What is thoracic outlet syndrome, and what does it mean for Markelle Fultz?

What is thoracic outlet syndrome, and what does it mean for Markelle Fultz?
According to ESPN's Adrian Wojnarowski, Philadelphia 76ers guard Markelle Fultz has been diagnosed with neurogenic thoracic outlet syndrome and is expected to miss three to six weeks as he undergoes rehabilitation. Thoracic outlet syndrome (TOS) refers to a collection of signs and symptoms resulting from neurovascular compression at the thoracic outlet. The word neurovascular denotes the structures -- both nerve (neuro) and artery/vein (vascular) -- that might be compromised. The thoracic outlet is an anatomical region between the neck and the shoulder where key blood vessels and nerves travel en route to supply the upper extremity. Compression or abnormal pressure of structures in the thoracic outlet can be due to soft tissue (such as muscle or ligament) or bone (such as a normal rib, an extra rib or the collarbone) anomalies. Symptoms are wide-ranging and variable. In vascular thoracic outlet syndrome, symptoms...