fibrosus and posterior longitudinal ligament
Posterior column:
includes all structures posterior to the posterior longitudinal ligament
Injuries are considered unstable when the middle osteoligamentous complex is
disrupted.
The acute stage
of spinal cord injury is generally considered to extend until 5 to 7 days after
the initial traumatic event. Clinically, the injury is designated “complete” if
the patient has lost all sensory and motor function below the level of injury;
otherwise, it is designated an “incomplete” injury. Patients with transient loss
of neurological function who return to normal within 24 hours are considered to have
cord concussions. MR examinations in these patients generally appear normal the
day after the injury. Incomplete injuries of the thoracic cord may reveal
swelling of the cord. Signal changes within the cord depend on the presence of
hemorrhage and edema and three patterns have been described in the acute phase.
1. Central hypointensity within the cord on T1W images that gets darker on T2W
images (deoxyhemoglobin)
2. Hyperintensity within the cord on T2W images that most likely represents cord
edema and is the most common pattern demonstrated
3.Central hypointensity surrounded by peripheral hyperintensity on T2W images
(presence of central hemorrhage surrounded by edema)
On follow-up
examinations in cases of spinal cord injury the following patterns may be
encountered:
Pattern I
shows normal signal intensity in the acute stage, with no abnormalities
identified on follow-up, and correlates with good neurological outcome
Pattern II
consists of normal signal on T1W images and bright signal on T2W images acutely,
with either conversion to a pattern I appearance on follow-up and good
neurological recovery or persistent abnormalities with no recovery. The subgroup
with persistent signal abnormalities generally had unrelieved cord compression,
which if decompressed occasionally resulted in neurological recovery
Pattern III
is characterized by dark signal on T1W images and bright signal on T2W images
on follow-up examinations and is believed to be caused by myelomalacia. These
patients have poor neurological outcome
Pattern IV is indicated by the presence of cord atrophy
Pattern V is
atrophy with syrinx formation
The last two patterns are usually associated with prolonged cord compression and
poor neurological outcomes.
Hyperintense signal on T2W images within the posterior column of the cord,
cephalad to the primary level of injury may be seen 10 weeks to 12 months after
the acute event and is believed to represent
Wallerian Degeneration.
An additional chronic change within the spine after spinal cord injury is
neuropathic spinal arthropathy, which results in disk space narrowing and bone
fragmentation. MRI with contrast enhancement can be useful in distinguishing
this entity from infection.
Thoracic spinal cord injuries are usually associated with fractures and
ligamentous disruptions within the spine.
Acute fractures on
MRI appear as areas of relatively higher signal disrupting the continuity of the
normally low signal of the vertebral cortical bone. These can be quite subtle,
especially posterior element fractures, and are seen more clearly on CT than on
MRI. Compression fractures are readily identified on sagittal imaging.
Retropulsed fragments may be evident on T1W images because of the presence of
fatty marrow and on T2W images because of the mass effect on the thecal sac and
cord. Subluxations and dislocations can also be appreciated on sagittal images.
Assessment of spinal ligament integrity may be made directly by MRI and appear
as areas of relatively higher signal intensity within and around the ligaments.
Traumatic disk herniations are also demonstrated quite well. Locked facets in
association with spinal trauma are much less commonly seen in the thoracolumbar
spine than in the cervical spine.
Trauma is also a major cause of spinal epidural hematomas. Because of the larger epidural space posteriorly, the hematoma usually involves the dorsal epidural space, although it may extend laterally, and it generally extends over two to four segments. On sagittal T1W and T2W images, the hematoma appears as a well-defined biconvex collection of variable intensity, resulting in anterior displacement of the cord. Within 24 hours, the hematoma is generally isointense with cord on T1W images and inhomogeneous or hyperintense on T2W images. After 24 hours, a bright and usually homogeneous signal appears on T1W and T2W images. Gadolinium enhanced images may reveal prominent enhancement of thickened meninges adjacent to the hematoma. The prognosis worsens if hematomas persist beyond 24 hours.
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