Delayed Occurrence of Hypertrophic Olivary Degeneration after Therapy of Posterior Fossa Tumors: A Single Institution Retrospective Analysis

Abstract

(1) Background: A lesion within the dentato-rubro-olivary pathway (DROP) in the posterior fossa can cause secondary neurodegeneration of the inferior olivary nucleus: so-called hypertrophic olivary degeneration (HOD). The clinical syndrome of HOD occurs slowly over months and may be overlooked in progressive neuro-oncological diseases. Posterior fossa tumors are often located near these strategic structures. The goal of this study was to analyze the systematics of HOD occurrence in neuro-oncological patients. (2) Methods: The neuroradiological database of the university healthcare center was scanned for HOD-related terms from 2010 to 2019. After excluding patients with other causes of HOD, 12 datasets from neuro-oncological patients were analyzed under predetermined criteria. (3) Results: Patients received multimodal tumor treatments including neurosurgery, radiotherapy, and chemotherapy. HOD occurred both unilaterally (left n = 4; right n = 5) and bilaterally (n = 3). Though the mass effect of posterior fossa tumors had already affected strategic structures of the DROP, none of the patients showed signs of HOD on MRI until therapeutic measures including neurosurgery affecting the DROP were applied. HOD was visible on MRI within a median of 6 months after the neurosurgical intervention. In 67%, the presumed underlying surgical lesion in the DROP lay in the contralateral dentate nucleus. (4) Conclusion: In a selected cohort of neuro-oncological patients, therapeutic lesions within the DROP were associated with HOD occurrence.

A Paravermal Trans-Cerebellar Approach to the Posterior Fossa Tumor Causes Hypertrophic Olivary Degeneration by Dentate Nucleus Injury

“…In contrast, the midline (telovelar and transvermian), lateral or supra-cerebellar approaches mostly spared the DN, thus seldomly causing HOD. Priorly, case series had indicated that interventional treatment with damage to the GMT is predominantly responsible for HOD occurrence in neuro-oncological patients, and not tumor growth [ 5 , 6 ]. This study supports this concept, as one in five patients developed HOD post-op, but none of these tumor patients showed signs of HOD on MRI prior to neurosurgery.…”

“…In posterior fossa tumor surgery, a lesion in the cerebellar dentate nucleus (DN) can trigger a series of trans-synaptic neurodegenerative events that ultimately lead to a hypertrophic olivary degeneration (HOD) of the inferior olivary nucleus in the medulla [ 1 , 2 , 3 , 4 ]. Previous clinical case series have indicated that surgical injury to the DN may be more closely associated with HOD occurrence than an invasive tumor growth [ 5 , 6 ]. However, which specific operative approaches constituted a risk factor remained unclear.…”

“…The HOD occurs after lesions to a functional loop called the Guillain–Mollaret triangle (GMT), which is composed of three anatomic structures: the red nucleus (RN) in the mesencephalon, the ipsilateral inferior olivary nucleus (ION) in the medulla and the contralateral dentate nucleus (DN) in the cerebellum ( Figure 1 ) [ 5 , 7 , 8 , 9 ]. It is also referred to as the dentato–rubro–olivary pathway (DROP).…”

“…The HOD is a radiological diagnosis based on the finding of a circumscribed hyperintensity of the ION on MRI T2-weighted or fluid attenuated inversion recovery (FLAIR) sequences—an additional olivary hypertrophy is optional [ 7 ]. Epidemiological aspects of HOD are still unknown and therapeutic strategies are merely palliative, which is why primary prevention is of particular importance [ 5 ]. Moreover, visibility of HOD on MRI has been discussed to be a radiological indicator and surrogate parameter for damage to contralateral cerebellar structures [ 16 ].…”

“…In review of the literature and consideration of the cerebellar topography, we hypothesized that a trans-cerebellar and paravermal surgical approach is most likely to injure the DN and consequently affect the GMT [ 5 , 6 ]. The goal of this study is to compare the paravermal trans-cerebellar operative approach to other operative approaches in posterior fossa tumor surgery and to analyze the associated risk of developing HOD on post-operative MRI as well as CMS in the aftermath.…”