Spinal Cord Mnemonics (Memorable Neurology Lecture 8)

Summary

This video provides an in-depth exploration of the spinal cord, focusing on its anatomy, sensory and motor pathways, and various spinal cord injuries. It covers the organization of the spinal cord, distinguishing between protopathic and epicritic neurons, as well as the dorsal column medial lemniscus and spinothalamic pathways. The video also explains motor pathways, primarily the corticospinal tract. The content extends to understanding common spinal cord injuries, including complete and incomplete injuries, Brown-Séquard syndrome, and cauda equina syndrome. The explanation is paired with mnemonics to help viewers remember key anatomical and physiological concepts.

Takeaways

• 😀 The spinal cord is divided into three regions: cervical (neck), thoracic (chest), and lumbar (abdomen), with the conus medullaris marking the tapered end.
• 😀 Even after the spinal cord ends, nerves continue to run downwards in the cauda equina, a cluster of nerves resembling a horse's tail.
• 😀 Sensory pathways are categorized into protopathic (crude touch, temperature, pain) and epicritic (fine touch, vibration, proprioception) neurons.
• 😀 The dorsal column carries epicritic neurons, with information from the lower body traveling medially in the gracile fasciculus and from the upper body laterally in the cuneate fasciculus.
• 😀 The spinothalamic tract carries protopathic neurons and involves an immediate crossover of sensory neurons in the spinal cord after they enter via the posterior lateral tract.
• 😀 The corticospinal tract is the main motor pathway, consisting of the lateral and anterior corticospinal tracts, responsible for voluntary motor function.
• 😀 Motor neurons in the corticospinal tract cross over in the medulla and travel in the spinal cord to synapse with motor neurons in the anterior horn, which then signal the muscles.
• 😀 A complete spinal injury results in the loss of all sensory and motor functions below the injury, while an incomplete injury affects only specific functions.
• 😀 An anterior cord injury causes loss of motor function and crude touch, temperature, and pain sensation, but preserves fine touch and proprioception.
• 😀 Cauda equina syndrome leads to deficits in the pelvic region, including loss of bladder and bowel control, muscle paralysis, and saddle anesthesia.
• 😀 Mnemonics like 'flexing involves pyramids' and 'list some proper avenues for sending temperature and pain' can help remember the pathways of the corticospinal and spinothalamic tracts.

Q & A

What are the three main regions of the spinal cord?

The spinal cord is traditionally divided into three regions: the cervical spinal cord (in the neck), the thoracic spinal cord (in the chest), and the lumbar spinal cord (in the abdomen).

What is the conus medullaris?

The conus medullaris is a tapered region at the end of the spinal cord, where the spinal cord begins to thin. It ends around the first or second lumbar vertebrae.

What is the cauda equina and why is it named that?

The cauda equina is a cluster of nerves that continue to run downwards after the spinal cord ends. It is named after the Latin term 'horse's tail' because of its appearance.

What is the difference between protopathic and epicritic neurons?

Protopathic neurons carry crude touch, temperature, and pain sensations and are less sensitive. Epicritic neurons carry fine touch, vibration, and proprioception and can provide detailed information about touch, including the sense of two distinct touch points.

How do epicritic neurons travel through the spinal cord?

Epicritic neurons travel in the dorsal column of the spinal cord, which is split into the gracile fasciculus (for lower body) and the cuneate fasciculus (for upper body). They cross over at the medulla and continue to the thalamus and somatosensory cortex.

What is the spinothalamic tract responsible for?

The spinothalamic tract carries sensory information related to crude touch, temperature, and pain. These neurons cross over immediately after entering the spinal cord and travel upwards to the thalamus and then to the parietal lobe.

What is the role of the corticospinal tract in motor function?

The corticospinal tract is responsible for carrying motor signals from the brain to the muscles. It is divided into the lateral corticospinal tract (which controls voluntary movement) and the anterior corticospinal tract. The lateral tract is the larger of the two and affects the majority of motor functions.

What is Brown-Séquard syndrome?

Brown-Séquard syndrome occurs when one half of the spinal cord is injured. This leads to motor function and fine touch sensations being affected on the same side as the lesion, while crude touch, temperature, and pain are lost on the opposite side.

What happens during an anterior cord injury?

An anterior cord injury leads to a loss of motor function as well as crude touch, temperature, and pain sensation below the level of the injury. However, fine touch, pressure, and proprioception remain intact because the epicritic neurons travel in the dorsal columns.

What is cauda equina syndrome?

Cauda equina syndrome is a condition where injury to the cluster of nerves at the end of the spinal cord causes deficits in motor and sensory functions in the pelvic region, including loss of bowel and bladder control, muscle paralysis, and numbness around the perineum.