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 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.