Frontotemporal Dementia 925-3

Eye Movements This patient with frontotemporal dementia (FTD) has a complete paralysis of horizontal saccadic eye movements when he is asked to look left on command, or to fixate on a target held on the left. He is unable to look at his own hand when held on the left side. He has no saccadic intrusions.

Neuroimaging Figure 1: Axial NECT scan shows striking frontal atrophy with relative preservation of the parietal gyri.

Neuroimaging Figure 2: Sagittal T1-weighted MR shows the disproportionate enlargement of the frontal sulci.

Neuroimaging Figure 3: Coronal FLAIR scan shows the frontal gyri are extremely atrophic and “knife-like.” Note increased signal intensity in the affected gyri and underlying white matter

Effects of Unilateral Lesions of the Frontal Eye Fields (FEF) Bilateral increase in reaction time of saccades made to visual targets in “overlap” task to remembered target locations and imaged targets during the “antisaccade” task. Hypometria of saccades made to visual or remembered targets located contralateral to the side of the lesion.

Effects of Unilateral Lesions of the Frontal Eye Fields (FEF) Reduced ability to make saccades in anticipation of predictable stepping movement of a target, when the target moves away from the side of the lesion. Impaired ability to inhibit inappropriate saccades to a novel visual stimulus. Impairment of smooth pursuit and optokinetic following of targets moving towards the side of the lesion.

Effects of Lesions of the Supplementary Eye Field (SEF) Memory-guided saccades become inaccurate if gaze shifts during the memory period. Impaired ability to make a remembered sequence of saccades to an array of visible targets (especially with left-sided lesions). Impaired ability to reverse saccade direction from an established pattern of response

Effects of Lesions of Dorsolateral Prefrontal Cortex (DLPC) Pharmacological blockade of D1 dopamine receptors causes inaccuracy of saccades made to remembered target locations lying contralateral to the side of injection Patients with lesions affecting this area show defects of predictive saccades, memory-guided saccades and antisaccades