Spinal Cord Column Function
Primary Functions
The posterior columns of the spinal cord transmit proprioception (position sense), vibration sense, and fine discriminative touch, while the lateral columns contain the corticospinal tracts (motor pathways) and the spinothalamic tracts (pain and temperature sensation). 1
Posterior Column Transmission
The posterior (dorsal) columns carry sensory information critical for:
- Proprioception and position sense - knowledge of limb and body position in space 2
- Vibration sense - detection of vibratory stimuli 2
- Fine discriminative touch - ability to distinguish between two closely spaced points and recognize texture 2
- Pressure sensation - deep pressure awareness 2
When the posterior columns are damaged, patients experience profound deficits in tactile discrimination, movement and position awareness, ataxia, and clumsiness in hand use, even though light touch may be preserved through alternative pathways 2. These deficits severely impact activities of daily living despite appearing subtle on routine examination 2.
Lateral Column Transmission
The lateral columns contain two major pathways:
Lateral Corticospinal Tracts
- Motor control - voluntary movement commands from motor cortex to spinal motoneurons 1
- Sensory modulation - the corticospinal tract also modulates sensory inputs at the spinal cord level through primary afferent depolarization 3
Lateral Spinothalamic Tracts
- Pain sensation - nociceptive information from the contralateral body 1, 4
- Temperature sensation - thermal stimuli from the contralateral body 1, 4
The spinothalamic fibers cross to the opposite side at the level they enter the spinal cord, then ascend in the contralateral lateral column 4. A lesion affecting the lateral spinothalamic tract therefore causes loss of pain and temperature sensation on the opposite side of the body below the lesion level 4.
Clinical Monitoring Applications
During thoracic aortic surgery, somatosensory evoked potentials (SSEPs) monitor the integrity of the lateral and posterior columns by recording cerebral responses to peripheral nerve stimulation 1. However, SSEP monitoring has limitations because it does not assess the anterior motor column, which is more vulnerable to ischemic injury 1. This explains why isolated anterior column injury can occur without SSEP changes 1.
Important Clinical Caveat
Combined lesions of both the posterior columns and spinothalamic pathways result in total loss of all tactile and pressure sensibility, whereas isolated lesions of either pathway alone cause only partial deficits 2. This demonstrates the complementary nature of these sensory pathways in maintaining overall somatosensory function.