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Posterior View of Cervical Spinal Cord In Situ

Surgical Correlation

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Posterior view of cervical spinal cord in situ. Laminectomy of cervical vertebrae provides in situ view of the spinal cord and canal. Posterior (dorsal) roots of cervical spinal nerves emerge from the dorsolateral segments of the cervical cord. Distally, the cell bodies of these sensory neurons are contained within dorsal root (spinal) ganglia near intervertebral foramina. At any give cord level (represented here by the C1 spinal nerve), dorsal and ventral roots exit the dural sac and unite to form very short, definitive spinal nerves (mixed nerves). These nerves exit the intervertebral foramen and divide into smaller diameter posterior (dorsal) primary rami that supply deep back muscles and a limited area of skin posteriorly, and larger diameter anterior (ventral) primary rami that supply motor innervation to body wall and limb musculature and remaining skin dermatomes. There are seven cervical vertebrae but eight pairs of cervical spinal nerves. The first cervical nerve emerges between the skull and the posterior arch of the first cervical vertebra (atlas). The remaining cervical nerves leave the vertebral canal above their corresponding vertebral level (e.g., C2 spinal nerves emerge above the C2 vertebra [axis], between the atlas and the axis). Along the lateral border of the spinal cord between dorsal and ventral roots, are longitudinal white glistening structures, the denticulate ligaments. These attach as tooth-like focal adhesions to the spinal dura to stabilize the cord within the dural sac. These ligaments represent consolidations of pia mater. The dorsal columns of the spinal cord convey somatosensory information from the body below the neck. In the cervical cord here, they are comprised of two separate tracts: the gracile and cuneate fasciculi. The gracile fasciculi represent the medial portion of the dorsal columns and carry somatosensory input from the lower trunk (T7 and below) and lower body. The cuneate fasciculi are located lateral to the gracile fasciculi and convey sensory input for the upper trunk (above T7), arms, and neck. The posterior portion of the spinal cord is drained by the median posterior spinal vein located in or near the posterior median fissure of the cord and situated in the pia mater. (Image courtesy of AL Rhoton, Jr.)

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