REGIONAL CORRESPONDENCE BETWEEN THE VENTRAL PORTION OF THE LUMBAR INTERVERTEBRAL DISC AND THE GROIN MEDIATED BY A SPINAL REFLEX - A POSSIBLE BASIS OF DISCOGENIC REFERRED PAIN

Study Design. Lumbar peripheral nerves were examined to determine whet her they were responsive to electrical stimulation of the ventral port ion of the lumbar disc in anesthetized rats, Objectives. To confirm by electrophysiologic means the neural correspondence between the ventra l portion of the lumbar disc and the groin. Summary of Background Data . Patients with a degenerated lumbar disc occasionally report groin pa in. However, its pathogenesis has not been investigated. The authors o f the current study found that chemical stimulation of the ventral por tion of rat lumbar disc caused cutaneous plasma extravasation in the g roin, and thereby hypothesize the neural relation between the lumbar d isc and the groin. Methods. The ventral portion of rat L5-L6 disc was electrically stimulated, and the elicited action potentials were recor ded from the iliohypogastric, genitofemoral, lateral femoral cutaneous , sural, and sciatic nerves. The roles of the lumbar sympathetic trunk s and spinal cord in the generation of the action potentials were exam ined. Results. Action potentials were elicited principally in the geni tofemoral nerve; the action potentials of the genitofemoral nerve were not influenced by transection of the cervical spinal cord, whereas th ey disappeared immediately after death, which indicates that they are induced by a spinal reflex. The action potentials were reduced conside rably after destruction of the lumber sympathetic trunks, suggesting t hat they comprise an afferent path of the reflex. Conclusions. The ven tral portion of the lumbar disc had spatial relation to the groin area via a spinal reflex. Such a relation suggests that a disorder in the ventral portion of the lumbar disc may be a possible source of groin r eferred pain.