Hypertrophic olivary degeneration following pontine haemorrhage: hypertensive crisis or cavernous haemangioma bleeding?

The clinical and magnetic resonance (MR) features of hypertrophic olivary degeneration are described, along with a rare but treatable cause of this entity—pontine cavernous haemangioma. Hypertrophic olivary degeneration occurs after focal lesions to the dentato-rubro-olivary pathway, typically following a pontine haemorrhage involving the ipsilateral central tegmental tract, the contralateral superior cerebellar peduncle, or the dentate nucleus. Clinically, there is palatal myoclonus and an uncontrollable tremor, presumably caused by loss of inhibitory control. On MR imaging, hypertrophic olivary degeneration is characterised by a non-enhancing T1 isointense, T2 hyperintense enlargement confined to the olivary nucleus. Typically, haemorrhages following a hypertensive crisis are responsible for hypertrophic olivary degeneration. However, in the three reported cases, imaging findings within the former bleeding cavity suggested a cavernous haemangioma as the source of the haemorrhage.