Aesthetic cranioplasty

History

A thorough history should be taken to screen for cranial abnormalities. Most often, cranial abnormalities are secondary to congenital, traumatic, or oncologic causes. In the case of congenital abnormalities, it is important to discern any prior surgeries that have been performed and, if applicable, whether autologous or nonautologous reconstruction was done with either permanent or resorbable plates. If the patient has a history of reconstruction, it is important to know what donor sites were used. In the case of a traumatic etiology, it is important to determine the degree of injury, prior infections, and the method of treatment. If an infection was present, the physician should discover which pathogens were implicated and the details of antibiotic therapy (duration and type). When evaluating postoncologic defects, it is important to discern the patient’s remission status, need for prior radiation therapy and chemotherapy, and which method of reconstruction was utilized. It is vitally important to make sure that the patient is receiving continued cancer-specific screening and is free of malignancy before repeat reconstruction is performed. If active malignancy exists, negative margins should be achieved before reconstruction is considered.

To address the patient’s complaint, particularly for aesthetic correction of morphology already considered to be within normal range, it is vital to elucidate the patient’s understanding of his or her appearance so that the clinician’s goals are in alignment with the patient’s goals. The patient should be asked about the perceived aesthetic and nonaesthetic components of his or her face. Part of this discussion should delve into the patient’s cultural background, if relevant.

The surgeon should uncover what factors the patient feels are contributing to any deficiency in appearance. This includes questions about both soft tissues and the facial skeleton. Asymmetries should be noted during visits with the surgeon.

Differential diagnosis

It is important to know what medical factors are contributing to the patient’s condition and appearance. Continued osteomyelitis can lead to recurrent infection and sinus tracts. Hypersensitivity reactions to prior implants can result in inflammation, swelling, and discoloration. Prior graft resorption can lead to deficiency in the appearance of the skull. Prior radiation therapy can distort the cranial skeleton and also cause microvascular thrombosis. Other comorbidities may also alter the appearance of the face. Human immunodeficiency virus (HIV) medication–associated lipodystrophy can accelerate temporal wasting and buccal fat pad atrophy. Other conditions affecting the skull include facial nerve palsy, Parry-Romberg syndrome, and chronic steroid use.

Physical examination

The physical examination is most vital for the surgeon’s preoperative planning. It is important to examine the patient’s skeletal cranium, soft tissue quality, prior scars, and areas of previous trauma.

High-quality digital images help guide the discussion of the patient’s goals and expectations. Standardized preoperative photographs (at a minimum, six views: anteroposterior, right lateral, right oblique, left lateral, left oblique, and vertex views) are useful for treatment planning and medical documentation. Newer three-dimensional imaging software with graphic manipulation, such as Vectra, can allow for an informative discussion and facilitate agreement between the surgeon and the patient on realistic goals. Standardized preoperative photos also aid in legal documentation for all involved parties.

Imaging and other preoperative diagnostic evaluation

Preoperative imaging with computed tomography (CT) is almost always necessary before developing a treatment plan. This allows the surgeon to visualize bone quality and quantity, as well as the presence of foreign bodies, such as previously placed implants or fixation. These images also are necessary to fabricate custom implants using virtual surgical planning (VSP).

Full-thickness cranial defects

Most frequently, cranioplasty is required after the loss of a craniotomy bone flap as a result of infection. Usually, the loss is caused by a combination of dehiscence and skin necrosis, resulting in exposure of the flap directly under the incision. This is exacerbated by the presence of dead space under the incision or foreign bodies—which include plates and screws often used in operative fixation. Not much is required to disrupt the incision. Even pressure necrosis due to lack of offloading can exert significant stress on the closure site. A possible solution here is to design large skin flaps so that incisions are located away from bone flaps and hardware to the extent possible.

Syndrome of the trephined

SoT is believed to be triggered by exposure of intracranial contents to the open atmosphere. It can present after craniectomy, manifest as a sunken calvarial skin flap, and is suspected to arise secondary to a dysregulated balance of intracerebral and external pressures. Patients present with reduced cerebral perfusion, impaired venous return, altered cerebrospinal fluid (CSF) flow, brain herniation, and other deformations, with subsequent metabolic changes and cortical dysfunction. ^, Neurologic sequelae include nonspecific symptoms, such as headache, as well as motor weakness and cognitive deficits affecting executive function and memory. Early cranioplasty within 6 to 12 months of craniectomy is an effective treatment for SoT and is associated with normalized CSF hydrodynamics and cerebral blood flow. ^,

Revision cranioplasty

Delayed hypersensitivity reactions and even death have occurred years after alloplastic cranioplasty. ^, Patients with a history of alloplastic calvarial reconstruction presenting with subacute–chronic nonspecific neurologic and dermatologic symptoms, such as suboccipital headaches, swelling of the head, and diffuse rash, should be suspected and tested with wide-range patch testing for common alloplastic materials, including bone cement.

If revision cranioplasty is being sought for aesthetic reasons, the surgeon needs to ensure that the recipient site is well-vascularized, has adequate soft tissue, and is free of infection. Although autologous bone can be used, due to variable resorption over time, it is less ideal for purely aesthetic cranioplasty. The primary approach to aesthetic cranioplasty is to use calcium hydroxyapatite (HA) bone paste or a prefabricated custom implant. If cost is a concern, polymethylmethacrylate (PMMA) is an inexpensive, safe material that the surgeon can use intraoperatively to make a custom implant. These PMMA kits are used frequently in orthopedic surgery and are inexpensive. PMMA is a safe, biocompatible material for cranioplasty and can even be mixed with antibiotic powders or solutions to prevent infection.