Cervical rib synostosis with the first rib and an elongated C7 transverse process: a rare variation causing thoracic outlet syndrome.

Morphological variants in the cervical and thoracic regions, although often asymptomatic, can have significant clinical implications when they contribute to conditions such as thoracic outlet syndrome (TOS). We report a rare case of a 39-year-old female patient presenting with vascular TOS. Detailed imaging via high-resolution computed tomography (CT) and magnetic resonance angiography (MRA) revealed a right-sided elongated transverse process (ETP) of the C7 (24.70 mm in length) articulating with a cervical rib (CR), which showed synostosis with the first rib. The coexistence of CR synostosis with the first rib and an ETP of C7 is a rare variation. Three-dimensional CT reconstructions were crucial in visualizing the osseous architecture, while dynamic MRA confirmed vascular compression. While both anomalies have been previously identified as independent contributors to TOS, their simultaneous presence has not been previously documented in symptomatic patients. This unique combination likely exacerbates neurovascular compression, complicating both diagnosis and surgical intervention. Preoperative imaging is crucial for identifying such rare variants and for informing surgical planning. This case highlights the diagnostic and surgical importance of recognizing complex rib and vertebral anomalies using advanced imaging modalities.