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 such as coldness and numbness reflect limitations in blood flow to the hand. In neurogenic thoracic outlet syndrome, nerve compromise can lead to sensory changes such as numbness, tingling, pain and potential weakness or early fatigue in the arm and hand.

Arriving at a diagnosis of TOS can be challenging. The variability of clinical presentations is reflective of the particular structures being compressed and the degree to which those tissues are compromised. In other words, TOS often looks very different from one person to the next. Additionally, the symptoms can fluctuate depending on the position of the head/neck/shoulder and arm, making reproducibility difficult.

Diagnostic testing and imaging can be helpful, though not always conclusive. In the case of imaging such as X-ray or MRI, a visible "extra" rib or soft tissue band clearly occupying the thoracic outlet and causing compression can support a TOS diagnosis. Doppler studies can identify areas of altered blood flow in vascular TOS. Electrodiagnostic testing can highlight impaired nerve conduction in neurogenic TOS. It is possible, however, for an athlete to have symptoms consistent with TOS in the absence of clear diagnostic findings, which can lead to frustration when trying to determine the root cause of the problem.

TOS typically affects athletes who perform repetitive overhead motion that narrows the thoracic outlet and either compresses or places tension on the vulnerable structures involved. Cases involving baseball players, especially pitchers, are perhaps the most familiar; in recent years, Chris Carpenter, Phil Hughes and Matt Harvey have all undergone surgical procedures to address TOS.

According to Dr. Jason Lee, professor of vascular surgery at Stanford University Medical Center, basketball players are not among those athletes commonly affected. In his more than 15 years of specializing in caring for TOS patients, Lee has treated collegiate to professional athletes with TOS hailing from a wide range of sports, including swimming, diving, water polo, rowing, volleyball, tennis, lacrosse, football, softball and, of course, baseball.

But never a basketball player.

"Typically, the athletes who develop thoracic outlet syndrome are performing a repetitive overhead motion of their shoulder and arm that involves force, such as throwing or hitting as hard as they can," Lee said. "Basketball shots, even though they involve repetitive motion, require more finesse than force."

Lee was quick to point out that there are always unique cases, potentially influenced by an athlete's specific sports, injury history, playing style, mechanics, workout regimen and anatomy. Former NBA player Ben Uzoh dealt with symptoms of the condition for multiple years, but the diagnosis remained a mystery until he stepped away from basketball.

Given that the presentation of TOS in a basketball player is so rare, it is difficult to provide any relevant comparable scenarios for Fultz with respect to a prognosis or a timetable.

When it comes to treatment, the approach ranges from conservative measures such as physical therapy to more aggressive surgical intervention. The goals of physical therapy are to alleviate compression by addressing areas of limited mobility in the athlete's spine or shoulder and by strengthening regional musculature that might be deficient as a result of sport-induced imbalance.

The athlete might have to relearn certain movement patterns as part of a return to play, particularly if there have been compensatory adjustments as a result of the condition. In cases where there is an obvious structural anomaly that is not amenable to conservative treatment, surgery to relieve the source of compression might be warranted.