Collision in the inferior olive: hypertrophic olivary degeneration complicated by radiation necrosis in brainstem primitive neuroendocrine tumor

Abstract

Hypertrophic olivary degeneration (HOD) is caused by disruption of the triangle of Guillain and Mollaret. We describe a child with a primitive neuroendocrine tumor who developed an expansile nonenhancing lesion in the olive after surgery and radiation therapy. Diffusion tensor imaging and tractography showed disruption of the central tegmental tract consistent with HOD. Subsequent transient enhancement of the olive was consistent with early radiation injury. Knowledge of coexisting complications such as HOD and radiation injury is essential for proper management.

Hypertrophic olivary degeneration resulting from posterior fossa masses and their treatments

“…HOD has also been described after posterior fossa tumor resection [6,9]. Unlike the seven posterior fossa tumor patients described by Shinohara et al [9]; however, 30% of our patients had HOD prior to any brain intervention for their medulloblastoma ( n =1), nonspecific cerebellar necrosis ( n =1), or demyelination ( n =1) (Fig.…”

“…The inferior olivary changes occur ipsilateral to tegmental lesions and contralateral to dentate nucleus lesions, also illustrated with the patients in this study. HOD is usually caused by hemorrhage due to hypertension, with other causes including infarction, surgery, RT, and demyelinating disease [3,4,6–9]. Hemorrhage was only present in four of our patients, suggesting that other space occupying masses and treatments that cause brain tissue destruction may also cause HOD.…”

“…DTI and tractography may be helpful in confirming injury to the Guillain-Mollaret triangle, especially if HOD is suspected [6,10]. Incorporation of diffusion tensor tractography creates a clear visualization of white fiber disruptions within the triangle.…”

“…The database query yielded 13 patients, with 2 patients excluded because of insufficient imaging and 1 patient excluded because there was no apparent lesion in the Guillain-Mollaret triangle. One patient with HOD complicated by radiation injury was previously reported [6]. We performed chart reviews of the 10 cohort patients (3 women and 7 men; range, 5–67 years; median age, 44 years) and collected clinical data from radiation oncology, pathology, and radiology records.…”