Point 5 Intro Pathway Deficits Summary Caveat Problems Contents Anatomy

Let's do some problem solving using this extremely important concept. What will happen if there is a lesion in the ventral horn at T1??? Well, it seems to me that the logical answer is that motor neurons in the ventral horn at this level, and only at this level, die. Their axons also die, and then the muscles innervated by these axons die, and atrophy. It's as simple as that!!!! T1 motor neurons innervate the intrinsic hand muscles. Since the muscles innervated by ventral motor neurons at spinal level T1 are dead, they atrophy and are flaccid (flaccidus L = flabby). They will not respond to stretch and therefore there is atonia and areflexia. Now, another important concept. The lateral corticospinal tract (LCST) synapses upon lower motor neurons in the spinal cord. This pathway is therefore called an UPPER MOTOR NEURON (UMN) pathway. Clinically, it is "THEEEEEE" UMN pathway. Star, underline in many colors, and remember for the rest of your life: LCST = UMNs while VENTRAL HORN CELLS = LMNs.