The pharmacologic approach in differential diagnosis of chronic pain.

Chronic pain of unknown cause below waist level was evaluated in 100 patients by using the Differential Spinal Block (DSB) in a multidisciplinary pain clinic setting. The classic DSB approach, refined for better control of psychologic variables, was found to be a safe and effective means of differentiating various pain mechanisms. We found that, of all patients tested, 55% had pain of central or psychogenic origin and 30% had sympathetically mediated pain, as compared with 15% who had somatic pain. A long-term follow-up of these patients confirmed this impression. These results substantiated the importance of psychologic variables, in dicating the necessity for use of behavioral-based therapies in conjunction with the routine use of the refined diagnostic DSB procedure in patients with chronic pain.