[The one and a half vertical syndrome as the only evidence of bilateral thalamo-subthalamic infarction]

The one and a half vertical syndrome consists of paralysis of upward vertical conjugated gaze and monocular paralysis of downward gaze or vice-versa. It occurs as a consequence of a mesencephalodiencephalic lesion, either unilaterally or bilaterally, due to effects on structures such as the interstitial nucleus of Cajal, posterior commissure and rostral interstitial nucleus of the medial longitudinal bundle. The arterial supply of the structures involved in the supranuclear control of vertical gaze depends on the paramedian thalamic arteries (or posterior thalamo-subthalamic arteries) and the paramedian peduncular arteries.

We present the case of a 58 year old woman with non-insulin dependent diabetes mellitus who presented with sudden onset of diplopia of vertical gaze. On examination there was paralysis of superior vertical conjugated gaze and monocular paralysis of ocular infraversion (one and a half syndrome) with no other pathological findings. Cerebral angioresonance and Doppler studies of the territory supplied by the posterior cerebral artery were normal.

Both unilateral and bilateral mesencephalodiencephalic infarcts usually present clinically as disorders of consciousness and of conduct (the almost universal form of presentation), involvement of the pyramidal tract, the third cranial nerves and a supranuclear disorder of vertical gaze. The unusual feature of the case we present is a bilateral thalamo-subthalamic infarct which presented solely as a one and a half vertical syndrome with no clinically apparent effect on anatomically adjacent structures. We have not found any similar cases in the literature.