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Accessory sinuses of frontal region

Accessory Sinuses of frontal region and their classification:

Frontal sinus drainage region is the most variable portion of the whole of the nasal cavity. These variations can lead to obstruction to the frontal sinus outflow tract causing frontal sinusitis.

Attempts have been made to classify the variations of these cells abutting this vital area. Going by their drainage channels these cells are generally believed to be ethmoidal in origin.

Synonyms: Air cells abutting the frontal sinus have been given various names. They include: Frontal cells, frontal bullae, Supernumerary frontal sinuses, supraorbital sinuses and supraorbital cells.

Why these cells are important ?
These cells can impinge on the frontal sinus and frontal recess area causing obstruction. These cells can also be mistaken for frontal sinus itself during endoscopic surgery. Failure to address these cells could lead to persistence of frontal sinus disease.

Accessory cells in the frontal region can be classified under three categories:
1. Frontal cells
2. Supraorbital cells
3. Intersinus septal cells

Frontal cells: are ethmoidal cells that have pneumatized into the frontal bone.
Van Alyea classified these cells into two groups:
1. Cells that occupy the area of frontal recess
2. Cells that have managed to invade the frontal sinus cavity. These cells have been described in three different locations: 1. the floor of the frontal sinus, 2. Medial wall of frontal sinus, 3. posterior wall of frontal sinus.
According to Van Alyea supra orbital and intersinus septal cells are invading cells.
Bent's classification of accessory frontal cells:
The classification proposed by Bent grouped these cells into four different types based on their location.
Type I: This type represents a single frontal cell just above the agger nasi cell
Type II:This type consists of a tier of two or more air cells superior to the agger nasi cell.
Type III: This type has a single frontal cell which is massive and it pneumatizes superiorly into the frontal sinus
Type IV: These cells are contained entirely within the frontal sinus, thus giving it a cell inside a cell appearance.
Among these types types III and IV are considered to be invasive types.

Fig showing type II frontal cell

Supraorbital cells: These cell pneumatize the orbital plate of the frontal bone posterior to the frontal recess and lateral to the frontal sinus. These cells appear to extend over the orbit, appearing as the lateral cell in a coronal CT scan. Endoscopically these cells appear as separate ostia present along the anterolateral aspect of the roof of the ethmoid. These cells lie postero lateral to the frontal sinus ostia and anterior to the anterior ethmoidal artery.

Intersinus septal cell: is a midline cell that pneumatizes the frontal bone between the two frontal sinuses.

Balasubramanian Thiagarajan,
Jun 10, 2008, 5:12 AM