Anterior (ventral) white commissure
Decussation · crosses 1-2 seg. above bilateral
Second-order axons from laminae I and V cross the midline obliquely, ventral to the central canal, over the one to two segments above their entry level, then turn upward in the contralateral anterolateral funiculus. Fibres from both sides cross in the same narrow band, so a central cord lesion cuts pain and temperature bilaterally at those segments while sparing the dorsal columns behind it.
Traced from the start
- Nociceptors and thermoreceptors (free nerve endings)
- Dorsolateral tract of Lissauer and dorsal horn synapse (Rexed laminae I, II and V)
- Anterior (ventral) white commissure
Detail
- Level
- One to two segments above the level of root entry
- Position
- Ventral to the central canal
- Fibres crossing
- Spinothalamic axons of both sides; anterior corticospinal fibres at their segmental level
When it goes wrong
Syringomyelia (central cavity, usually cervical, often with a Chiari I malformation)
Bilateral cape-like loss of pain and temperature over the shoulders and arms with preserved touch, vibration and proprioception (dissociated sensory loss); painless burns and hand injuries; later hand wasting and spastic legs as the syrinx expands into the anterior horns and lateral columns
Central cord syndrome after hyperextension neck injury in an older patient with cervical spondylosis
Bilateral segmental loss of pain and temperature at the injured levels plus arm-predominant weakness with sacral sparing
Practise this structure
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