Overview Snapshot A 26-year-old male presents with lower back pain that radiates down the side of his right leg and into his right foot. The pain started after he was recently lifting furniture into his new home. On physical exam, there is notable weakness on dorsiflexion of the foot and extension of the toe. Sensory loss is noted between the first and second digit of the foot. Knee and ankle reflexes are normal. There is no saddle anesthesia, and anal wink is appreciated. When raising the extended leg while in the supine position, pain radiates from the lower back, down the leg, and into the foot. (L5 radiculopathy due to disc herniation) Introduction Spinal nerves 31 pairs 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal vertebral exit C1-C7 exit via intervertebral foramina above corresponding vertebra all other nerves exit via intervertebral foramina below corresponding vertebra Spinal cord termination adults spinal cord ends at L1-L2 login to view 1 more bullet subarachnoid space extends to lower border of S2 see Lumbar puncture topic Pathology vertebral disk herniation nucleus pulposus herniates posteriolaterally through annulus fibrosis most commonly occurs between L5 and S1 cauda equina affects S2-S5 nerve roots spinal cord syndromes anterior cord syndrome login to view 1 more bullet Spinal Cord Pathways Sensory pathways dorsal columns function login to view 1 more bullet subdivisions login to view 4 more bullets pathway login to view 6 more bullets Spinothalamic tract function login to view 1 more bullet pathway login to view 6 more bullets Motor pathways lateral corticospinal tract function login to view 1 more bullet pathway login to view 4 more bullets anterior spinal artery strokes leads to login to view 2 more bullets