DEAR DR. ROACH: I read with interest the letter from the reader who had shoulder pain and was identified with Parsonage-Turner syndrome. I had never heard of it before. I am a 64-year-old woman with severe shoulder pain. It has persisted for more than five years.

In addition to the ball of fire in the top of my arm/shoulder, I’m bothered by a feeling like a hard pebble on my upper back when I try to sleep. A shoulder specialist ordered an MRI and did not see anything that would cause this.

Over the past five years, I’ve had physical therapy from multiple sources. Despite many different approaches (cortisone shots, exercises, cupping, massages, a new mattress/pillow and new glasses), nothing has made a dent in the pain. Are there other avenues I should pursue?

• M.C.K.

ANSWER: Five years is a long time, and I don’t know if you will be able to get relief from your pain. However, the burning quality of the pain and the sensation of something (like a pebble) being there when it isn’t makes me concerned about a neurological cause.

Parsonage-Turner syndrome (neuralgic amyotrophy) is a possibility, but there are other neurological causes of shoulder pain. I suggest a visit to a neurologist, who may order nerve studies (such as an EMG) or even try medications to help with the pain coming from the damaged nerves.

A colleague asked whether neuralgic amyotrophy could possibly be triggered by a COVID-19 vaccination. I did find a case of painless neuralgic amyotrophy after a COVID-19 vaccination, as well as a handful of cases of the more-common painful neuralgic amyotrophy after vaccinations. In every case that was reported, the pain resolved by itself.

DEAR DR. ROACH: I’ve used several pain creams that contain lidocaine. A few of them are somewhat helpful in minimizing my joint discomfort. Novocaine, as every dental patient knows, completely eliminates pain, so why isn’t it used in any of these pain-relief products? Is something preventing it from being used?

— W.R.G.

ANSWER: Both procaine (Novacaine is an old brand name) and lidocaine (Xylocaine is its old brand name) are topical anesthetics, and both are still used. Lidocaine is actually better at penetrating the skin than procaine is, so this is why patches are typically made from lidocaine. They can both be injected, and when everything goes right, there is near-complete block of the pain. It doesn’t always go right, even when done by experienced dentists and surgeons.