of the facial nerve. These structures, as well as the inner ear, could be in danger at surgery. Patients with Down syndrome may have a narrow ear canal and middle ear malformation leading to impaired hearing. Some part of the cognitive delay seen in these children may be partly due to their poor hearing. The surgery can only take place once the skull is at least 2.5 mm thick. Children with certain syndromes may have a slighter build, thinner bone, or unusual anatomy. Other children may have a thicker skull at a younger age, so it is difficult to give a specific age for surgery. In the U.S., the Food and Drug Administration only approves BAHA implantation of children aged five years or older. For infants and young children prior to surgery, the sound processor can be worn on a head band or soft band which the infant wears to hold it against the skull. Side effects Complications of BAHA systems can be considered as either related to the bone (hard tissue) or the soft tissue. Bone Failure of osseointegration Chronic infection Trauma Soft tissue Irritation of the skin surrounding the implant Skin flap necrosis (death of the skin flap, e.g. due to interrupted blood supply) Overgrowth of skin over the device Wound dehiscence (splitting apart of the wound) Bleeding or hematoma formation Persistent pain Soft-tissue complications are much more common, and most are managed with topical treatments. Children are more likely to develop both kinds of complications than adults. Sometimes, a second surgical procedure is required. Complications are less likely with good wound hygiene. Other drawbacks of BAHA include accidental or spontaneous loss of the bone implant, and patient refusal for treatment due to stigma. Surgical procedure The bone behind the ear is exposed through a U-shaped or straight incision or with the help of a specially designed BAHA dermatome. A hole, 3 or 4 mm deep depending on the thickness of the bone, is drilled. The hole is widened and the implant with the mounted coupling is inserted under generous cooling to minimize surgical trauma to the bone. Some surgeons perform a reduction of the subcutaneous soft tissue. The rationale for this is to reduce the mobility between implant and skin to avoid inflammation at the penetration site. This reduction of the soft tissue has been questioned and some surgeons do not perform any or a minimum of