Скачать или смотреть The Pyramidal Tract: Corticospinal Anatomy, Spasticity & UMN vs LMN Lesions

Where does voluntary movement actually travel — and how do you localize weakness to cortex, brainstem, or spinal cord?

In this physician-scientist level lecture from Integrated Neurobiology: Structure, Function, and Pathology, we trace the corticospinal (pyramidal) tract from the primary motor cortex to the spinal lower motor neuron, integrating anatomical precision with clinical localization.

We begin with the cortical origins of the upper motor neuron, follow its descent through the internal capsule, cerebral peduncle, pons, and medullary pyramids, and examine the functional implications of the pyramidal decussation. Special emphasis is placed on somatotopy — both at the internal capsule and within the spinal cord — and how these organizational rules explain real-world stroke patterns.

The second half of the lecture develops the physiological distinction between Upper Motor Neuron (UMN) and Lower Motor Neuron (LMN) syndromes. Rather than memorizing signs, we analyze the circuitry behind spasticity, hyperreflexia, fasciculations, atrophy, and the Babinski response.

Finally, we apply these principles to clinical localization across cortex, internal capsule, brainstem (crossed findings), and spinal cord lesions, including Brown-Séquard syndrome and spinal shock.

You’ll learn:

• The full anatomical trajectory of the lateral corticospinal tract
• The significance of the pyramidal decussation
• Internal capsule somatotopy and “bottleneck” stroke syndromes
• Why UMN lesions cause spasticity and hyperreflexia
• The physiology behind Babinski and clonus
• Why acute spinal cord injury can initially appear flaccid (spinal shock)
• How to distinguish cortical, capsular, brainstem, and spinal cord lesions
• A diagnostic framework for answering the question: “UMN or LMN?”

This lecture is designed for medical students, neurology and neurosurgery residents, PM&R trainees, and physician-scientists seeking mechanistic understanding rather than pattern memorization.

If you’re following the series, this lecture builds directly on spinal cord tract anatomy and sets the foundation for future discussions of motor neuron disease, neuromuscular junction disorders, and myopathies.

Subscribe for advanced neuroanatomy, systems-level physiology, and clinical reasoning.

Tags:
#CorticospinalTract #UpperMotorNeuron #LowerMotorNeuron #UMNvsLMN #Neuroanatomy #MotorNeuronSyndrome #Spasticity #BabinskiSign #InternalCapsule #PyramidalTract #BrownSequard #SpinalShock #ClinicalNeurology #MedicalEducation #PhysicianScientist #NeurologyLecture #BrainstemLocalization #Neuroscience #IntegratedNeurobiology #MotorPathways