Presentation
Known old right cerebellar hemorrhage. New palatal myoclonus.
Patient Data
Hemosiderin staining centered on the right dentate nucleus is dimensions are 10 x 12 mm and T2 weighted sequence, with blooming on the susceptibility-weighted imaging. On T1 sequences this corresponds to a central region of signal dropout. Intrinsic T1 hyperintensity but no pathological contrast enhancement. No adjacent developmental venous anomaly is identified. Two further susceptibility foci are identified, one in the right thalamus and the other in left temporal white matter.
9 mm rounded T2 hyperintensity in the left inferior pons without enhancement. This is consistent with hypertrophic olivary degeneration related to a contralateral dentate nucleus lesion.
The remainder of the brain is normal for age, with a few scattered white matter foci of T2 hyperintensity compatible with mild changes of chronic small vessel ischemia. No hydrocephalus.
T2 hypointense and T1 hyperintense ovoid mass in the midline to left pituitary, between anterior and posterior pituitary has dimensions of 5.7 x 7 x 13 mm.
MR angiogram demonstrates foetal supply of the left posterior cerebral artery and asymmetrically large caliber right A2 and A3 segments of the anterior cerebral artery.
No intracranial aneurysm or evidence of vascular malformation.
Conclusion:
Left hypertrophic olivary degeneration secondary to previous bleed in the right dentate nucleus.
The site of the previous hemorrhage does not have a clear underlying popcorn lesion of an underlying cavernoma.
Based on location, the previous dentate nucleus hemorrhage and right thalamic microbleed could have hypertensive etiology, but the susceptibility focus in the left temporal white matter would be an atypical location for hypertensive hemorrhage and could represent a tiny cavernoma.
No AVM identified.
Probable Rathke's cleft cyst.
Rounded T2/FLAIR hyperintensity in the left inferior pons. This is consistent with hypertrophic olivary degeneration related to a contralateral dentate nucleus lesion.
Case Discussion
Hypertrophic olivary degeneration is a rare condition characterized by a 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. In this case, the previous hemorrhagic lesion in the right dentate nucleus caused the interruption that led to hypertrophic olivary degeneration.
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