Abstract
Hypertrophic olivary degeneration (HOD) is a rare form of transsynaptic degeneration
characterized by hypertrophy of the inferior olivary nucleus situated in the olivary
body, part of the medulla oblongata, representing a major source of input to the cerebellum.
HOD typically results from focal lesions interrupting connections from the inferior
olive within the dentato-rubro-olivary pathway, a region also known as the triangle
of Guillain-Mollaret (TGM) (red nucleus, inferior olivary nucleus, and contralateral
dentate nucleus). Clinically, HOD presents classically as palatal tremor and can include
dentatorubral tremor and/or ocular myoclonus. The pathologic changes associated with
HOD feature radiologic changes with the inferior olivary nucleus appearing larger
and increasing its T2-weighted signal intensity on magnetic resonance images. HOD
is commonly managed with pharmacotherapy but may require surgical intervention in
extreme cases. HOD has been found to develop as a consequence of any injury that disrupts
the TGM pathways (e.g., pontine cavernoma).These findings highlight the critical importance
of a thorough knowledge of TGM anatomy to avoid secondary HOD. We present a patient
who developed HOD secondary to resection of a tectal plate cavernous malformation
and review the literature with an emphasis on the current knowledge of this disorder.
Keywords
hypertrophic olivary degeneration (HOD) - triangle of Guillain-Mollaret (TGM) - symptomatic
tremor - neurosurgical intervention
