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Show Letter to the Editor Mesencephalic Lesions Involving the Third Nerve Complex To the Editor: I would like to take this opportunity to reply to the thoughtful response of Dr. Burde et al. to my letter which appeared in the December 1982 issue of The Journal of Clinical Neuro-ophthalmology. I think most of us easily recognize mesencephalic lesions involving the third nerve complex when they are associated with the appropriate hemiplegia, hemisensory, or lateralized cerebellar signs. Cases that I thought represented nuclear third nerve palsies have all been associated with a contralateral hemiplegia; and they all have had bilateral superior rectus palsies giving the appearance of a vertical gaze palsy. I believe this occurs because the fibers of the superior rectus subnucleus appear to cross through the opposite superior rectus subnucleus at corresponding rostral-caudal levels of that particular subnucleus before joining the opposite third nerve fasicles. Therefore, it would seem that a unilateral lesion in any particular portion of the superior rectus subnucleus would affect both superior rectus muscles symmetrically. It should be emphasized, since it bears on the whole issue that the axons, after passing through the subnucleus on the opposite side, go on to emerge from the ventral portion of the nucleus, after which they group to form the complete bundle known as the third cranial nerve. If, in fact, this anatomy applies to man, it would still seem to me that a small rostral lesion in the superior rectus subnucleus would result in an apparently symmetrical paralysis of upward gaze, albeit perhaps expressing itself only as a mild paresis. Don C. Bienfang, M.D. Boston, Massachusetts Journal of Clinical Neuro-ophthalmology |