Impaired Smooth Pursuit During Transient Global Amnesia.

BACKGROUND AND PURPOSE

During transient global amnesia (TGA), selective impairment of episodic memory is assumed to occur due to alteration in the neuronal network between the hippocampus and parietooccipital cortices that also include a hub for smooth pursuit (SP) eye movements. This study aimed to determine whether SP is impaired during TGA, and to identify any anatomical and functional linkage present between the oculomotor and memory systems.

METHODS

Within a median of 1.0 day of TGA, horizontal SP was evaluated in 145 patients with a target moving at peak velocities of 10°/s and 20°/s. The average SP gains of patients were compared with those of the age-matched controls.

RESULTS

The patients with TGA showed lower SP gains in both directions for both peak target velocities. While the normal controls showed symmetric SP in the rightward and leftward directions, in the TGA patients the SP gain was lower during rightward than leftward SP regardless of bilaterality or the side of the lesions.

CONCLUSIONS

The cortical regions processing information about visual motion appeared to be affected during or soon after an amnestic episode of TGA, and more so in the right hemisphere. This means that disturbed processing of dynamic visual information may be related to the impaired spatial orientation observed during TGA.