Dorsal column

Dorsal column

Diagram of the spinal cord showing the dorsal column in blue.
Latin	Funiculus posterior
System	Nervous system

The dorsal column, also known as the posterior column, is a major sensory pathway of the central nervous system. It is located in the dorsal (posterior) part of the spinal cord and is responsible for transmitting fine touch, vibration, and proprioceptive information from the body to the brain.

Anatomy

The dorsal column is composed of two main tracts:

• The fasciculus gracilis, which carries sensory information from the lower half of the body.
• The fasciculus cuneatus, which carries sensory information from the upper half of the body.

These tracts are located in the dorsal part of the spinal cord and ascend ipsilaterally (on the same side) until they reach the medulla oblongata.

Function

The primary function of the dorsal column is to convey sensory information related to:

• Fine touch: The ability to discern the texture and shape of objects.
• Vibration: The sensation of oscillatory motion.
• Proprioception: The sense of the relative position of body parts and strength of effort being employed in movement.

These sensory modalities are crucial for tasks that require precise movements and coordination, such as writing or playing a musical instrument.

Pathway

The dorsal column pathway involves several key steps:

1. First-order neurons: Sensory receptors in the skin and joints send signals through the dorsal root ganglia into the spinal cord, where they enter the dorsal column. 2. Second-order neurons: These neurons are located in the nucleus gracilis and nucleus cuneatus of the medulla oblongata. Here, the first-order neurons synapse, and the second-order neurons cross over (decussate) to the opposite side of the brainstem. 3. Third-order neurons: The second-order neurons ascend to the thalamus, where they synapse with third-order neurons. These neurons then project to the somatosensory cortex of the brain, where the sensory information is processed and perceived.

Clinical Significance

Damage to the dorsal column can result in a loss of fine touch, vibration, and proprioceptive sensations. This can occur due to:

• Multiple sclerosis: A disease that can cause demyelination of the dorsal column fibers.
• Tabes dorsalis: A form of neurosyphilis that affects the dorsal columns.
• Trauma: Physical injury to the spinal cord.

Patients with dorsal column damage may experience difficulty with balance and coordination, especially when their eyes are closed, as they rely heavily on proprioceptive feedback.

Also see

• Spinal cord
• Somatosensory system
• Fasciculus gracilis
• Fasciculus cuneatus
• Medulla oblongata