Prevertebral soft tissue measurements in thyroid enlargement: the value of lateral neck radiographs.

Background: Measurement of prevertebral soft tissue is commonly used to assess prevertebral abnormalities, such as retropharyngeal abscess or injury to the cervical spine. In the presence of goitres, the widened prevertebral tissue seen on plain lateral neck radiograph may be diagnostic of an enlarged tubercle of Zuckerkandl (ZT), which may be responsible for most pressure symptoms. The aim of this study was to substantiate the value of plain lateral neck radiographs in preoperative demonstration of enlarged ZT.

Methods: Fifty patients who underwent thyroid surgery between June and December 2000 were included in this prospective, non-randomized study. Measurements of prevertebral soft tissue were taken at C4, C5 and C6, and were correlated with the weight of goitres and the grades of changes in the ZTs.

Results: Of patients, 44% had large goitres weighing more than 100 g; 52% of ZTs were classified as grade 3. Of the large ZTs, 82% were associated with large goitres and, of these, 88% were associated with significant pressure symptoms. Prevertebral measurements were abnormal, particularly at C4, C5 and C6. The most promising predictor of the presence of an enlarged ZT is the measurement taken at C4 (p<0.05). The ratio of the prevertebral space to the vertebral body (PVS/VB) in grade 3 ZT was also increased at C4, C5 and C6. However, these ratios were not statistically significant. A measurement of prevertebral soft tissue, particularly at C4, greater than 16.5 mm correlates 100% with an enlarged grade 3 ZT.

Conclusions: The results of this study support the concept that the plain radiograph shows significant widening of the lateral neck in the presence of an enlarged ZT. Plain lateral radiography is a simple procedure that could provide valuable information for preoperative assessment of an enlarged ZT, particularly in patients with large goitres who have significant pressure symptoms.