Spinal Cord Tracts

Overview

• Spinal cord tracts are divided into ascending and descending tracts.
• White matter: Made up of these tracts, named for the whitish color of myelin around the axon.
• Grey matter: Located centrally, includes ventral and dorsal horns.

Ascending Pathways

• Function: Transport sensory information from the body to the brain.
• Color code: Blue

Dorsal Column (Posterior Column)

• Tracts: Fasciculus cuneatus and fasciculus gracilis
• Functions: Fine touch, tactile sensation, vibration, proprioception
• Locations:
  • Fasciculus gracilis: Medial, lower limb signals (below T6)
  • Fasciculus cuneatus: Lateral, upper limb signals (T6 and above)
• Characteristics: Run ipsilaterally through the spinal cord and decussate in the medulla.
• Clinical Note: Spinal cord injury leads to loss of ipsilateral fine touch, vibration, and proprioceptive sensation.

Anterolateral Pathways

• Tracts: Anterior and lateral spinothalamic
• Functions:
  • Anterior spinothalamic: Crude touch, pressure
  • Lateral spinothalamic: Pain, temperature
• Characteristics: Decussate within the spinal cord and travel up to the brain.
• Clinical Note: Spinal cord lesion results in contralateral loss of crude touch, pressure, pain, and temperature sensation.

Spinocerebellar Pathways

• Tracts: Anterior and posterior spinocerebellar, spinolivary
• Function: Carry unconscious proprioceptive information of the lower limbs to the cerebellum.
• Additional Pathways: Cuneocerebellar and rostral spinocerebellar (proprioceptive signals from upper limbs and neck to cerebellum)

Descending Pathways

• Function: Responsible for muscle movement.

Pyramidal Tracts

• Tracts: Anterior and lateral corticospinal
• Function: Carry signals for voluntary movement of the limbs.
• Characteristics: Lateral corticospinal tract is decussated, while anterior corticospinal tract fibers decussate at the spinal cord level they innervate.

Extrapyramidal Tracts

• Tracts:
  • Rubrospinal tract: Contralateral innervation for fine motor control.
  • Reticular spinal tracts:
    • Medial reticular spinal tract: Facilitates voluntary muscle contraction, increases muscle tone.
    • Lateral reticular spinal tract: Inhibits voluntary movement, reduces muscle tone, role in automatic breathing.
  • Vestibular spinal tract: Controls balance and posture.
  • Tectospinal tract: Coordinates head movements with vision.