Reliability and validity of ICARS in focal cerebellar lesions

To evaluate the therapies for cerebellar diseases appropriate neurological assessment methods to measure severity of ataxia are required. Reliability and validity of the semiquantitative International Cooperative Ataxia Rating Scale (ICARS) has recently been examined in patients with degenerative ataxias. We evaluated reliability (internal consistency), criterion-related validity and internal construct validity of ICARS for the first time in patients with focal cerebellar lesions (68 patients with surgical lesions and 68 patients with ischemic lesions). For comparison 45 patients with degenerative cerebellar ataxia were included. We found an excellent Cronbach's alpha as a measurement for internal consistency which was independent from underlying disease. Criterion-related validity was high. Total ICARS score mirrored clearly the immediate postsurgical worsening and the improvement during the first 3 months after focal surgical and ischemic lesions, whereas in chronic state of focal and degenerative cerebellar disorders ICARS score remained nearly unchanged. Principal component analysis in patients with focal lesions revealed five distinct and clinically meaningful factors which corresponded to the four ICARS subscores and reflected the laterality of kinetic functions. In degenerative disorders, however, the items for the subscore "kinetic function" loaded to more than one factor. Total ICARS score seems to be a useful and valid measurement to describe the time course of ataxia in patients with focal and degenerative disorders affecting primarily the cerebellum. Validity of subscores however is good in focal, but not in degenerative disorders.