Anatomical Analysis of the S1 Neural Foramen Using Three-Dimensional Computed Tomography Imaging: Insights for Effective S1 Nerve Root Block.

OBJECTIVE: The first sacral nerve root block (S1 NRB) is used to diagnose and treat lumbosacral and radicular pain. This study aims to clarify the anatomy of the S1 neural foramen using three-dimensional (3D) computed tomography (CT) images and to establish the optimal fluoroscopic angle, localize the S1 neural foramen on fluoroscopy, and determine the safe puncture depth for S1 NRB. METHODS: In this single-center cohort study, 200 patients with lumbar degenerative disease who underwent preoperative CT were enrolled. Four distinct studies were conducted using the CT data. Study 1 examined the correlation of the sacral slope angle and the supine and prone positions. Study 2 analyzed the tunnel view angle (TVA) using 3D reconstruction. Study 3 ascertained the location of the S1 neural foramen in fluoroscopy images. Study 4 investigated the safe depth for performing S1 NRB. RESULTS: The regression analysis in Study 1 revealed a correlation of the sacral slope angle and the supine and prone positions. Study 2 determined an optimal fluoroscopic TVA of approximately 30° for the S1 NRB. Study 3 found that the S1 neural foramen was located caudal to the L5 pedicle 1.7 ± 0.2 times the distance between the L4 and L5 pedicles. Study 4 revealed that the depths of the S1 neural foramen and root were 27.0 ± 2.1 mm and 16.5 ± 2.0 mm, respectively. CONCLUSIONS: Our study suggests an optimal fluoroscopic angle, a simple method to locate the S1 neural foramen on fluoroscopy, and an ideal puncture depth for a safe and effective S1 NRB.

A comparative study of the anatomy and MRI images of the lumbar foraminal ligaments at the L1-L5 levels.

PURPOSE: The purpose of this study was to evaluate the ability of MRI images to reveal foraminal ligaments at levels L1-L5 by comparing the results with those of anatomical studies. METHODS: Eighty lumbar foramina were studied. First, the best MRI scanning parameters were selected, and the transverse and sagittal axes of each lumbar foramina were scanned to identify and record the ligament-like structures in each lumbar foramen. Then, the cadaveric specimens were anatomically studied, and all ligament structures in the lumbar foramina were retained. The number, morphology and distribution of ligaments under anatomical and MRI scanning were observed. Histological staining of the dissected ligament structures was performed to confirm that they were ligamentous tissues. Finally, the accuracy of ligament recognition in MRI images was statistically analyzed. RESULTS: A total of 233 foraminal ligaments were identified in 80 lumbar intervertebral foramina through cadaveric anatomy. The radiating ligaments (176, 75.5%) were found to be attached from the nerve root to the surrounding osseous structures, while the transforaminal ligaments (57, 24.5%) traversed the intervertebral foramina without any connection to the nerve roots. A total of 42 transforaminal ligament signals and 100 radiating ligament signals were detected in the MRI images of the 80 intervertebral foramina. CONCLUSION: The MRI can identify the lumbar foraminal ligament, and the recognition rate of the transforaminal ligament is higher than that of the radiating ligament. This study provides a new method for the clinical diagnosis of the relationship between the lumbar foraminal ligament and radicular pain.

Extradural Contralateral Ventral Root Transfer to Treat Lower Limb Motor Dysfunction in Paraplegia.

STUDY DESIGN: Eight cadavers were included in this anatomical study. OBJECTIVE: This study aimed to confirm the anatomical feasibility of extradural transfer of the contralateral T11 ventral root (VR) to the ipsilateral L2 level and the contralateral L1 VR to the ipsilateral L3 level to restore lower limb function in cases of paraplegia. SUMMARY OF BACKGROUND DATA: Motor dysfunction due to hemiplegia significantly affects the daily life of patients. To date, unlike in cases of upper limb dysfunction, there are few studies on the surgical management of lower limb movement dysfunction. MATERIALS AND METHODS: Eight cadavers were included in this study to confirm the feasibility of the nerve transfer. After separating the VR and dorsal root at each level, the VRs at the T11 and L1 levels were anastomosed with the VRs of L2 and L3, respectively. The length of the VRs of donor roots and the distance between the donor and recipient nerves were measured. H&E staining was performed to verify the number of axons and the cross-sectional area of the VRs. Lumbar x-rays of 60 healthy adults were used to measure the distance between the donor and recipient nerves. RESULTS: After exposing the bilateral extradural each root, the VRs could be easily isolated from the whole root. The distance between the VRs of T11 and L2, L1, and L3 was significantly longer than the length of the donor nerve. Therefore, the sural nerve was used for grafting. The measurements performed on the lumbar x-rays of the 60 healthy adults confirmed the results. The number of axons and cross-sectional area of the VRs were measured. CONCLUSION: Our study confirmed the anatomical feasibility of transferring the VRs of T11 to L2 and that of L1 to L3 to restore lower limb function in cases of hemiplegia. LEVEL OF EVIDENCE: 5.

Anatomical description of the ventral and dorsal cervical rootlets in rats: A microsurgical study.

PURPOSE: To describe the anatomical aspects of the cervical rootlets and to quantify the number of rootlets that compose C1 to T1. METHODS: Twenty male rats were used in this study. The dorsal rootlets from C1 to T1 were analyzed. To study the ventral rootlets, the posterior root avulsion was performed using a microhook, allowing exposure of the ventral roots through manipulation of the denticulate ligament and arachnoid mater. The parameters analyzed were the number of ventral and dorsal rootlets by side and level. RESULTS: The formation of the respective spinal nerve was observed in the spinal roots the union of the ventral and dorsal roots. In four animals the C1 spinal root had no dorsal and/or ventral contribution. There is no normal pattern of numerical normality of the dorsal and ventral rootlets. The average number of fascicles per root was 4.08, with a slight superiority on the left side. There was a slight superiority of the dorsal rootlets compared to the ventral rootlets. CONCLUSIONS: This investigation was the first to study cervical rootlets in rats. In 20% of the sample studied, the dorsal root of C1 was absent mainly on the left side. There is a nonlinear numerical increase from C1 to T1 in the rootlets. There is a numerical predominance of cervical fascicles on the left side, confronting several studies related to the functional predominance of right laterality, requiring new studies that correlate these variables.

Clinical Anatomy of Human Donor C7 Nerve Roots for Surgical Transfer in Patients with Spastic Arm Paralysis.

BACKGROUND: Contralateral C7 (CC7) nerve transfer has successfully restored hand function in patients with spastic hemiplegia from chronic central nervous system injuries. However, little is known about the morphology and anatomy of the donor C7 nerve root in patients undergoing this procedure. This study quantified intraoperative measurements of donor C7 nerve roots during CC7 transfer surgery for spastic hemiplegia in patients treated at a high-volume center to describe observed anatomical variations for successful direct anastomosis. METHODS: A database of images from 21 patients (2 females, 19 males) undergoing CC7 surgery was searched for photographic data that contained a standard ruler measuring donor C7 nerve root length after surgical sectioning and before transfer. Two independent observers analyzed these images and recorded C7 nerve root diameter, length, and branch lengths. RESULTS: Mean (SD) values of donor C7 nerve measurements were length, 53.5 (8.0) mm; diameter, 5.1 (0.9) mm; branch length following surgical sectioning, 18.3 (6.3) mm. Right-sided donor C7 nerve roots yielded significantly longer branches compared with left-sided donor C7 nerve roots (P = 0.01). Other patient factors such as age, sex, or laterality of brain injury did not influence intraoperative anatomy. CONCLUSIONS: We report detailed intraoperative measurements of the donor C7 root during CC7 nerve transfer for spastic hemiplegia. These findings describe existing variation in surgical C7 nerve root anatomy in patients undergoing this procedure and may serve as a general reference for the expected donor C7 length in successful direct anastomosis.

Intra-dural intercommunications between dorsal roots of adjacent spinal nerves and their clinical significance.

PURPOSE: The dorsal roots of adjacent spinal nerves are known to communicate with each other through rami communicantes. These intercommunications can cause deviations in the normal dermatomal organization which leads to errors during clinical decision-making. The objective of the study was to augment the existing knowledge of these communications which shall help minimize the diagnostic and therapeutic errors. METHODS: The present study examined thirty cadaveric spinal cord specimens to document the data of intra-dural, intercommunications between dorsal roots of adjacent spinal nerves. RESULTS: All the regions of the spinal cord exhibited the presence of intercommunications with variable frequency. The intercommunications were categorized into a total of nine groups based on their patterns. The levels of spinal cord exhibiting higher and lower frequencies of intercommunications were identified. CONCLUSION: This information will be useful during the clinical evaluation of patients with spinal cord pathologies or radiculopathies. The outcomes of rhizotomy can also be improved with knowledge of intercommunications.

Segment-Specific Orientation of the Dorsal and Ventral Roots for Precise Therapeutic Targeting of Human Spinal Cord.

OBJECTIVE: To provide precise description of the dorsal and ventral roots orientation along with the main spinal cord anatomical measurements and their segment-specific variations. PATIENTS AND METHODS: We collected and analyzed the measurements of the spines, spinal cords, and dorsal and ventral roots (C2-L5) of nine adult cadavers (five males and four females). RESULTS: This study for the first time provides analysis of the dorsal and ventral roots orientation along with spinal cord anatomical measurements and their segment-specific distribution. The results of this study showed less variability in rostral root angles compared with the caudal. Dorsal and ventral rootlets were oriented mostly perpendicular to the spinal cord at the cervical level and had more parallel orientation to the spinal cord at the thoracic and lumbar segments. The number of rootlets per root was greatest at dorsal cervical and lumbar segments. Spinal cord transverse diameter and width of the dorsal columns were largest at cervical segments. The strongest correlation between the spinal cord and vertebrae structures was found between the length of intervertebral foramen to rostral rootlet distance and vertebral bone length. CONCLUSION: These results demonstrate consistent variation in spinal cord anatomical features across all tested subjects. The results of this study can be used to locate spinal roots and main spinal cord landmarks based on bone marks on computed tomography or X-rays. These results could improve stereotactic surgical procedures and electrode positioning for neuromodulation procedures.

Basivertebral foramina of true vertebrae: morphometry, topography and clinical considerations.

PURPOSE: Basivertebral foramina (BVF) are openings of the posterior wall of vertebral body (VB) that lead to basivertebral canals (BVC), where homonymous neurovascular bundle courses. BVF and BVC are implicated with spinal fractures, vertebral augmentation and basivertebral nerve radiofrequency ablation. Despite their essential clinical impact, knowledge of BVF precise anatomy is scarce. The current study describes in detail the BVF typical morphological and topographical anatomy, morphometry and variants. METHODS: In total, 1561 dried true vertebrae of 70 Greek spines of known gender and age were examined. BVF number, location, shape and size (in foramina > 1 mm), BVF distance from VB rims and pedicles, as well as VB morphometry (diameters, heights and distance between pedicles) were studied. Ten spines were re-examined by computed tomography and BVC depth and shape were recorded. Correlations and differences were statistically analyzed. RESULTS: C1 lack BVF (3.4%). One BVF was found in 45.1%, two in 36.9%, three in 3.8% and four BVF in 0.6%. Multiple small (< 1 mm) foramina were observed in 10.1%. Asymmetry was detected in 12.3%. C2 and T10-L1 presented typical pattern, whereas C3 and T2 had the greatest variability. BVF were significantly closer to the upper rim in C2 and T10-L4 and to the lower rim in C7-T4, T6-T8 and L5. The mean BVC depth was 12-21.8% of the VB anteroposterior diameter. CONCLUSION: BVF number, shape, size and topography are described, in detail, per vertebral level. The provided morphological classification and the created cumulative BVF topographic graphs should assist in clinical practice and surgery.

Structure of Lumbar Intervertebral Foraminal Ligaments Based on 3-Dimensional Reconstruction Through Ultrathin Cryomilling of a Human Cadaver.

BACKGROUND: This study aimed to assess the feasibility of using the 3-dimensional (3-D) reconstruction technique based on ultrathin cryomilling to show the lumbar intervertebral foraminal ligaments in situ. METHODS: Cryomilling was performed on an embalmed human cadaver to acquire successive cross-sectional images. In each of the images, the boundaries of lumbar intervertebral foraminal ligaments and their adjacent structures were outlined, labeled, and reconstructed for 3-D modeling. The morphology, attachments, and spatial orientation of ligaments were described. RESULTS: A total of 9 ligaments in 10 lumbar intervertebral foramina (IVFs) were identified and reconstructed. These ligaments can be divided into 5 types. The IVFs were divided into 2 or 3 main portions by the first 4 types of ligaments (transforaminal ligaments, corporotransverse ligaments, "reticular" ligaments, and "Y-shaped" ligaments). The radiating ligaments (the fifth type of ligaments) attached to the surrounding structures of the IVF and were connected directly to the nerve root sleeves. Although there was no indication of neurovascular compromise in this normal specimen, these ligaments limit the space within the bony IVF such that under certain pathologic conditions (e.g., inflammation), their presence would make neurovascular compression more likely than if they were absent. CONCLUSIONS: The 3-D reconstruction technique based on ultrathin cryomilling can effectively show the lumbar intervertebral foraminal ligaments and their anatomical characteristics in situ, providing a new way to clarify the relationships between these ligaments and their adjacent structures.

Foraminal Origin of the Dorsal Scapular Nerve: An Anatomical Study.

BACKGROUND: Although distal dorsal scapular nerve (DSN) anatomy has been well characterized, a paucity of literature exists detailing its proximal origin. To our knowledge, this is the first study examining DSN origin and its anatomy relative to the C5 nerve root, which may help localize pathology and provide insight into timing of DSN or C5 nerve root clinical and electrophysiological recovery. METHODS: Eighteen cadaveric dissections were performed using a posterior-midline approach. Calipers were used for DSN branching and course characterization with statistical analysis completed for the following measurements: DSN diameter, C5 nerve root diameter, distance of DSN branch-point from the C5 ganglion, dural edge, and posterior foraminal tubercle (intra-vs. extraforaminal origin), as well as C5 root-SC branch-point distance. RESULTS: Average/mean measurements (standard error) were as follows: DSN diameter: 3.7 mm (0.3 mm), C5 nerve root diameter: 6.2 mm (0.5 mm), DSN origin to C5 DRG: 12.4 mm (1.9 mm) distal, DSN origin to dural edge: 19. 6mm (1.8 mm), DSN origin to C5 root origin: 23.3 mm (2.2 mm), DSN origin to the posterior foraminal tubercle: 2.3 mm (2.5 mm) proximal/intraforaminal (first branch from C5 in all cases, and the majority [12 of 18, 67%] of DSNs originating from the C5 spinal nerve root within the foramen). CONCLUSIONS: The C5 nerve root contributed to the DSN in all specimens that originated from the proximal, intraforaminal, C5 nerve root in the majority of specimens. As the first C5 nerve branch, surgeon knowledge of this proximal DSN pattern will help localize lesional pathology, as well as may help monitor clinical and electrophysiological recovery.

The Geometry of the roots of the Brachial Plexus.

Diffusion tensor magnetic resonance imaging (DTI) can be used to reconstruct the brachial plexus in 3D via tracts connecting contiguous diffusion tensors with similar primary eigenvector orientations. When creating DTI tractograms, the turning angle of connecting lines (step angle) must be prescribed by the user; however, the literature is lacking detailed geometry of brachial plexus to inform such decisions. Therefore, the spinal cord and brachial plexus of 10 embalmed adult cadavers were exposed bilaterally by posterior dissection. Photographs were taken under standardised conditions and spatially calibrated in MATLAB. The roots of the brachial plexus were traced from the dorsal root entry zone for 5 cm laterally using a 2.5-mm2 Cartesian grid overlay. The trace was composed of points connected by lines, and the turning angle between line segments (the step angle) was resolved. Our data show that the geometry of the roots increased in tortuosity from C5 to T1, with no significant differences between sides. The 1st thoracic root had the most tortuous course, turning through a maximum angle of 56° per 2.5 mm (99% CI 44° to 70°). Significantly higher step angles and greater variability were observed in the medial 2 cm of the roots of the brachial plexus, where the dorsal and ventral rootlets coalesce to form the spinal root. Throughout the brachial plexus, the majority of step angles (>50%) were smaller than 20° and <1% of step angles exceeded 70°. The geometry of the brachial plexus increases in tortuosity from C5 to T1. To reconstruct 99% of tracts representing the roots of the brachial plexus by DTI tractography, users can either customise the step angle per root based on our findings or select a universal threshold of 70°.

Microsurgical anatomy of the spinal cord in human fetuses.

PURPOSE: To determine the microsurgical features of the spinal cord and ventral and dorsal rootlets in fetal period. METHODS: Twelve formalin-fixed fetuses (six females and six males) with a mean gestational age of 27.0 ± 2.04 weeks (range between 25 and 32 weeks) were dissected to evaluate morphological properties of the spinal cord and rootlets. RESULTS: Length and width of each spinal cord segment, number of dorsal and ventral rootlets, length of dorsal root entry and ventral root exit zones of each spinal nerve, spinal cord termination level, and the whole spinal cord length were determined in all fetuses. Contrary to previous reports, the number of ventral rootlets was always more than that of dorsal rootlets in all segments. No statistically significant gender difference was found for all parameters. Rootlet number and segment width in cervical region were larger than those of thoracic, while the lengths of dorsal root entry and ventral root exit zones in thoracic region were longer than those of cervical. In lumbar region, dorsal and ventral rootlet numbers were increasing again, while lengths of dorsal root entry and ventral root exit zones were decreasing. Number of dorsal and ventral rootlets of C5 and C6 segments was statistically higher than other cervical segments. The mean spinal cord length was found as 105.55 ± 11.30 mm and there was a positive significant relationship with gestational age. Conus medullaris level was detected between L1 and L3 segments. CONCLUSION: Detailed microsurgical data about the fetal spinal cord and the dorsal and ventral rootlets presented in this study provide significant information which may be essential during surgical interventions in early postnatal period and childhood targeting the spinal cord and spinal nerve roots.

The anatomical features of denticulate ligament in human fetuses.

PURPOSE: To determine the morphological features of the denticulate ligament in fetal period. METHODS: Twelve formalin-fixed fetuses (six females and six males) with a mean gestational age of 27.0 ± 2.04 weeks (range between 25 and 32 weeks) were dissected to reveal morphological properties of the denticulate ligaments. RESULTS: Denticulate ligament was observed as a continuous ligament extending throughout the length of spinal cord in all fetuses. It separated the vertebral canal into two as anterior and posterior parts and was anchored to the dura mater on either side of the spinal cord with mostly triangular processes as well as thin band-like extensions. The first denticulate ligament process was always a large and prominent fibrous band and was arising from the spinal cord surface, extending in an oblique direction upward to the anterolateral rim of foramen magnum, below and posterior to the hypoglossal canal. The last denticulate ligament process was observed either in the T11-12 (2 sides, 8%), T12-L1 (15 sides, 62%) or L1-2 (7 sides, 30%) and all were band-like processes. At certain spinal cord levels, denticulate ligament had no processes to attach duramater while in some other fetuses double denticulate ligament processes were detected within the same interval. The distance between the denticulate ligament process and the superior spinal nerve root and the distance between the denticulate ligament process and the inferior spinal nerve root were measured at each spinal level. This distance was found to be increased from upper to lower levels of the spine. CONCLUSION: Detailed morphological data about fetal denticulate ligament presented in this study provide significant information which may be essential during several surgical interventions performed in early postnatal period and childhood focusing on the spinal cord, spinal nerve roots and meningeal structures.

Sonographic measurements of normal C5-C8 nerve roots in children.

INTRODUCTION: The aim of this study was to use ultrasound to measure the cervical nerve roots in normal children to determine normal reference values. METHODS: A total of 441 children of different ages at the Children's Hospital of Chongqing Medical University were examined by ultrasound. The diameter, circumference, and cross-sectional area of the nerve roots were measured. RESULTS: Ultrasonographic measurements were consistent with the ranking C5 < C6 < C7. The C8 nerve root was thicker than C7 in 60% of the participants. The nerve root measurements increased with increasing age, height, weight, and body surface area. DISCUSSION: Normal reference ranges of the cervical nerve roots in children of different ages were established, and can serve as the basis for measurement in future studies.

Relationship of the Exiting Nerve Root and Superior Articular Process in Kambin's Triangle: Assessment of Lumbar Anatomy Using Cadavers and Computed Tomography Imaging.

BACKGROUND: Percutaneous transforaminal endoscopic diskectomy has been a major treatment for lumbar disk herniation. However, damage to exiting nerve roots is one of the most severe complications in this surgery. In this paper, the relationship of the exiting nerve root and the superior articular process in Kambin's triangle of the lumbar intervertebral foramen was assessed using cadavers and computed tomography (CT) imaging. METHODS: The anatomic relationship between the exiting nerve root and the superior articular process in Kambin's triangle of the intervertebral foramen was investigated on 6 cadavers. The distance between the exiting nerve and the superior articular process of the L1-2 to L5-S1 intervertebral foramina was measured using multiplane reconstruction. RESULTS: The bone-nerve space between the exiting nerve root and the superior articular process in Kambin's triangle was quite narrow both in cadaver and CT imaging study. The distance of the L5-S1 intervertebral foramen was the greatest, which was no more than 5.77 ± 0.56 mm. The distances increased gradually from the tip to the root, and the distances between the root and the tip were 0.91 ± 0.31 to 1.86 ± 0.57 mm, which took on a trapezoid shape that was relatively narrow at the proximal end and wider at the distal end. CONCLUSIONS: The bone-nerve space between the exiting nerve root and the superior articular process in Kambin's triangle of the lumbar intervertebral foramen was exceedingly narrow. It is necessary to perform a foraminoplasty to enlarge the working space and decrease the possibility of injury to the exiting nerve root.

Dynamic mapping of the corticospinal tract in open cordotomy and myelomeningocele surgery.

OBJECT: Spinal cord surgeries carry a high risk for significant neurological impairments. The initial techniques for spinal cord mapping emerged as an aid to identify the dorsal columns and helped select a safe myelotomy site in intramedullary tumor resection. Advancements in motor mapping of the cord have also been made recently, but exclusively with tumor surgery. We hereby present our experiences with dynamic mapping of the corticospinal tract (CST) in other types of spinal cord procedures that carry an increased risk of postoperative motor deficit, and thus could directly benefit from this technique. CASE REPORTS: Two patients with intractable unilateral lower extremity pain due to metastatic disease of the sacrum and a thoraco-lumbar chordoma, respectively underwent thoracic cordotomy to interrupt the nociceptive pathways. A third patient with progressive leg weakness underwent cord untethering and surgical repair of a large thoracic myelomeningocele. In all three cases, multimodality intraoperative neurophysiologic testing included somatosensory and motor evoked potentials monitoring as well as dynamic mapping of the CST. CONCLUSION: CST mapping allowed safe advancement of the cordotomy probe and exploration of the meningocele sac with untethering of the anterior-lateral aspect of the cord respectively, resulting in postoperative preservation or improvement of motor strength from the pre-operative baseline. Stimulus thresholds varied likely with the distance between the stimulating probe and the CST as well as with the baseline motor strength in the mapped myotomes.

Microanatomy Relevant to Intrathecal Drug Delivery.

This chapter describes the microanatomy of the spinal cord that is relevant to intrathecal drug delivery started with covering of the spinal cord that are pierced to enter the intrathecal space. The dural sac is mostly constituted by the outer layer of dura and the inner layer called arachnoid membrane, which regulates diffusion of drugs into the intrathecal space. The pia matter surrounding the spinal cord is a permeable structure allowing the passage of drugs through intercellular spaces. The relationship between nerve roots, CSF, and subarachnoid catheters determines the passage of an intrathecal catheter which can cause damage to nerve roots and spinal cord. Multiple factors may be involved in the mechanisms of drug diffusion across the membranes of the spinal cord, as well as in their dilution with the CSF, which will lead to the final drug distribution and availability at nerve roots and the spinal cord.

The projection of the thoracic nerve roots and their connection with intervertebral discs: a cadaver and radiological study.

BACKGROUND: The anatomical features of the thoracic nerve roots in connection with intervertebral discs may prevent surgery-related complications and improve patients' neurological functional status during thoracic spine surgery. There is limited literature evidence regarding this concept using cadavers. PURPOSE: To elucidate the qualitative anatomical features of the thoracic nerve roots in connection with intervertebral discs. MATERIAL AND METHODS: Fifteen formalin-preserved spine specimens were used in this study. Small pieces of stainless-steel wires were placed along the root sleeves from their points of origin, after exposing the dural sac and bilateral nerve roots. The standard anteroposterior and lateral radiographs were taken after the placement of the wires. Measurements were done on radiographs using the picture archiving communication system. RESULTS: Take-off angles of the nerve roots at the coronal plane gradually increased from the level of T2 (36.1°±2.72°) to T9 (84.1°±1.84°) and from T9, it decreased to T12 (46.3° ± 2.67°). Similar variation tendency was discovered in take-off angles of the nerve roots at the sagittal plane. No consistent tendency was found both in the distance from the origin of the root sleeve to its superior and inferior vertebral endplate. Distance from the origin of the root sleeve to the posterior midline (DM) exponentially decreased from T1 (8.2 ± 0.87 mm) to T4 (6.0 ± 0.93 mm). It slowly increased from T5 (5.5 ± 0.68 mm) to T12 (10.9 ± 1.79 mm), with T5 having the smallest DM. Distance between the origins of neighboring nerve roots showed an obvious increase from the T1-T2 interval (23.1 ± 2.22 mm) to T7-T8 interval (30.9 ± 2.68 mm). However, it progressively decreased at the T10-T11 interval (26.0 ± 2.40 mm). CONCLUSION: The dimensions of the thoracic nerve roots vary greatly from T1 to T12 intervertebral discs. Sound knowledge of these anatomical features of the thoracic nerve is mandatory for the thoracic spine surgery, especially in the posterolateral approach and transforaminal endoscopic surgery.

Intraspinal characteristics of thoracic spinal nerve roots anomalies.

Purpose: The anomalous anatomical arrangement of the thoracic spinal nerve roots within the spinal canal can complicate the surgical treatment of several pathologies. The aim of this work was to reveal intraspinal anatomical variations of the thoracic spinal nerve roots.Methods: Anatomical study on 43 cadavers with a mean age of 53.7. After opening the spinal canal and dural sac, intradural and extradural anomalies of the thoracic spinal nerve roots were documented. Extradural communicating branches were excised, histologically processed and examined for the presence of nervous tissue.Results: We found 14 cases (32.6%) of intraspinal thoracic nerve root variations: intradural in 8 cases (18.6%), intradural communicating branches in 3 cases (6.97%), extradural anatomical variations occurred 6 cases (13.95%), 2 cases (4.65%) had extradural communicating branches between the nerve roots, 1 case had simultaneous occurrence of intradural and extradural communications (0.23%). All the results are differentiated according to the plexus type. In macroscopic extradural thoracic communicating branch had no nervous tissue on microscopy.Conclusions: This study describes intraspinal anatomical variations of thoracic spinal nerve roots. Knowledge of these variables should help prevent the failure of several medical procedures.

Ipsilateral S2 nerve root transfer to pudendal nerve for restoration of external anal and urethral sphincter function: an anatomical study.

Patients suffer bilateral sacral plexus injuries experience severe problems with incontinence. We performed a cadaveric study to explore the anatomical feasibility of transferring ipsilateral S2 nerve root combined with a sural nerve graft to pudendal nerve for restoration of external anal and urethral sphincter function. The sacral nerve roots and pudendal nerve roots on the right side were exposed in 10 cadavers. The length from S2 nerve root origin to pudendal nerve at inferior border of piriformis was measured. The sural nerve was used as nerve graft. The diameters and nerve cross-sectional areas of S2 nerve root, pudendal nerve and sural nerve were measured and calculated, so as the number of myelinated axons of three nerves on each cadaver specimen. The length from S2 nerve root to pudendal nerve was 10.69 ± 1.67 cm. The cross-sectional areas of the three nerves were 8.57 ± 3.03 mm2 for S2, 7.02 ± 2.04 mm2 for pudendal nerve and 6.33 ± 1.61 mm2 for sural nerve. The pudendal nerve contained approximately the same number of axons (5708 ± 1143) as the sural nerve (5607 ± 1305), which was a bit less than that of the S2 nerve root (6005 ± 1479). The S2 nerve root in combination with a sural nerve graft is surgically feasible to transfer to the pudendal nerve for return of external urethral and anal sphincter function, and may be suitable for clinical application in patients suffering from incontinence following sacral plexus injuries.