The Dorsal Nasal Complex in Asians: Anatomical Variations and Injection Guide for Botulinum Toxin Type A.

Abstract

Multiple muscles contribute to the formation of dorsal nasal lines (DNLs) and affect nasal aesthetics. Few attempts have been made to explore the range of distribution of DNLs in relation to injection planning. The aim of this study was to classify the distribution types of DNLs and propose a refined injection technique validated by clinical study and cadaver dissection. Patients were classified into 4 types according to their DNL distribution type. Botulinum toxin type A injections were administered at 6 regular points and 2 optional points. The effect on wrinkle reduction was assessed. Patient satisfaction was recorded. Cadaver dissection was conducted to explore the anatomical evidence of DNL variation. The study included 349 treatments in 320 patients (269 females and 51 males), whose DNLs were classified into complex type, horizontal type, oblique type, and vertical type. The severity of DNLs was significantly reduced after treatment. Most patients were satisfied. From the cadaver study, connecting muscular fibers were clearly observed among the muscles involved in the formation of DNLs, and these muscles were collectively named the dorsal nasal complex (DNC) by the authors. Four anatomical variations of the DNC were discovered, corroborating the DNL classification system. A novel anatomical concept, the DNC, and a classification system for DNLs were proposed. Each of the 4 distribution types of DNLs corresponds to a specific anatomical variation of the DNC. A refined injection technique for DNLs was developed, and its efficacy and safety were demonstrated.