Objective:To investigate the efficacy and safety of selective dorsal rhizotomy with small incision under electrophysiological monitoring in lower limb spasticity.Methods:Twenty patients with lower limb spasticity due to craniocerebral injury admitted to Department of Neurosurgery,Tianjin Huanhu Hospital from January 2019 to December 2023 were selected. Target muscles (Ashworth Scale graded 1 + or higher) were identified preoperatively. Intraoperatively, the lower L 1 spinous process and the upper L 2 spinous process were resected to expose the cauda equina nerves. A bipolar stimulator was applied to electrically stimulate the cauda equina nerves root by root to identify the sensory nerves of the target muscles; subsequently, strings of electrical stimulation were given, 50% cauda equina nerves were cut off if no contraction of the contralateral muscles was seen, and 75% were cut off if contraction of the contralateral muscles was noted. Motor function and muscle tension were assessed and compared before and 6 months after surgery by Gross Motor Function Measure (GMFM)-66, Gross Motor Function Classification System (GMFCS), and Ashworth spasticity scale. Complications early after surgery and 6 months after surgery were observed. Results:The most common targeted muscles in these 20 patients included the gastrocnemius (the medial and lateral side, n=20), followed by the biceps femoris ( n=12) and the adductor muscles of thigh ( n=9). Number of nerves intraoperatively cut in patients with GMFCS grading 1-4 was 5.40±1.84, 9.50±6.36, 11.67±5.86, and 14.00±5.66, respectively, with significant differences ( F=5.506 , P=0.009). Grading of Ashworth spasticity scale of the target muscles before surgery in these 20 patients showed significant difference compared with that at 6 months after surgery ( P<0.05), and average rank indicated that Ashworth spasticity scale of target muscles 6 months after surgery was graded obviouly better than that before surgery. In addition, the GMFM-66 total scores and major joint motion scores of the patients 6 months after surgery were significantly higher than those before surgery ( P<0.05). Fifteen patients had fever early after surgery, 18 patients had incisional pain, and 1 patient developed reversible hypesthesia of the lower extremities; these symptoms disappeared 0.5-4.0 years after surgery. No patients developed lower limb hypokinesia, urinary and defecation disorders, or spinal deformities. Conclusion:Selective dorsal rhizotomy with small incision under electrophysiological monitoring used in this study can effectively reduce surgical trauma and relieve lower limb spasticity due to craniocerebral injury, enjoying high surgical safety.