Hypertrophic olivary degeneration

Hypertrophic olivary degeneration (HOD) is a rare condition characterised by unique pattern of trans-synaptic degeneration. It is caused by a lesion in the triangle of Guillain and Mollaret, resulting in hypertrophy of the inferior olivary nucleus. The three corners of the triangle are:

Palatal myoclonus is a classically described feature.

Interruption of either connections between the dentate nucleus and contralateral red nucleus (dentatorubral tract, superior cerebellar peduncle) or the connection between the red nucleus and ipsilateral inferior olivary nucleus (central tegmental tract) 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. Isolated lesions of the inferior cerebellar peduncle do not cause HOD, as anatomically there are no direct connections between the inferior olivary nucleus and the contralateral dentate nucleus (fibres from the inferior olivary nucleus project to the cerebellar cortex via the olivocerebellar tracts and then to the dentate nucleus).

It is often seen several months after the original insult.

MRI brain

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 by 3-4 years.

Clinically lesions in the triangle of Guillain and Mollaret, present as palatal tremor.

General imaging differential considerations include:

Share article

Article Information

rID: 1478
Section: Pathology
Tag: refs
Synonyms or Alternate Spellings:
  • Hypertrophic olivary degeneration (HOD)

Support Radiopaedia and see fewer ads

Cases and Figures

  • Drag
    Case 1
    Drag here to reorder.
  • Drag
    Case 2: (bilateral)
    Drag here to reorder.
  • Drag
    Case 3
    Drag here to reorder.
  • Drag
    <br />
    Case 4
    Drag here to reorder.
  • Drag
    Case 5
    Drag here to reorder.
  • Updating… Please wait.
    Loadinganimation

    Alert accept

    Error Unable to process the form. Check for errors and try again.

    Alert accept Thank you for updating your details.