Inability to preserve a drainage pathway for the frontal sinus requires obliteration or cranialization. Cranialization is generally preferred since it avoids the risk of delayed mucocele formation and possible infection from incomplete removal of mucosa from the sinus and simplifies the radiographic interpretation of follow-up scans.

CONTRAINDICATIONS

There are no absolute contraindications to this surgery. However, patients with severe medical comorbidities, such as cardiovascular disease, pulmonary impairment, debilitation, or severe dementia, and those with end-stage renal disease may not benefit from undergoing the indicated surgical procedure. In patients suspected of having advanced malignancy, with massive brain invasion, bilateral orbital invasion, or cavernous sinus involvement, surgery may be contraindicated. Also, in patients with a known primary in which the frontal bone neoplasm represents metastatic disease, palliative therapy may be indicated, rather than a heroic effort at resection.

PREOPERATIVE PLANNING

Imaging Studies

Imaging plays a critical role in the evaluation of patients being considered for frontal sinus cranialization. Both computed tomography (CT) and magnetic resonance imaging (MRI) are used in the evaluation of this patient population. CT scan with contrast provides considerable information about the integrity of the bone of the frontal sinuses including the roof of the orbit. CT scan also provides insight into soft tissue filling the frontal sinus. MRI provides improved definition between any soft tissue mass in the frontal sinus and adjacent soft tissues, such as the orbit, dura, and/or brain. Edema of the frontal lobe is frequently indicative of invasion through the dura with involvement of the frontal sinus, by any disease process. MRI is also helpful in differentiating tumor from secretions in obstructed sinuses.

Preoperative Biopsy

For patients with an isolated process in the frontal sinus, it is the rare instance in which a preoperative biopsy is feasible. In patients suspected of having either a benign or malignant tumor destroying the anterior wall, it may be feasible to perform direct needle biopsy of the soft tissue mass. The other instance in which biopsy may be feasible is a patient with a tumor in the superior nasal cavity or frontal duct region. Care must be taken in performing the biopsy to avoid injury to the dura and/or brain.

SURGICAL TECHNIQUE

The classic surgical technique is readily used for the patients with suspected isolated tumors of the frontal sinus, as well as those with chronic inflammatory and infectious process. A similar approach is also employed for patients undergoing anterior craniofacial resection. A cosmetically appealing incision is designed using a bicoronal approach in the hairline. This allows for preservation of the skin and access down to the superior orbital rims bilaterally. As will be described, a galeal–pericranial flap can be elevated for reinforcement of any dural defect. The frontal sinus is removed in a monobloc fashion, including the anterior and posterior walls of the sinus. Assistance can be obtained with the use of a neuronavigation device in designing osteotomies. The posterior wall of the frontal sinus is removed with preservation of the underlying dura.

Any breach or involvement of the dura and/or brain is resected, and in these instances, multilayer closure of the dura is performed to prevent a CSF leak. In the instance of involvement of the anterior wall of the frontal sinus or in a comminuted fracture, reconstruction may be indicated. Due to the risk of infection, this may be performed as a secondary procedure. Care must be taken to obstruct the frontal ducts with temporalis muscle fascia or other adjacent available tissue to prevent communication between the nasal cavity and the exposed dura. All mucosa must be removed from the frontal sinus to prevent secondary mucocele formation.

Description of Technique

The patient is placed under general endotracheal anesthesia with paralytic agents, and the endotracheal tube is secured at the oral commissure. The patient is prepped and draped in a sterile fashion with exposure of the superior portion of the nose, the orbits, and the forehead. The eyes are protected with tarsorrhaphies bilaterally taking care not to injure the eye during placement. Every effort is made not to shave the head except for a narrow strip along the incision line in parallel to the hairline approximately 2 cm posterior to the hairline, from one anterior temporal region to the other anterior temporal region. Typically, I employ a three-drug combination of antibiotics for prophylaxis: CMV—ceftazidime, metronidazole and vancomycin. Steroids are typically administered to prevent cerebral edema. In rare instances in which concerns exist regarding dural reconstruction, a lumbar drain is placed at the beginning of the surgical procedure.

The bicoronal incision is carried through the skin and subcutaneous tissue. I usually harvest a galeal–pericranial flap. The distal one-half of the flap consists purely of the pericranium to allow for closure of the galea at the incision site. Galea is incorporated in the more proximal one-half of the flap to provide a more vigorous and thicker flap. As one approaches the supraorbital vessels, care must be taken not to interrupt the vessels, as they provide the blood supply to the flap. This provides exposure to the frontal bone and allows for direct inspection to assure integrity of the anterior aspect of the frontal bone.

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