Isolated Leg Monoparesis in a Patient with Atrial Fibrillation and Acute Ischemic Small Vessel Disease

Monoparesis is most commonly caused by dysfunction of the lower motor neurons (LMNs) which innervates the affected limb. This includes lesion affecting the anterior nuclei, ventral nerve roots, lumbosacral plexus, or peripheral nerve. Nevertheless, it can also be due to upper motor neuron lesion, typically seen in lesions of the spinal cord. In general, many conditions that cause hemiplegia, paraplegia or quadriplegia may begin as monoplegia. We illustrate an elderly patient with hypertension, diabetes mellitus, dyslipidemia and atrial fibrillation, who presented with acute monoparesis and radiological evidence suggestive of recent infarct and small vessel disease.