Peak B endorphin concentration in cerebrospinal fluid: reduced in chronic pain patients and increased during the placebo response.

The level of an endogenous opioid (peak B endorphin) was measured in chromatographically fractionated cerebrospinal fluid (CSF) sampled from two groups of chronic pain patients before and after intrathecal saline (placebo) injection. As assessed by a verbal rating scale, one group reported no change in their level of pain (non-responders, NR; n = 6) while the other group reported complete or greater than 50% pain relief (placebo responders, PR; n = 14). We find, as has been reported previously, that initial peak B levels were lower (by 50%) in these chronic pain patients' CSF than in CSF from pain-free (PF) normal controls (P less than 0.001, t-test). Peak B levels measured from CSF of the NR group undergoing this procedure did not change (P greater than 0.4, paired t-test). In contrast, a significant 2.3-fold increase was measured in the CSF peak B level of the PR group (P less than 0.05, paired t-test). This is the first direct evidence that a CSF opioid is correlated with placebo pain relief in chronic pain patients. Peak B is a potent analgesic substance when administered by the intracerebroventricular route in mice and its level is related to the patients' pain status in a presumably causal manner.

Local analgesia without anesthesia using peripheral perineural morphine injections.

Twenty-five patients with chronic pain were treated with nerve blocks. They were divided into two groups, A and B, according to the volume of local anesthetic required for surgical anesthesia by standard nerve block techniques. The 16 patients in group A had pain in the distribution of small nerves, which could be blocked with 5 ml or less. They were blocked in a random, double-blind crossover fashion using 0.5% bupivacaine or 0.02% morphine. The nine patients in group B were injected simultaneously with saline, 30 ml perineurally and 1 ml intramuscularly. Morphine (6 mg) was added, in a random, double-blind fashion, to one of the injections. A second pair of injections was subsequently done, using morphine by the alternative route. Perineural morphine provided statistically longer lasting pain relief than did either intramuscular morphine or perineural bupivacaine.

Relief of postlaminectomy syndrome in selected patients by injection of autogenous cerebrospinal fluid.

We have been using the differential spinal block to study patients referred to our Pain Clinic for treatment of their chronic pain syndromes. In a selected group of chronic-pain patients from whom cerebrospinal fluid (CSF) could not be obtained at the L4 or L5 interspace, administration of autogenous CSF obtained at a higher interspace gave immediate and complete but temporary pain relief. Endorphins were present in these autogenous CSF samples. These studies, indicating that CSF even from chronic-pain patients contains analgesic substances (possibly endorphins), may point to new treatment modalities for certain chronic back pain syndromes.