[Does the differential block by the epidural route provide a diagnostic aid in chronic pain?]

Sixty-two patients with chronic pain below the waist level were evaluated with a differential epidural block performed after an overall somatic and psychological assessment. The pain and neurophysiologic variations under block were compared with the somatic and psychological findings. No consistent relationship was found between pain variations and sympathetic sensory effects of the graduated epidural block. The presence of neurological diseases and depressive or hysterical disorders influenced particularly the pain responses to the block. It is concluded that the differential epidural block is not sufficient to affirm the somatic origin of a chronic pain and must be always confronted with the somatic and psychosocial findings.