Case of the Month: May 2013, Page 4

Answer: A)  Hypertrophic olivary degeneration

Discussion:

A form of trans-synaptic degeneration which results in enlargement of the inferior olivary nucleus  after damage to  the neuronal connections of the Guillain-Mollaret triangle.

  • Guillain-Mollaret triangle is made up of the contralateral dentate nucleus of the cerebellum, ipsilateral red nucleus, and ipsilateral inferior olivary nucleus (dentatorubral-olivary pathway)
  • A unique form of degeneration because it is associated with enlargement rather than atrophy
  • Unusual vacuolar degeneration and increase in number of astrocytes results in enlargement
  • In this case, the initially shown hemorrhage of the patients cavernous malformation interrupted the Guillain-Mollaret triangle
  • As in this case, olivary hypertrophy is not seen immediately, and usually appears in 4-6 months
    • Hypertrophy usually resolves in 10-16 months
  • Palatal myoclonus is a typical finding, as are ocular myoclonus and dentatorubral tremor
    • Abnormal movements rarely resolve

Imaging findings

  • Enlargement and increased T2 signal of inferior olivary nucleus (may be unilateral or bilateral depending on initial insult)
    • Increased T2 signal may persist for years after resolution of hypertrophy
  • No enhancement
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