Spinal Lemniscus: Ascending Sensory Pathways in the Brainstem

The spinal lemniscus is the collective term for the ascending sensory tracts in the lateral brainstem that convey somatic sensation from the spinal cord to the thalamus. It comprises two main components:

Medial Lemniscus

• Carries: fine touch, vibration, proprioception, two-point discrimination.
• Origin: dorsal column nuclei (gracile, cuneate) → decussate → ascend contralaterally.
• Termination: VPL nucleus of thalamus.

Lateral Lemniscus

• Carries: pain, temperature, crude touch.
• Origin: spinothalamic tract → ascends in anterolateral spinal cord → joins lateral lemniscus.
• Termination: VPM nucleus of thalamus.

Both cross the midline; thus, lesions above the decussation cause contralateral sensory loss. The term "spinal lemniscus" emphasizes their spinal origin and parallel brainstem course.