Sensory Systems: Pain Pathways

Question 1

What is the lowest level that you will have an AWARENESS of pain?

Answer 1

THALAMUS

Question 2

Describe the Direct Spinothalamic Pathway.

Answer 2

Sharp, pricking and highly localized pain (PRECISE PAIN)

“Fast-Pain”

Neospinothalamic System

*** Enter in the DORSAL ROOT via the LATERAL PORTION!!!

ASCEND and DESCEND in the Dorsolateral Fasciculus of Lissaur

Primary Neuron Ascends or Descends 2 segments then terminates on Substantia Gelatinosa

Secondary Neuron will decussate in the ANTERIOR WHITE COMMISSURE and will ascend as the Lateral Spinothalamic Tract; Joins up with the VENTRAL SPINOTHALAMIC TRACT in the medulla to form the Spinal Lemniscus; Terminates in the Ventral Posterior Lateral Nucleus

Tertiary Neuron: Leave the VPL as THALAMIC RADIATIONS and will terminate in the Postcentral Gyrus (Primary Somesthetic Cortex)

Question 3

Describe the Indirect Spinothalamic Pathway.

Answer 3

Bruning pain and deep, dull, aching, diffuse pain (CRUDE PAIN)

“Slow Pain” Pathway (Type C fibers)

Paleospinothalamic Pathway

Primary Neurons will terminate in the Nucleus Proprius

Secondary Neurons will course BILATERALLY through the spinal cord to the thalamus as Spinoreticular Fibers (located in the anterior, lateral and posterior regions of the fasciculus proprius); Terminate in the midline reticular formation of the brainstem

Question 4

What is meant by “Somatotropic Lamination” of the Lateral Spinothalamic Tract?

Answer 4

Sacral levels enter the tract first and are located in the posterolateral aspect of the tract.

Cervical levels enter the tract last and are located in the anteromedial aspect of the tract.

Question 5

Describe the various lesions associated with the Direct Spinothalamic Pathway:

1. Unilateral lesions of the spinal lemniscus
2. Unilateral Lesions of the lateral spinothalamic tract

Answer 5

1. Unilateral lesions of the spinal lemniscus - result in a contralateral hemianalgesia and thermal hemianesthesia (BRAINSTEM)

2. Unilateral Lesions of the lateral spinothalamic tract - result in a contralateral loss of pain and temperature sensation two sensory dermatomal segments below the level of the lesion (i.e. if the lesion is at T6 on the Left Side, you will lose pain and temperature sensations at T8 on the Right side)(SPINAL CORD)

Question 6

Answer 6

1. A
2. C
3. A
4. B
5. A

Question 7

Describe how a lesion with the Indirect Spinothalamic Pathway will present:

1. Unilateral lesion of the Spinoreticular Fibers

Why is this pathway Clinically Significant?

Answer 7

Do not result in significant sensory deficits. The indirect spino-reticulo-thalamic pathway is too bilateral and diffuse to be affected by unilateral lesions. This is part of the neuroanatomical basis of persistent or intractable pain. Bilateral lesions such as spinal cord transections may eliminate crude pain sensations along with other sensations as well.

*** Very difficult to get rid of the Dull-Aching pain!

*** Pathway that you check with the Gloscow Coma Scale!