Detection of silent cerebellar lesions by increasing the inertial load of the moving hand.

In a previous study, we analyzed the hypermetria of wrist flexion movements in patients with a cerebellar syndrome. We found that hypermetria augmented when the inertial load of the moving hand was artificially increased. In the present study, we applied the same protocol to patients with an apparently normal neurological examination, in spite of a cerebellar lesion documented by magnetic resonance imaging. In all of these patients, the addition of a mass to the moving hand caused the appearance of a hypermetria. This lack of adaptation of fast and accurate movements to an increased inertia thus appears as a new diagnostic tool enabling the detection of silent cerebellar lesions.