How long does it take for nerve damage to heal after miraDry treatment?

Hello and thank you for your question. miraDry uses a hand-held applicator to apply heat to the under-arm area, targeting and destroying sweat glands. Your doctor will perform this quick, non-invasive procedure under a local anesthetic, and you will not likely experience much pain.
The results of the treatment are permanent but will have temporary side effects, including swelling, soreness and numbness. These side effects typically resolve in a few days. Of those symptoms, numbness may take the longest to resolve, anywhere from a few weeks to a few months.
Currently, most practitioners use the tumescent method when performing the miraDry procedure. Application of tumescent anesthetic in the under arm area provides additional comfort to you and protection to the underlying dermis and nerves.
After four months, you still may not have fully recovered from your procedure. Share your concerns with your doctor, and if your numbness fails to resolve in the coming months, return for a re-evaluation, or get a second opinion from another board-certified practitioner near you. Best of health!
- Carl N. Williams, Jr., MD

The numbness in the underarm and down to the inside of the elbow after miraDry is fairly common.  It should return but can take months.   No nerves are cut during miraDry but they can be temporarily injured from the microwave energy and the swelling.  You should follow up with the physician who performed it.