Sagittal Section of the Midbrain Showing Structures Related to Normal Eyelid Function

Update item information
Identifier Eyelid_Midbrain
Title Sagittal Section of the Midbrain Showing Structures Related to Normal Eyelid Function
Subject Figures; Mesencephalon OMS
Creator Daniel R. Gold, DO, Departments of Neurology, Ophthalmology, Neurosurgery, Otolaryngology - Head & Neck Surgery, Emergency Medicine, and Medicine, The Johns Hopkins School of Medicine
Description During a vertical saccade, the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) is activated, which excites the superior rectus (SR) and inferior oblique (IO) (IIIrd nerve) subnuclei. Additionally, the riMLF activates the nearby M-group. The M-group's primary excitatory output is to the CCN (central caudal nucleus), resulting levator palpebrae contraction and eyelid elevation. The opposite occurs during downgaze, resulting in levator relaxation. Eyelid retraction in midbrain disease may result from overstimulation of the M-group in an effort to overcome upgaze paresis, or could be related to loss of M-group inhibition by lesions involving the nearby interstitial nucleus of Cajal and/or nucleus of the posterior commissure. During a blink, the LPS abruptly ceases firing and the orbicularis oculi (OO), which is innervated by the facial nerve, briefly contracts. The coordination of LPS and OO is mediated by the superior colliculus (SC). The SC projects to the supraoculomotor area directly overlying the CCN as well as to the facial nuclei and is inhibited by the pars reticulata of the substantia nigra (SNr). This explains why in parkinsonism, due to increased activity of the SNr (which normally inhibits the SC), there is greater inhibition of the SC and reduced spontaneous blinking.
Contributor Daniel R. Gold, D.O.
Publisher Spencer S. Eccles Health Sciences Library, University of Utah
Date 2017
Type Image
Format image/jpeg
Relation is Part of NOVEL: Neuro-ophthalmology Virtual Education Library Examination Collection
Rights Management Copyright 2017. For further information regarding the rights to this collection, please visit:
Holding Institution Spencer S. Eccles Health Sciences Library, University of Utah, 10 N 1900 E, SLC, UT 84112-5890
Collection Neuro-ophthalmology Virtual Education Library: NOVEL
Language eng
ARK ark:/87278/s65n00pk
Setname ehsl_novel_gold
Date Created 2017-08-10
Date Modified 2021-05-06
ID 1260004
Reference URL
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