Midsagittal plane: the face's axis of symmetry
Quick facts
- Definition
- Vertical plane that passes through the middle of the body and divides the face into right and left sides.
- Reference points
- Glabella, nasion, tip of the nose, philtrum, point between the central incisors and pogonion.
- Use
- Basis of symmetry analysis and of the facial midline.
- Point of attention
- No face is perfectly symmetrical; small differences are expected.
The midsagittal plane is an imaginary vertical plane that passes through the middle of the head and divides the face into a right side and a left side. In photography and in clinical examination, it appears as the line that runs from the forehead to the chin, and serves as the reference for any assessment of symmetry.
Which points define the axis?
In practice, the axis is drawn by connecting facial points that line up on the midline.
| Point | Where it is |
|---|---|
| Glabella | Space between the eyebrows |
| Nasion | Depression at the root of the nose |
| Nasal tip | Most projecting point of the nose |
| Philtrum | Central groove of the upper lip |
| Interincisal point | Between the central incisors |
| Pogonion | Most anterior point of the chin |
The facial midline is the projection of this plane onto the surface of the face. It is the reference for checking whether the nose, lip and chin are aligned.
Why does the midsagittal plane matter in HOF?
The complaint "my face is crooked" is common, and the plane is the tool for turning perception into objective observation.
- Structural asymmetry: deviation of the chin, nose or jaw from the axis may have a bony or dental origin. Filler does not correct bone, but it can adjust perception. See facial asymmetry.
- Line of the teeth and lips: deviation between the dental midline and the facial midline is a frequent finding, and the patient does not always notice it.
- Volume planning: when dividing the ml between sides, the professional considers which side has less projection, without promising perfect symmetry.
- Photography: head position and tilt change how the axis reads. See standard views of the face.
How to avoid misreading?
Head tilt is the most common cause of false asymmetry. If the patient tilts the head to one side, the midline looks deviated. The bipupillary line helps correct this: it should be parallel to the floor for the reading to be valid.
Also known as: median plane, plane of symmetry.
Frequently asked questions
Is every face symmetrical about the midsagittal plane?
No. Small asymmetries are normal and usually go unnoticed. What matters is the difference that bothers the patient or that points to a structural change.