Post-traumatic segmental myoclonus associated with bilateral olivary hypertrophy

We present clinical and magnetic resonance (MR) findings in three patients with segmental myoclonia occurring 11-18 months after severe brainstem injury. Palatal myoclonus and vertical ocular myorhythmia were present in all three patients and synchronous involuntary movements of the upper extremities ("wing beating") in two patients. MR-imaging showed multiple post-traumatic lesions within the dentato-rubro-olivary pathway ("myoclonic triangle"), associated with bilateral enlargement and increased signal intensity of the inferior olives. The signal abnormality was more prominent on proton density weighted images than on T2-weighted images, suggesting underlying pathological changes different from typical gliosis.