Failure of downward gaze: the site and nature of the lesion.

We report four patients with paralysis of downward gaze but with intact upward gaze, including one with detailed clinico-pathological studies and another with a focal computerized axial tomographic (CT) scan abnormality confirming the presence of bilateral lesions of the dorsomedial red nucleus, including the fasciculus retroflexus. It is suggested that sudden, permanent selective failure of downward gaze accompanied by transient disturbance of consciousness is an embolic syndrome of the posterior thalamosubthalamic or rubral artery.