Myelotomies for chronic pain.

The literature on myelotomy for the treatment of chronic pain was reviewed and a total of 635 published cases scrutinized. Two main modes of myelotomy can be distinguished 1) a longitudinal commissural section tuned to the segmental pain level and 2) a focused central lesion, irrespective of considerations of the metameric pain distribution, mainly carried out at a high cervical level. Of the longitudinal commissural myelotomy, a posteriorly restricted and a complete type can moreover be discerned. The pain relief decays with time after myelotomy of any kind. Central myelotomy scores better than complete commissural section for malignant pain in a statistically significant manner but its superiority over posterior commissurotomy cannot be statistically proven. Except of a girdle-shaped hypo-algesia, which is expected after the section of the decussating spinothalamic fibers in a complete commissurotomy, other--irregular--patterns of hypo-algesia have been observed, especially after central myelotomy. This unusual lesion, provoking unusual hypo-algesia patterns, together with phenomena like a preserved sharp-blunt-discrimination within the hypo-algesic area, points at a different sensory channel that might be severed in a central myelotomy as compared with an anterolateral chordotomy or a complete commissurotomy. This hypothesis is matched with recent physiological evidences.