Sensory Spinal Cord Tracts
Sensory Spinal Cord Tracts
Overview
- Focus on sensory spinal cord tracts.
- Important guiding question: How do the various sensory tracks in the spinal cord influence our functional abilities?
- There are seven ascending spinal tracts that carry sensory information to various destinations:
- Brainstem
- Thalamus
- Cerebellum
- Cortex
Seven Ascending Sensory Tracks
Dorsal Column / Medial Lemniscus / Posterior Column
- Different names refer to the same tract.
- Carries sensory information related to:
- Touch
- Pressure
- Vibration
- Proprioception
- Kinesthesia
- Crosses over at the medulla before traveling to the primary sensory cortex located in the postcentral gyrus.
- Injury consequences:
- Complete spinal cord injury (entire dorsal column on both sides):
- Results in bilateral sensory loss of touch, pressure, vibration, proprioception, and kinesthesia below the injury level.
- Unilateral injury (one side of the cord):
- Ipsilateral sensory loss (same side) if below medulla;
- Contralateral sensory loss (opposite side) if at the medulla.
Lateral Spinothalamic Tract
- Carries pain and temperature information to the primary sensory cortex.
- Crosses over immediately upon entering the spinal cord.
- Injury consequences:
- Complete spinal cord injury: Bilateral loss of pain and temperature function below the injury.
- Unilateral cord injury:
- At the level of injury: Bilateral loss;
- Below the injury: Contralateral loss.
- Also, if damage is at the brainstem or cortex: contralateral loss occurs.
Anterior Spinothalamic Tract
- Carries crude touch and light touch information to the primary sensory cortex.
- Also believed to support pain and temperature processing, offering redundancy in pathways with the lateral spinothalamic tract.
- Crosses over immediately.
- Injury consequences:
- Complete spinal cord injury: Bilateral loss of crude and light touch below the injury level.
- Unilateral injury:
- At the level of injury: Bilateral loss;
- Below the injury: Contralateral loss.
Posterior Spinocerebellar Tract
- Carries unconscious sensory information, mainly proprioception from the legs to the cerebellum.
- Involves sensory information from:
- Muscle spindles
- Golgi tendon organs
- Joint receptors
- Remains ipsilateral throughout its path.
- Injury consequences:
- Causes incoordination or ataxia of the trunk and legs.
Anterior Spinocerebellar Tract
- Carries proprioceptive information from lower extremities to the cerebellum, similar to the posterior spinocerebellar tract.
- Involves sensory receptors:
- Golgi tendon organs
- Muscle spindles
- Joint receptors
- Crosses over immediately upon entering the spinal cord but most fibers cross back just before entering the cerebellum.
- Injury consequences:
- Complete spinal cord injury: Bilateral loss of lower extremity proprioception.
- Unilateral cord injury:
- At the level of injury: Bilateral proprioceptive loss;
- Below the injury: Contralateral proprioceptive loss.
- Ipsilateral proprioceptive loss occurs if damage is to the cerebellum.
Cuneocerebellar Tract and Rostral Spinocerebellar Tract
- Both carry proprioceptive information from the trunk and upper extremities to the cerebellum.
- Involves sensory information:
- Muscle receptors
- Special sensory receptors in muscles and joints
- These are ipsilateral tracts that do not cross over.
- Injury consequences:
- Complete injury: Bilateral proprioceptive loss;
- Unilateral injury: Ipsilateral proprioceptive loss.
- While there are slight differences in origin and nuclei in the gray matter, the two tracts largely run together.
Functional Implications
- There are two tracts for proprioceptive information from the lower extremities (posterior and anterior spinocerebellar tracts) and two tracts for information from the trunk and upper extremities (cuneocerebellar and rostral spinocerebellar tracts).
- Redundancy in pathways means if one tract in a pair is lost, the other still carries essential proprioceptive information. Full loss occurs only if both tracts are damaged in a set, highlighting the functional importance of these structures for clients.
Summary
- Three sensory tracks carry information to the primary sensory cortex:
- Dorsal column: Touch, pressure, vibration, kinesthesia
- Lateral spinothalamic tract: Pain, temperature
- Anterior spinothalamic tract: Crude touch, light touch
- Four tracts carry proprioceptive information to the cerebellum:
- Posterior spinocerebellar tract: Legs
- Anterior spinocerebellar tract: Lower extremities
- Cuneocerebellar tract: Upper extremities
- Rostral spinocerebellar tract: Trunk