Disease model with lesion sites: The Guillain–Mollaret-triangle (yellow) and its unidirectional course of inhibitory fibers that ascent from the dentate nucleus (DN) to the contralateral red nucleus (RN) and then descend ipsilateral to the inferior olivary nucleus (ION). The bilateral overlapping Guillain–Mollaret triangles (yellow and grey) together form a “tilted star of David configuration” [5]. The numbers in octagons indicate the position of the operative lesions in Patients 1–10 of this study, who ultimately developed a HOD appearance on MRI. In bilateral lesions, octagons are shown on both sides. Fibers of the GMT, which is also called the dentato–rubro–olivary-pathway, overlap with dentato–thalamo–cortical pathways proceeding into both hemispheres (black arrows) [10]. Abbreviations: GMT = Guillain–Mollaret-triangle; HOD = hypertrophic olivary degeneration; SCP = superior cerebellar peduncle; ICP = inferior cerebellar peduncle; RN = red nucleus; CTT = central tegmental tract; DN = dentate nucleus; ION = inferior olivary nucleus.