Longitudinal saccadic changes in Huntington's disease and Alzheimer's disease

Abstract

Saccadic latency and velocity-amplitude relationships were examined over approximately six years in two patients, one with Huntington's disease (HD) and one with Alzheimer's disease (AD). In both cases this was a period that began relatively early in the course of the disorder and included significant clinical deterioration. The HD patient showed markedly slow saccades upon initial recording; subsequent studies showed some velocity fluctuations without a clear trend. Latency varied similarly, generally being close to normal.

In contrast to the HD patient, the AD patient's first two studies showed normal saccadic latencies and velocities. Also, the latency suddenly became significantly prolonged one year prior to the time that her dementia progressed.

Both patients showed a significant correlation, from session to session, between latency and peak velocity asymptote; this, despite the marked differences in the way their diseases affected these saccadic characteristics. Longer latencies corresponded to lower peak velocities, suggesting a common source, arising in the frontal eye fields, for difficulties in both saccadic initiation and motor programming.

Key Words:

• Huntington's disease
• Alzheimer's disease
• saccades
• latency
• velocity