Conus-level combined dorsal and ventral lumbar rhizotomy for treatment of mixed hypertonia: technical note and complications

Combined dorsal and ventral rhizotomy is an effective treatment for patients with concurrent spasticity and dystonia, with the preponderance of complaints relating to their lower extremities. This operative approach provides definitive relief of hypertonia and should be considered after less-invasive techniques have been exhausted. Previously, the surgery has been described through an L1–S1 laminoplasty. In this series, 7 patients underwent a conus-level laminectomy for performing a lumbar dorsal and ventral rhizotomy. Technical challenges included identifying the appropriate-level ventral roots and performing the procedure in children with significant scoliosis. Techniques are described to overcome these obstacles. The technique was found to be safe, with no infections, CSF leaks, or neurogenic bladders.

Intraoperative electrophysiology during single-level selective dorsal rhizotomy: technique, stimulation threshold, and response data in a series of 145 patients

OBJECTIVESelective dorsal rhizotomy (SDR) is effective at permanently reducing spasticity in children with spastic cerebral palsy. The value of intraoperative neurophysiological monitoring in this procedure remains controversial, and its robustness has been questioned. This study describes the authors’ institutional electrophysiological technique (based on the technique of Park et al.), intraoperative findings, robustness, value to the procedure, and occurrence of new motor or sphincter deficits.METHODSThe authors analyzed electrophysiological data of all children who underwent SDR at their center between September 2013 and February 2019. All patients underwent bilateral SDR through a single-level laminotomy at the conus and with transection of about 60% of the L2–S2 afferent rootlets (guided by intraoperative electrophysiology) and about 50% of L1 afferent roots (nonselectively).RESULTSOne hundred forty-five patients underwent SDR (64% male, mean age 6 years and 7 months, range 2 years and 9 months to 14 years and 10 months). Dorsal roots were distinguished from ventral roots anatomically and electrophysiologically, by assessing responses on free-running electromyography (EMG) and determining stimulation thresholds (≥ 0.2 mA in all dorsal rootlets). Root level was determined anatomically and electrophysiologically by assessing electromyographic response to stimulation. Median stimulation threshold was lower in sacral compared to lumbar roots (p < 0.001), and 16% higher on the first operated (right) side (p = 0.023), but unrelated to age, sex, or functional status. Similarly, responses to tetanic stimulation were consistent: 87% were graded 3+ or 4+, with similar distributions between sides. This was also unrelated to age, sex, and functional status. The L2–S2 rootlets were divided (median 60%, range 50%–67%), guided by response to tetanic stimulation at threshold amplitude. No new motor or sphincter deficits were observed, suggesting sparing of ventral roots and sphincteric innervation, respectively.CONCLUSIONSThis electrophysiological technique appears robust and reproducible, allowing reliable identification of afferent nerve roots, definition of root levels, and guidance for rootlet division. Only a direct comparative study will establish whether intraoperative electrophysiology during SDR minimizes risk of new motor or sphincter worsening and/or maximizes functional outcome.

The serotonin reuptake blocker citalopram destabilizes fictive locomotor activity in salamander axial circuits through 5-HT1A receptors

Serotoninergic (5-HT) neurons are powerful modulators of spinal locomotor circuits. Most studies about 5-HT modulation focused on the effect of exogenous 5-HT and these studies provided key information about the cellular mechanisms involved. Less is known about the effects of increased release of endogenous 5-HT with selective serotonin reuptake inhibitors. Such molecules were shown to destabilize the locomotor output of spinal limb networks through 5-HT1A receptors. However, in tetrapods little is known about the effects of increased 5-HT release on the locomotor output of axial networks, which are coordinated with limb circuits during locomotion from basal vertebrates to mammals. Here, we examined the effect of citalopram on fictive locomotion generated in axial segments of isolated spinal cords in salamanders, a tetrapod where raphe 5-HT reticulospinal neurons and intraspinal 5-HT neurons are present as in other vertebrates. Using electrophysiological recordings of ventral roots, we show that fictive locomotion generated by bath-applied glutamatergic agonists is destabilized by citalopram. Citalopram-induced destabilization was prevented by a 5-HT1A receptor antagonist, whereas a 5-HT1A receptor agonist destabilized fictive locomotion. Using immunofluorescence experiments, we found 5-HT-positive fibers and varicosities in proximity with motoneurons and glutamatergic interneurons that are likely involved in rhythmogenesis. Our results show that increasing 5-HT release has a deleterious effect on axial locomotor activity through 5-HT1A receptors. This is consistent with studies in limb networks of turtle and mouse, suggesting that this part of the complex 5-HT modulation of spinal locomotor circuits is common to limb and axial networks in limbed vertebrates.

Segment-specific orientation of the dorsal and ventral roots for precise therapeutic targeting of human spinal cord

An understanding of spinal cord functional neuroanatomy is essential for diagnosis and treatment of multiple disorders including, chronic pain, movement disorders, and spinal cord injury. Till now, no information is available on segment-specific spinal roots orientation in humans. In this study we collected neuroanatomical measurements of the dorsal and ventral roots from C2-L5, as well as spinal cord and vertebral bone measurements from adult cadavers. Spatial orientation of dorsal and ventral roots were measured and correlated to the anatomical landmarks of the spinal cord and vertebral column. The results show less variability in rostral root angles compared to the caudal angles across all segments. Dorsal and ventral rootlets were oriented mostly perpendicular to the spinal cord at the cervical level and demonstrate more parallel orientation at the thoracic and lumbar segments. The number of rootlets was the highest in dorsal cervical and lumbar segments. Spinal cord transverse diameter and size of the dorsal columns were largest at cervical and lumbar segments. The strongest correlation was found between the length of intervertebral foramen to rostral rootlet and vertebral bone length. These results could be used to locate spinal roots and spinal cord landmarks based on bone marks on CT or X-rays. These results also provide background for future correlations between anatomy of spinal cord and spinal column structures that could improve stereotactic surgical procedures and electrode positioning for spinal cord neuromodulation.One Sentence SummaryThis is the first detailed analysis of the segment-specific dorsal and ventral spinal roots spatial orientation measured and correlated to the anatomical landmarks of the spinal cord and vertebral column for human.

Anatomical study of the origin and area of innervation that form the brachial plexus of monkey-nail (Sapajus libidinosus)

We studied, and herein describe, the anatomy of the brachial plexus in the Sapajus libidinosus, a New World primate species. The study of origin and distribution of the nerves that form the brachial plexus of primates contributes to the body of knowledge of veterinary functional anatomy, and can have important ramifications to clinical, surgical, and anesthetic procedures, as well as to the understanding of injuries in these species. We found that the brachial plexus of Sapajus libidinosus is composed of neural fibers originating from the union of the dorsal and ventral roots of the cervical vertebral segments C5 to C8 and thoracic T1. These fibers then are organized in four main trunks, with a subdivision in the middle trunk. We concluded that the origins, trajectories and territory of innervation of the nerve trunks of the brachial plexus of Sapajus libidinosus are similar to those of other primates, with some variations occurring in the course.