Spinal Cord Pathways

Summary

This video simplifies the understanding of key spinal cord pathways necessary for board exams. It covers the posterior column, corticospinal tract, and lateral spinothalamic tract, explaining their functions, clinical manifestations, and testing methods. The presenter uses engaging mnemonics like 'Some Doctors Think Politically' for the posterior column and 'Lower Segment Three' for the lateral spinothalamic tract to aid memorization. The video also introduces the concept of Brown-Séquard syndrome, illustrating how injuries to different spinal cord pathways result in distinct symptoms. Overall, it provides a high-yield, simplified approach to understanding complex spinal cord pathways for exams.

Takeaways

• 😀 The lecture emphasizes high-yield spinal cord pathways relevant for board exams, focusing on three main tracts: the posterior column, corticospinal tract, and lateral spinothalamic tract.
• 😀 The posterior column is responsible for discriminative touch and proprioception, with three synapses: sensory neuron, dorsal column, and thalamus to the primary sensory cortex.
• 😀 A mnemonic for the posterior column pathway is 'Some Doctors Think Politically' (SDTP), linking each step to a key function of the pathway.
• 😀 The corticospinal tract controls movement through upper motor neurons, descending from the motor cortex and splitting at the medullary pyramids into anterior and lateral corticospinal tracts.
• 😀 A mnemonic for the corticospinal tract is 'PPLM' (Primary motor, Pyramids, Lateral corticospinal, Movement) to remember its components and functions.
• 😀 The lateral spinothalamic tract handles pain and temperature sensation and manifests symptoms 2-3 segments below the level of injury on the contralateral side.
• 😀 For the lateral spinothalamic tract, a mnemonic 'Lower Segment Three' (LST) helps remember that the pain and temperature sensation deficit appears two to three segments below the injury.
• 😀 The lecture covers the concept of Brown-Séquard syndrome, explaining how a hemisection of the spinal cord leads to a mix of sensory and motor deficits, with distinct effects on each pathway.
• 😀 In Brown-Séquard syndrome, damage to the corticospinal tract and posterior column results in deficits on the same side as the injury, while the lateral spinothalamic tract affects the opposite side below the injury.
• 😀 The key to understanding Brown-Séquard syndrome is knowing the differences in how each pathway affects the body: posterior column (same side), corticospinal tract (same side), and lateral spinothalamic tract (opposite side, 2-3 segments down).

Q & A

What are the three main spinal cord pathways discussed in the video?

The three main spinal cord pathways discussed are the posterior column (for discriminative touch and proprioception), the corticospinal tract (for upper motor neurons and movement control), and the lateral spinothalamic tract (for pain and temperature sensation).

What mnemonic is suggested to remember the posterior column pathway?

The mnemonic for the posterior column pathway is 'Some Doctors Think Politically' (SDTP), where 'S' stands for sensory neuron, 'D' for dorsal column, 'T' for thalamus, and 'P' for primary sensory cortex.

Why is the posterior column pathway important to understand for the USMLE and COMLEX exams?

The posterior column pathway is important because it controls discriminative touch and proprioception, which are often tested in clinical scenarios on the USMLE and COMLEX exams.

What does the corticospinal tract control, and how does it function?

The corticospinal tract controls voluntary motor functions, specifically upper motor neurons that descend from the motor cortex to the muscles. It splits into the anterior and lateral corticospinal tracts, with the lateral tract being the primary one involved in movement control.

What mnemonic helps remember the corticospinal tract pathway?

The mnemonic for the corticospinal tract is 'Prickly Plants Lack Moisture' (PPLM), where 'P' stands for primary motor cortex, 'P' for pyramids (medullary pyramids), 'L' for lateral corticospinal tract, and 'M' for movement.

What happens when there is a lesion in the corticospinal tract?

A lesion in the corticospinal tract results in upper motor neuron signs, such as weakness, hyperreflexia, and spasticity, below the level of the injury.

How is the lateral spinothalamic tract different from the other pathways in terms of lesion effects?

Unlike the posterior column and corticospinal tract, a lesion in the lateral spinothalamic tract causes pain and temperature sensation loss on the contralateral side, 2-3 segments below the level of the injury.

What is Brown-Séquard syndrome and how does it relate to the discussed pathways?

Brown-Séquard syndrome occurs when one half of the spinal cord is damaged. It affects all three discussed pathways, leading to ipsilateral motor deficits (from the corticospinal tract), loss of discriminative touch (from the posterior column), and contralateral pain and temperature loss (from the lateral spinothalamic tract).

Why is it important to understand how the spinal cord pathways affect sensory and motor functions in clinical exams?

Understanding these pathways is crucial because injuries to different pathways result in distinct clinical symptoms, which are frequently tested on exams like the USMLE and COMLEX to assess a student's ability to diagnose and understand neurological conditions.

How do you remember the difference between the effects of posterior column and lateral spinothalamic tract lesions?

For posterior column lesions, symptoms occur on the same side at the level of the injury or below. For lateral spinothalamic tract lesions, symptoms occur 2-3 segments below the injury and on the opposite side, which can be remembered with the mnemonic 'Lower Segment Three' (LST).