Magnetic resonance imaging features of neonatal congenital pyriform sinus fistula: a retrospective study of 12 patients.

BACKGROUND

Congenital pyriform sinus fistula (CPSF) is a rare condition in which accurate preoperative imaging and diagnosis is critical for surgical modality selection and outcomes. The purpose of the study is to analyze the MRI characteristics of CPSF in newborns for improved diagnosis.

METHODS

This retrospective study included 12 cases of neonatal CPSF diagnosed at our hospital from January 2016 to January 2023, with available MRI data. The clinical and MRI characteristics of these cases were systematically analyzed. Descriptive statistical methods were utilized to characterize the study population and summarize the key features of the observed data.

RESULTS

Nine cases (75.0%) presented with a neck mass. The MRI of all cases revealed irregular unilocular cystic masses in the left neck, closely related to the thyroid gland. All cysts demonstrated consistent anatomical boundaries: anteriorly by the anterior cervical soft tissues, laterally by the sternocleidomastoid muscle, superiorly at the atlas (C1) level (41.7%) or pyriform sinus level (58.3%), inferiorly to the thyroid gland level (41.7%) or superior mediastinum (58.3%), posteriorly adjacent to the anterior vertebral surface (75.0%) or extending posteriorly from the paravertebral region (25.0%), and medially crossing the midline anterior to the vertebral body via the retropharyngeal space (66.7%) or abutting the left tracheal border (33.3%). Thyroid parenchymal involvement was observed in seven cases (58.3%), and the carotid sheath was located on the posterolateral side of the mass in 11 cases (91.7%). The presence of air bubbles within the cyst was observed in six cases (50.0%), and a high signal fluid level within the cyst was noted in nine cases (81.8%) on DWI. A strip-like high-signal intensity in the retropharyngeal space was observed in all 12 cases on T2WI-STIR images.

CONCLUSIONS

Cyst location proved critical for diagnosing neonatal pyriform sinus fistula and all cysts demonstrated consistent anatomical boundaries in this case series. MRI demonstrates a cystic lesion adjacent to the thyroid and carotid sheath, frequently characterized by intralesional gas bubbles and a fluid level with restricted diffusion.