Spinal segment: The part of spinal cord to which a pair of spinal nerves (right and left) is attached.
Cause of mismatch between spinal segments and vertebral level:
- The spinal cord lags in growth compared to the vertebral column after 3rd embryonic month
- Spinal cord is shorter (45 cm) compared to the vertebral column (65 cm)
- Spinal segments always lie above their numerically corresponding vertebral spines
General rule:
| Vertebral level | Add | Spinal segment |
| Cervical | + 0 | Same |
| C7-T1 | C8 | |
| T1-T3 | +1 | T1-T4 |
| T3-T6 | +2 | T5-T8 |
| T7-T8 | +3 | T9-T11 |
| T8-T9 | T12 | |
| T9-T11 | Lumbar | |
| T12-L1/2 | Sacral |
During clinical examination, when you get any sensory level, always consider this longitudinal discrepancy between cord level and vertebral level.
