Medial lemniscus
The medial lemniscus, also known as Reil's band or Reil's ribbon, is a large ascending bundle of heavily myelinated axons that decussate in the brainstem, specifically in the medulla oblongata. The medial lemniscus is formed by the crossings of the internal arcuate fibers. The internal arcuate fibers are composed of axons of the gracile nucleus and the cuneate nucleus. The cell bodies of the nuclei lie contralaterally.
The medial lemniscus is part of the somatosensory dorsal column–medial lemniscus pathway, which ascends in the spinal cord to the thalamus. Lesions of the medial lemniscus cause an impairment of vibratory and touch-pressure sense.
Etymology
Lemniscus means "ribbon", reflecting the elongated tract of the medial lemniscus.Anatomy
Path
After neurons carrying somatosensory proprioceptive or fine touch information synapse at the gracile and cuneate nuclei, axons from second-order neurons decussate at the level of the medulla and travel up the brainstem as the medial lemniscus on the contralateral side. It is part of the posterior column-medial lemniscus pathway, which transmits touch, vibration sense, as well as the pathway for proprioception.The medial lemniscus carries axons from most of the body and terminates by synapsing with third-order neurons in the ventral posterolateral nucleus of the thalamus. at the level of the mamillary bodies. Sensory axons transmitting information from the head and neck via the trigeminal nerve synapse at the ventral posteromedial nucleus of the thalamus.