Aktuelle Neurologie 2006; 33 - P249
DOI: 10.1055/s-2006-953074

Preserved eye-hand coordination in spinocerebellar ataxia type 17

P. Trillenberg 1, A. Sprenger 1, A. Hiller 1, C. Klein 1, G. Weinberger 1, S. Krug 1, A. Rolfs 1, C. Helmchen 1
  • 1Lübeck

Background/Aim: SCA17 is caused by a trinucleotide expansion in the gene encoding the TATA binding protein (TBP). We intended to characterize combined eye-hand movements in this ataxic disorder by using hand pointing tasks.

Methods: Subjects were included after molecular genetic diagnosis of SCA17. Hand pointing movements were recorded in 12 patients and 12 controls matched for age with an ultrasound based system (ZEBRIS). Eye movements were recorded with the video-based EYELINK II system. Subjects were asked to point towards targets at 8° and 12° to the left and to the right, respectively. In different conditions, they were supposed to simultaneously carry out saccades towards the target (condition “sac“) and to continue fixating a straight-ahead target while pointing to the lateral target (“nosac“).

Results: SCA17 mutation carriers (age range 19–53) showed a broad phenotypic spectrum (cerebellar, pyramidal, extrapyramidal signs). Hand movements in SCA17 subjects were characterized by reduced peak acceleration (group means 1469 and 858cm/s2 in control and patient group, respectively) and peak velocity (109 vs. 84cm/s). These parameters decreased with increasing ataxia score. The mutation carriers increased peak acceleration (from 799cm/s2 to 916cm/s2) and peak velocity (81cm/s to 87cm/s) in the “sac“ condition as compared with the “nosac“ condition, whereas controls did not. Pointing error was increased in the patient group (1.1cm vs. 3.3cm). The differences between the groups was not influenced by a simultaneous saccade or the blanking of the target.

Discussion: The kinematic parameters (acceleration, velocity) of hand pointing movements were profoundly altered in SCA17 patients leading to hand dysmetria while approaching the target. These abnormalities are compatible with cerebellar disease of other origin (Topka et al. 1998). A simultaneous eye movement facilitated hand pointing movements. Thus, hand pointing deficits reflect a disorder of the motor system rather than an inherent deficit of eye-hand coordination.