A NEUROANATOMICAL ANALYSIS OF LID-EYE COORDINATION IN CASES OF PTOSISAND DOWNGAZE PARALYSIS

Ptosis and downgaze paralysis, in a case of vascular insufficiency, we re the result of a specific loss of levator palpebrae (LP) motoneurons in the oculomotor nucleus, and a partial cell loss in the rostral int erstitial nucleus of the MLF (riMLF), respectively. In a previous case with similar symptoms there was a comparable riMLF cell loss, but som e LP motoneurons were spared; in addition there was destruction of a c ell group on the mesencephalic midline, which projects to all motoneur ons involved in upward eye movements including LP. This cell group is called the M-group in the monkey. The M-group was intact in the presen t, but not in the previous case, which may have contributed to the pto sis and to the loss of upward ocular pursuit in the latter. The result s show that there is more than one premotor cell group responsible for upward eye movements in the rostral mesencephalon.