Hypertrophic olivary degeneration after surgical removal of cavernous malformations of the brain stem: report of four cases and review of the literature

Background. Hypertrophic olivary degeneration (HOD) is a pathological phenomenon that occurs after injury to the dentato-olivary pathway. Its hallmarks include hypertrophy of the olive with increased T2 signal intensity on magnetic resonance imaging, and it often manifests with palatal tremor and oscillopsia clinically. Method. We report the cases of four patients who developed delayed HOD after surgical resection of pontine lesions. Findings. We discuss the anatomical and pathological details of this disease and review the few other reported cases of HOD after resection of lesions within the brainstem. Conclusions. HOD should be recognized as a possible complication of surgery within the brainstem and must be diagnosed promptly so that patients can be appropriately counseled and symptoms can be treated.