Saccade initiation in ocular motor apraxia

Sirs: Ocular motor apraxia (OMA) is characterized by the loss of voluntary saccade control but the simultaneous preservation of saccades of the optokinetic and the vestibulo-ocular reflex (VOR) [1, 4, 6]. While the suitability of the term is still being debated [6, 10], it is not yet clear which of the conceiv- able compensation strategies adult patients with OMA use to elicit saccades. Saccades can be initiated in three possible ways: by using the vestibulo-ocular reflex (VOR) [2], signals of voluntary head com- mands [11], or blinks [2]. We tested for the first time the competing hypotheses in two adult patients with OMA to elucidate the mecha- nism that helps to restore the saccadic behaviour.