Hypertrophic olivary degeneration after gamma-knife radiosurgery for pontine metastasis

Abstract

We present a case of a 57-year-old woman who underwent gamma-knife radiosurgery (GKRS) for pontine metastasis. Magnetic resonance (MR) imaging 2.8 months after GKRS showed T2 hyperintensity and hypertrophy of the left inferior olivary nucleus (ION) without gadolinium enhancement and smaller pontine metastasis. We diagnosed the signal change in the left ION as hypertrophic olivary degeneration (HOD) resulting from damage to the left central tegmental tract. We believe this is the first report to describe HOD after GKRS for pontine metastasis.