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Spectrum of saccade system function in Alzheimer disease
Ruxsana Shafiq-Antonacci1, Paul Maruff, Colin Masters
1Neuropsychology Research Laboratory, Alzheimer's Disease Research Group, The Mental Health Research Institute of Victoria, Parkville, Australia. rantonacci@mhri.edu.au
Archives of Neurology
|September 17, 2003
Summary
Saccade measures show impairments in Alzheimer disease (AD) patients, but individual variability limits their diagnostic sensitivity and specificity. Longitudinal studies may offer better classification for AD.
Area of Science:
- Ophthalmology
- Neurology
- Gerontology
Background:
- Alzheimer disease (AD) may be more reliably assessed using first-order capabilities like reaction time or motor ability.
- Saccade system impairments are observed in AD, but their diagnostic sensitivity and specificity are not well-established.
Purpose of the Study:
- To evaluate the sensitivity and specificity of saccade measures for diagnosing AD.
- To identify precise saccade impairments in AD patients.
- To examine the relationship between dementia severity and saccade system function.
Main Methods:
- A case-control study compared saccade system function in 35 AD patients and 245 healthy volunteers.
- Tasks included random saccades, predictive saccades, and antisaccades, measuring latencies, velocities, accuracies, and error rates.
- Sensitivity, specificity, and predictive values were calculated; correlations with dementia severity were analyzed.
Main Results:
- AD patients exhibited significantly longer/variable latencies, more hypometric/anticipatory random saccades, and higher antisaccade error rates.
- Antisaccade error rates correlated with dementia severity (Spearman r = -0.59, P =.02).
- Antisaccade measures showed high specificity (0.70-0.90), while random saccade gain demonstrated high sensitivity (0.87).
Conclusions:
- While AD patients show group-level saccade impairments, individual function varies, limiting the diagnostic sensitivity and specificity of these measures.
- Longitudinal evaluations may enhance the reliability of saccade measures for classifying AD.