Purpose: To describe MR changes in the cerebellar cortex and the dentate nucleus in patients with inferior olivary nucleus hypertrophy.
Methods: MR scans of 11 patients with palatal myoclonus were reviewed. Among them, we selected 5 cases that showed lesions in the central tegmental tract and the ipsilateral inferior olivary nucleus. We evaluated MR changes of the cerebellar cortices and dentate nuclei contralateral to the affected inferior olivary nuclei. Evaluation was performed by side-to-side comparison in each case. Six cases were excluded, because comparison of the cerebellar hemispheres or dentate nuclei with those of the opposite sides was not possible.
Results: The dentate nuclei opposite affected inferior olivary nuclei showed mild to moderate shrinkage of the normal low-signal areas and increases in signal intensity on T2-weighted images in 4 of 5 patients. The cerebellar cortices on the same sides as the involved dentate nuclei showed atrophic changes in 4 of 5 patients.
Conclusion: Our MR findings suggest that there is a degenerative process involving the dentate nucleus and the cerebellar cortex associated with the hypertrophic degeneration of the inferior olivary nucleus.