[Midbrain infarction presenting with unilateral blepharoptosis, trochlear nerve paresis and MLF syndrome]

We report a 75-year-old hypertensive man presented with unilateral MLF syndrome combined with ipsilateral blepharoptosis and trochlear nerve paresis due to midbrain infarction. He was admitted to our hospital for sudden onset of diplopia. Neurological examination revealed left ptosis, infraduction disorder of the left eye and left MLF syndrome. Horner's syndrome or other focal neurological signs were not observed; convergence was preserved. Hess-charts confirmed left superior oblique paresis and left internuclear ophthalmoplegia. Laboratory data were all normal. T2-weighted images of brain MRIs demonstrated a high-signal intensity lesion in the paramedian dorsal midbrain at the inferior colliculus level, anterior to the cerebral aqueduct. The oculomotor dysfunction and diplopia had disappeared at discharge, although slight ptosis persisted. It is likely that the lesion in our case affected the left MLF, the right trochlear nucleus or its fascicles and the left partial oculomotor fascicles. Cases with MLF syndrome associated with trochlear nerve palsy have been rarely reported. Our case suggests that the fibers controlling for the musculus levator palpebrae superioris are located more caudally in the oculomotor fascicles.