The Pre-DIT Technique: A Fascicle-Specific Dual-Plane Approach for Correcting and Preventing Paradoxical Masseteric...

Paradoxical masseteric bulging (PMB) is an uncommon but clinically relevant complication following masseter botulinum toxin type A injection. From mid-2024 onward, 4 cases of PMB were identified among patients treated at our department, with onset typically occurring within the first week after injection. Dynamic ultrasonography consistently demonstrated persistent contraction of the superficial fascicle while the deep fascicle remained fully inhibited, challenging the prevailing assumption that PMB results from insufficient deep-plane diffusion across the deep inferior tendon. Corrective treatment consisting of 4 targeted superficial injections of 3-4 units each resulted in noticeable improvement within 48 hours and near-complete resolution within 1 week. Implementation of a preventive superficial plane-the Pre-deep inferior tendon technique-in subsequent treatment cycles prevented recurrence. This article describes the anatomical rationale, technical execution, and clinical performance of this fascicle-specific dual-plane approach.