Symmastia develops either as a complication of breast augmentation surgery, or as a rare congenital birth defect. It occurs as a result of breast surgery when the implants migrate toward the center of the chest. In individuals who develop the condition as a result of a birth defect, called congenital symmastia, soft tissue from each breast grows toward the center of the chest, connecting over the sternum. Both types of symmastia can be corrected surgically.
The condition is most common when the plastic surgeon is overly aggressive about releasing chest muscle during surgery. The release extends the opening of the muscle towards the middle of the chest, providing a pathway for the implants to migrate. To correct augmentation caused symmastia, the surgeon removes the implants and uses internal sutures to close the opening leading to the mid-chest area. The recovery time for this is at least 12 weeks. After the surgeon is confident that the opening is healed, the implants can be replaced. If the implants are replaced too soon, their weight can cause the chest muscle to reopen.
Symmastia only develops when the implant is placed under the pectoral and serratus muscles. It is one of the potential side effects of choosing a submuscular breast augmentation. Other possible complications of this form of breast augmentation include more pain and swelling during recovery, as well as additional recovery time. There are advantages to placing the implant below the muscle however, including a more natural look, particularly in individuals with little natural breast tissue. Other advantages may include less interference during a mammography, and a lower risk of capsular contracture, or hardening of the breast.
The alternative placement for breast implants, that eliminates the risk of symmastia, is over the muscle, directly below the breast tissue. The recovery time is quicker and less painful with this placement, and the implant has more influence over the shape of the breast. Drawbacks of this placement are that the implant is easier to see and feel, particularly in individuals with little existing breast tissue.
The second type of the symmastia is congenital. Treatment in this case requires separating the soft tissue, and reattaching it to the sternum. During the healing process, a special bra is worn, called a thong bra, which maintains the flat area between the breasts. This allows the internal sutures to heal without experiencing pressure.
This condition is not considered to be dangerous, but can make the affected individual self-conscious. Regardless of the size of the breast, it is normal for there to be a space between the breasts known as the medial fold. This space creates form, and is responsible for the appearance of cleavage. Individuals with symmastia do not have a visible medial fold, and may look like they have a single, large, misshapen breast.