Medial lemniscus

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Medial lemniscus
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The sensory tract. (Medial lemniscus labeled at center right.)
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Coronal section through mid-brain. ("e" is Portion of medial lemniscus, which runs to the lentiform nucleus and insula. "a’" is also the medial lemniscus.)
Details
Latin lemniscus medialis
Identifiers
Gray's p.803
NeuroNames ancil-736
NeuroLex ID Medial lemniscus
Dorlands
/Elsevier
l_06/12483115
TA A14.1.04.111
A14.1.08.672
FMA FMA:83675
Anatomical terms of neuroanatomy

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 brain stem, specifically in the medulla. The medial lemniscus is formed by the crossings of internal arcuate fibers. The internal arcuate fibers are composed of axons of nucleus gracilis and nucleus cuneatus. The axons of the nucleus gracilis and nucleus cuneatus in the medial lemniscus have cell bodies that lie in the contralaterally.

Lesion of the medial lemnisci causes an impairment of vibratory and touch-pressure sense.

The medial lemniscus is part of the medial lemniscus pathway, which ascends from the skin to the thalamus.[1]


Path[edit]

After neurons carrying proprioceptive or touch information synapse at the gracile and cuneate nuclei, axons from secondary neurons decussate at the level of the medulla and travel up the brainstem as the medial lemniscus on the contralateral (opposite) side. It is part of the posterior column-medial lemniscus system, which transmits touch, vibration sense, as well as the pathway for proprioception.

The medial lemniscus carries axons from most of the body and synapses 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.

Location of the medial lemniscus through the brainstem[edit]

  • The cuneate and gracile nuclei reside at the closed (lower) medulla, so the lemniscus isn't formed at this level. Fibres from these nuclei will pass to the contralateral side of the brainstem, as the internal arcuate fibres.
  • At the open medulla (further up the brainstem), the medial lemniscus contains axons from the trigeminal nerve (which supplies the head region), as well as the arms and legs. It sits very close to the midline, at the same orientation of the midline, with head fibres more dorsal (closer to the back), towards the fourth ventricle.
  • By mid-pons, the medial lemniscus has rotated. Fibres from the head are medial, fibres from the leg are lateral.
  • The orientation in the midbrain is similar to that in the pons.

See also[edit]

Additional images[edit]

References[edit]

  1. ^ Kamali A, Kramer LA, Butler IJ, Hasan KM. Diffusion tensor tractography of the somatosensory system in the human brainstem: initial findings using high isotropic spatial resolution at 3.0 T. Eur Radiol. 2009 19:1480-8. doi: 10.1007/s00330-009-1305-x.

External links[edit]