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Prevertebral Soft Tissues – Knowledge of Upper Limits of Normal Can Aid in Injury Detection

February 11, 2009
Written by: , Filed in: Neuroradiology
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Background
Detection of swelling in the PVSTs is an important part of the evaluation of plain films of the cervical spine, and remains so with the increasing use of MDCT. Measurements that have been established as norms were based upon studies from plain films.

The objective of a recent study was to determine normal values for the thickness of PVSTs of the cervical spine in adults on MDCT.

Knowledge of the upper limits of normal of prevertebral soft tissues (PVSTs) at various levels, and familiarity with normal appearance of PVSTs on MDCT images, can aid in the detection of subtle osseous or ligamentous injury.

Design
Retrospective study.

Participants
192 patients who underwent CT of the cervical spine for trauma were discharged without a diagnosis of bony or soft tissue ligamentous injury of the spine, and who remained without such diagnosis for one year. Patients with any spine pathologies and history of intubation were excluded.

Methodology
Patients underwent CT scanning in the neutral position with 16-section MDCT and high-resolution 3-mm thick sagittal reconstructions. Measurements of the PVST were obtained on bone windows on midline sagittal images from the mid-anterior vertebral body to the closest point in the air column from C3 to C7.

At C1, measurement was from the craniocaudal midpoint of the anterior arch; at C2, it was from the craniocaudal midpoint excluding the dens.

Neuroradiology Review

The Johns Hopkins University School of Medicine
Course Directors: David Yousem, MD, MBA and Doris Lin, MD, PhD Maintaining certification requires not only medical knowledge to deliver quality care but also other essential elements that must be developed and maintained throughout every radiologist’s career. Therefore, this program serves as a comprehensive review of neuro-radiology and prepares the participants to tackle imaging of the brain, spine, head and neck, as well as the vascular anatomy of the central nervous system. Click here to read more or order: Neuroradiology Review

Results
Mean PVST at C1, C2, and C3 was 4.4, 3.7, and 4.2 mm respectively, with upper normal limits of 8.5, 6.0, and 7.0 mm respectively. Standard deviation at C1 was 1.9 mm, whereas at C2 and C3, it was 1.2 and 1.3 mm respectively.
At C4 and C5, thickness was widely variable due to the position of the larynx, and therefore it was not calculated. At C6 and C7, means were 13.0 and 11.6 respectively, with upper normal limits of 18.0 at both.

Conclusions
Knowledge of the upper limits of normal of PVST at various levels, and familiarity with the normal appearance of the PVST on MDCT images, can aid in the detection of subtle osseous or ligamentous injury.

Reviewer’s Comments
It is useful to have normal and upper limit values for PVST measurement in MDCT, as long as these are used carefully, without over reliance on them. The authors have an excellent discussion of the normal appearance of PVSTs and give an example of an abnormal case, as evidenced by loss of the normal prevertebral fat, despite a normal prevertebral thickness.

They reference, but do not discuss, potential contour abnormalities that can aid in detecting pathology as described by Harris and Harris. Soft tissues that exceed normal values, particularly at C2-C3 where the range of normal is much narrower, warrant additional evaluation with MRI.

Author: Yaron Lebovitz, MD

Reference:
Rojas CA, Vermess D, et al. Normal Thickness and Appearance of the Prevertebral Soft Tissues on Multidetector CT. AJNR Am J Neuroradiol; 2009;30 (January): 136-141.

Neuroradiology Review

The Johns Hopkins University School of Medicine
Course Directors: David Yousem, MD, MBA and Doris Lin, MD, PhD Maintaining certification requires not only medical knowledge to deliver quality care but also other essential elements that must be developed and maintained throughout every radiologist’s career. Therefore, this program serves as a comprehensive review of neuro-radiology and prepares the participants to tackle imaging of the brain, spine, head and neck, as well as the vascular anatomy of the central nervous system. Click here to read more or order: Neuroradiology Review
.

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