BACKGROUND Botulinum toxin type A (BTA) injection is a widely-used procedure to correct cosmetic problems caused by muscular hyperactivity. "Cobblestone chin" refers to the appearance of remarkable chin creases caused by mentalis contraction. AIMS The aim of this case report is to raise the awareness of paradoxical bulging after BTA injection in mentalis. PATIENT/METHODS A 26-year-old female asked for cosmetic correction of the "cobblestone chin". BTA injection was performed routinely to the mentalis muscle. However, on the second day after injection, an unusual paradoxical bulging at chin was presented. RESULTS We speculated that the imbalanced relaxation of mentalis caused by improper injection and uneven diffusion of BTA is responsible for the bulging. After a supplementary injection of BTA in the remaining hyperactive muscle fibers based on the ultrasound examination, the bulging was relieved and chin contour improved significantly. CONCLUSION Injection of BTA in mentalis should cover the whole thickness of the muscle to prevent imbalanced paralysis and paradoxical chin bulging, especially in severe mentalis hyperactivity cases.

中文翻译：

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A型肉毒杆菌毒素注射后精神病的反常膨胀。

背景技术A型肉毒杆菌毒素（BTA）注射是纠正由肌肉活动过度引起的美容问题的广泛使用的程序。“鹅卵石下巴”是指由精神分裂引起的下巴明显皱纹的出现。目的本病例报告的目的是提高对精神分裂症注射BTA后出现矛盾矛盾的认识。患者/方法一名26岁的女性要求对“鹅卵石下巴”进行美容矫正。BTA注射常规进行到精神肌肉。然而，在注射后的第二天，下巴出现了异常的反常凸起。结果我们推测，由于BTA注射不当和BTA扩散不均匀导致的精神错乱的不平衡是造成鼓胀的原因。根据超声检查，在剩余的多动肌纤维中补充注射BTA后，肿胀得到缓解，下巴轮廓明显改善。结论在精神病患者中注射BTA应该覆盖整个肌肉厚度，以防止不平衡的麻痹和矛盾的下巴膨出，尤其是在严重的精神病患者中。