Reflexive contraction of the levator palpebrae superioris muscle to involuntarily sustain the effective eyelid retraction through the transverse trigeminal proprioceptive nerve on the proximal Mueller's muscle: verification with evoked electromyography

Cell bodies of the trigeminal proprioceptive neurons that transmit reflex contraction of the levator muscle are located in the mesencephalic trigeminal nucleus in rats

“…Therefore, weight-loading due to swelling (Figure 1a), aponeurotic blepharoptosis due to disinsertion of the aponeurosis from the tarsus [4], and up-gaze increase stretching of the mechanoreceptors in Müller's muscle to evoke trigeminal proprioception, which enhances reflex contraction of the levator and frontalis slow-twitch muscle fibres [2][3][4][5]. In contrast, injury (Figure 1b), anaesthesia (Figure 1c), and resection (Figures 1d-f) of the trigeminal proprioceptive neurons from the mechanoreceptors in Müller's muscle to the ophthalmic division of the trigeminal nerve decrease stretching of the mechanoreceptors in Müller's muscle to evoke trigeminal proprioception, which impairs reflex contraction of the levator and frontalis slow-twitch muscle fibres.…”

“…Since we earlier reported that electrical stimulation of the trigeminal proprioceptive nerve on the proximal Müller's muscle induces a short-latency monosynaptic reflex contraction of the ipsilateral levator muscle in humans, the presence of the trigemino-oculomotor reflex was electromyographically proven [3]. This study served to anatomically confirm the presence of cell bodies of the trigeminal proprioceptive neurons that transmit reflex contraction of the levator and frontalis muscles through the lacrimal nerve.…”

“…Voluntary contraction of non-skeletal fast-twitch fibres of the levator muscle stretches the mechanoreceptors in Müller's muscle to evoke trigeminal proprioception, which induces reflex contraction of the levator slow-twitch muscle fibres [4]. Increased stretching of the Müller's muscle, such as up-gaze, not only enhances reflex contraction of the levator slow-twitch muscle fibres, but also induces reflex contraction of the frontalis slow-twitch muscle fibres against gravity ( Figure 2a) [2][3][4][5].…”

“…Local anaesthetic injection of lidocaine under the lateral horn of the levator aponeurosis to be released sometimes induces blepharoptosis without compensatory, involuntary lifting of the ipsilateral eyebrow ( Figure 1c) [2]. Resection of the lacrimal gland which contains the lacrimal nerve induces blepharoptosis ( Figure 1d) [3]. After levator resection procedure for congenital blepharoptosis, in which the proximal levator muscle belly was sutured directly to the tarsus with resection of the anterior levator muscle belly and Müller's muscle, blepharoptosis sometimes relapses without compensatory, involuntary lifting of the ipsilateral eyebrow (Figures 1e, f).…”

“…The levator and frontalis muscles lack interior muscle spindles, although they are antigravity mixed muscles to involuntarily sustain effective eyelid opening and eyebrow lifting against gravity [2][3][4][5][6][7]. The superior rectus muscle is composed mainly of indefatigable fast-twitch fibres that differ from fatigable fast-twitch fibres in the skeletal muscles; however, this muscle was divided morphologically into orbital and global layers ( Figure 2a) [8].…”