Hypertrophic olivary degeneration (HOD) is a rare condition characterised by unique pattern of trans-synaptic degeneration.
Palatal myoclonus is a classically described feature
Interruption of either of the two limbs passing to the contralateral dentate nucleus, leads to changes in the olive. Pathologically, this is characterised by "trans-synaptic degeneration resulting in vacuolation of the neurons" and an increase in astrocytes.
It is often seen several months after the original insult.
In radiology-laymen terms - the inferior olivary nucleus gets larger and increases in T2 signal intensity.
Typically, within a few months T2 signal increases, and lasts 3 - 4 years, whereas hypertrophy occurs later, at about one year, and resolves also by 3 - 4 years.
Clinically lesions in the triangle of Guillain and Mollaret, present as palatal tremor.
General imaging differential considerations include
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- 1. Goyal M, Versnick E, Tuite P et-al. Hypertrophic olivary degeneration: metaanalysis of the temporal evolution of MR findings. AJNR Am J Neuroradiol. 21 (6): 1073-7. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 2. Salamon-Murayama, N. et al "HOD secondary pontine haemorrhage" Radiology 1999, 213:814-817
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