Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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July 18, 2011
Hypertrophic Olivary Degeneration
- Secondary degeneration of inferior olivary nucleus (HOD), usually caused by primary lesions in dento-rubro-olivary pathway (triangle of Guillain and Mollaret).
- Triangle of Guillain and Mollaret (3 structures): dentate nucleus of cerebellum, contralateral red nucleus, and inferior olivary nucleus.
- HOD is presumed to be due to transsynaptic degeneration resulting in neuronal vacuolation, increase in number of glial cells, demyelination and shrunken neurons. It is a unique type of transneuronal degeneration that undergoes hypertrophy rather than atrophy. Atrophy can occasionally be seen in chronic stages.
- Clinical manifestation: symptomatic palatal tremor/myoclonus.
- Key imaging features: enlargement of the inferior olivary nucleus with increased signal on long-TR sequences. The primary lesion affecting the triangle of Guillain and Mollaret may be visualized, and hypertrophic olivary degeneration occurs ipsilateral to the lesion if the lesion is in the brainstem, or contralateral to the lesion if the lesion is located in the cerebellum.
- DDx: Tumor, Trauma, demeylination, infarction, amyotrophic lateral sclerosis
- Treatment: No specific treatment