Upper motor neuron (UMN) and lower motor neuron (LMN) lesions represent distinct pathophysiological disruptions within the central nervous system that result in opposing clinical presentations based on the location of neural damage relative to the anterior horn cell. UMN pathology, involving lesions proximal or superior to the anterior horn cells, causes dysregulated innervation leading to hypertonicity, hyperreflexia, and a positive Babinski sign due to loss of cortical inhibition. Conversely, LMN pathology involves direct destruction of neurons in the anterior horn or their peripheral projections, resulting in flaccid paralysis, hypotonia, areflexia, immediate denervation atrophy, and a negative (normal) Babinski sign due to complete loss of motor innervation.
Upper motor neuron (UMN) and lower motor neuron (LMN) lesions represent distinct pathophysiological disruptions within the central nervous system that result in opposing clinical presentations based …