Diffusion Tensor Imaging in a Case of Pontine Bleeding Showing Hypertrophic Olivary Degeneration and Cerebellar Ataxia.

We present diffusion tensor tractography (DTT) findings in a case of hypertrophic olivary degeneration (HOD) and cerebellar ataxia. A 56-year-old man presented with abnormal ataxic gait and dysarthria. MRI 5 months after onset showed chronic pontine hematoma and enlarged bilateral inferior olivary nuclei. DTT showed decreased volume of the bilateral central tegmental tract, in accordance with the conventional hypothesis that HOD is associated with neurologic insult to the Guillain-Mollaret triangle. The patient's cerebellar ataxia was speculated to be due to decreased decussating fibers of the superior cerebellar peduncle, and this was confirmed by DTT.