A reformed “release hypothesis” for Marcus Gunn Syndrome, based on newer clinic observations and experimental evidences

Liang, Houcheng; Zhang, Jingdong

doi:10.1016/j.mehy.2020.110210

Cited by 3 publications

(11 citation statements)

References 69 publications

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“…What role of these Vme neurons that receive both eyelid and masseter afferent signals may play in normal mammals is currently unknown, but it might be an add-on for a masticatory oculomotor reflex in amphibian [ 4 , 8 , 36 ]. Direct projections from masticatory primary afferent Vme neurons to the III was observed in Xenopus toad [ 36 ].…”

Section: Discussionmentioning

confidence: 99%

“…Direct projections from masticatory primary afferent Vme neurons to the III was observed in Xenopus toad [ 36 ]. This neuronal circuit may assistant a toad to stare on its prey when it opens mouth widely to prey [ 4 , 8 , 36 ]. This kind of reaction was considered as “primitive reflex” [ 2 , 4 , 8 , 25 ] and may be gradually extinguished during phylogenic development.…”

Section: Discussionmentioning

confidence: 99%

“…“Release hypothesis” is one of the hypotheses that has been long overlooked [ 8 ]. The key idea of release hypothesis is that MGS is a physiological reflex in lower animals but has been either concealed or extinguished during phylogenic development [ 3 , 4 , 8 ]. In human, the phylogenic old reflex is “released” as MGS in certain pathological circumstance [ 3 , 4 , 8 ].…”

Section: Introductionmentioning

confidence: 99%

“…The key idea of release hypothesis is that MGS is a physiological reflex in lower animals but has been either concealed or extinguished during phylogenic development [ 3 , 4 , 8 ]. In human, the phylogenic old reflex is “released” as MGS in certain pathological circumstance [ 3 , 4 , 8 ]. The proposers of “release hypothesis” thought that basic neuronal circuit of that old reflex is preserved, to some extent, in higher animals.…”

Section: Introductionmentioning

confidence: 99%

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Mesencephalic trigeminal nucleus neurons with collaterals to both eyelid and masseter muscles shown by fluorescent double-labeling, revealing a potential mechanism for Marcus Gunn Syndrome

Shi,

Zhang,

Shi

et al. 2023

PLoS ONE

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Poking palpebral conjunctiva evoked upper-eyelid retraction during ophthalmic surgery. Iatrogenic eyelid ptosis occurred if eyelid branch of lachrymal nerve was sectioned. Mesencephalic trigeminal nucleus (Vme) neurons were labeled when tracer injected into lachrymal nerve innervating eyelid Mueller’s muscle. Masseter afferent Vme neurons projecting to oculomotor nucleus (III) was observed in toad and rat, which helps amphibians to stare prey when they open mouth widely to prey. We hypothesized single Vme neurons may have peripheral collaterals to both eyelid and masseter muscles. WGA-594 was injected into upper eyelid, and WGA-488 was simultaneously delivered into ipsilateral masseter muscle in the same rat. Then, double labeled Vme neurons were found under both conventional and confocal microscope. Meanwhile, contact of WGA-594 positive eyelid afferent Vme neurons with WGA-488 labeled masseter afferent ones were observed sometimes. Combined with our previous observation of oculomotor projection Vme neurons, we thought WGA-594/488 double labeled Vme cells, at least some of them, are oculomotor projecting ones. Contact between eyelid and masseter afferent Vme neurons are supposed to be electrotonically coupled, based on a line of previous studies. If exogenous or genetic factors make these Vme neurons misinterpret masseter input as eyelid afferent signals, these Vme neurons might feedforward massages to eyelid retractor motoneurons in the III. Besides, oculomotor projecting Vme neurons might be co-fired by adjacent masseter afferent Vme neurons through electrotonic coupling once the masseter muscle is activated. In these cases, Marcus Gunn Syndrome might occur. This finding leads to a new hypothesis for the Syndrome.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mesencephalic trigeminal nucleus neurons with collaterals to both eyelid and masseter muscles shown by fluorescent double-labeling, revealing a potential mechanism for Marcus Gunn Syndrome

Shi,

Zhang,

Shi

et al. 2023

PLoS ONE

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“…Coincidently, we found a projection from mesencephalic trigeminal nucleus (Vme) to oculomotor and trochlear nuclei (III/IV) when we re-assessed a hypothesis on Marcus Gunn Syndrome [ 25 – 28 ]. We did not see the projection from the Vme to the VN; instead, the projections travel directly to the III/IV, and even to their premotor neurons in the INC and Darkschewitsch nucleus (DN).…”

Section: Introductionmentioning

confidence: 87%

Convergent innervations of mesencephalic trigeminal and vestibular nuclei neurons onto oculomotor and pre-oculomotor neurons—Tract tracing and triple labeling in rats

et al. 2022

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In studies of vestibulo-ocular reflex (VOR), the horizontal VOR circuit is much clearer than vertical-torsional VOR. The circuit and mechanism of gravity-related vertical-torsional VOR is probably weak. “Somatosensory vestibular interaction” is a known extra source to facilitate VOR, and cervico-ocular reflex is a representative for torsional VOR compensation. Whereas, how the cervical afferents finally reach the oculomotor system is less documented. Actually, when the head tilts, which generates cervico-ocular reflex, not only the neck muscle is activated, but also the jaw muscle is stretched by gravity dragged mandible and/or tissue-muscle connection between the mandible and clavicle. We have previously identified a projection from the jaw muscle afferent mesencephalic trigeminal nucleus (Vme) neurons to oculomotor nuclei (III/IV) and their premotor neurons in interstitial nucleus of Cajal (INC)–a well-known pre-oculomotor center manipulating vertical-torsional eye movements. We hypothesized that these projections may interact with vestibulo-ocular signals during vertical-torsional VOR, because effects of gravity on jaw muscles and bones has been reported. Thus, we injected different anterograde tracers into the Vme and medial vestibular nucleus (MVN)—the subnuclear area particularly harboring excitatory vestibulo-ocular neurons, and immunostained III/IV motoneurons. Retrograde tracer was injected into the III in the same animals after dual anterograde tracers’ injections. Under confocal microscope, we observed the Vme and MVN neuronal endings simultaneously terminated onto the same III/IV motoneurons and the same INC pre-oculomotor neurons. We consider that jaw muscle proprioceptive Vme neurons projecting to the III/IV and INC would sense spindle activity if the jaw muscle is stretched by gravity dragged mandible or connection between mandible and clavicle during head rolling. Therefore, the convergent innervation of the Vme and MVN neurons onto the oculomotor and pre-oculomotor nuclei would be a neuroanatomic substrate for interaction of masticatory proprioception with the vestibulo-ocular signals upon the oculomotor system during vertical-torsional VOR.

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Eyelid retraction during smiling in a patient with monocular congenital ptosis: a case report

Zhao,

Fu,

Hao

2024

BMC Ophthalmol

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Background Blepharoptosis is a common symptom in ophthalmology clinic, but eyelid retraction when smiling in a ptosis eye is a rare manifestation. Here we report a novel manifestation that eyelid retraction during smiling in a patient with monocular congenital ptosis. Case description A 10-year-old girl with isolated and mild unilateral congenital ptosis showed eyelid retraction in ptotsis eye when smiling together with a lid lag on downgaze. She didn’t have any systematic and ocular diseases other than myopia and astigmatism.Eyelid retraction during smiling is 5 mm, resulting in a significant difference in the height of bilateral palpebral fissures.As for ptosis, is mild.The margin to reflex distance 1 is 1.0 mm on the right eye(ptosis eye) and 3.0 mm on the left eye. A lid lag of 1.0 mm on downward gaze was noted on the right, she could close her eyes fully while sleeping.The ice pack test, laboratory test for thyroid function, whole-exome sequencing (WES) and magnetic resonance imaging(MRI) of the orbital and ocular motor nerves showed normal results.Her symptoms alleviated after 6 months, with the retraction of the right upper eyelid when smiling was approximately 3 mm, thus the difference in the palpebral fissure height when smiling was smaller than that at the initial presentation. Conclusion Blepharoptosis may accompanied with abnormal innervation like eyelid retraction, this phenomenon can be alleviated with age.The results of the levator muscle function test should be carefully examined to determine whether it is ptosis in an impaired innervation eyelid.

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A reformed “release hypothesis” for Marcus Gunn Syndrome, based on newer clinic observations and experimental evidences

Cited by 3 publications

References 69 publications

Mesencephalic trigeminal nucleus neurons with collaterals to both eyelid and masseter muscles shown by fluorescent double-labeling, revealing a potential mechanism for Marcus Gunn Syndrome

Mesencephalic trigeminal nucleus neurons with collaterals to both eyelid and masseter muscles shown by fluorescent double-labeling, revealing a potential mechanism for Marcus Gunn Syndrome

Convergent innervations of mesencephalic trigeminal and vestibular nuclei neurons onto oculomotor and pre-oculomotor neurons—Tract tracing and triple labeling in rats

Eyelid retraction during smiling in a patient with monocular congenital ptosis: a case report

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