Radicular pain derives from irritation of the proximal portion of the spinal nerve as a result of ischemia, chemical irritation by contents of the nucleus pulposus, or mechanical compression. Kuslich,13 performing progressive local anesthesia during spinal surgery, has observed that compressed or chemically irritated nerve roots are perceived as painful when stretched, while normal nerve roots do not reproduce pain. The outer annulus and posterior longitudinal ligament also could be stimulated to produce pain.13 Ninety-five percent of disk herniations occur at L4-L5 or L5-S1. Without complaint of sciatica, or pain below the knee in a dermatomal distribution, the chance of a herniated nucleus pulposus is 1 in 1000. Complaints of muscular pain in the myotome and sensory dysesthesias in the dermatome distribution of a spinal root may be accompanied by referred pain in the sclerotome distribution. Compromise of L5 and S1 roots can be experienced, respectively, as muscular pain in the anterior tibial compartment simulating "shin splints," and muscular pain in the calf mimicking a thrombophlebitis. Proximal L5 and S1 root compression is suggested distally by the presence of pain to palpation over the peroneal nerve (L5) at the fibular head and the tibial nerve (S1) in the tarsal tunnel. Sensory complaints in the presence of radicular syndromes may be useful in localizing root levels of involvement. Paresthesias in the great toe suggest L5 root involvement, and in the little toe S1 radiculopathy.
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