Imaging assessment of thoracic outlet syndrome.

The thoracic outlet includes three compartments (the interscalene triangle, costoclavicular space, and retropectoralis minor space), which extend from the cervical spine and mediastinum to the lower border of the pectoralis minor muscle. Dynamically induced compression of the neural, arterial, or venous structures crossing these compartments leads to thoracic outlet syndrome (TOS). The diagnosis is based on the results of clinical evaluation, particularly if symptoms can be reproduced when various dynamic maneuvers, including elevation of the arm, are undertaken. However, clinical diagnosis is often difficult; thus, the use of imaging is required to demonstrate neurovascular compression and to determine the nature and location of the structure undergoing compression and the structure producing the compression. Cervical plain radiography should be performed first to assess for bone abnormalities and to narrow the differential diagnosis. Computed tomographic (CT) angiography or magnetic resonance (MR) imaging performed in association with postural maneuvers is helpful in analyzing the dynamically induced compression. B-mode and color duplex ultrasonography (US) are good supplementary tools for assessment of vessel compression in association with postural maneuvers, especially in cases with positive clinical features of TOS but negative features of TOS at CT and MR imaging. US may also allow analysis of the brachial plexus. However, MR imaging remains the method of choice when searching for neurologic compression.

Ultrasonographic assessment of arterial cross-sectional area in the thoracic outlet on postural maneuvers measured with power Doppler ultrasonography in both asymptomatic and symptomatic populations.

OBJECTIVE: The purpose of this study was to evaluate the feasibility and potential usefulness of power Doppler ultrasonography (PDU) in the assessment of changes in arterial cross-sectional area in the thoracic outlet during upper limb elevation. METHODS: Forty-four volunteers and 28 patients with a clinical diagnosis of arterial thoracic outlet syndrome were evaluated by B-mode imaging and PDU. Arterial cross-sectional area was assessed in the 3 compartments of the thoracic outlet with the arm alongside the body and at 90 degrees, 130 degrees, and 170 degrees of abduction. The percentage of arterial stenosis was calculated for each of these arm positions. Nineteen of the 28 patients were also assessed by magnetic resonance (MR) imaging. RESULTS: No significant arterial stenosis was shown in the interscalene triangle and in the retropectoralis minor space of the volunteers and patients. A significant difference (P < .01) in stenosis between volunteers and patients was seen for all degrees of abduction in the costoclavicular space. The 130 degrees hyperabduction maneuver appeared to be the most discriminating postural maneuver. Seven patients assessed with MR imaging did not have any arterial stenosis on MR images, whereas an appreciable degree of arterial stenosis was shown with ultrasonography. CONCLUSIONS: Arterial compression inside the thoracic outlet can be detected and quantified with B-mode imaging in association with PDU.

Sonographic mapping of the normal brachial plexus.

BACKGROUND AND PURPOSE: Mapping of the brachial plexus with MR imaging has been reported and may have potential clinical applications (eg, precise localization of traumatic or tumoral nerve lesions, selective anesthesia of the brachial plexus). We sought to demonstrate that mapping of the brachial plexus may be performed by means of sonography. METHODS: Twelve healthy adult volunteers (seven women and five men; age range, 24-38 years; mean, 31 years) underwent bilateral sonographic examination for the assessment of the nerve structures of the brachial plexus from the extraforaminal part to the axillary part. Four formolated cadavers (two male and two female; age range, 66-84 years; mean, 77.5 years) were frozen and sawed into 3-mm-thick contiguous sections in the same plane as that used for the sonographic exploration. RESULTS: A satisfactory sonographic examination was performed in 10 of 12 volunteers, leading to a good association with anatomic sections. Two volunteers were excluded from the study because a clear depiction of the brachial plexus was difficult owing to a short neck and low echogenicity at examination. The association between sonographic images and anatomic sections allowed us to map the brachial plexus. The subclavian and deep cervical arteries were useful landmarks for this mapping. The eighth cervical nerve root and the first thoracic nerve root were the most difficult part of the brachial plexus to depict because of their deep location. CONCLUSION: The brachial plexus can be mapped with sonography. However, this technique requires a good grounding in anatomy and may be impossible in short-necked individuals.