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Unicoronal synostosis refers to the premature fusion of the unilateral coronal cranial suture, a condition that affects the shape of the skull and face. It is the second most common type of craniosynostosis after sagittal synostosis. In Western countries, it occurs in about one in 10,000 newborns, with a higher incidence in girls compared to boys.
The most common early sign is a forehead tilt. On the affected side, the forehead appears flatter, while the unaffected side is more prominent. In a frontal view, the eye on the affected side may appear larger, with the eyebrow bone positioned higher. Parents often notice one eye looking larger than the other, and the forehead on the side with the larger eye is flatter.
Another common feature includes a crooked nose, where the upper nasal bones tilt toward the affected side. The skull on the affected side may bulge more, while the normal side does not.
Similar to other single suture synostoses, unicoronal synostosis carries about a 17% risk of increased intracranial pressure. Treatment considers both functional and aesthetic aspects. This condition is particularly asymmetrical and noticeable, especially in girls, so surgery is often recommended once diagnosed. The optimal timing is between 9 and 12 months, when bone healing is most favorable. However, a crooked nose may persist post-surgery, as the procedure focuses on the forehead and upper orbital rim. If the nasal deviation remains into adolescence, additional surgical adjustment can be considered.
For all types of craniosynostosis detected early (before 4 months), endoscopic-assisted cranial suture resection can be used, followed by wearing a customized molding helmet. This technique has been refined over 20-30 years, with recent improvements incorporating helmets due to better outcomes.
For unicoronal synostosis, the forehead asymmetry and unequal eye sizes are significant challenges. Cranial surgery alone may not fully address these issues. Combining it with a post-operative molding helmet can help, but from a plastic surgery perspective, the long-term aesthetic and symmetrical results for the forehead are limited.
The recommended approach is forehead reshaping surgery, similar to that for metopic synostosis. This involves shaping the forehead and upper orbital bones together, which can increase intracranial volume while achieving cosmetic improvements.
Modern techniques use 3D computer simulations to plan the surgery. Pre-operative modeling includes designing bone cuts and arrangements, with 3D-printed surgical guides used during the procedure for smoother execution.