Infra-Conus Single-Level Laminectomy for Selective Dorsal Rhizotomy: Technical Advance

Abstract

Background/Aims: Selective dorsal rhizotomy for spastic cerebral palsy is an effective and well-validated surgical approach. Multiple techniques have been described in the past including multiple laminectomies and a single-level laminectomy at the level of the conus. There is considerable technical challenge involved with a single-level laminectomy approach. Methods: We report here a modification of the single-level laminectomy that selectively analyzes each individual nerve root with electromyography to separate dorsal and ventral nerve roots through comparison of stimulus responses. Results: In 18 children with cerebral palsy who underwent this operation there was a mean improvement in the Modified Ashworth Scale of 2.0 with no reported incidence of muscle weakness, sensory loss, or neurogenic bladder. Conclusion: This approach allows for a modification of selective dorsal rhizotomy through a single-level laminectomy and tailors the selection of nerve root sectioning to the individual patient of interest while still maintaining its effectiveness.

Whether the newly modified rhizotomy protocol is applicable to guide single-level approach SDR to treat spastic quadriplegia and diplegia in pediatric patients with cerebral palsy?

“…With the reduction of muscle tone of spastic muscles on their affected lower limbs, their motor function improved dramatically after post-op rehabilitation therapy. Spasticity of lower extremities in spastic diplegic and quadriplegic cases usually affects muscles of adductor, hamstring, gastrocnemius, and soleus with bilateral involvement in a varied degree [3][4][5][6]. Besides the spasticity found in these major muscles, muscle tone prominent increase in rectus femoris is observed as well in some of spastic CP children.…”

Intraoperative neurophysiological monitoring in selective dorsal rhizotomy (SDR)

“…The use of Park's method could allow SDR to be performed via a single-level approach, particularly in cases with moderate or severe spasticity [2][3][4][5][6][7][8]. In an attempt to find a universally applicable EMG interpretation scheme that could be applied to all kinds of spastic CP cases (including mild ones), Browd developed a new rhizotomy protocol in 2016 [10]. In addition to applying the EMG response grading system, Browd's rhizotomy scheme also took preoperative assessment results (identifying the "target muscle" in CP cases before SDR) into account when EMG responses were interpreted during surgery [9,10].…”

“…Studies have shown that different anesthetics can affect intraoperative electrophysiological outcomes [16][17][18], including changes in threshold, latency to stimulus, and EMG response patterns. Because, to date, there is no proven anesthetic protocol used specifically for SDR, clinical practitioners have either just applied those protocols conducted in other neurosurgical procedures requiring IONM or simply developed their own [2][3][4][5][6][7][8][9][10][11][12][13].…”

“…Over the past 20 years, needle electrodes have been used for recording purposes, whereas bipolar probes are used as stimulation electrodes in almost all medical centers that perform IONM-guided SDR [2][3][4]. To avoid recording noise, rootlet stimulation must be elevated in the air using stimulation probes without tension, so as to keep the rootlet away from the cerebrospinal fluid [10].…”

“…The word "selective" refers to the intraoperative selection and dissection of the afferent nerve rootlets in the spinal cord that are considered to be more involved in spasticity, decreasing the afferent signaling to the motor neurons in the anterior horn of the spinal cord, so as to achieve a reduction in muscle tone after surgery. At present, some centers that perform SDR use intraoperative neurophysiological monitoring (IONM) to assist or even fully guide the operation [2][3][4][5][6][7][8][9][10][11][12][13]. Because the role of IONM in SDR has never been fully discussed, its importance and necessity have been long questioned.…”