Zero echo time MRI for detecting osseous anomalies in neurogenic thoracic outlet syndrome

To evaluate the additive value of a zero echo time (ZTE) sequence to standard brachial plexus MR neurography (MRN) for detecting and characterizing osseous anomalies in patients with suspected neurogenic thoracic outlet syndrome (nTOS).

In this retrospective, case-control study (January 2022-March 2025), unilateral brachial plexus MRN examinations with ZTE and reference imaging (radiographs and/or CT) were included. Two board-certified radiologists determined case status and osseous anomaly subtype (cervical rib, rib synostosis, or elongated C7 transverse process) on the reference imaging. Age- and sex-matched controls were randomly selected. Three musculoskeletal radiologists independently reviewed each examination in 3 rounds (MRN-only, ZTE-only, MRN + ZTE). Inter-reader agreement was assessed, and diagnostic performance was compared with reference standard.

Thirty examinations from 27 subjects (20 female; median age 31 years) were analyzed, including 15 case examinations (elongated C7 transverse process n = 7, cervical rib n = 4, rib synostosis n = 4) and 15 control examinations. Accuracy for osseous anomaly detection was highest in ZTE-only (0.90; sensitivity 0.80; specificity 1.00), followed by MRN + ZTE (0.87; 0.73; 1.00) and MRN-only (0.73; 0.53; 0.93). MRN + ZTE identified anomaly-related nerve impingement more frequently than MRN-only. MRN + ZTE showed the highest agreement for osseous anomaly detection and subtype (κ = 0.68 and 0.61), compared with MRN-only (κ = 0.53 and 0.56) and ZTE-only (κ = 0.59 and 0.54). Agreement for nerve impingement improved from fair with MRN-only (κ = 0.40) to substantial with MRN + ZTE (κ = 0.62).

ZTE improves detection of osseous anomalies in brachial plexus MRN and increases inter-reader agreement and diagnostic confidence, supporting its incorporation into MR protocols for nTOS evaluation.