S3 motor branch stimulation failure due to nerve fiber burning at the nerve–wire junction: A historical technical note
A 28-year-old male developed a C6-C7 quadriplegia after a motor vehicle accident in 1998. In the acute phase, he underwent spinal cord decompression and fusion. He developed lower urinary tract dysfunction (LUTD) that did not respond to conservative therapy and subsequently underwent SNM. The patient was operated on in the prone position. A skin incision was made between L5 and S4 L5 and the sacral vertebrae were identified. Sacral laminectomy was performed from S1 to S4. The bilateral L5 and S1 roots were identified and evaluated with electrical stimulation for observation of toe dorsiflexion and plantar flexion, respectively. Sacral roots were identified bilaterally at S2, S3, and S4. To correctly identify sacral roots, a Foley catheter was placed and attached to a micro-set, which was partially filled with normal saline. During the operation, the nerve roots were stimulated and urinary bladder contraction was observed by elevation of fluid in the micro-set. When S2 and S4 roots were stimulated, slight bladder contraction was observed by way of elevation of fluid in the micro-set. However, the maximum elevation of fluid was observed following S3 stimulation. Dorsal and ventral S3 roots were distinguished from each other by anatomical landmarks and size. In each nerve root, the motor rootlets are located ventrally and medially to the sensory rootlets. To prevent cerebrospinal fluid (CSF) leakage, both anterior and posterior S3 roots were cut a few millimeters distal to the dura. Two urethral guide wires were used as electrodes and inserted into the S3 motor branches. The leads were tunneled subcutaneously to the anterior abdominal wall and then they were connected to a receiver block. An external stimulator transmits radiofrequency signals to the receiver block. Our stimulator was a Faradic stimulator. The stimulation was initiated with amplitude of 90-100 milliampere (mA) and gradually increased until signals excited the sacral ventral roots. Stimulation was delivered to the sacral anterior roots to induce bladder contraction for bladder emptying.\nDuring the surgery, minor thermal destruction of the nerve fibers was seen microscopically due to this simulation. More powerful stimulation was gradually employed to induce effective bladder contraction over the next 3-4 days. By 2 weeks following the surgery, the electrodes were removed due to ineffectiveness. This patient was followed for 12 years; in 2010 he died from an infectious disease.