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The sacral spinal nerve 1 (S1) is a spinal nerve of the sacral segment. [1] It originates from the spinal column from below the 1st body of the sacrum.
For epidural anesthesia an anesthetic agent is injected into the space just outside the thecal sac and diffuses through the dura to the nerve roots where they exit the thecal sac. [ 4 ] [ 5 ] For spinal anaesthesia in general, an injection can be given intrathecally into the subarachnoid space, or into the spinal canal .
After the conus medullaris (near lumbar vertebral levels 1 (L1) and 2 (L2), occasionally lower), the spinal canal contains a bundle of nerve fibers (the cauda equina or "horse-tail") that branches off the lower end of the spinal cord and contains the nerve roots from L1–L5 and S1–S5. The nerve roots from L4–S4 join in the sacral plexus ...
The sciatic nerve comprises nerve roots L4, L5, S1, S2, and S3 in the spine. [26] These nerve roots merge in the pelvic cavity to form the sacral plexus and the sciatic nerve branches from that. Sciatica symptoms can occur when there is pathology anywhere along the course of these nerves. [27]
The thoracic, lumbar, and sacral nerves are then numbered by the vertebra above. In the case of a lumbarized S1 vertebra (also known as L6) or a sacralized L5 vertebra, the nerves are typically still counted to L5 and the next nerve is S1. Scheme showing structure of a typical spinal nerve 1. Somatic efferent. 2. Somatic afferent. 3,4,5.
In humans myotome testing can be an integral part of neurological examination as each nerve root coming from the spinal cord supplies a specific group of muscles. Testing of myotomes, in the form of isometric resisted muscle testing, provides the clinician with information about the level in the spine where a lesion may be present. [7]
A nerve root (Latin: radix nervi) is the initial segment of a nerve leaving the central nervous system.Nerve roots can be classified as: Cranial nerve roots: the initial or proximal segment of one of the twelve pairs of cranial nerves leaving the central nervous system from the brain stem or the highest levels of the spinal cord.
Tarlov cysts are most commonly located in the S1 to S4/S5 region of the spinal canal, but can be found along any region of the spine.They usually form on the extradural components of sacrococcygeal nerve roots at the junction of dorsal root ganglion and posterior nerve roots and arise between the endoneurium and perineurium. [10]