Prolonged Nicu Course in Pediatrics — 2yo Child | Paediatric Neurology | SMLE Q#17470

A 2-year-old boy is brought to the pediatric clinic because he has had difficulty walking since he started trying to stand. When held upright under the arms, his legs cross over each other in a “scissoring” pattern. Pregnancy history is notable for delivery at 30 weeks’ gestation with a prolonged NICU course. Vital signs: T 36.8°C; BP 94/58 mmHg; HR 108/min; RR 24/min; SpO2 99% on room air. Neurologic examination shows increased tone in both lower extremities with brisk deep tendon reflexes and ankle clonus; upper extremities are less affected. Brain MRI report notes periventricular leukomalacia. Which of the following findings most strongly supports the diagnosis suggested by this presentation?