Medial lemniscus
Second-order tract · contralateral vibration proprioception
The crossed second-order dorsal column axons ascend as a compact bundle through the medulla (dorsal to the pyramid, beside the midline), pons and midbrain to the ventral posterolateral nucleus of the thalamus. It carries fine touch, vibration and conscious proprioception from the contralateral body.
Traced from the start
- Cutaneous mechanoreceptors (Meissner, Pacinian, Merkel, Ruffini)Proprioceptors (muscle spindle, Golgi tendon organ, joint receptors)
- Fasciculus gracilis (medial dorsal column)Fasciculus cuneatus (lateral dorsal column)
- Nucleus gracilis and cuneatus to internal arcuate fibres (sensory decussation, caudal medulla)
- Medial lemniscus
Detail
- Modalities
- Fine touch, vibration, proprioception of the contralateral body
- Course
- Paramedian medulla, then pons and midbrain, to VPL thalamus
- Companions
- Joined by the spinothalamic (spinal lemniscus) and trigeminal lemniscus in the pons
When it goes wrong
Medial medullary syndrome (paramedian branches of the vertebral or anterior spinal artery)
Contralateral loss of vibration and joint position sense with contralateral hemiparesis and ipsilateral tongue deviation; pain and temperature are spared because the spinothalamic tract lies laterally
Practise this structure
1 question in the bank tagged Brainstem.