I took the handle of my knee hammer and, while Dr. Hamdi was lying in bed, stroked the outer border of his right foot and then the left foot, running the tip of the hammer handle from the pinky to sole. Nothing much happened in the normal foot, but when I repeated the procedure on the paralyzed right foot, the big toe instantly curled upward and all the other toes fanned out. This is Babinski’s sign, arguably the most famous sign in neurology. It reliably indicates damage to the pyramidal tracts, the great motor pathway that descends from the motor cortex down into the spinal cord conveying
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