Hypertrophic olivary degeneration

Description

A 30-year-old man underwent MRI of the internal auditory meatus as a routine follow-up after excision of a large left vestibular schwannoma, 2.5 years previously. MRI images showed an incidental finding of left hypertrophic olivary degeneration (figure 1 and figure 2). This phenomenon occurs as a result of Wallerian degeneration of the olivary nucleus secondary to a lesion in the triangle of Guillain and Mollaret, also known as the dento-rubro-olivary pathway (figure 3). The differential diagnoses of hypertrophic olivary degeneration include infarction, infection, neoplasms and demyelination. Differentials can be excluded by the absence contrast enhancement (figure 2).

Figure 1

Axial T2-weighted sequence showing intratumoral haemorrhage within a large left cerebello-pontine angle lesion in keeping with a vestibular schwannoma (panel A). Axial fluid attenuated inversion recovery (FLAIR) image through the posterior fossa after 6 months demonstrating atrophic changes and haemosiderin deposition in the left middle cerebellar peduncle...

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