What Is Hidden Behind Microform Cleft Lip: A Case-Control Study Based on Ultrasound Imaging

Microform cleft lip is a subtle type of cleft lip characterized by a notched Cupid's bow peak, vermilion deficiency, nasal deformity, and a distinctive vertical philtral groove that deepens on puckering. However, the cause of the dynamic cutaneous depression is poorly understood.

A case-control study including untreated microform cleft lip patients and healthy controls was conducted from 2024 to 2025. Each participant underwent ultrasound examinations in both static and puckering states. The correlation between the clinical manifestation of dynamic philtral depression and ultrasound findings was analyzed.

A total of 20 microform cleft lip patients and 20 control subjects were included, with mean ages of 16 years and 20 years, respectively. In 19 patients (95%), ultrasound revealed a hypoechoic band along the philtrum on the affected side. Among these patients, 16 who were capable of cooperation underwent ultrasound imaging in the puckering state, and all showed an increase in thickness and prominence of the band during puckering. Magnetic resonance imaging further validated the correlation between the underlying band and the dynamic groove. In the single patient without dynamic philtral depression and in 20 control subjects, no significant abnormalities were detected on ultrasound. Pathologic examination revealed that the band was composed of abnormally aggregated, underdeveloped skin appendages and excessive collagen tissue.

The ultrasound hypoechoic band is prevalent in most microform cleft lip cases and directly correlates with philtral dynamic deformity. Ultrasound examination may serve as a reliable diagnostic adjunct for microform cleft lip.