Abstract
We present a case and video of a 31-year-old man with biopsy-confirmed tumefactive demyelination affecting the right internal capsule causing left hemiplegia, excessive yawning, and the curious but well-described phenomenon of parakinesia brachialis oscitans (PBO) with transient tonic elevation of his paralyzed arm while yawning. PBO is most commonly reported in ischemic stroke with internal capsule or pontomedullary brainstem lesions. Our case uniquely demonstrates this phenomenon in the case of tumefactive demyelination. We also highlight excessive yawning which has also been described in multiple sclerosis.