Saccade abnormalities in autopsy-confirmed frontotemporal lobar degeneration and Alzheimer disease

Abstract

Background: Deficits in the generation and control of saccades have been described in clinically defined frontotemporal dementia (FTD) and Alzheimer disease (AD).

Objective: To determine the saccade abnormalities associated with autopsy-defined cases of frontotemporal lobar degeneration (FTLD) and of AD, because clinical FTD syndromes can correspond to a number of different underlying neuropathologic FTD and non-FTD diagnoses.

Design: An infrared eye tracker was used to record visually guided saccades to 10° targets and antisaccades in subjects with autopsy-confirmed FTD and subjects with autopsy-confirmed AD, a mean (SE) of 35.6 (10.0) months prior to death, and age-matched normal controls. Twelve subjects with FTD had an FTLD-TAR DNA-binding protein 43 pathology, 15 had an FTLD-tau pathology, and 1 subject showed an FTLD-fused in sarcoma protein pathology. Receiver operating curve statistics were used to determine the diagnostic value of the oculomotor variables. Neuroanatomical correlates of oculomotor abnormalities were investigated using voxel-based morphometry.

Setting: Memory and Aging Center, Department of Neurology, University of California, San Francisco.

Participants: A total of 28 subjects with autopsy-confirmed FTD, 10 subjects with autopsy-confirmed AD, and 27 age-matched normal controls.

Results: All subjects with FTD or AD were impaired relative to normal controls on the antisaccade task. However, only FTLD-tau and AD cases displayed reflexive visually guided saccade abnormalities. The AD cases displayed prominent increases in horizontal saccade latency that differentiated them from the FTD cases. Impairments in velocity and gain were most severe in individuals with progressive supranuclear palsy but were also present in other tauopathies. By using vertical and horizontal saccade velocity and gain as our measures, we were able to differentiate patients with progressive supranuclear palsy from other patients. Vertical saccade velocity was strongly correlated with dorsal midbrain volume.

Conclusion: Decreased visually guided saccade velocity and gain are suggestive of underlying tau pathology in FTD, with vertical saccade abnormalities most diagnostic of progressive supranuclear palsy.

Figures

Figure 1. Examples of upward saccades and fixation abnormalities

Eye position versus time plot for three successive upward saccades to 10 degree targets in: (A) a control subject, showing intervals for subsequent saccade measurements, including latency, velocity (slope of eye position vs. time), first and end gains; (B) clinical CBDS subject with FTLD-TDP pathology, (C) clinical CBDS subject with CBD pathology, (D) clinical bvFTD subject with Pick’s disease pathology; (E) clinical PSPS subject with PSP pathology; (F) clinical AD subject with AD pathology. Examples of fixation abnormalities in horizontal eye position versus time traces: (G) macrosaccadic oscillations in the same CBDS subject as (C), (H) PSPS patient with PSP pathology.

Figure 2. Saccade performance in autopsy-confirmed FTD subtypes and AD

Mean ± SEM values for saccade parameters. (A) Latency, (B) Velocity, (C) Gain: * = p

Figure 3. Dorsal midbrain volume is correlated with vertical saccade velocity

(A) Dorsal midbrain region correlated with vertical saccade velocity from VBM analysis of 77 FTLD subjects (25 autopsy-confirmed plus 52 clinically diagnosed) displayed at p