Trunk nerves (intercostal, sympathetic, vagus nerve)
Posterior horn of the spinal cord (Cornu posterius)
Cornu posterius medullae spinalis
- Origin
- Dorsal extension of the grey matter along the whole length of the cord; it holds the relay neurons on which the sensory posterior root fibres end, among them the substantia gelatinosa
- Insertion
- Relays to the ascending tracts of the opposite side (spinothalamic tract) and to the anterior horn for the reflex arc
- Function
- First central relay for pain, temperature and crude touch; this is also where the gate control of pain input takes place
- Innervation
- Somatosensory and viscerosensory; receives the posterior roots from the spinal ganglion
- Movement & chain
- Processes incoming sensory signals
- Palpation
- Not palpable; assessed through dermatome by dermatome sensory testing (sharp and blunt, temperature, touch)
- Clinical
- Syringomyelia first interrupts the crossing pain and temperature fibres next to the posterior horn, giving a dissociated sensory loss in a cape distribution over shoulders and arms with touch preserved. Also herpes zoster and the posterior horn syndrome. The substantia gelatinosa is the target of the gate control theory that TENS is based on.
- Segmental innervation
- Along the whole length C1-Co1
- In clinical practice
- Mapping dermatomes in sensory loss, pain assessment and treatment including TENS, and recognising a dissociated sensory loss
- Region in the model
- Trunk nerves (intercostal, sympathetic, vagus nerve)