A surprising number of yoga students have told me they have been diagnosed with Thoracic Outlet Syndrome (TOS), as a result of their headstanding practice.
Now while it's certainly possible that Headstand, which involves flexion at the shoulders in the direct area where the thoracic outlet is, could trigger an existing injury or even cause TOS, there may be other factors at hand. And a diagnosis of TOS doesn't mean you have to give up yoga, either.
First, what is Thoracic Outlet Syndrome? TOS occurs when the blood vessels and nerves in the space between your collarbone (clavicle) and the first rib—the thoracic outlet—are compressed, causing pain in the neck and shoulders, and numbness in the fingers. It's typically caused by things like poor posture; pressure on the joints (like from carrying a heavy purse or backpack); trauma, such as from a car accident; repetitive activity, such as on the job or from sports; pregnancy, which loosens joints; and anatomical things like having an extra rib. Still, sometimes the cause of TOS isn't known.
Usually any condition that carries the term “syndrome” means that on some level, we Western doctors can’t always nail down the exact source of the problem. With TOS, sometimes X-ray and nerve and blood flow studies can point to a definitive cause, like that extra rib. Interestingly, a family member of mine, an active athlete and avid golfer, fell and hit this area of her shoulder and developed TOS. Because a blood clot formed in one of her veins, she opted for surgery. Many people with the condition don’t have to go to that extreme, and will improve with physical therapy and medication. Oddly, this same women was found to have TOS on the side not affected by the fall, and had both sides operated on. So her fall alone did not explain her TOS. Other factors were likely in play, both anatomical and physiological.
There are several kinds of TOS: neurogenic (neurological) thoracic outlet syndrome, caused by pressure on the Brachial Plexus, the network of nerves from your spinal cord that control muscle movements and sensation in your shoulder, arm and hand; vascular thoracic outlet syndrome, caused by pressure to the blood vessels that travel through the area; nonspecific-type thoracic outlet syndrome, where an exact cause is hard to pin down, but symptoms are present. This last type is controversial, as some docs believe it exists, while other don’t.
Now, back to yoga students with TOS. The thing that drives most people to seek medical help is pain, and in the case of TOS, pain and numbness, sometimes weakened hand grip.
In general, patients with TOS often notice symptoms the most when the arms are lifted above the head, as the delicate structures in that thoracic outlet could theoretically get compressed in that position. Often, the pain and numbness will subside or resolve completely once the arms are lowered to at least parallel with the floor. Since Headstand does involve the arms in flexion at the shoulder joint, or essentially overhead if you were to recreate it standing up, it is very possible that Headstand could bring on the symptoms. And oftentimes students haven't developed enough strength and space in the shoulder joints to prevent compression of the thoracic outlet before attempting the pose.
If the student’s symptoms only come on in Headstand, I’d recommend eliminating that pose, at least temporarily, and seeing what happens. If other poses done with the arms overhead, such as Warrior 1, or even Handstand, don't trigger symptoms, then there could be other explanations, like cervical disc problems, that could be the underlying cause. If the tests done to identify an underlying anatomical cause of TOS were normal, I might get a few other opinions before scrapping any future attempts at a full yoga practice. The good news, of course, is that there are a huge number of other poses to do that could be equally satisfying, even if you have to leave a few out. As always, working with an experienced teacher will keep you in the yoga! And as one of my senior teachers once proclaimed when a student bemoaned the fact of not being able to Shoulderstand anymore, “No one ever got enlightened from doing Shoulderstand!”
I’d have to say the same goes for Headstand.