CSF Endorphins Level in Patients with Cancer Pain Treated by Cervical Percutaneous Cordotomy

Since 1975 various Authors (3, 5, 7, 13) have pointed out a c1ear correlation between endogenous polypeptides - endorphins and enkephalins - and pain mechanisms. Terenius (14) found CSF endorphins level significantly lower in patients with chronic organic pain and much higher in patients with psychiatric disorders. Re explains this finding by suggesting that the organic pain induces a general depression on the endor­ phinergic system followed by hypersensitivity to other painful stimuli. An alternative interpretation is that the low endorphins level in pain patients is caused by the increas­ ed consumption of the endorphinergic system which inhibits nociception. This system, chronically stimulated in subjects with persistent pain, could be saturated and unable to defend the patient from other nociceptive impulses. It is already well known that stimulation of such descending pathways with pain in­ hibitory function, both at periaqueductallevel (1, 4) or by percutaneous (12) or trans­ cutaneous (6) electrostimulation, provokes analgesia or hypoalgesia and increases CSF endorphins level. This behaviour could signify an activation of the endorphinergic sys­ tem, according to Terenius' hypothesis (14), with transient increase of CSF endorphin levels. At this point, the main problem is: if electrotherapy definitely produces pain reduc­ tion by increasing CSF endorphins level, are the other pharmacologic or surgical pro­ cedures able to stimulate the endorphinergic system? In particular, if the afferent no­ ciceptive pathway is interrupted by surgical procedures such as cervical percutaneous cordotomy in patients with chronic pain, do the CSF endorphins level remain unchan­ ged - i.e. low with respect to normal subjects - or increase? For this purpose we studied CSF levels of ~-endorphins in a group of ten patients with chronic cancer pain before and after cervical percutaneous radiofrequency cor­ dotomy.