[Surgery in the dorsal root entry zone for treatment of chronic pain]

Microsurgical drezotomy (MDT) consists of an incision and bipolar coagulations performed ventro-laterally in the Dorsal Root Entry Zone (DREZ) at the entrance of the rootlets into the dorso-lateral sulcus. The lesion is directed at 35 ventro-medially, and to 2-3 mm deep according to the pre-operative neurological status and the desired effects. MDT i) interrupts the small (nociceptive) fibres regrouped laterally and the large (myotatic) afferents which runs centrally, whilst sparing part of the large medial (lemniscal) fibres, ii) destroys the (excitatory) medial part of the Lissauer's tract, iii) and the cells of the dorsalmost layers of the dorsal horn, which can be the site of hyperactivity, as we were able to record in patients with deafferentation pain. Best indications are: i) well-localized cancer pain, such as Pancoast syndrome; ii) neuropathic pain due to: brachial plexus injuries; cauda equina and/or spinal cord lesions (especially for pain corresponding to segmental lesions); peripheral nerve injuries, amputation, herpes zoster - especially when the predominant component of pain is of the paroxysmal type and/or corresponds to provoked hyperalgesia/allodynia); iii) excess of spasticity, especially when associated with severe pain.