Dorsolateral tract of Lissauer and dorsal horn synapse (Rexed laminae I, II and V)
First-order neurone / UMN · segmental ipsilateral entry
A-delta and C central processes enter the dorsolateral tract of Lissauer, run up or down one to two segments, then synapse on second-order cells of the dorsal horn: the marginal zone (lamina I), substantia gelatinosa (lamina II, mainly interneurones) and nucleus proprius (lamina V). This synapse is the 'gate' modulated by descending brainstem pathways and by opioids.
Traced from the start
- Nociceptors and thermoreceptors (free nerve endings)
- Dorsolateral tract of Lissauer and dorsal horn synapse (Rexed laminae I, II and V)
Detail
- Fibres
- A-delta to laminae I and V; C fibres to lamina II
- Course
- Ascends one to two segments in Lissauer's tract before synapsing
- Second-order cell bodies
- Laminae I and V of the dorsal horn
- Transmitters
- Glutamate and substance P
When it goes wrong
Brown-Sequard hemisection
Ipsilateral band of loss of all sensation at the level of the lesion, because the entering root and dorsal horn are destroyed before any fibre has crossed
Herpes zoster (reactivation in the dorsal root ganglion)
Dermatomal burning pain preceding a unilateral vesicular rash, with post-herpetic neuralgia in the same dermatome
Dorsal root compression (radiculopathy from disc prolapse)
Dermatomal pain and paraesthesia with loss of the corresponding reflex (C5/6 biceps, C7 triceps, L3/4 knee, S1 ankle)
Practise this structure
1 question in the bank tagged Dermatomes.