Effects of Head and Neck Cancer Radiotherapy on Cricothyroid Membrane Related Dimensions.

Background: Radiation treatment can modify soft tissue dynamics depending on the extent and location of irradiation. We hypothesized that head and neck radiotherapy caused alterations in cricothyroid membrane (CTM) related dimensions.

Objectives: Primary objective was to evaluate changes in the cricothyroid membrane height (CTMH) and skin-to-CTM distance (STCD) in patients who underwent radiation treatment for head and neck cancers.

Methods: Pre- and post-head-and-neck cancer-radiated computed tomography (CT) scans were analyzed retrospectively. The patients' demographics (age, sex, body mass index, cancer location), radiation dose and laterality, time from radiation initiation to CT scan assessments were summarized. CTMH and STCD were measured from pre-and post-radiation CT scans. Pre- and post-radiation comparisons were conducted using a paired t-test, or Wilcoxon signed-rank test if more appropriate. Chi-squared or Fisher's Exact test were used for categorical variables.

Results: Among 231 study patients, who underwent head and neck radiotherapy in our institution 73.2% were males, and the median age of total population was 66 years (31-93). The median BMI was 25.2 kg/m² (13.8-47.2). The median time from first radiation dose to CT scan assessment was 29.5 months (2-115).The median pre- and post-radiation CTMH were 8.7 mm (3-16.2) and 7.5 mm (3.1-14.3) respectively. The median pre- and post-radiation STCD were 11.7 mm (2.9-71.1) and 10.2 mm (3.9-38) respectively.

Conclusion: In summary our patient population had significant reduction of cricothyroid membrane related dimensions following head-and-neck radiotherapy, which can limit the localization of the cricothyroid membrane.

Level of evidence iii: Retrospective cohort study.