Spinal Cord Tutorial

Question 1

Describe the pathway of the lateral corticospinal tract.

Answer 1

Motor information for the limbs originates in cortex, crosses over in the pyramids, and descends contralaterally in the lateral white matter
as part of the LCST.

Question 2

Describe the pathway of the anterior corticospinal tract.

Answer 2

Motor information for the axial musculature originates in cortex, (enters the pyramids but does not cross, and descends ipsilaterally in the ventral white matter as part of the ACST. Some fibres will then cross at the level in which they terminate.

Question 3

Describe the pathway of the gracile fasciculus.

Answer 3

Sensory information (fine touch, pressure) for the lower limbs originates in periphery, travels in through the dorsal root ganglia and into the
dorsal root to enter the spinal cord (without crossing), it ascends ipsilaterally in the gracile fasciculus where it crosses over in the caudal medulla becoming the medial lemniscus travelling up to the cortex

Question 4

Describe the pathway of the cuneate fasciculus.

Answer 4

Sensory information (fine touch, pressure) for the upper limbs originates in periphery, travels in through the dorsal root ganglia and into the
dorsal root to enter the spinal cord (for Thoracic spinal level T5/T6 and above) without crossing, it ascends ipsilaterally in the cuneate fasciculus where it crosses over in the caudal medulla becoming the medial lemniscus travelling up to the cortex

Question 5

Describe the pathway of the spinothalamic tract (anterolateral system).

Answer 5

Sensory information (pain, temperature) originates in periphery, travels through the dorsal root ganglia and into the spinal cord, ascends or
descends 1-2 levels in Lissauer’s tract (ipsilaterally) synapsing in the dorsal horn, and then crosses the midline in the anterior white commissure, where it ascends contralaterally in the spintothalamic tract up to the cortex. Most important point is the fact that it crosses in the cord!

Question 6

Describe the pathway of the posterior spinocerebellar tract.

Answer 6

Sensory information (proprioception - musculature) originates in periphery, travels through the dorsal root ganglia and into the spinal cord
without crossing, and ascends ipsilaterally in the dorsal column until it reaches Clarke’s nucleus (C8-L3) where it synapses and then ascends as the PSCT. All ipsilateral for this pathway, but remind them of the ASCT which is also ipsilateral but crosses 2X!

Question 7

Describe the main blood supply to the spinal cord.

Answer 7

• Posterior spinal arteries: From the vertebral arteries and the posterior inferior cerebellar arteries. These arteries are paired.
• Anterior spinal artery: From the vertebral arteries.
• Segmental arteries: From the vertebral arteries, cervical arteries, lumbar arteries
• Medullary arteries, can anastomose with anterior
  spinal artery.
• Artery of Adamkiewicz. Typically arises from a left posterior intercostal artery at the level of the 9th to 12th intercostal artery, which branches from the aorta, and supplies the lower two thirds of the spinal cord via the anterior spinal artery.

Question 8

Describe the rubrospinal tract, what information is carried and where the fibres cross the midline.

Answer 8

• Motor
• Activation of flexor muscles in the upper limbs and inhibition of extensors on the contralateral side.
  (If corticospinal tract interrupted (stroke) the rubrospinal influence on the upper limbs becomes apparent (contralateral (to side of stroke) flexed upper limb))
• Fibres cross in the midbrain

Question 9

Describe the recticulospinal tract, what information is carried and where the fibres cross the midline.

Answer 9

• Motor
• The two reticulospinal tracts have differing functions:
  The medial reticulospinal tract arises from the pons. It facilitates voluntary movements, and increases muscle tone AND
  The lateral reticulospinal tract arises from the medulla. It inhibits voluntary movements, and reduces muscle tone.
• Fibres do not cross midline

Question 10

Describe the vestibulospinal tract, what information is carried and where the fibres cross the midline.

Answer 10

• Motor What type of information is carried in this pathway?
• There are two vestibulospinal pathways; medial and lateral. They arise from the vestibular nuclei, which receive input from the organs of balance. The tracts convey this balance information to the spinal cord.
  Fibres in this pathway control balance and posture by innervating the ‘anti-gravity’ muscles (flexors of the arm, and extensors of the leg).
• Fibres do not cross midline

Question 11

Describe the tectospinal tract, what information is carried and where the fibres cross the midline.

Answer 11

• Motor
• This pathway begins at the superior colliculus of the midbrain. The superior colliculus is a structure that receives input from the optic tract. The neurones then quickly decussate, and enter the spinal cord. They terminate at the cervical levels of the spinal cord.
  The tectospinal tract coordinates movements of the head in relation to vision stimuli.
• Fibres cross in the midbrain

Question 12

Describe the cuneocerebellar tract, what information is carried and where the fibres cross the midline.

Answer 12

• Sensory
• Unconscious proprioception from upper limbs.
• Fibres do not cross midline

Question 13

Describe the anterior spinocerebellar tract, what information is carried and where the fibres cross the midline.

Answer 13

• Sensory
• Unconscious proprioception from lower limb and trunk.
• Fibres cross1st at the level of entry to spinal cord segment, cross to contralateral side. 2nd in the cerebellum, cross back to ipsilateral side of entry
  to spinal cord. Information from right side peripheries carried to right cerebellum.