Matsuo Kiyoshi, Kaneko Ai
Plastic Surgery Oculoplastic Surgery, Matsuo Plastic and Oculoplastic Surgery Clinic, Hamamatsu, JPN.
Plastic and Reconstructive Surgery, Shinshu University School of Medicine, Matsumoto, JPN.
Cureus. 2024 Jul 12;16(7):e64438. doi: 10.7759/cureus.64438. eCollection 2024 Jul.
Levator palpebrae superioris muscle (LPSM) and facial muscles comprise fast-twitch fibers (FTFs) and slow-twitch fibers (STFs) but lack muscle spindles required to contract STFs reflexively. Voluntary contractions and microsaccades of FTFs in LPSM stretch mechanoreceptors in superior tarsal muscle (STM) to induce phasic contractions of STFs in LPSM and frontalis muscle via mesencephalic trigeminal nucleus (MTN). They also induce prolonged contractions of STFs in bilateral frontalis and orbital orbicularis oculi muscles and physiological arousal via MTN and rostral locus coeruleus (LC). We hypothesized that stretching of mechanoreceptors in STM also induces prolonged contractions of STFs in other facial expression muscles (FEMs) via rostral LC. To verify this hypothesis, we reported a case series of abnormal contractions of FEMs due to aponeurosis disinsertion and disordered mechanoreceptor stretching. The first and second cases, which showed unilaterally and bilaterally sensitized mechanoreceptors, respectively, recorded increased prolonged contractions of ipsilateral and bilateral grimacing muscles, respectively. The third and fourth cases with asymmetrically and bilaterally desensitized mechanoreceptors experienced asymmetrically and bilaterally decreased prolonged contractions of grimacing and smiling muscles, respectively. Preoperatively and after surgery was performed to adjust mechanoreceptor stretching and reinsert aponeuroses into tarsi, we evaluated prolonged contractions of grimacing and smiling muscles during primary gazing and facial expression movements. Surgery satisfactorily cured abnormal prolonged contractions of grimacing and smiling muscles. Stretching of mechanoreceptors in STM by microsaccades or voluntary contractions of FTFs in LPSM might activate rostral LC via MTN, which tonically or phasically stimulates FEM motor neurons to reflexively contract their STFs, respectively.
提上睑肌（LPSM）和面部肌肉包含快肌纤维（FTFs）和慢肌纤维（STFs），但缺乏使STFs进行反射性收缩所需的肌梭。LPSM中FTFs的自主收缩和微扫视会拉伸睑板上肌（STM）中的机械感受器，从而通过中脑三叉神经核（MTN）诱导LPSM和额肌中STFs的相位性收缩。它们还会通过MTN和蓝斑头端（LC）诱导双侧额肌和眼轮匝肌中STFs的持续性收缩以及生理唤醒。我们假设，STM中机械感受器的拉伸也会通过蓝斑头端LC诱导其他面部表情肌（FEMs）中STFs的持续性收缩。为了验证这一假设，我们报告了一系列因腱膜分离和机械感受器拉伸紊乱导致的FEMs异常收缩的病例。第一例和第二例分别显示单侧和双侧机械感受器敏感，分别记录到同侧和双侧做鬼脸肌肉的持续性收缩增加。第三例和第四例分别为机械感受器不对称和双侧脱敏，分别出现做鬼脸和微笑肌肉的不对称和双侧持续性收缩减少。在进行手术以调整机械感受器拉伸并将腱膜重新插入睑板之前和之后，我们评估了在初次注视和面部表情运动期间做鬼脸和微笑肌肉的持续性收缩。手术成功治愈了做鬼脸和微笑肌肉的异常持续性收缩。LPSM中FTFs的微扫视或自主收缩对STM中机械感受器的拉伸可能会通过MTN激活蓝斑头端LC，进而分别持续性或相位性刺激FEM运动神经元，使其STFs进行反射性收缩。
