Spinal Cord Infarction Presenting with Abnormal F Waves

A 42-year-old female presented with acute onset of asymmetric lower extremity weakness, bilateral lower extremity areflexia and sensory loss, and urinary incontinence. Initial investigation with a spine MRI for a spinal cord process was negative, leading to further investigation with nerve conduction studies/electromyography (NCS/EMG). This revealed absent F waves bilaterally in the fibular nerves, and there was only one isolated F wave with decreased amplitude and increased latency in the left tibial nerve and had lack of heterogeneity in the right tibial nerve. Given the early presentation of her symptoms, this led to a working diagnosis of Guillain-Barré Syndrome, which was treated with plasmapheresis without improvement. After plasmapheresis, the diagnosis was revisited, and a repeat spine MRI revealed an extensive lower thoracic and lumbar spinal cord infarction. In this unique scenario, the properties and abnormalities of F waves are discussed and reviewed, along with the influence of acute central nervous system lesions on their configuration.