Dorsal root reflexes: Do they play a role in chronic “Neuropathic” pain patients?

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A t a break during the meeting on Abnormal Somatosensory Mechanisms organized by Lillian Pubols and Barry Sessle and held at Timberline Lodge, Oregon, in 1986, Wilfrid Janig and one of us wondered whether dorsal root reflexes might involve primary C-nociceptor afferents.The question was prompted by the amazing case of Mr. B, a patient who had suffered from persistent burning pain in the right upper extremity for 17 years. Together with spontaneous pain and mechanical hyperalgesia, Mr. B expressed substantial hyperthermia of the symptomatic part. There were some trophic changes.The patient had been investigated and treated unsuccessfully through the sympathetic dystrophy paradigm. We suspected Mr. B. had sensitized primary nociceptors but could not raise definitive proof. Eventually, we diagnosed a benign intramedullary spinal tumor in the cervical cord. Skilled neurosurgical approach ablated much of the tumor with minimal cord complications. The hyperalgesia was replaced by hypoesthesia, which the patient preferred. The spontaneous pain and the hyperthermia were relieved.The clinical picture was rationalized as the consequence of irritation of the central branches of primary nociceptor afferents within the spinal cord, with resultant pain and antidromically determined neurogenic inflammation and hyperalgesia. If we had known that Manfred Zimmermann had published a very pertinent basic paper on C-fiber stimulation and dorsal root potentials [reference 94 in Focus article; Zimmermann M: Dorsal root potentials after C-fiber stimulation. Science 160:896-898, 1968], we might have written the case of Mr. B. at that time. In a related context, a few years later we argued that human radiculopathy may