Hypertrophic olivary degeneration after surgical resection of brain tumors

Abstract

Background Hypertrophic olivary degeneration (HOD) can be seen as high signal intensity with enlargement of the inferior olivary nucleus (ION) on T2-weighted magnetic resonance (MR) images 4–6 months after injury of the Guillain-Mollaret triangle. To the best of our knowledge, there has been no systematic evaluation with regard to the relationship between neurosurgical intervention affecting this pathway and the appearance of HOD. Purpose To evaluate MR findings of HOD after surgical resection of brain tumors with the temporal evolution in focus. Material and Methods MR images of seven patients that showed signal changes in the ION after surgical resection of brain tumors in the posterior fossa were retrospectively reviewed. T1-weighted imaging with and without gadolinium (Gd) contrast enhancement and T2-weighted imaging were performed in all patients before and after surgery. Results Before surgery, no patient had a signal change in the ION. T2-high signal intensity of the ION initially appeared 5 days to 2.5 months after surgery. Five patients showed enlargement of the ION with T2-high signal intensity 11 days to 3.5 months after surgery: three patients showed the enlargement of the ION subsequent to the T2-signal change on serial follow-up MR images. On Gd-enhanced T1-weighted images, there was no enhancement at the ION in any patient. Each signal change of the ION was consistent with HOD, according to the relationship between the resection site of the tumor and the Guillain-Mollaret triangle on follow-up MRI. Conclusion HOD can be caused after neurosurgical intervention of brain tumors involving the Guillain-Mollaret triangle. It is important for radiologists to distinguish HOD from tumor recurrence.