Go Back Brain/15. Brain and meninges, Infratentorial/Other/15.9 Hypertrophic Olivary Degeneration/ Go to Index
14 y.o. female with h/o pineal region teratoma.
Findings
Axial imaging reveals symmetric enlargement of the medullary olives with abnormally increased signal hyperintensity on T2 and FLAIR. There is no enhancement post Gadolinium administration.
Imaging questions…
Could the findings be suggestive of metastatic disease? Why or why not?
Is there another etiology to explain the imaging findings?
Would you expect the patient to have palatal tremor?
In favor of Against tumor tumor
Olivary enlargement
Abnormal hyperintensity
Non-enhancing
Bilateral & symmetrical
Direct extension, hematogenous spread, or subarachnoid seeding?
Imaging questions…
Could the findings be suggestive of metastatic disease? Why or why not?
Is there another etiology to explain the imaging findings?
Would you expect the patient to have palatal tremor?
Hypertrophic Olivary Degeneration
In general, caused by ischemia, neoplasia, or vascular insult to the components of the triangle of Guillain and Mollaret.
De-afferentation of the inferior olivary nucleus (ION) leads to T2 hyperintensity and hypertrophy of the ION. Delayed cerebellar atrophy can be seen in the hemisphere contralateral to the lesion.
“Palatal myoclonus.”
Hypertrophic Olivary Degeneration
The triangle of Guillain and Mollaret consists of connecting tracts including the cerebellar dentate nucleus, the brachium conjunctivum, and the contralateral olive.
Hypertrophic Olivary Degeneration
Efferents from the dentate ascend through the superior cerebellar peduncle, cross in the decussation of the brachium conjunctivum inferior to the red nucleus, and then descend to the ION by way of the central tegmental tract.
ION efferents cross the midline, enter the inferior cerebellar peduncle, and terminate on the original dentate nucleus.
HOD is associated with lesions of the first two limbs of the triangle, but not the olivodentate fibers.
Hypertrophic Olivary Degeneration
It is olivary de-afferentation that is thought to result in hypertrophic degenerative changes.
The olivodentate fibers appear to be important for maintenance of a normal cerebellar hemisphere; the integrity of the first two limbs of the triangle are essential for the health of the olives.
With olivodentate fiber disruption, cerebellar atrophy can occur.
Hypertrophic Olivary Degeneration
“HOD is due to presumed transsynaptic degeneration resulting in vacuolation of neurons, an increase in the number of glial cells, demyelination, and shrunken neurons.”
In patients with symptomatic palatal tremor, hyperintense signal is present on T2-weighted images within the first month after disease onset. The hyperintensity persists for many years and may be permanent.
Hypertrophic Olivary Degeneration
Hypertrophy of the olives typically appears 10 to 18 months after the insult but may be seen as early as 6 months and disappears by 4 years.
