By Raghu Athre, MD

The  frontal sinus is a hollowed out area in the frontal bone consisting of an anterior table and a posterior table.  Its size is highly variable amongst individuals; and even in the same individual, symmetry between left and right is rarely noted.  The frontal sinus is not developed in the pediatric patient and only attains full size in adolescence.  Therefore, frontal sinus fractures are far more common in adults than in children.

The etiology of frontal sinus fractures is primarily through motor vehicle accidents and blunt force trauma to the forehead.  Statistical analyses show that frontal sinus fractures constitute approximately 5-12% of maxillofacial trauma cases and occurs at a frequency of about 9 per 100,000 adults.  Several biomechanical studies have reported that a force between 800-2200 lbs. is required to fracture the frontal sinus.  Due the high energy involved in these fractures, concomitant maxillofacial trauma and intracranial injuries are common and a complete exam is necessary.

The primary problem in frontal sinus fractures is the nasofrontal duct.  This duct drains the frontal sinus into the nasal vault.  Depending on the location of the fracture, there is a risk of outflow interruption secondary to injury of the duct.  If outflow obstruction occurs, sinus stasis results.  This can lead to long-term complications such as mucocele formation.  Superinfection of the mucocele can lead to mucopyocele, erosion of the posterior table, meningitis or brain abscess.  The focus of this paper is to describe treatment algorithms to prevent these devastating complications.  It is important to remember that the majority of these complications can occur decades after the original injury.  Therefore, regardless of the initial management of the fracture, it is imperative to follow these patients on annual basic with CT scans of the face to r/o sinus obstruction.  Any symptoms consistent with frontal sinusitis should also prompt a timely workup.

The same terms (simple, displaced, and comminuted) are used to describe frontal sinus fractures.  Also, frontal sinus fractures are subdivided into fractures of the anterior table, fractures of the posterior table, or fractures involving both tables.  Most anterior table fractures present a cosmetic deformity only.  Therefore, repair of these fractures can be elective.  However, anterior table fractures that occur medial to the supraorbital notches, in the glabellar area, and at the base of the frontal sinus carry a high risk for nasofrontal duct obstruction.  Posterior table fractures usually occur with anterior table fractures.  Posterior table fractures that are displaced more than the width of the posterior table are at an increased risk for dural injury and CSF leaks.  Also, sinus mucosa can become impinged between fracture segments and lead to mucocele formation.  Intracranial injury is common with posterior table fractures and once again, fractures that involve the lower aspect of the sinus or occur medial to the supraorbital notches are at a high risk for disturbing the nasofrontal duct.

Workup of frontal sinus fractures is similar to all maxillofacial fractures.  A complete trauma exam should be completed first.  Following that, a CT scan of the face that contains bone windows at 1.5-3mm cuts in the axial and coronal plane should be obtained.  Frontal sinus fractures are primarily assessed in the axial plane, though coronal cuts are very useful as well.  A 6-foot Caldwell radiograph, which is a 1:1 AP view of the skull, should also be obtained for operative planning.

Indications to perform operative repair of frontal sinus fractures include:
" Fractures that involve base of frontal sinus, anterior ethmoidal area, or fracture involving area medial to supraorbital nerve
" Posterior table fracture greater than width of posterior table
" Posterior table fracture with CSF leak
" Cosmesis
It is important to repair patients with a CSF leak within 8 days because studies have shown an increased risk of meningitis in patients where repair was delayed.

Once the decision has been made to go to the operating room, several approaches are available to the frontal sinus.  Of course, one may utilize existing lacerations in the forehead.  The standard approach in recent days has been a bicoronal flap for exposure of the frontal sinus.  Gullwing suprabrow flaps have been used, but are not cosmetically appealing.  Once the soft tissue over the frontal sinus has been raised, the next task is to remove the anterior table.  The 6-foot Caldwell radiograph is useful to obtain a 1:1 view of the frontal sinus.  The frontal sinus is cut out of the radiograph and sterilized.  The template is placed on the patient, and an outline is drawn on the skull.  This outline represents the margins of the frontal sinus.  A drill is used to carefully cut along the inside of the outline to remove the anterior table.  Potential complications of this portion of the procedure include intracranial injury, dural tear, and CSF leakage.

To check the integrity of the nasofrontal duct, cocaine is applied to constrict the mucosa.  Fluorescein is placed in the frontal sinus.  Appearance of fluorescein in the nose indicates integrity of the duct.  Lack of fluorescein in the nose represents injury to the duct and the patient should undergo obliteration of the frontal sinus or cranialization.  Obliteration involves removing all of the mucosa from the frontal sinus, filling the sinus with autogenous material such as fat or pericranium, and plugging the nasofrontal recesses with fat to essentially isolate the frontal sinus from the nose.  Cranialization involves removing the posterior table, removing mucosa from the anterior table, plugging the nasofrontal ducts, and allowing the brain to expand into the cavity.  Attempts at repairing the nasofrontal duct with placement of a stent similar to dacrocystorhinostomy have bben described.  Despite leaving the stent in place for weeks, these cases have a 30% re-stenosis rate of the nasofrontal duct after removal of the stent.

Algorithms for management of anterior table fractures and posterior table fractures are presented in the images below.  If the patient has a fracture of both tables, the posterior table algorithm should be followed.  It is important to recognize that if there is a question of nasofrontal duct injury, it is better to obliterate/cranialize because the long-term complication rate without surgical obliteration is 10%, whereas the long-term complication rate with obliteration is less than 1%.

Management algorithm for anterior table fractures  (Diagram link)