[Friedreich's ataxia: analysis of magnetic resonance imaging parameters and their correlates with cognitive and motor slowing].

INTRODUCTION: The heredodegenerative ataxias are a heterogeneous group of disorders affecting especially the cerebellum and its tracts. Magnetic resonance imaging (MRI) studies using quantitative methodology are scarce, particularly in Friedreich's ataxia (FA). On the other hand, slowness of information processing speed has been described in FA, but no empirical relation with MRI parameters has been established.

OBJECTIVE: The aim of the present study was to quantitatively assess infra and supratentorial atrophy in patients with clinical diagnosis of FA and to establish the relationship with a information processing speed measure.

PATIENTS AND METHODS: Twelve FA patients that fulfilled clinical diagnostic criteria and twelve control subjects were studied. A computerized system that differentiate reaction time and movement time, as well as a semiautomated technique of binarization and analysis of MRI were used.

RESULTS: Patients showed a poorer performance in movement time and in reaction time. Analyzing the frequency of pathologic changes, vermal atrophy was present in 67% of the patients and cerebellar hemisphere atrophy in 50%. Only a minority of patients showed signs of supratentorial cerebral atrophy (17%). Statistically significant negative correlations were obtained between reaction time and the size of the cerebellum.

CONCLUSIONS: Cerebellar hemisphere atrophy is a usual finding in FA, although vermal atrophy is more frequent. The relation between cerebellar atrophy and reaction time supports the claim about cerebellar involvement in the information processing and response speed.