Fact-sheet: Hypertrophic olivary degeneration


Updated on 05/08/2025 at 1:58 PM

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Definition

Hypertrophic olivary degeneration corresponds to degenerative involvement of the inferior olivary nucleus (ION) secondary to a lesion of the dentato-rubro-olivary pathway ("Guillain-Mollaret triangle").

Any lesion (regardless of cause) resulting in damage to the afferent pathways to the ION can lead to its degeneration. In some cases, no causal lesion is identified.

Hypertrophic olivary degeneration is bilateral in 75% of cases.

The Guillain-Mollaret triangle comprises three anatomic structures:

  • the dentate nucleus of the cerebellum (blue, contralateral to the ION - dentato-rubral afferent pathway to the red nucleus).
  • the red nucleus (red, ipsilateral to the ION - rubro-olivary afferent pathway to the ION).
  • and the inferior olivary nucleus (green, ipsilateral to the red nucleus - efferent pathway to the dentate nucleus).

Dégénérescence hypertrophique de lolive bulbaire

Clinical features

  • Palatal myoclonus or tremor
  • Oscillopsia (pendular nystagmus)
  • Upper limb tremor (Holmes tremor), facial, cervical, intercostal, diaphragmatic tremor

MRI

  • MRI findings appear with a delay of several days
  • 2-7 days: T2 hyperintensity surrounding the ION, then involving the entire ION
  • from 3 weeks onward: hypertrophy and hyperintensity of the ION
  • Possible loss of the normal SWI hypointensity of the ipsilateral red nucleus
  • No contrast enhancement or ADC drop

Differential diagnosis

  • Ischemic stroke
  • Demyelinating disease
  • Astrocytoma
  • Metastasis
  • Lymphoma
  • Tuberculosis & infectious diseases