Hypertrophic olivary degeneration after posterior cranial fossa tumor resection in adults: illustrative case.

backgroundPosterior cranial fossa tumor resection can be complicated by a rare but potentially debilitating condition known as hypertrophic olivary degeneration (HOD). This condition is diagnosed using a high degree of clinical suspicion as well as T2/FLAIR MRI findings of nonenhancing, hyperintense enlargement of the inferior olivary nucleus. OBSERVATIONS: The authors present a unique case of HOD in a 49-year-old female 4 months after resection of a low-grade pilocytic astrocytoma from the cerebellar vermis. The patient displayed classic signs associated with HOD, including palatal tremor, ocular nystagmus, and ocular myoclonus. Management will likely be challenging, and the patient was referred to movement disorder specialists to discuss potential treatment options. LESSONS: Few case reports of HOD after neurosurgical intervention in adults are available in the literature. In this work, the authors conducted a literature review of available data for 23 cases of HOD in adult patients after midline posterior cranial fossa tumor resection. The prognosis of symptomatic HOD is generally poor, as no standardized treatment regimen for these patients currently exists. https://thejns.org/doi/10.3171/CASE25130.