Spinal nerve nerve roots result in typical patterns of neurologic defects (muscle weakness, abnormal sensation, changes in reflexes) that allow localization of the responsible lesion. There are several procedures used in sacral nerve stimulation for the treatment of various related disorders. Sciatica is generally caused by the compression of lumbar nerves L4, or L5 or sacral nerves S1, S2, or S3, or by compression of the sciatic nerve itself. Spinal nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal
Trochlear nerve Trochlear nerve The trochlear nerve, also called the fourth cranial nerve or CN IV, is a motor nerve (a somatic efferent nerve) that innervates only a single muscle: the superior oblique muscle of the eye, which operates through the pulley-like trochlea. The trochlear nerve is unique among the cranial nerves in several respects: Homologous trochlear nerves are found in all jawed vertebrates. The unique features of the trochlear nerve, including its dorsal exit from the brainstem and its contralateral innervation, are seen in the primitive brains of sharks. The human trochlear nerve is derived from the basal plate of the