From 85-95% of all patients with TOS are affected by neurogenic TOS.
Neurogenic TOS is most frequently characterized by compression of the brachial plexus nerve roots (C5 to T1) within the scalene triangle.
Compression may be due to one or more of the following factors:
- congenital variations in anatomy – such as anomalous scalene musculature, aberrant fibrofascial bands, or cervical ribs
- history of neck or upper extremity injury resulting in scalene muscle spasm, fibrosis, and other pathological changes
An additional site of nerve compression may occur just beyond the first rib, within the space underlying the pectoralis minor muscle tendon.
Symptoms of brachial plexus nerve root compression consist of the following, located in the shoulder, arm, or hand:
- Tingling (paresthesias)
Symptoms of neurogenic TOS often can be:
- Variable throughout the day
- Differing day-to-day, depending on levels of activity
- Typically dynamic, with marked positional exacerbation during arm abduction, elevation, and other maneuvers
- Accompanied by localized tenderness
- Known to include pain and muscle spasm frequently extending to the upper arm, neck, and back
The results of conventional electrophysiological testing and imaging in patients with neurogenic TOS are often within normal ranges or are nonspecific. TOS specialists therefore rely largely on clinical findings and a limited number of additional tests to identify patients with neurogenic TOS.
Neurogenic TOS can be especially debilitating as it can result in chronic pain syndromes that are challenging to treat with conservative care modalities. Properly identified and selected patients can nonetheless respond quite well to treatment, consisting of one or more of the following treatment options:
- TOS-specific physical therapy
- botulinum toxin chemodenervation of the scalene/pectoralis muscles to eliminate muscle spasm
- surgical decompression based on scalenectomy and brachial plexus neurolysis, with or without first rib resection
For patients with symptoms referable to the subpectoralis space (sometimes termed the “hyperabduction syndrome”), surgical decompression may include a tenotomy, or surgical division of the pectoralis minor tendon.
There are still many unresolved issues related to neurogenic TOS including:
- The precise changes to the body caused by the syndrome
- Diagnostic criteria to differentiate neurogenic TOS from other cervical-brachial syndromes
- Criteria to help select patients for different forms of treatment
- Expected outcomes following different types of surgical and non-surgical treatments
- Best methods to reduce symptomatic recurrence
TOS specialists with the Thoracic Outlet Syndrome Center at Washington University and Barnes-Jewish Hospital are working to gain a better understanding of these issues as well as to provide expert care to patients affected by all forms of TOS.