Dorsal Midbrain Syndrome from Stroke - Collier's Sign & Pseudoabducens

This is a 70-yo-man who suffered a right midline thalamic/rostral midbrain hemorrhagic stroke causing a pretectal (Parinaud's) syndrome. There was prominent eyelid retraction (Collier's sign), a left pseudo-abducens, and upgaze palsy with convergence retraction nystagmus. There was no light-near dissociation. Eyelid retraction is thought to be related to damage of the the M-group, which is adjacent to the riMLF (generates vertical and torsional saccades). The M-group sends projections to the central caudal nucleus (i.e., where the fibers that will innervate the levator palpebrae muscles originate) and superior rectus and inferior oblique subnuclei. Disruption of these pathways can lead to eyelid retraction, thought to be related to a dissociation between eye position and eyelid position, where the brain perceives that the eyes are higher than they actually are. One theory is that this represents an overactivation of the M-group in an effort to overcome an upgaze palsy. ; His abduction paresis OS was thought to represent a "pseudoabducens" palsy in the absence of pontine ischemia and given his mesodiencephalic hemorrhage, a localization that is often associated with contralateral pseudoabducens due to presumed disinhibited pathways and overaction of the medial rectus muscle. When the vergence pathways are affected rostrally (as in this case), pseudoabducens palsies tend to be contralateral. When the vergence pathways are affected more caudally in the midbrain, they tend to be ipsilateral. Despite his abduction paresis being due to a presumed "supranuclear" etiology, it was not clearly overcome by VOR, although this has been previously described. There was also no clear abduction lag OS with saccades. ; For an explanation of CRN/upgaze paresis in the Parinaud's syndrome, see video "Parinaud's in a man with glioblastoma multiforme of the pineal gland."