Frontal Sinus Cranialization

Historical Perspective

The concept of cranialization came from the evolution of treatment of extensive wounds in the frontal sinus and anterior skull base. The initial paradigm in the management of complex fractures of the frontal sinus was to remove all the bone fragments, resulting in a defect that allowed for expansion of the edematous frontal lobes. As a result, cosmetic issues were significant because of the resultant deformity of the forehead. With this paradigm, mucocele formation and mucocele-related infections remained a serious issue. In an attempt to address these issues, the surgery of the frontal sinus evolved into “cranialization.” The anterior table is maintained, thereby avoiding a deformity of the forehead. The posterior table of the frontal sinus and the mucosa of the frontal sinus are meticulously removed. The anterior cranial fossa is permanently separated from the frontal recess. This eliminates the presence of the frontal sinus, provides additional space for the brain to expand, and decreases the risk of mucocele formation.

Initial reports by Donald in 1982 and Luce in 1987 concluded that the mucosa of the frontal sinus should be removed and the sinus ostia occluded in order to isolate the frontal sinus from the nasal cavity. Donald introduced the term “cranialization” in 1982, referring to removal of the posterior table of the frontal sinus, leaving the brain and dura to expand into the former frontal sinus cavity. Rodriguez (in 2008) clarified the debate between cranialization and frontal sinus obliteration with a seminal work summarizing his 26-year experience with fractures of the frontal sinus. He reported a complication rate for cranialization of 10%, compared with 22% for frontal sinus obliteration.

History

Patients who require frontal sinus cranialization classically present with a history related with the following:

• Patients with a malignant tumor of the anterior skull base usually have a history of nasal obstruction, epistaxis, hyposmia or anosmia, diplopia, facial pain, or sinus pressure associated with purulent rhinorrhea.

• Regarding patients with facial trauma, it is important to determine the type of trauma, either penetrating or blunt trauma. The history in these patients should include symptoms such as visual loss, diplopia, clear rhinorrhea (CSF leak), neurologic symptoms of meningitis, and mass lesions such as intracranial hematoma.

• Patients with inflammatory processes (chronic sinusitis) usually present with purulent rhinorrhea, facial pain, or pressure.

Physical Examination

Physical examination for patients requiring frontal sinus cranialization should emphasize the underlying pathology mentioned earlier.

• A complete examination of the head and neck must be performed, including the cranial nerves.

• It is important to evaluate for cervical metastasis in those patients with suspected underlying malignant disease.

• The use of nasal endoscopy is critical to obtain valuable information on tumor characteristics such as vascularity and extent.

• In patients with trauma, a complete examination of the orbit is mandatory, including checking pupillary reflexes and extraocular movements. In addition, the examiner should check for ptosis, chemosis, and proptosis.

• In trauma patients, one must be suspicious for CSF rhinorrhea.

• Ophthalmologic consultation should be obtained in patients with abnormal signs/symptoms involving the eyes.

• Examination of the anterior wall of the frontal sinus will determine its integrity.

• In patients with suspected frontal sinus inflammatory disease, palpation of the anterior table of the frontal sinus is important to rule out bone erosion or soft tissue mass (e.g., Pott’s puffy tumor).

Imaging

Patients with tumors of the anterior skull base require both a computed tomography (CT) scan and magnetic resonance imaging (MRI) with and without contrast. These studies complement each other in determining the bony anatomy, bone erosion, extension of tumor, involvement of the dura, and edema of the brain. In patients with facial trauma, MRI should be obtained in selected cases. Sinus or head CT scan should be obtained to evaluate the following:

• Anatomy and integrity of the frontal sinus, with particular attention to the integrity of the anterior and posterior tables.

• Anatomy and integrity of the frontal sinus recess, especially with fractures through the frontal recess. This will allow the surgeon to predict stenosis of the frontal recess.

• Integrity of the facial bones and orbit.

• Acute neurosurgical sequelae of facial trauma, including pneumocephalus or intracranial hemorrhage that may need emergent management.

Indications

The main indication for frontal sinus cranialization is determination that the frontal sinus drainage cannot be restored. Examples of indications for cranialization are as follows:

• Severe traumatic injury of the frontal sinus with involvement of both anterior and posterior tables

• Displaced fracture of the frontal recess (outflow tract)

• Displaced fracture of the posterior wall of the frontal sinus with the presence of a CSF leak

• Need for neurosurgical intervention

• Cranialization should be considered as the final remedy for refractory chronic frontal sinusitis.

• Tumors of the anterior skull base or frontal sinus with erosion of the posterior table of the frontal sinus

Contraindications

• Patients who are poor surgical candidates because of associated injuries or severe medical comorbidities should not undergo this procedure.

• Patients with unresectable tumor determined by invasion of the brain, cavernous sinus, or orbit may not benefit from this surgical procedure.

• If the posterior table component is nondisplaced or minimally displaced with an intact frontal sinus outflow tract, consider a less aggressive procedure such as open reduction and internal fixation (ORIF) of the anterior table and close follow-up leaving salvage surgery using endoscopic frontal sinus procedures in reserve.