images in clinical medicineT h e ne w e ngl a nd jou r na l o f m e dic i ne n engl j med 360;9 nejm.org february 26, 2009 e12 A 50-year-old woman with hypertension had an acute pontine hemorrhage, as seen on computed tomography (Panel A, arrow), which resulted in quadriplegia. Thirty months later, she reported having difficulty reading because of oscillopsia. The physical examination revealed pendular nystagmus (two cycles per second) with a predominantly vertical component and some horizontal and torsional eye movements (Video 1). She also had palatomyoclonus, seen as rhythmic, involuntary contractions of the soft palate and pharyngopalatine arch (one to two cycles per second) (Video 2). T 2 -weighted magnetic resonance imaging of the brain showed hyperintensity and enlargement of the inferior olivary nuclei, findings that were compatible with a diagnosis of hypertrophic olivary degeneration (Panel B, arrowheads). The condition, which may be caused by trauma, infection, demyelination, neoplasm, or vascular injury in the components of the dentatorubroolivary pathway, results in olivary hypertrophy rather than atrophy. Myoclonic contractions of the soft palate and nystagmus represent the effects of transsynaptic degeneration of the inferior olivary nuclei. After treatment with trihexyphenidyl, there was some improvement in the patient's visual symptoms.

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