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

(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 case of hypertrophic olivary degeneration after resection of cavernomas of the brain stem and review of the literature

Hypertrophic olivary degeneration is a transsynaptic form of degeneration, which is also a result of primary or secondary lesion and can damage the dento-rubro-olivary pathway. The dento-rubro-olivary pathway was first described by Guillain and Mollaret and is referred to as "the triangle of Guillain and Mollaret". Multiple factors can destroy the dento-rubro-olivary pathway, such as surgical operation, hemorrhage, tumor, trauma, inflammation, demyelination, degeneration, and radiation damage. All of the above factors can result in delayed hypertrophic olivary degeneration. Articles related to this disease cover etiology, clinical presentation, pathology changes, etc. However, to our knowledge, there has been no literature reporting the use of diffusion tensor imaging and diffusion tensor tractography to improve the diagnosis of hypertrophic olivary degeneration following resection of cavernomas in the brain stem. Herein, we report a case who was diagnosed with hypertrophic olivary degeneration following resection of cavernomas of the brain stem, verify the significance of diffusion tensor imaging and diffusion tensor tractography, and review previous literature. The development of imageology promotes and improves hypertrophic olivary degeneration diagnosis and differential diagnosis.

Hypertrophic olivary degeneration after surgical resection of brain tumors

BACKGROUND

Hypertrophic olivary degeneration (HOD) can be seen as high signal intensity with enlargement of the inferior olivary nucleus (ION) on T2-weighted magnetic resonance (MR) images 4-6 months after injury of the Guillain-Mollaret triangle. To the best of our knowledge, there has been no systematic evaluation with regard to the relationship between neurosurgical intervention affecting this pathway and the appearance of HOD.

PURPOSE

To evaluate MR findings of HOD after surgical resection of brain tumors with the temporal evolution in focus.

MATERIAL AND METHODS

MR images of seven patients that showed signal changes in the ION after surgical resection of brain tumors in the posterior fossa were retrospectively reviewed. T1-weighted imaging with and without gadolinium (Gd) contrast enhancement and T2-weighted imaging were performed in all patients before and after surgery.

RESULTS

Before surgery, no patient had a signal change in the ION. T2-high signal intensity of the ION initially appeared 5 days to 2.5 months after surgery. Five patients showed enlargement of the ION with T2-high signal intensity 11 days to 3.5 months after surgery: three patients showed the enlargement of the ION subsequent to the T2-signal change on serial follow-up MR images. On Gd-enhanced T1-weighted images, there was no enhancement at the ION in any patient. Each signal change of the ION was consistent with HOD, according to the relationship between the resection site of the tumor and the Guillain-Mollaret triangle on follow-up MRI.

CONCLUSION

HOD can be caused after neurosurgical intervention of brain tumors involving the Guillain-Mollaret triangle. It is important for radiologists to distinguish HOD from tumor recurrence.