Diffusion tensor imaging of the cortico-ponto-cerebellar pathway in patients with adult-onset ataxic neurodegenerative disease
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We sought to determine whether diffusion-tensor imaging (DTI) can detect in vivo axonal damage in the corticopontocerebellar pathway of patients with adult-onset ataxic neurodegenerative disease.
Conventional MRI and DTI were performed on 18 patients with adult-onset ataxic neurodegenerative disease and 28 age-matched control subjects. Fractional anisotropy (FA) and the mean diffusivity (MD) were measured in the ventral, central, and dorsal pons, middle cerebellar peduncle (MCP) and internal capsule to evaluate corticopontocerebellar projection. Changes in FA and MD values were compared between patients and controls. Clinical disability was assessed according to the International Cooperative Ataxia Rating Scale (ICARS). The relationship between DTI measurements and ICARS was studied. Follow-up MRI was performed in five patients approximately 1 year later.
FA values were significantly lower in the ventral and central portions of the pons, MCP, and internal capsules than in these areas in control subjects (P < 0.05) with the lower FA values correlating with poorer ICARS (r > −0.57, P < 0.05). MD values were elevated in these areas, but the differences were smaller than for the FA values. No relationship was observed between the MD and ICARS. In the five patients who underwent the follow-up study, there were significant decreases between the initial study and the follow-up DTI study for FA in the MCP and internal capsule (P < 0.05).
DTI can demonstrate a degenerated corticopontocerebellar pathway in patients, and FA values can be correlated with ataxia severity. DTI may be a clinically useful tool as a quantitative surrogate marker for monitoring disease progression.