Trunk nerves (intercostal, sympathetic, vagus nerve)
Spinal cord (Medulla spinalis)
Medulla spinalis
- Origin
- Continues the medulla oblongata from the foramen magnum, at the level of the upper border of the atlas
- Insertion
- Ends in the adult as the conus medullaris at vertebral level L1-L2; below that only the filum terminale and the cauda equina continue within the dural sac
- Function
- Carries the motor tracts from the brain to trunk and limbs (corticospinal tract) and the sensory tracts back (dorsal columns for touch, vibration and proprioception; spinothalamic tract for pain and temperature), and closes segmental reflexes on its own, without the brain
- Innervation
- Central nervous system itself; gives off 31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal) through the anterior and posterior roots
- Movement & chain
- Moves within the vertebral canal during flexion and extension of the spine and is stretched by several millimetres in flexion
- Palpation
- Not palpable; it lies inside the vertebral canal. Assessed clinically through reflexes, muscle strength, a sensory level on the trunk and imaging (MRI)
- Clinical
- Spinal cord injury (complete or incomplete, with a sensory level; above T1 the arms are affected too, above C4 the diaphragm and therefore breathing), cervical myelopathy in canal stenosis (spastic paresis, gait disturbance, Babinski sign), Brown-Sequard syndrome after a hemisection (ipsilateral loss of power and proprioception, contralateral loss of pain and temperature), syringomyelia, and spinal shock in the first phase after acute trauma. The cord ending at L1-L2 is exactly why a lumbar puncture is performed safely below that level.
- Segmental innervation
- 31 segments: C1-C8, T1-T12, L1-L5, S1-S5 and Co1
- In clinical practice
- Monitoring the neurological level after trauma or surgery (ASIA classification), spinal immobilisation until injury is excluded, bladder and bowel care and pressure ulcer prevention in spinal cord injury, and recognising autonomic dysreflexia in lesions above T6
- Region in the model
- Trunk nerves (intercostal, sympathetic, vagus nerve)