Pearls and Oy-sters: Stroke in the Wrong Hemisphere

A young woman presented with sudden-onset dysarthria and right-sided weakness and hypoesthesia. MRI revealed an acute infarct in the right hemisphere, the same side as the patient's clinical deficits. This unusual alignment between symptoms and lesion laterality raised important diagnostic challenges. Standard vascular and etiologic investigations were unrevealing, and initial treatment with intravenous thrombolysis led to partial recovery. The persistence of a paradox between lesion location and motor deficit prompted further evaluation with diffusion tensor imaging with tractography (DTI) that demonstrated imaging findings consistent with a nondecussating corticospinal tract at the level of the medullary pyramids, providing a plausible anatomical explanation for the paradoxical ipsilateral presentation. Although tractography cannot definitively establish the anatomical absence of pyramidal decussation, the structural configuration observed was strongly suggestive of an uncrossed corticospinal organization. This case underscores the importance of diagnostic flexibility when fundamental neuroanatomical rules appear violated and highlights the role of advanced diffusion imaging in resolving clinical-radiologic discordance.