Reference of pain following percutaneous cervical cordotomy.

In order to clarify the mechanism of reference of pain following cordotomy (ROPC), the authors investigated ROPC in 66 patients undergoing percutaneous cervical cordotomy (PCC) and examined the features of ROPC and the correlation between the occurrence of ROPC and the pre-operative pain states, as well as the results of PCC. ROPC was observed in 7 patients. It occurred immediately after PCC in 6 of 7 patients and 6 h after PCC in 1 patient. The pain was referred horizontally and cranially from the region rendered totally or largely analgesic by PCC to the normally innervated region. The region to which the pain was referred was not fixed. The referred pain disappeared by rendering the region where referred pain was felt analgesic with additional PCC. There was no correlation between the occurrence of ROPC and pre-operative pain states, or the results of PCC. From these results we postulate that: (1) ROPC occurs via a subsidiary pathway consisting of ascending chains of short neurons connecting dorsal horn neurons longitudinally and latitudinally; (2) the subsidiary pathway is inhibited under normal conditions by feedback inhibition from second-order neurons and/or higher central neurons of the nociceptive pathway; and (3) ROPC results from the release of the feedback inhibition by cordotomy.