100 90 80 70 60 50 40 30 20 10 0 baseline(preop) 6 mths post op. Tone <strong>of</strong> hip adductors Passive ROM <strong>of</strong> hip adductors Motor power <strong>of</strong> quadriceps(MRCS) Figure 3: Comparison <strong>of</strong> outcome parameters between preoperative and postoperative assessment at 6 months. 8
Discussion: The concept <strong>of</strong> SDR is improving spasticity and range <strong>of</strong> movement, with preservation <strong>of</strong> muscle strength, by identifying components <strong>of</strong> dorsal roots involved in spasticity on the basis <strong>of</strong> <strong>intraoperative</strong> <strong>electrophysiological</strong> stimulation. [3, 13, 26 31] Comparable to other studies, a decrease <strong>of</strong> spasticity, and increase <strong>of</strong> ROM, with preservation <strong>of</strong> power were detected. The impact <strong>of</strong> EPM on clinical outcome, a matter <strong>of</strong> debate, could not be addressed and needs further comparable research (EP guided SDR versus non EP guided SDR). Controversy regarding the utility <strong>of</strong> EP recording has centered around the lack <strong>of</strong> technical standardisation [19, 24] ; absence <strong>of</strong> normal controls 19 ; the inconsistency <strong>of</strong> motor responses 26 ; the effect <strong>of</strong> anaesthetic drugs on spinal reflexes 2 ; time consumption by the procedure [19, 26] ; and the variability <strong>of</strong> segmental innervations <strong>of</strong> lower-extremity muscles [18, 26] . Variation in EPM techniques <strong>during</strong> SDR is established in different centers and the need for EPM has been questioned. [13, 24, 32] To overcome different obstacles facing EMG recording; muscle relaxants are not used; depth <strong>of</strong> anaesthesia were minimal <strong>during</strong> recording; and time consumption is decreased by time. The <strong>intraoperative</strong> EMG <strong>monitoring</strong> <strong>during</strong> SDR provides valuable information and help to neurosurgeons. First, it differentiates ventral roots, which need low amplitude to be [15, 19, 26] stimulated, from dorsal roots, hence decreasing its related motor complications. Second, EP <strong>monitoring</strong>, beside <strong>intraoperative</strong> clinical assessment, provide objective way to determine the percentage <strong>of</strong> selected rootlets. The alternative way is the random transection <strong>of</strong> dorsal roots from L2-S1 according to clinical severity. [ 13, 23, 24, 26] The average percentage <strong>of</strong> different groups ranges from 18%-68%, with most centers cutting more than 40%. [ 15, 16, 24, 28] A high percentage (64%) is associated with using other criteria for selecting transected rootlets as tonic contraction <strong>of</strong> related muscle <strong>during</strong> stimulation and occurrence <strong>of</strong> after discharge. 29 Percentage <strong>of</strong> transected rootlets in this study (52.8%) is within the reported [3, 13, 16, 23, 26, 28, 31] range <strong>of</strong> the previous studies. Third, EMG mapping <strong>of</strong> anal sphincter fibers running in S1 roots enables safe transaction <strong>of</strong> S1 rootlets producing optimum functional outcome, without sphincteric dysfunction. Deletis et al 2 recorded sphincteric EMG response from stimulation <strong>of</strong> S1 in 8 out <strong>of</strong> 31 patients (25%) underwent SDR. Moreover, Ojemann et al 17 detected EMG responses on stimulation <strong>of</strong> dorsal roots <strong>of</strong> L4 and caudally. Similarly, we spared 27% <strong>of</strong> S1 roots that produced anal sphincter EMG response on stimulation. This explans the preserved sphincteric control in all patients in whom either S1 roots contain sphincter related fibers and, in the other hand, no sphincteric disturbance occur in those in whom S1 stimulated rootles showed no sphincteric responses and were transected, and these findings are going with Deletis et al 21 and Ojemann et al 17 findings. The preservation <strong>of</strong> other sacral roots (S2-4) is essential for protecting bladder and sexual functions. 16 Lastly, EPM, in SDR and other cauda equina and sacral surgery, identifies and distinguishes roots from fibrous tissue or filum terminal. 9 9
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