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 28, 2022
Idiopathic (Nonlesional) Bilateral Hypertrophic Olivary Degeneration
- Background:
- Hypertrophic olivary degeneration (HOD) is a rare type of transsynaptic degeneration characterized by enlargement of the olivary nuclei, which can be either bilateral or unilateral.
- It is usually secondary to lesions in the Guillain-Mollaret triangle, but bilateral involvement is usually idiopathic. The triangle is formed by the red nucleus, the inferior olivary nucleus, and the contralateral dentate nucleus.
- Clinical Presentation:
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Is usually delayed by several months after the initial insult
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The classic finding is palatal myoclonus, which may not always be present.
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Other symptoms include dentatorubral or Holmes tremor and ocular myoclonus.
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- Key Diagnostic Features:
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Bilateral symmetric hyperintense signal changes on T2, FLAIR WI in the inferior olivary nuclei
- Hypertrophy of the inferior olivary nuclei (Stage 2)
- T1WI + Gad contrast: No enhancement
- DWI: No diffusion restriction
- Spatial confinement of the lesion within the inferior olivary nucleus
- Absence of any lesions within the dentate-rubro-olivary pathway or in the brain parenchyma - idiopathic HOD
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- Differential Diagnoses:
- The bilateral symmetric involvement of inferior olivary nuclei is quite unique, without any major differential diagnoses.
- Absence of diffusion restriction helps to differentiate HOD from acute infarct. Temporal evolution of signal intensities is also useful in ruling out changes due to infarction.
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Treatment:
- Symptoms are difficult to treat, but management with benzodiazepines and carbamazepine has been reported.
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