Cumulative Corticospinal Pathway Disruption after Recurrent Brainstem and Anterior Circulation Stroke Presenting as Bilateral Motor Deficit: A Case Report

Background Brainstem infarctions are relatively uncommon but often result in significant neurological deficits due to the dense concentration of motor pathways within a limited anatomical space. Bilateral motor weakness following stroke is rare and usually associated with extensive supratentorial or bilateral brainstem involvement. Case Presentation: We report the case of a 56-year-old male with multiple vascular risk factors, including type 2 diabetes mellitus, hypertension, dyslipidaemia, and double-vessel coronary artery disease, who developed an unusual pattern of asymmetric bilateral lower limb weakness with bilateral foot drop following recurrent strokes. In 2018, magnetic resonance imaging revealed acute infarcts involving the bilateral anterosuperior medulla and right paramedianpontomedullary junction, presenting as left hemiparesis. In 2022, he experienced a recurrent vascular event with near-total occlusion of the right internal carotid artery confirmed on angiography. Subsequent to this event, he developed bilateral lower limb weakness, more pronounced on the left, accompanied by bilateral foot drop. Neurological examination demonstrated mild left lower limb spasticity, exaggerated reflexes, impaired coordination, and gait abnormalities with moderate fall risk, while cognition and higher mental functions were preserved. Nerve conduction studies excluded peripheral neuropathy, confirming a central origin of the deficit. Discussion The sequential involvement of the medulla at the level of pyramidal decussation and later anterior circulation compromise likely resulted in cumulative disruption of corticospinal pathways. Partial injury to decussating fibres during the initial brainstem infarct may have created bilateral motor vulnerability, which was further unmasked by reduced cortical motor drive following right internal carotid artery occlusion. Conclusion This case highlights the cumulative and dynamic nature of recurrent stroke, emphasizing the importance of detailed neuroanatomical correlation and individualized, task-oriented rehabilitation to optimize functional recovery in atypical bilateral motor presentations.