Frontal sinus: the air cavity of the forehead
- Highlighted area
Quick facts
- Definition
- Paired air cavity inside the frontal bone, above the orbits and the root of the nose.
- Development
- Appears in childhood and is complete in adolescence; size and shape vary widely.
- Drainage
- Communicates with the nose through a small channel, the frontonasal duct.
- Relevance in facial harmonization
- Explains part of the variation in the projection of the forehead bone and glabella, which soft tissue does not change.
The frontal sinus is an air-filled cavity inside the frontal bone, located above the orbits and the root of the nose. There are two, one on each side, usually separated by a thin bony partition. It is part of the group of paranasal sinuses, which communicate with the nasal cavity.
Where is it and how does it develop?
It occupies the forehead region just above the brow ridge and the bony glabella. It does not exist at birth: it begins to form in childhood and reaches adult size by the end of adolescence. That is why size varies widely between people, and in a small share of the population it may be very small or absent on one side.
| Feature | Observed variation |
|---|---|
| Size | From very small to quite extensive |
| Symmetry | The two sinuses are usually different from each other |
| Septum between the sinuses | May deviate from the midline |
| Forehead projection | Related to sinus size and the brow ridges |
The sinus drains through a narrow channel, the frontonasal duct, into the nasal cavity. When this channel becomes blocked, frontal sinusitis can develop, with forehead pain, a feeling of heaviness and, sometimes, fever.
Why does this matter for assessing the forehead?
The shape of the frontal bone is, to a large extent, the shape of the sinus. Larger sinuses tend to go along with more prominent brow ridges and a more protruding glabella, a feature more common in men. In many women, the forehead is smoother and more rounded.
This knowledge helps separate bone from soft tissue when assessing the upper third. When a patient complains of a "heavy" forehead or a very pronounced glabella, part of the cause is bony and does not change with injectables. The conversation needs to make this difference clear to avoid expectations of a change the anatomy does not allow.
Precautions for the area
The forehead and glabella are vascular risk areas, with branches of the supratrochlear and supraorbital arteries that communicate with the ocular circulation. The frontal sinus itself is not the target of any aesthetic procedure, but the presence of a bony cavity behind the skin reinforces why deep anatomy matters. The frontalis muscle, which lifts the eyebrow, rests on this region.
Persistent frontal headache, nasal congestion or signs of sinusitis before a procedure deserve medical assessment. A local infection can be a reason to postpone.
Also called: sinus frontalis, frontal paranasal sinus.
Frequently asked questions
Does the frontal sinus influence the shape of the forehead?
Yes. Large sinuses tend to go along with more prominent brow ridges and a more projected glabella, especially in men. The bone is the base on which the skin and muscles rest.