True neurological thoracic outlet syndrome: 10 cases

The thoracic outlet syndrome (TOS) encompasses various clinical entities af fecting the neurovascular bundle crossing the thoracic outlet Unfortunately , this term often proves to be confusing because many of these entities hav e little in common beyond their known or presumed lesion site. Neurogenic T OS (true TOS) is caused by Compression bf the lower trunk in the brachial p lexus, the cervical ribs or fibrous band. This syndrome is extremely rare. We consider that this neurological form of TOS is a clearly defined neurolo gical syndrome. We report 10 patients with true TOS. All were females. Stat ing the onset was difficult because symptoms were progressive and insidious . Pain was the most frequently reported symptom. Sensory deficit was slight or absent All patients showed unilateral severe atrophy of the thenar musc les. Wasting and weakness developed later. A reduced amplitude of ulnar and median compound muscle action potential associated with a normal amplitude of median sensory nerve action and a reduced amplitude of ulnar sensory ne rve action potential were indicative of a chronic axon loss in the lower tr unk of the brachial plexus. In all cases, we performed medial antebrachial cutaneous sensory nerve action potential, a C8-T1 innervated nerve. The abs ence of the medial antebrachial cutaneous sensory nerve action potential in 9 patients and a reduction in amplitude of 50 p. 100 compared to the unaff ected side in the other patient indicated the diagnostic value of this easy and reproductible test It confirmed a C8-T1 post-ganglionic radicular lesi on or a lower brachial plexus neuropathy, Radiography showed a rudimentary bilateral cervical rib or an elongated C7 transverse process in all cases. Surgery was performed in the affected side in 7 patients and in each case t he lower part of the brachial plexus was found to be stretched and angulate d over a fibrous band, which was removed. Pain was relieved after 1 to 4 we eks. A minimal motor improvement was observed after one year, Electrophysio logical results were unchanged.