Evaluation of Different MRI Sequences in Diagnosis of Cause and Effect in Thoracic Outlet Syndrome

Background: Thoracic outlet syndrome is a rare pathologi-cal condition characterized by compression of the neurovascu-lar bundle at the thoracic outlet region. Many imaging modal-ities could be used in the evaluation of TOS, but MRI plays an important role in the diagnosis of the cause and detecting the compressed structures. Aim of Study: To evaluate the role of different MRI se-quences in detecting the cause of compression in TOS and de-tect the affected (compressed) neurovascular structure. Patients and Methods: A total of 35 patients with signs of TOS (neurogenic, vascular, or combined) were included in the study. MRI examination was performed for all patients includ-ing axial, sagittal, and Coronal T2WI, sagittal STIR, 3D STIR SPACE, and DWI sequences. Results: MRI revealed the cause of compression was bony in 13 cases, compressing hypertrophied muscle was seen in 12 cases, combined hypertrophied muscle and prominent C7 trans-verse process in 1 case, and compressing fibrous bands was de-tected in 4 patients, while compression by soft tissue masses was detected in 2 cases, and no compressing cause was detected in 3 patients. In the 31 patients with radiological signs of neurogenic TOS, as shown in MRI, the affected neural segment exhibits high signal intensity in the 3D STIR SPACE sequence with no detectable thickening and restricted signal in the DWI se-quence. Conclusion: MRI is the preferred modality of choice in the diagnosis of TOS; its role is not only to diagnose the cause of compression but also to detect the compressed edematous nerve segments that support the diagnosis.