Abstract 3540: Characteristics Of The Hypertrophic Olivary Degeneration Following Aggressive Treatment Including Surgical Resection And Gamma Knife Radiosurgery Of The Brainstem Cavernous Malformations

Introduction: Hypertrophic olivary degeneration (HOD) is an unusual phenomenon involving hypertrophy of the olivary nucleus, which occurred due to a neuronal connection injury to the dentato-rubro-olivary pathway of the brainstem. The purpose of this study is to explore the characteristics of the HOD following surgical resection and Gamma Knife radiosurgery of the brainstem cavernous malformation. Methods: The medical records from January 2001 through May 2011 were reviewed retrospectively to identify patients who underwent surgical resection or Gamma Knife radiosurgery in the brainstem cavernous malformation. Total 77 cases (including 32 in surgical group and 45 in Gamma Knife radiosurgery group) of the brainstem cavernous malformations were treated in our institute except for the patients who received conservative treatment and we selected and investigated in 13 patients who developed HOD at T2 high signal intensity on follow-up MRI. We divided into 2 groups as the surgical group and the radiosurgery group. The detailed informations of the two each groups were carefully reviewed. Results: The HOD group was composed of 5 men and 8 women, ranging in age from 9 to 67 years with mean of 44.6 years. Among 13 HOD patients, 7 patients were cases who were developed after surgical resection and 6 patients after Gamma Knife radiosurgery. The mean follow-up period was 32 months (2∼108 months). Bilateral HOD patients were 7 including 4 in the surgical group and 3 in the radiosurgery group. The HOD associated symptoms were showed in 6 of 13 patients including 3 patients (2 palatal tremors, one ataxia) in the surgery group and the same in the radiosurgery group. All 6 patients that had these symptoms had recovered incompletely until the last clinical follow-up period (mean 22.6 months). There are significant differences including the time interval between HOD diagnosis and treatment, and mean age in each two groups. Conclusions: It is concluded that HOD should be recognized as a potential complication of the aggressive surgery within the brainstem. It is important not to confuse HOD for a new ischemic event, neoplastic disease and inflammatory or infectious diseases through the following special features: typical symptom (palatal tremor), the remote primary lesion, non enhancing lesion and delayed occurrence months after insult.