Botulinum Toxin Treatment for Thoracic Outlet Syndrome Induced by Subclavius Muscle Hypertrophy

Thoracic outlet syndrome (TOS) is frequently caused by bone abnormalities and congenital or acquired soft-tissue alterations. Among these, isolated Subclavius Muscle (SM) hypertrophy represents a rare condition that could lead to a reduction in costoclavicular space and brachial plexus compression. A 47-year-old forest ranger with a history of gun shooting during animal hunting and training sessions of skeet shooting for 20 years developed TOS due to ultrasonography-detected isolated SM hypertrophy, successfully treated with an ultrasound-guided Botulinum Toxin (BTX)-A injection. In our patient, ultrasonography of the brachial plexus has allowed SM hypertrophy to be recognized and to perform BTX-A injection just in the muscle, with a complete resolution of the symptoms.

Improved functional outcome in NTOS patients following resection of the subclavius muscle with radiological signs of nerve impingement: indication of participation of the subclavius in brachial plexus compression

OBJECTIVEBoth clinical and radiological reports have suggested that the subclavius, a muscle in the costoclavicular space of the thoracic outlet, participates in neurogenic thoracic outlet syndrome (NTOS) in some instances, especially during movements narrowing the costoclavicular space. Magnetic resonance imaging can identify subclavius muscles with signs of nerve impingement, yet the impact of the subclavius in such situations remains unclear. Therefore, the authors investigated whether dividing or sparing the subclavius characterized by nerve impingement on MRI would affect surgical outcomes.METHODSIn this retrospective nonrandomized study, authors analyzed all NTOS patients with a subclavius muscle characterized by nerve impingement on MRI (loss of normal fat planes surrounding the brachial plexus) in the period between March 2010 and November 2016. Patients were divided into two groups: the sparing group, in which patients had undergone conventional supraclavicular scalenectomy and first rib resection (FRR), and the dividing group, in which patients had undergone scalenectomy, FRR, and subclavius dividing using a modified supraclavicular incision. The Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, a shoulder range of motion subscale (DASH items 6, 12–15, and 19) concerning overhead activities that can significantly narrow the costoclavicular space, postoperative MRI studies, and patient self-assessments were used to assess surgical outcomes. Univariate and multivariate analyses were conducted to identify independent factors associated with subscale scores.RESULTSFrom a total of 261 patients screened, 71 were eligible for study inclusion. Compared with the sparing group (33 patients), the dividing group (38 patients) had similar postoperative DASH scores and self-assessments but better subscale scores (9.50 ± 2.76 vs 11.94 ± 2.87, p = 0.0005). Postoperative MRI on hyperabduction showed that the brachial plexus became surrounded by normal fat tissue in the costoclavicular space in the diving group but still had signs of impingement from the untreated subclavius muscle in the sparing group. This observation agreed with a better functional recovery in terms of overhead activities in the dividing group, which was reflected by better subscale scores. Multivariate analyses indicated that the type of treatment and symptom duration prior to surgery influenced the subscale scores independently.CONCLUSIONSThis study revealed that an untreated radiological nerve-compressing subclavius muscle could lead to a relatively lower degree of recovery in the ability to perform overhead activities for NTOS patients postoperatively, suggesting that such subclavius muscles may participate in positional brachial plexus compression during movements narrowing the costoclavicular space. Dividing the muscles could decompress the costoclavicular space more effectively and may lead to better functional recovery.

The Relationship of the Subclavius Muscle with Relevance to Venous Cannulation below the Clavicle

Introduction. The catheter “pinch-off syndrome” has been described to be secondary to crimping of the catheter between the clavicle and the first rib, as well as entrapment of the catheter at the site of penetration of the subclavius muscle. The lateral insertion technique has been recommended to prevent catheter pinch-off, but it is unknown if this technique can prevent entrapment by the subclavius muscle. We undertook this study to evaluate the anatomical relationship of the subclavius muscle and the subclavian vein.Methods. Twenty-eight adult cadavers were studied on both right and left sides. The adherence between the subclavian vein and subclavius muscle was subjectively assessed and the distance between the two structures was measured in mm.Results. The subclavius muscle and subclavian vein were tightly adherent in 72% of specimens, partly adherent in 14% with a mean distance of 4.5 mm and loosely connected in 14% with a mean distance of 6.1 mm.Conclusions. The anatomical relationship between the subclavius muscle and vein was very close in the majority of specimens, suggesting that the lateral insertion technique may not prevent penetration of the muscle, which may contribute to catheter pinch-off. The real-time ultrasound-guided technique may prevent penetration of the subclavius muscle.