Spinal Cord Ascending Tracts: Clinical Significance

• File name: Spinal Cord 9+10
• Topic: Neuroanatomy Modified
• Written by Ghina Hammouri
• Edited by Lana Abdullah
• Doctor, Mohamed AlSalem

Clinical Significance of Lamination of Ascending Tracts

• External pressure on the spinal cord in the spinothalamic tracts region causes a loss of pain and temperature sensations in the sacral dermatome initially.
• Increased pressure leads to the affection of higher segmental dermatomes.
• Cervical to sacral segments are located medial to lateral in spinothalamic tracts.

Intramedullary vs Extramedullary

• Intramedullary tumors affect cervical fibers, which are located medially.
• Extramedullary tumors affect lower limb fibers, located laterally.
• Sacral sparing occurs at intramedullary tumors where the sacral part is not affected in infra-medullary tumors.

Destruction of Lateral Spinothalamic Tract (LSTT)

• Results in the loss of pain and thermal sensation on the contralateral side
• Occurs below the level of the lesion

Destruction of Fasciculus Gracilis and Cuneatus

• Causes loss of muscle joint sense, position sense, vibration sense, and tactile discrimination on the same side
• Occurs below the level of the lesion
• Lesions localized to one sensory tract are rare due to anatomical overlap and broad lesion patterns.

Arterial Blood Supply to the Brain

• Supplied by pairs of internal carotid and vertebral arteries.
• The four arteries lie within the subarachnoid space.
• Their branches anastomose on the inferior surface of the brain to form the circle of Willis.
  • The internal carotid artery enters skull via the carotid canal and foramen lacerum.
  • The vertebral artery enters the skull via foramen magnum.
  • The basilar artery forms at the lower part of medulla from union of right and left vertebral arteries
  • Vertebral artery originates from the first part of the subclavian artery.

Blood Supply of the Spinal Cord

• Longitudinal arteries extend the length of the spinal cord.
• One anterior spinal artery arises from the vertebral arteries in the anterior median fissure.
• Two posterior spinal arteries arise from the posterior inferior cerebellar artery in the posterolateral sulcus.
• Segmental spinal arteries (vertebral, deep cervical, posterior intercostal, and lumbar) arise from the vertebral arteries, and deep cervical arteries in the neck.

Branches of the Spinal Cord

• Anterior and posterior radicular arteries.
• Segmental medullary arteries.
• The artery of Adamkiewicz reinforces the arterial supply to the lower spinal cord, usually on the left side.
• It originates from the left posterior intercostal artery at the level of the 9th to 12th intercostal artery
• Branches from the aorta and supplies the lower two-thirds of the spinal cord
• Anastomoses with the anterior spinal artery.
• Upper spinal cord is supplied directly by longitudinal arteries that originate above, but these are insufficient for the lower spinal cord, which relies on segmental medullary arteries like the artery of Adamkiewicz
• Anterior spinal artery supplies primarily gray matter.

Central Cord Syndrome

• Results from hyperextension of the neck.
• Occludes blood supply to the cord via the anterior spinal artery.
• Causes bilateral weakness of the extremities.
  • Affects the upper extremities more than the lower extremities
• Involves pain and thermal sensation loss, and bladder dysfunction In upper extremities, more is affected because the spinal artery supplies the upper segments as it comes from the upper part of the cord, and there is secondary reinforcement with the artery of Adamkiewicz.

Compromise of Blood Flow

• Occurs in the posterior spinal artery
• Ipsilateral reduction or loss of discriminative, positional, and vibratory tactile sensations happens at and below the segmental level of the injury