Bilateral Decompressive Craniectomy
Yup. Medicine's gotten that cool. Just like they transplant organs, surgeons can now implant cadaver bone into regions where patients seem to be missing it. And not only does it provide a framework for a vital area of the face, doctors can seed it with the patient's own cells, so that it will grow into their own entirely new and strong cheekbones that protect the eyes.
In Episode "Start Me Up," we meet fifteen-year-old Sarah Cassidy, who has lived her entire life without cheekbones. Sarah suffers from Treacher Collins syndrome, which leaves her orbital floor completely unprotected and vulnerable to severe injury. Like many of these patients, Sarah wants to live a more normal life and comes to Seattle Grace Mercy West, hoping our doctors' treatment will enable her to start playing sports with her friends.
What exactly is Treacher Collins Syndrome?
A rare and genetic condition, Treacher Collins syndrome affects the development of bones and other tissues in the face. Characterized by craniofacial deformities, TCS patients typically are not born with cheekbones (like Sarah). The condition's presentation varies from patient to patient, but symptoms may include: clefts in the face, abnormal eye shape, flat cheekbones, a small jaw, low-set ears, abnormally formed ears, abnormal ear canal, hearing loss, defects in the eye (coloboma that extends into the lower lid), and decreased eyelashes on the lower eyelid. However, even though affected with these physical defects, these kids do grow up displaying normal intelligence.
Do they know what causes the disease?
Affecting 1 in 50,000 people, Treacher Collins syndrome is caused by a mutation on the TCOF1 gene, which is responsible for producing a protein called treacle. Researchers think that treacle helps the development of bones and other tissues in the face before birth. Therefore, with a mutation, less treacle is made within cells, signaling other cells (that may be vital to the development of facial bones) to "self-destruct." The disease has an autosomal dominant pattern of inheritance, meaning that even one copy of the mutated gene could cause the disorder.
What types of treatment exist?
If not treated, TCS may cause complications such as feeding difficulty, speaking difficulty, communication problems, and vision problems. An immediate concern after birth is if the deformities lead to any airway obstruction. In severe cases, emergent intubation with or without tracheostomy may be required, followed by surgical management to lengthen the mandible. Also, when the patients are still very young, doctors will test them for hearing loss, so that they may still perform at a normal level in school. For the physical defects, plastic surgery techniques exist, such as the bone grafts discussed in this episode; however, many surgeons recommend waiting to repair any hard defects until skeletal maturity.
In Sarah's case, initially, Dr. Sloan and Dr. Robbins plan to extract pieces of bone from the back of her skull in order to implant them into the face to build cheekbones. Using the patient's own bone reduces the chances of an immune response to the implants as well as prevents soft tissue contracture. However, as Dr. Sloan indicates, this technique also has its negative aspects. For example, the extraction from the patient's skull may not be adequate enough for the size of the defect, and it may be difficult to match the contour of the skull to the contour of the face. Secondly, the additional surgical site can bring more complications with the harvesting such as dural tears, hemorrhage from the dural sinus, hematomas, meningitis, and accidental entry into the brain parenchyma or sagittal sinus. And finally, results have shown with skull bone grafts that the implanted bone may degrade over time and require a repeat procedure.
Dr. Sloan prefers a newer technique pioneered at Cincinnati Children's Hospital, in which cadaver bones injected with the patient's stem cells are used to build the cheekbones. During the procedure, surgeons take donor bone (from a cadaver) to construct scaffolding implants to be used as a growth guide for the new bones. Surgeons then drill holes into these implants and subsequently fill them with mesenchymal stem cells taken from the patient's abdominal fat. They also inject a growth hormone to instruct these stem cells to essentially become "bone cells" (called osteoblasts).
Using cadaver bone allows the surgical team to pick the size and shape of the necessary graft and to have a greater availability of membranous bone from which to choose. This method also has a lower rate of infection and a greater capacity to heal and grow with the patient, lasting longer. And the surgical team does not need to spend as much time in the operating room. Cons of the treatment can include a local inflammatory response to the grafts, the need for soft tissue coverage, encapsulation, and possible migration or extrusion of the implants. Evaluation of each patient and their individual deformities help to narrow down which technique might be best utilized.
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