[Chronological changes in MR imaging of inferior olivary pseudohypertrophy--report of two cases]

Olivary pseudohypertrophy (OH) and its chronological change was examined by MR images in two patients with brainstem vascular disease. Patient 1 was a 63-year-old woman who developed an infarction in the red nuclei associated with "top of the basilar" syndrome. Two months later, she showed 2-4 c/s rhythmic myoclonus (rubral tremor) involving four extremities. Palatal myoclonus was absent. MR images of the inferior olives did not demonstrate a significant lesion in 10 days after the onset, but showed OH in 6 months, and then their size attained a maximum in 10 months after. On T2-weighted (T2) images and proton-density-weighted (PD) images obtained at 20 and 24 months, OH gradually became irregular but discrete in their intensity, and the intensity had also decreased to some extent. Rhythmic myoclonus had subsided to some extent after 20 to 24 months. Patient 2 was a 62-year-old woman who had a small hemorrhage in the pontine tegmentum. She developed 2.5 c/s vertical ocular myoclonus without palatal myoclonus two months after the onset. MR images showed OH in 6 and 8 months after the onset. On T2 and PD images obtained at 20 months, the image of OH gradually developed to become irregular in intensity and slightly atrophic in size. The ocular myoclonus somewhat reduced in their intensity 12 months after the onset. These serial changes in MR images were considered to correspond to the chronological changes of the pathology of OH. Appearance and subsidence of the myoclonic movement was also considered to correlate to the sequential changes of MR images of OH.