Teaching NeuroImage: Latent Axonal Degeneration in Patient With Anterior Circulation Stroke

A 74-year-old man presented within 6 hours of acute left-sided weakness (Medical Research Council scale 4-/5), including left facial droop and dysarthria (NIH Stroke scale 7).Baseline MRI and magnetic resonance angiography revealed a right striatocapsular infarct from a subocclusive right middle cerebral artery thrombus.He presented outside the intravenous thrombolysis treatment window but was consented to the NINDS Natural History of Stroke Study (NCT00009243) for serial MRI follow-up.At 6 months, fluid-attenuated inversion recovery MRI demonstrated a new, asymptomatic, hyperintense signal (Figure 1), hypointense on 3D T1 (Figure 2), extending from the internal capsule to midbrain without corresponding changes on diffusion-weighted imaging/apparent diffusion coefficient or perfusion-weighted imaging.He had mild residual deficits (modified Rankin Scale score of 1) at 1 year; however, the MRI signal persisted, suggesting axonal degeneration.Axonal degeneration from ischemic injury is routinely detected on fluid-attenuated inversion recovery 14 weeks poststroke, 1 with early diffusion-weighted imaging signal in 14 days. 2We report a patient in whom axonal degeneration on MRI appeared unusually late at 6 months