Agenesis of the corrugator supercilii: a benign condition.

We report 2 neonates with frontonasal masses. The frontonasal masses were only present while the neonates were crying. The rest of the general examination and the neurological examination of the neonates were normal. The first patient had an extensive neuroimaging evaluation that included skull radiograph, computed tomography (CT) and magnetic resonance imaging (MRI) of the brain, and ultrasound of the frontonasal mass. The second patient was evaluated with ultrasound of the frontonasal mass. The mother of the second patient had no frontonasal creases and was unable to frown. In both patients, the ultrasonographic studies revealed nonspecific soft tissue thickening in the region of the glabella only while crying. The ultrasonographic findings and the similarity between the mother's findings and those of adult patients receiving botulinum toxin injection to the corrugator supercilii muscle point to the absence of this muscle as the cause of the frontonasal mass in these patients.