Incorrect

Correct! These are square wave jerks, in which the eyes make conjugate saccades to one side of fixation, and then, after a very brief stationary (“inter saccadic”) interval, move back to fixation. These “saccadic intrusions” on steady fixation represent lack of inhibition of the brainstem saccadic generator. They occur most commonly in progressive supranuclear palsy (PSP), but also in severe brainstem trauma, and many other disorders that affect the brainstem. If they are of very low amplitude and infrequent, they can be dismissed as a normal variant. Even pathologic square wave jerks do not usually cause blurred vision or other symptoms because vision is suppressed during saccades. Often overlooked by examiners, square wave jerks are an important clue that PSP is the cause of a parkinsonian state. They do occur in the other conditions you were offered as answer choices, but less frequently than in PSP.

Incorrect

Incorrect