Intraoperative mapping in C4 to Th1 nerve roots on Cervical Microsurgical DREZotomy of Patients with Pain from Brachial Plexus Injury: Practical Implications

OBJECTIVE: Cervical Microsurgical DREZotomy (MDT) aims to relieve neuropathic pain in patients with brachial plexus injury by destroying the nociceptive neural structures and the hyperactive neurons in the dorsal horn. Useful information can be harvested by intraoperative mapping and testing of cervical C4–Th1 roots. METHODS: 18 patients with intractable pain due to brachial plexus injury underwent cervical MDT. 216 roots were tested (6 ventral and 6 dorsal roots for each patient). Each root (ventral component) was electrically stimulated by bipolar probe (2Hz, 0,2mA) to identify its muscular distribution and functional value. Responses were observed in the diaphragm for the C4 root by ventilation recordings on the anesthesia machine, and C5–Th1 roots muscular responses. RESULTS: Macroscopic observations under the operating microscope showed 108 dorsal roots: 68 totally avulsed, 8 partially avulsed, 18 atrophic and 14 intact; and 108 ventral roots: 58 totally avulsed, 11 partially avulsed, 16 atrophic, 5 with neuroma and 18 intact. A comparison of dorsal and ventral root lesions was almost equally important. In 6 patients (33%), the C4 ventral root stimulation showed alteration in waveforms on anesthesia machine; to shoulder abduction (C5 level) in 5 patients (27%); to elbow flexion (C6 level) in only one patient (5%); to elbow and wrist extension (C7 level) in 3 patients (17%); to thenar and hypothenar muscles (C8 and Th1 levels) in 3 patients (17%). In approximately 30% of the atrophic roots, the intraoperative electrical stimulation of the ventral roots obtained a response in muscular corresponding muscular, indicating a remaining functional activity. CONCLUSION: The intraoperative anatomical mapping and functional testing of the injured cervical roots help to evaluate the extent and degree of the damages and thus better understand the mechanism(s) of the pain. Topography and degree of root impairment and pain territory were concordant in all patients.