Ascending Spinal Cord Pathways
Ascending Spinal Cord Pathways
Summary
Anatomy
Posterior Column Pathway
- Fiber size: large
- Function: carry proprioceptive sensation (sense of position) – vibration, two-point discrimination, and joint position information
- Course: ascends the spinal cord ipsilateral to their side of the origin
- Cuneate fasciculus carries sensory information from the upper body (from T6 and above)
- Gracile fasciculus carries sensory information form the lower body (from T6 and below)
Clinical Correlation: Subacute Combined Degeneration
Anterolateral system (aka spinothalamic tract)
- Fiber size: small
- Function: carry pain, temperature, and itch sensation
- Course: ascends the spinal cord contralateral to their side of origin
- Inner fibers: arms
- Outer fibers: leg
- Generally, the lateral regions of the anterolateral system subserve pain and temperature and the anterior regions subserve tactile and pressure sensation.
Spinocerebellar pathways
- Fiber size: large
- Function: carry joint proprioception to the cerebellum for coordination
- Posterior and anterior sections
Pathways
Dorsal Root Ganglia
- Cell bodies lie within the dorsal root ganglia.
- Each cell body contains a short axon.
Anterolateral system
- Passes peripherally and centrally to join the motor root toward the spinal cord
- Lissauer's tract: entry zone for fibers along the dorsal edge of the dorsal horn
- Ventral commissure: fibers cross midline between the anterior horns of the spinal cord
Posterior column pathway
- Directly ascends the spinal cord within the ipsilateral posterior column
- Posterior median septum separates the bilateral sides of the posterior column
- The posterior intermediate septum separates ipsilateral fasciculi
Clinical Correlation
- A cervical syringomyelia occurs when a fluid-filled cavity (a syrinx) expands outward and encroaches upon the anterolateral system, which affects the inner (arm) fibers prior to the outer (leg) fibers as well as affecting the crossing fibers at that level.