Clinical features of olivary hypertrophic degeneration in brain magnetic resonance image

ABSTRACT

Olivary hypertrophic degeneration (OHD) is caused by lesions in dentato-rubro-olivary pathway(myoclonic triangle) and responsible for palatal myoclonus and other involuntary movements. We report the clinical features and magnetic resonance imaging(MRI) findings of 5 patients with OHD. All patients had previous brainstem hemorrhage mainly involving pontine tegmentum in four patients and right superior cerebellar peduncle in one patient T2-weighted MR] revealed round or oval shaped high signal area in the ventral or ventrolateral portion of the medulla. Their clinical presentations were as followings palatal myoclonus (4 case), ocular myoclonus (3 case), pharyngeal and laryngeal myoclonus (2 case), limb myoclonus (2 case), head shaking (I case) and perioral tremulous movement (1 case). The frequency of myoclonus was 70-170/minute and the median time interval between the insult of the primary lesion and the onset of myoclonic symptoms was 2 months. OHD shown as hyperintense lesions on T2 weighted MRI should be differentiated from ischemic, neoplastic or other pathologic lesions. The characteristic clinical presentations and the location of primary lesions involving myoclonic triangle may be helpful in differential diagnosis from primary medullary lesions.