Background and Objectives: A 50-years-old patient progressively developed ataxia, nystagmus and palatal tremor. Conventional MRI revealed inferior olivary nuclei (IONs) enlargement and hyperintensity in T2-weighted images, posing the diagnosis of hypertrophic olivary degeneration (HOD). The patient’s past medical history reported proton-therapy for an VIII cranial nerve Schwannoma. The aim of this study was to investigate the potential alterations involving the tracts and nuclei composing the dentato-rubro-olivary pathway, i.e. the Guillain-Mollaret triangle (GMT), using an advanced ultra-high field 7T-MRI protocol.

Methods: The patient underwent a 7T-MRI scan, including a multi-echo gradient echo sequence (GRE) for the elaboration of quantitative susceptibility mapping (QSM) and diffusion tensor imaging (DTI). The DTI dataset was elaborated for tractography and computation of tensor metrics (fractional anisotropy, radial diffusivity, axial diffusivity and apparent diffusion coefficient).

Results: 7T-MRI allowed the depiction of the brainstem substructures composing the GMT (tracts and nuclei). Both qualitative and quantitative analysis of these structures demonstrated damage to the right red nucleus and to the dentato-rubral tracts bilaterally. These findings are consistent with the pathophysiology of HOD. The damage documented in the 7T-MRI was confirmed in a conventional follow-up MRI performed 8 months later.

Discussion: This study highlights the capability of 7T-MRI to depict and directly investigate brainstem substructures such as tracts and nuclei using advanced techniques such as QSM and DTI. To current authors’ knowledge, there are no studies to successfully depict all tracts composing the GMT and directly document their alterations in HOD.