Neurology | Upper Motor Neuron vs Lower Motor Neuron Lesion | UMN vs LMN Lesion

Official Ninja Nerd Website: https://ninjanerd.org Ninja Nerds! Join us for this lecture where Professor Zach Murphy will be comparing and contrasting Upper Motor Neuron (UMN) lesions and Lower Motor Neuron (LMN) lesions. We begin with a detailed review of the motor pathway anatomy, from the motor cortex through the corticospinal tract, down to the anterior horn cells and peripheral nerves. This foundational understanding allows us to clearly distinguish where lesions occur and how their locations affect motor function. We then examine the hallmark clinical features of UMN lesions, including spasticity, hyperreflexia, clonus, and the presence of pathologic reflexes such as the Babinski sign. In contrast, we break down the defining characteristics of LMN lesions, such as flaccid paralysis, hyporeflexia, fasciculations, and muscle atrophy, emphasizing the pathophysiologic basis for each finding. Along the way, we explore why certain features occur, such as increased tone in UMN lesions due to loss of inhibitory modulation, versus decreased tone in LMN lesions from direct damage to the motor unit. Finally, we integrate these concepts into a clinical framework by discussing common etiologies of each lesion type, their diagnostic implications, and how localization on neurologic examination helps guide further workup. This comparison solidifies recognition of the two lesion patterns and underscores their importance in neurology and clinical medicine. Enjoy the lecture and support us below! 🌐 Official Links Website: https://www.ninjanerd.org Podcast: https://podcast.ninjanerd.org Store: https://merch.ninjanerd.org 📱 Social Media   / ninjanerdlectures     / ninjanerdlectures     / ninjanerdlectures   https://x.com/ninjanerdsci/   / ninja-nerd   💬 Join Our Community Discord:   / discord   #ninjanerd #UMNvsLMN #Neurology