When a pharyngeal flap is used, a flap of the posterior wall is attached to the posterior border of the soft palate. The flap consists of mucosa and the superior pharyngeal constrictor muscle. The muscle stays attached to the pharyngeal wall at the upper side (superior flap) or at the lower side (inferior flap). The function of the muscle is to obstruct the pharyngeal port at the moment that the pharyngeal lateral walls move towards each other. It is important that the width and the level of insertion of the flap are properly constructed, because if the flap is too wide, the patient can have problems with breathing through the nose, which can result in sleep apnea. Alternatively, a postoperative situation can be created with the same symptoms as before surgery. Some complications are possible; for example, the flap's width can change because of contraction of the flap. This results in a situation with the same symptoms of hypernasality after a few weeks of surgery. Also a fistula can occur in 2.4% of the cases.