Dennis Kraus
INTRODUCTION
Cranialization of the frontal sinus is used in the management of a number of disease processes. Classically, it has been employed as part of anterior craniofacial resection in which the posterior wall of the frontal sinus is removed, which allows for the expansion of the frontal lobes and effectively obliterates the frontal sinuses. Other instances in which this procedure has been employed include disease processes such as fungal sinusitis and isolated tumors of the frontal sinus that erode through the posterior wall of the frontal sinus, in some instances involving the dura and/or brain. The last instance in which cranialization may be employed is in both blunt and penetrating trauma with disruption of the posterior wall of the frontal sinus.
HISTORY
The most common history for patients undergoing cranialization of the frontal sinus classically is the presence of a malignant tumor of the anterior skull base requiring craniofacial resection. These patients typically present with symptoms of nasal obstruction, epistaxis, visual changes, and mucopurulent discharge.
For the patients presenting with trauma, the history can consist of both blunt and penetrating trauma. This again covers a wide spectrum of traumatic events including high-velocity vehicular trauma, falls from heights, and a series of other blunt and penetrating traumas, including gun shots and other penetrating injuries. In evaluating these patients, appropriate history includes signs of orbital dysfunction, visual loss, cerebrospinal fluid (CSF) rhinorrhea, meningitis, and other injuries to the craniomaxillofacial skeleton.
For patients with either isolated tumors or sinusitis, symptoms are typically relegated to the region of the frontal sinus. This can include orbital proptosis, pressure, epistaxis, or fever. Prior history of sinonasal surgery, including nasal tumor surgery, is a salient feature of the history. Specifically, a prior history of inverted papilloma resected from the lateral nasal wall may present with an isolated recurrence in the frontal sinus.
PHYSICAL EXAMINATION
Physical examination of the patient being considered for frontal sinus cranialization will again be predicated on the aforementioned underlying pathology.
For those who are undergoing anterior craniofacial resection, the necessity of performing nasal endoscopy, assessment of orbital function, and sensory testing of the trigeminal distribution is essential. It is also critical to exclude metastatic cancer in the cervical lymph nodes.
For those who have sustained trauma, it is critical to exclude additional craniomaxillofacial and skull base fractures. Orbital function should be assessed. Evaluation to exclude CSF rhinorrhea should be performed with nasal endoscopy. Orbital function including pupillary response and the absence of a Marcus Gunn pupil (afferent papillary defect) is critical. Formal ophthalmologic examination may be indicated on a selective basis. Evaluating the anterior wall of the frontal sinus to exclude a penetrating wound and a comminuted fracture is critical. Moreover, looking for and palpating for subcutaneous air is an important part of the examination and will provide clues as to the extent of the injury.
For individuals presenting with a suspected isolated tumor of the frontal sinus or infection, palpation of the wall of the anterior frontal sinus to exclude erosion is critical, including the presence of a soft tissue mass. It is important to assess ocular function. Nasal endoscopy will often provide significant clues as to previous intranasal surgery. It may also provide insights regarding the presence of active infection.
INDICATIONS
Cranialization of the frontal sinus is performed as an alternative to a frontal sinusotomy with preservation of normal sinus drainage and obliteration of the sinus with an adipose graft or other tissue. If the pathologic process can be treated with preservation of normal anatomy and drainage pathway, then this is usually the preferred option. The development of advanced endoscopic techniques has dramatically reduced the need for open frontal sinus procedures. A Draf III frontal sinusotomy provides access for the drainage of mucoceles and chronic frontal sinusitis, removal of benign tumors such as osteomas and inverting papilloma, and oncologic resection for sinonasal malignancy.
Open approaches for frontal sinus disease are typically reserved for pathologic processes associated with destruction of the walls of the frontal sinus or complications such as intracranial infection (Table 24.1). If the frontal craniotomy is confined to the anterior table of the frontal sinus, then the frontal sinus can be preserved or obliterated with tissue (adipose tissue or pericranial flap). If the frontal craniotomy incorporates the entire sinus, then cranialization is preferred since this avoids future problems with frontal sinus drainage and mucocele formation. When a craniofacial resection is performed for sinonasal malignancy, cranialization provides an additional oncologic margin.
Table 24.1 Diseases Necessitating Frontal Sinus Cranialization
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.
In instances where neuronavigation is employed, registration of the device is performed using fiducials or anatomical landmarks prior to beginning the procedure. This can assist in appropriately designing the anterior frontal bone osteotomies and preventing inadvertent injury to the dura and/or brain. A small burr hole can be performed with a rotating high-speed drill. This will assure entry into the frontal sinus. A fine side-cutting burr is used to minimize bone loss and prevent a visually evident or palpable step-off at the osteotomy site. The frontal bone flap is secured on the back table in a sterile preparation. The contents of the frontal sinus as well as the posterior frontal sinus wall are removed (Fig. 24.1). All of the mucosa is stripped from the remnants of the frontal sinus as well as the bone flap. The posterior table of the frontal sinus is removed with rongeurs and smoothed with the drill (Fig. 24.2). It is important to remove all vestiges of mucosa from the frontal sinus with the drill (Fig. 24.3). In instances of involvement of the dura and/or brain, the neurosurgical team is included. This is the case for primary tumors of the frontal sinus and any inflammatory/infectious process. In the instance of open anterior craniofacial resection, the cribriform plate is usually resected with the dural invaginations involving the cribriform plate and the fovea ethmoidalis. This necessitates reconstruction of the dura. Typically, bovine pericardium is employed to close the dural defect as part of a multilayer closure.
FIGURE 24.1 A bifrontal craniotomy has been performed for a sinonasal malignancy with intracranial extension and orbital involvement. The craniotomy includes the anterior and posterior tables of the frontal sinus (FS).
FIGURE 24.2 The mucosa and posterior table of the frontal sinus are removed from the bone flap.
FIGURE 24.3 All remnants of mucosa and bony septations are drilled from the remnant of the frontal sinus (FS).
A galeal–pericranial flap is employed as a second-layer closure to reinforce the primary dural closure and prevent a CSF leak (Fig. 24.4). By removing the posterior wall of the frontal sinus, the brain expands and essentially fills the frontal sinus. Care must be taken to remove all the mucosa from the anterior osteoplastic frontal sinus flap to prevent subsequent mucocele formation. Care must also be taken to plug the frontal sinus ducts to prevent communication between the contaminated nasal cavity and the exposed dura and brain. Moreover, in patients suspected of having chronic infection, cultures should be performed including aerobic, anaerobic, acid-fast bacilli, and fungal organisms.
FIGURE 24.4 A. A pericranial flap pedicled on one or both supraorbital vessels is used for separation of the nasal cavity from the cranial cavity and for coverage of the dural graft. (FS, frontal sinus remnant prior to cranialization; PF, pericranial flap; FD, frontal dura.) B. The pericranial flap is placed over the supraorbital bar following obliteration of the nasofrontal ducts with tissue. The flap can be folded back on itself to provide complete coverage of the dural graft. The arrows mark the distal margin of the flap at the edge of the craniotomy.
In patients with either a comminuted fracture of the anterior wall or invasion by infection or tumor, the anterior wall of the frontal sinus is also resected. Although one can collect the bone remnants of a comminuted fracture, it is rare that it is feasible to adequately plate these bones together and provide an intact frontal sinus wall. The decision must be made whether to perform immediate reconstruction of the frontal bone defect or allow for collapse of the wound and secondary reconstruction. In patients with open comminuted fractures or osteomyelitis of the anterior wall of the frontal bone, delayed reconstruction is typically indicated. For the patients with primary tumors, immediate reconstruction can be performed with a number of materials. Potentially, this could include use of a free bone graft harvested from the iliac crest, the scapula, or from another portion of the cranium. Free tissue transfer from the iliac crest or the scapula is also feasible but is a challenge given the spherical structure of the frontal bone. Alloplastic materials such as mesh, synthetic material, or hydroxyapatite bone paste have all been employed. The major risk associated with the use of alloplastic materials is the potential for either infection and/or extrusion. Finally, when there is loss of the frontal skin due to avulsion or frontal skin flap loss due to local vascular insufficiency, a free flap is essential, accepting the cosmetic limitations at this site.
When the skin and the frontal bone flap are preserved, the anterior frontal bone flap is secured with multiple titanium miniplates (Fig. 24.5). As noted earlier, there is no need to fill the frontal sinus defect as the brain will expand and effectively fill the space. The bicoronal incision is closed in multiple layers with 2-0 Vicryl sutures, and the skin edges are reapproximated with staples. In the majority of the cases, a Hemovac drain is placed above the frontal bone and below the skin flap and is left in place for several days. A turban-style pressure dressing is kept in place for 1 or 2 days.
FIGURE 24.5 The bone flap is secured with titanium mini plates and mesh. Additional bone may be removed from the inferior margin of the bone flap to prevent compression of the vascular pedicle of the pericranial flap.
POSTOPERATIVE MANAGEMENT
The Hemovac is placed to self-suction for 1 to 2 days. Once drainage has tapered, the drain is removed. The pressure dressing is removed on postoperative day 2. Staples are removed on postoperative day 7 to 10 during the first operative visit. The patient receives approximately 2 to 3 days of the previously described regimen of intravenous antibiotics.
COMPLICATIONS
Complications of the surgical procedure are listed in Table 24.2. Hematoma is a rare event occurring in less than 5% of procedures. Infection is rare with the use of the three-drug regimen; but when it occurs, it is associated with loss of the anterior bone flap and the need for secondary reconstruction, as well as prolonged intravenous antibiotics as an outpatient.
Table 24.2 Complications—Frontal Sinus Cranialization
Injury to the eye including blindness is an extremely rare occurrence and occurs in less than 1% of patients. Loss of the skin flap is an extremely rare event and can be avoided by preserving the superior orbital blood supply bilaterally. Again, this occurs in no more than 1% or 2% of cases. CSF leak is also a rare event, especially in patients with intact dura. There is a slightly higher incidence when patients require a dural reconstruction; a meticulous multilayer closure with use of the galeal–pericranial flap reduces the risk to less than 5%. Occasionally, there may be hair loss at the site of the incision. Meticulous management of the soft tissues with preservation of the subdermal tissue prevents injury to the hair follicles.
RESULTS
It is often challenging to assess the results of a surgical procedure that is employed for a number of disease processes. Cranialization of the frontal sinus after traditional open craniofacial resection has been associated with a low incidence of frontal bone osteomyelitis, a low incidence of CSF leak, and favorable oncologic outcome for many patients with sinonasal/skull base malignancy. Similarly, in the patients with trauma to the frontal sinus, this approach has been associated with prevention of frontal sinus mucocele, acceptable cosmetic outcomes depending on the degree of soft tissue injury to the face and skin, and management of any intracranial injury. In patients with inflammatory and chronic infectious processes involving the frontal sinus necessitating cranialization, this technique is often successful in controlling local symptoms. Many of these patients will require prolonged antibiotics based on intraoperative cultures.
Two patients are worth describing. One patient presented with an isolated recurrence of an inverted papilloma extending to the frontal sinus and involving the posterior wall of the frontal sinus and dura. The patient underwent transfrontal resection of the tumor with cranialization. The patient did require a limited dural resection with immediate reconstruction with a dural graft and galeal–pericranial flap. There was no evidence of malignant degeneration, and the patient remains free of disease 7 years after extirpation.
The second patient presented with severe frontal headaches. Imaging studies revealed a soft tissue process involving the frontal sinus, posterior wall of the frontal sinus, and the adjacent dura and brain. Using the frontal osteoplastic approach, the patient underwent resection of the frontal sinus soft tissue mass including the posterior wall, dura, and involved brain. Intraoperative frozen section showed fungal hyphae. The patient received prolonged postoperative antifungal antibiotics and recovered with no sequelae.
PEARLS
· Perform a thorough radiologic assessment prior to surgical management.
· Educating the patient regarding postoperative appearance and possible complications is critical. Expected results will differ significantly based on whether the patient is undergoing this procedure for trauma, neoplasm, or chronic frontal sinusitis.
· Elevation of the galeal–pericranial flap will allow for secondary closure and reinforcement of any dural defect and prevent CSF leak.
· Removal of all remaining mucosa from the anterior wall of the frontal sinus will prevent mucocele formation.
· Meticulous management of the soft tissues of the bicoronal flap will prevent hair loss resulting in a superior cosmetic outcome.
PITFALLS
· Incomplete imaging preoperatively may result in unanticipated findings at the time of surgery.
· Injury to the supraorbital vessels may result in loss of the galeal–pericranial flap or loss of the skin flap.
· Failure to use broad-spectrum antibiotics may result in osteomyelitis of the frontal bone.
INSTRUMENTS TO HAVE AVAILABLE
· High-speed drill with cutting burr and low-profile side-cutting burr.
· Titanium microplating system.
SUGGESTED READING
Donath A, Sindwani R. Frontal sinus cranialization using the pericranial flap: an added layer of protection. Laryngoscope 2006;116(9):1585–1588.
Rodriguez ED, Stanwix MG, Nam AJ, et al. Twenty-six-year experience treating frontal sinus fractures: a novel algorithm based on anatomical fracture pattern and failure of conventional techniques. Plast Reconstr Surg 2008;122(6):1850–1866.
Rontal ML. State of the art in craniomaxillofacial trauma: frontal sinus. Curr Opin Otolaryngol Head Neck Surg 2008;16(4):381–386.
van Dijk JM, Wagemakers M, Korsten-Meijer AG, et al. Cranialization of the frontal sinus–the final remedy for refractory chronic frontal sinusitis. J Neurosurg 2012;116(3):531–535.
Pollock RA, Hill JL Jr, Davenport DL, et al. Cranialization in a cohort of 154 consecutive patients with frontal sinus fractures (1987–2007): review and update of a compelling procedure in the selected patient. Ann Plast Surg 2012;71(1):54–59.