On the importance of the innervation of the human cervical longitudinal ligaments at vertebral level.

PURPOSE: In our aging society, the prevalence of degenerative spinal diseases rose drastically within the last years. However, up till now, the origin of cervical pain is incompletely understood. While animal and small cadaver studies indicate that a complex system of sensory and nociceptive nerve fibers in the anterior (ALL) and posterior longitudinal ligament (PLL) at the level of the intervertebral disc might be involved, there is a lack of data exploring whether such a network exists and is equally distributed within the cervical vertebrae (VB). We, therefore, aimed to investigate the spatial distribution of the mentioned nerve networks in human tissue. METHODS: We performed macroscopic (Sihler staining, Spalteholz technique, and Plastination) and microscopic (immunohistochemistry for PGP 9.5 and CGRP) studies to characterize spatial differences in sensory and nociceptive innervation patterns. Therefore, 23 human body donors were dissected from level C3-C6. RESULTS: We could show that there is a focal increase in sensory and nociceptive nerve fibers at the level of C4 and C5 for both ALL and PLL, while we observed less nerve fiber density at the level of C3 and C6. An anatomical vicinity between nerve and vessels was observed. CONCLUSION: To our knowledge, these findings for the first time report spatial differences in sensory and nociceptive nerve fibers in the human cervical spine at VB level. The interconnection between nerves and vessels supports the importance of the perivascular plexus. These findings might be of special interest for clinical practice as many patients suffer from pain after cervical spine surgery.

Sensory innervation of the dorsal longitudinal ligament and the meninges in the lumbar spine of the dog.

Although intervertebral disc herniation is a well-known disease in dogs, pain management for this condition has remained a challenge. The goal of the present study is to address the lack of information regarding the innervation of anatomical structures within the canine vertebral canal. Immunolabeling was performed with antibodies against protein gene product 9.5, Tuj-1 (neuron-specific class III ß-tubulin), calcitonin gene-related peptide, and neuropeptide Y in combination with the lectin from Lycopersicon esculentum as a marker for blood vessels. Staining was indicative of both sensory and sympathetic fibers. Innervation density was the highest in lateral areas, intermediate in dorsal areas, and the lowest in ventral areas. In the dorsal longitudinal ligament (DLL), the highest innervation density was observed in the lateral regions. Innervation was lower at mid-vertebral levels than at intervertebral levels. The presence of sensory and sympathetic fibers in the canine dura and DLL suggests that pain may originate from both these structures. Due to these regional differences in sensory innervation patterns, trauma to intervertebral DLL and lateral dura is expected to be particularly painful. The results ought to provide a better basis for the assessment of medicinal and surgical procedures.

[Treatment and mechanism of cervical spondylosis with sympathetic symptoms].

OBJECTIVE: To evaluate the role of anterior decompression with resection of the posterior longitudinal ligament (PLL) on the cervical degenerative disease with sympathetic symptoms and to primarily validate our speculation on the mechanism of this entity. METHODS: Forty-seven cases suffered from cervical spondylosis from 2002 to 2007 were retrospectively reviewed. The inclusive criteria were: (1) cervical myelopathy or radiculopathy or both secondary to cervical degenerative disease; (2) complaining of unexplainable and irrelievable sympathetic symptoms such as dizziness, vertigo, etc; (3) performed with anterior cervical decompression with PLL resection and internal fixation. The JOA scores were recorded and evaluated. The sympathetic symptoms were evaluated by both 20 points evaluation system and patient's satisfaction evaluation. The posterior longitudinal ligaments of 8 rabbits were harvested and stained by Sucrose-Phosphate-glyoxylic acid (SPG) to distinguish the sympathetic nerve fibers. The results were observed and evaluated by fluorescent microscope and Image-pro plus 5.0. RESULTS: All the patients were followed up for 10 to 48 months. The JOA scores before operation were 12.6 and increased to 15.2 at the final follow up. The sympathetic symptoms evaluation was 6.0 before operation and 2.8 after. The satisfactory evaluation was excellent in 19 cases, good in 16, fair in 8 and poor in 4. The effective rate was 87.5%. The SPG stain showed that there were plenty of sympathetic post-ganglia fibers in the cervical PLL, which were distributed like a web, and there were more fibers distributed at the interspaced zone than at the vertebral body zone. The density of the sympathetic nerve fibers in the C(2/3), C(3/4) and C(4/5) were greater than those in C(5/6) and C(6/7); while the density in the shallow layer were greater than those in the deep layer. CONCLUSIONS: The sympathetic nerve fibers distributed in the cervical PLL maybe another one significant factor causing sympathetic symptom of cervical spondylosis. The anterior cervical decompression with resection of PLL can relieve the sympathetic symptoms of the patients.

Neurological deterioration induced by sitting in patients after cervicothoracic posterior decompression with instrumented fusion surgery for ossification of the longitudinal ligament: two cases reports.

BACKGROUND: We report on Japanese patients who showed neurological deterioration induced by sitting after cervicothoracic posterior decompression with instrumented fusion, but showed immediate neurological recovery after bed rest. CASE PRESENTATION: Patients showed incomplete paraparesis caused by the ossification of the posterior longitudinal ligament at uppermost thoracic spine. Cervicothoracic posterior decompression with instrumented fusion was performed. Postoperatively, the patients showed partial paraparesis when they were sitting. They showed rapid recovery from lower extremity paralysis upon lying down. After strict bed rest for one month, those patients showed no apparent development of paralysis during sitting. CONCLUSION: In patients with postoperative residual anterior spinal cord compression, micromotion might exacerbate neurological symptoms.

Comparison of sensory and sympathetic innervation of the dura mater and posterior longitudinal ligament in the cervical spine after removal of the stellate ganglion.

Although cervical spinal tissues are rich in sensory and sympathetic fibers, which play a significant role in clinical phenomena, there is little information available regarding their anatomical characteristics. In this study, we compared the innervation of the cervical dura mater and the posterior longitudinal ligament (PLL) to that after removal of the stellate ganglion to determine whether the anatomical background plays a significant role in clinical manifestations. Immunoreactivities for calcitonin gene-related peptide (CGRP) and substance P (SP) were used as sensory markers, and immunoreactivity for neuropeptide Y (NPY) was used as a sympathetic marker. Sensory fibers in the cervical dura mater were distributed within each cervical segment, but those in the PLL extended beyond the segmental borders. A dense sensory fiber network forming a single layer was seen at the intervertebral disc region in the cervical PLL, whereas sympathetic fibers in this region were sparsely distributed. Sympathetic fibers were distributed not only around the vascular wall but also in the region independent from vessels, and some occasionally ran together with sensory fibers in both the dura mater and the PLL. Removal of the stellate ganglion had little effect on the distribution of sensory fibers but denervated the sympathetic fiber networks in the region independent from vessels of the upper ipsilateral cervical PLL. In conclusion, the cervical dura mater and the PLL have different sensory and sympathetic innervations. Sympathetic fibers pass through the stellate ganglion to project to the region independent from vessels in the upper cervical PLL. Clinical symptoms may be attributed to this characteristic innervation of the cervical spine.

Innervation of the rabbit lumbar intervertebral disc and posterior longitudinal ligament.

STUDY DESIGN: The present study sought to determine to what extent the lumbar intervertebral disc and posterior longitudinal ligament are innervated in the New Zealand white rabbit. The intent is to use this disc model in future neurophysiology studies. OBJECTIVE: To characterize the distribution of nerve fibers and endings in the lumbar intervertebral disc and posterior longitudinal ligament in an animal model. SUMMARY OF BACKGROUND DATA: The results of previous disc innervation reports are somewhat conflicting regarding the density and depth of innervation into the anulus. METHODS: A silver impregnation technique was used to analyze sections from lumbar intervertebral disc and posterior longitudinal ligament of the New Zealand white rabbit. RESULTS: Numerous fine profiles of nerve fibers were demonstrated in the lumbar disc anulus and posterior longitudinal ligament. In the disc, the nerves were limited to the superficial anulus and anular surface. The nerve axons typically were 1 to 3 microns in diameter and were found around the entire periphery of the disc. No encapsulated endings were seen within the anulus, while occasional encapsulated endings were seen on the anular surface and posterior longitudinal ligament. CONCLUSION: This study demonstrates an extensive distribution of small nerve fibers in the size range of C and A-delta fibers throughout the peripheral anulus and provides an illustration of this distribution. These findings support a role for the disc as a source of low back pain.

An ultrastructural study of calcitonin gene-related peptide-immunoreactive nerve fibers innervating the rat posterior longitudinal ligament. A morphologic basis for their possible efferent actions.

STUDY DESIGN: The present study investigated ultrastructural characteristics of calcitonin gene-related peptide-immunoreactive nerve fibers in the posterior longitudinal ligament of the rat lumbar spine. OBJECTIVES: To provide a morphologic basis for assessment of the afferent and, in particular, efferent functions of calcitonin gene-related peptide immunoreactive nerves in the posterior longitudinal ligament and their eventual role in degenerative spondylarthropathies and low back pain. SUMMARY OF BACKGROUND DATA: Previous studies using light-microscopic localization of sensory neuronal markers such as calcitonin gene-related peptide have reported the presence of sensory fibers in the supporting structures of the vertebral column. Meanwhile, accumulating research data have suggested efferent properties for calcitonin gene-related peptide, i.e., a trophic action that alters the intrinsic properties of target cells not through transient action of synaptic transmission, but through long-lasting signal transmission by the secreted neuropeptides. To verify such trophic, paracrine actions of the calcitonin gene-related peptide-containing fibers in the posterior longitudinal ligament, however, ultrastructural details of the terminals and their spatial relationship to their eventual target structures have to be elucidated. METHODS: Rat posterior longitudinal ligaments were stained immunohistochemically for calcitonin gene-related peptide. Light-microscopic analysis of the semithin sections facilitated subsequent electron microscopy of specific sites of the posterior longitudinal ligament to determine ultrastructural details and nerve fiber-target relationships. RESULTS: The rat lumbar posterior longitudinal ligament was found to be innervated by two distinctive calcitonin gene-related peptide immunoreactive nerve networks. In immunoelectronmicroscopy, the fibers of the deep network had numerous free nerve endings, whereas those of the superficial network showed spatial associations with other non-calcitonin gene-related peptide immunoreactive components of the network. In both systems, naked axons not covered by the Schwann cells made close spatial contact with smooth muscle cells: of blood vessels and resident posterior longitudinal ligament fibroblasts. CONCLUSIONS: The ultrastructural characteristics of the innervation of the rat posterior longitudinal ligament would be compatible not only with a nociceptive function, but also with neuromodulatory, vasoregulatory, and trophic functions, as has already been established in some visceral organs.

Mechanosensitive afferent units in the lumbar posterior longitudinal ligament.

STUDY DESIGN: The mechanosensitive afferent units in the lumbar posterior longitudinal ligament were investigated in an animal model using an electrophysiologic technique. OBJECTIVES: The objectives of this study were to identify the mechanosensitive receptive fields in the lumbar posterior longitudinal ligament and to investigate their distribution and characteristics. SUMMARY OF BACKGROUND DATA: The lumbar posterior longitudinal ligament has a nerve network originating from the sinuvertebral nerve. These fibers are thin, and most of their terminals are free nerve endings. Some immunohistochemical studies have indicated that they are immunoreactive to calcitonin gene-related peptide and/or substance P, suggesting a nociceptive function. Most of these studies investigated morphologic aspects, and there have been few studies employing electrophysiologic techniques to examine mechanosensitive units. METHODS: We used 13 adult cats. They were anesthetized and then laminectomy was performed. The L5 and L6 dorsal rootlets were draped over a recording electrode. To investigate the receptive fields in the posterior longitudinal ligament, afferent impulses were evoked by mechanical stimulation with a glass probe. When the receptive fields were located, they were stimulated electrically to obtain conduction velocity and were stimulated with a set of 17 nylon filaments to determine their mechanical thresholds. RESULTS: Thirteen units were identified in the lumbar posterior longitudinal ligament. The majority of the units were located around the intervertebral disc level of the posterior longitudinal ligament. The mean mechanical threshold was 47.04 +/- 15.25 g. According to the conduction velocities of the units, 12 units were classified into Group III (0.5-2.5 m/sec) and one unit into Group IV (2.5-20 m/sec). CONCLUSION: Mechanosensitive units classified into Group III or Group IV and with a high mechanical threshold (>7.0 g) were thought to act as nociceptive units. All units identified in this study satisfied these criteria. Our result suggests that afferent fibers from the lumbar posterior longitudinal ligament have a principally nociceptive function.

Innervation of the spinal dura. Myth or reality?

STUDY DESIGN: Cranial and spinal dura from nine Sprague Dawley male rats were examined immunocytochemically for the presence of nerve fibers and mast cells and for innervation. The posterior longitudinal ligament and peridural membrane were also examined for these elements. OBJECTIVE: To examine the pattern of sensory innervation and the presence of mast cells in rat spinal dura. SUMMARY OF BACKGROUND DATA: The cranial dura is richly innervated and has a robust population of mast cells, which have been implicated in the pathogenesis of vascular headache. Moskowitz's explanation for vascular headache focused on the dura mater and neurogenic inflammation. Essential to his model are dural trigeminovascular fibers and mast cells. Previous studies provide contradictory and inconclusive results regarding spinal dural innervation. METHODS: Immunocytochemical techniques using antibodies to calcitonin gene-related peptide and substance P were used to identify sensory nerve fibers and antibodies to serotonin were used to identify mast cells. Specimens dissected included dura of the cranial vault in continuity with the dorsal cervical dura, dura of the skull base in continuity with the ventral cervical dura, lumbar dura, and posterior longitudinal ligament from the cervical and lumbar regions. RESULTS: A rich neural network and an abundant mast cell population were identified in the supratentorial and infratentorial cranial dura, both dorsally and ventrally. A paucity of nerve fibers and mast cells was observed in the cervical and lumbar dura; in contrast, these elements were prominent in the posterior longitudinal ligament and peridural membrane. CONCLUSIONS: Spinal dura does not have a rich innervation of calcitonin gene-related peptide- and substance P-positive nerve fibers or a robust population of mast cells. The spinal dura may serve as a protective covering. Unlike the cranial dura, it may not be implicated in the pathogenesis of pain. Additional studies on primate and human spinal dura are warranted to corroborate findings that the spinal dura may be relatively insensitive.

Dually innervating nociceptive networks in the rat lumbar posterior longitudinal ligaments.

STUDY DESIGN: The present study investigated the distribution of sensory and autonomic nerves to the posterior longitudinal ligament of the rat lumbar vertebra. OBJECTIVE: The results were analyzed to provide a new insight into the pathogenesis of low back pain. SUMMARY OF BACKGROUND DATA: Previous studies that have descriptively reported on posterior longitudinal ligament innervation have attributed important roles to the sinuvertebral nerve as an output of nociceptive sensation. Meanwhile, development of immunohistochemistry has made it possible to identify numerous neurotransmitters, and thus various suggested pathophysiologic roles of the nerve fibers in the posterior longitudinal ligament. However, such microscopic identification of the nerve fibers has not been able to reveal comprehensive distributions of the various fibers, which are presumed to be derived from the sinuvertebral nerve. METHODS: Rat posterior longitudinal ligaments of whole thickness was immunohistochemically stained for calcitonin gene-related peptide and tyrosine hydroxylase, which have been considered markers of nociceptive and noradrenergic fibers respectively. Light-microscopic and electron-microscopic observation was reinforced with another experimental study in which resection of the dorsal root ganglia induced characteristic denervation patterns to the rat posterior longitudinal ligament. RESULTS: The present study revealed that the lumbar. PLL was dually innervated by two distinctive systems of nociceptive fibers. One of the systems was polysegmentally innervated and closely associated with autonomic innervation, whereas the other was unisegmentally innervated and not associated with autonomic fibers. CONCLUSION: Pathogenesis of low back pain can be better understood if the presence of the two distinctive nerve systems innervating the posterior longitudinal ligament is taken into account.

Mechanoreceptors in intervertebral discs. Morphology, distribution, and neuropeptides.

STUDY DESIGN: The present study investigated the occurrence and morphology of mechanoreceptors in human and bovine intervertebral discs and longitudinal ligaments. OBJECTIVE: To determine the type and frequency of mechanoreceptors present in intervertebral discs and anterior longitudinal ligaments in two patient groups, those with low back pain and those with scoliosis. Bovine coccygeal discs were examined. SUMMARY OF BACKGROUND DATA: Nerves have been described in intervertebral tissues, but there is little information on the endings of these nerves and their receptors, stimulation of which can cause a nerve impulse. METHODS: The presence of mechanoreceptors were investigated by immunolocalization of nerves and neuropeptides. By examining sequential sections, the frequency of receptors was assessed. RESULTS: Immunoreactivity to neural antigens showed mechanoreceptors in the anulus fibrosus and longitudinal ligaments of bovine and human specimens. Their morphology resembled Pacinian corpuscles, Ruffini endings, and, most frequently, Golgi tendon organs. They were found in 50% of discs investigated from patients with low back pain and in 15% of those with scoliosis. CONCLUSIONS: Mechanoreceptors were found in the outer 2-3 lamellae of the human intervertebral disc and anterior longitudinal ligament. Physiologic studies in other tissues indicate that these provide the individual with sensation of posture and movement, and in the case of Golgi tendon organs, of nociception. In addition to providing proprioception, mechanoreceptors are thought to have roles in maintaining muscle tone and reflexes. Their presence in the intervertebral disc and longitudinal ligament can have physiologic and clinical implications.

Anatomical study of lumbar spine innervation.

To precisely evaluate low back pain, identification of the detailed innervation of the lumbar spine is necessary. On twenty-five sides of adult cadavers we investigated various patterns of rami communicantes (RC) and their relationship to the psoas major muscle (PM). In ten sides, we focused our dissection on the minute nerve supply of the anterior (ALL) and posterior longitudinal ligaments (PLL), vertebral bodies and the intervertebral discs (IVD). According to the mode of piercing PM, two types of RC were observed: superficial oblique rami (SOR) and deep transverse rami (DTR). SOR ran obliquely between superficial heads of PM, connecting sympathetic trunk (ST) and T12-L2 (3) spinal nerves non-segmentally. DTR ran segmentally close to the vertebral bodies and were situated deep to the PM slips. On the lateral side of the lumbar spine, the vertebral bodies and IVD received branches from DTR and ventral rami segmentally, as well as branches from the sympathetic trunk (ST) and, in the upper lumbar region, SOR non-segmentally. On the anterior aspect of the lumbar spine, ALL received branches from ST and splanchnic nerves non-segmentally. Within the vertebral canal, the posterior aspect of IVD and PLL received the sinu-vertebral nerves originating from DTR. These findings suggest the coexistence of two different types of innervation: one originating directly from the spinal nerve segmentally, and one reaching vertebral structures via the sympathetic nerves non-segmentally. Therefore, sympathetic nerves are likely involved in the proprioception of the spinal column.

Sympathetic nerve innervation in cervical posterior longitudinal ligament as a potential causative factor in cervical spondylosis with sympathetic symptoms and preliminary evidence.

UNLABELLED: Sympathetic symptoms associated with cervical disorders, such as vertigo, headache, dizziness, etc., are common clinical disorders bewildering both clinicians and patients. In our clinical practice we observed that sympathetic symptoms associated with cervical disorders were apparently relieved in some patients after undergoing routine anterior cervical decompression and fusion plus posterior longitudinal ligament (PLL) resection. This study was designed to investigate the sympathetic nerve innervations in the cervical PLL and its potential correlation with cervical sympathetic symptoms such as vertigo. METHOD: In animal research, cervical PLLs of 9 adult rabbits were harvested and stained with sucrose-phosphate-glyoxylic acid (SPG), which is a specific fluorescence staining method for sympathetic postganglionic fibers. In human research, cervical PLL of 8 patients of cervical spondylosis with sympathetic symptoms were harvested during surgery and stained with SPG. All sections were observed under fluorescence microscope. Sympathetic symptoms were evaluated using the sympathetic symptom 20-point score preoperatively and at 1 week, 2-month, and 6-month postoperatively. RESULTS: In rabbit specimens, a large number of sympathetic postganglionic fibers were distributed in the cervical PLL of every segment. The density of sympathetic fibers distributed in the intervertebral portion of PLL was more than that in the vertebral portion. Compared with deep layer section, the nerve fibers in the superficial PLL layer section were thicker and more densely populated. Existence of sympathetic postganglionic fibers was also confirmed in human specimens. Those nerve fibers were mostly short and isolated in areatus form, with non-interwoven branches. The mean sympathetic symptoms score decreased significantly from 6.6 ± 2.6 before surgery to 2.0 ± 1.9 at 6 months postoperatively after anterior cervical decompression and fusion with PLL removed. CONCLUSION: According to the experimental result and clinical practice, we hypothesized that sympathetic nerve fibers distributed in PLL may represent a pathologic basis of stimulation induced by cervical vertebral degenerative changes and thus are susceptible to being a potential causative factor in cervical spondylosis with sympathetic symptoms.

Effect of the L2 ramus communicans on the nociceptive pathway in lumbar intervertebral discs in rats.

The mechanism underlying discogenic low-back pain is unclear. It is difficult to explain this type of pain by the segmental innervation theory because the groin area is innervated by the genitofemoral or ilioinguinal nerves, which are the terminal branches of the L1 or L2 spinal nerves. Recently, some studies have indicated that sympathetic trunks are closely related to discogenic low-back pain. However, sympathetic trunk resection can severely affect the function of the abdominal organs and lower extremities and may cause retrograde ejaculation in human beings. This study was initiated to evaluate the role of selective transection of the L2 ramus of the nociceptive pathway in the lumbar intervertebral discs in rats, by using the fluorogold (FG) retrograde transport method and immunohistochemistry of substance P (SP). Of the FG-labeled neurons in the L2 and L5 dorsal root ganglia (DRGs), the cross-sectional area of the SP-immunoreactive (ir) neurons ranged from 210 to 1140 microm(2); the mean cross-sectional area was 652+/-320 microm(2). We demonstrated that FG-labeled SP-ir neurons in L2 DRGs decreased when FG was applied to the ventral or dorsal portions of L5-6 discs. The results indicated that the L2 ramus communicans played an important role in the afferent pathway of both the ventral and dorsal portions of the L5-6 disc. Nociceptive information from the L5-6 disc may be transmitted mainly by L2 DRG neurons through the L2 ramus communicans.

Topography and distribution of nerve fibers in the posterior longitudinal ligament of the rat: an immunocytochemical and electron-microscopical study.

The distribution and immunocytochemical characterization of nerve fibers and their terminals in the posterior longitudinal ligament of the rat lumbar vertebral column was studied in whole-mount preparations and serial semithin and ultrathin sections. Differences in the localization, distribution pattern and density of peptidergic and catecholaminergic nerve fibers were found in the vertebral and intervertebral regions of the posterior longitudinal ligament. For immunocytochemistry, free floating specimens were incubated with primary antibodies against protein gene product 9.5, substance P, calcitonin gene-related peptide, dopamine-beta-hydroxylase, vasoactive intestinal polypeptide and neuropeptide Y together with the avidin-biotin-peroxidase method. In whole-mount preparations, the neural marker protein gene product 9.5 is immunostained in all unmyelinated nerve fibers in the posterior longitudinal ligament, thus giving a panoramic view of the nerve fiber plexus. The most striking nerve fiber plexus is localized in the intervertebral region. In this region, the posterior longitudinal ligament is rich in capillaries that form a dense plexus within its ventral part and extend to the outer layer of the annulus fibrosus. The peptidergic and catecholaminergic innervation of the posterior longitudinal ligament is discussed in the context of pain syndromes related to the vertebral column and degenerative lumbar spine diseases.

Tyrosine hydroxylase-immunoreactive nerve fibres in rat posterior longitudinal ligament.

The nerve supply to the posterior longitudinal ligament (PLL) of the lumbar vertebrae has been the focus of considerable interest to gain insight into the pathogenesis of low back pain. The present study aimed to characterize the sympathetic fibres in the PLL by immuno-electronmicroscopy for tyrosine hydroxylase (TH), the rate limiting enzyme in catecholamine synthesis. The posterior central branches of the segmental lumbar arteries received numerous communicating fibres from the sinuvertebral nerve (SVN), but only shortly after their entrance to the spinal canal. The non-vessel-associated branches of the SVN formed transverse bundles, which met fibres from the opposite side in a plexus-like mid-sagittal network. As these fibres approached the midline, they gradually lost their Schwann cell cover. The free and naked fibres contained numerous terminal-like varicosities. The TH-ir and 6-hydroxydopamine (6-OH-DA) sensitive fibres were intermingled with non-TH-ir fibres. The TH-ir sympathetic fibres had no obvious target structures except for the numerous, intermingled, closely related and communicating terminal-like axons in the mid-sagittal network in contact with non-TH-ir fibres. This may represent a neuroanatomical equivalent reflecting modulatory functions, which could participate in the pathogenesis of low back pain.

[Neuroanatomic basis for discogenic pain]. / Neuroanatomische Grundlagen des diskogenen Schmerzes.

AIMS: The aim of this study is to give a short overview about the innervation of the intervertebral disc and the nerve connections between the somatosensible and autonomous nervous systems in the paravertebral region. METHODS: A short review of the clinical and experimental literature including gross-anatomical, histochemical and immunohistochemical studies as well as functional studies after application of tracer substances has been made. We also present our own experimental immunohistochemical and molecular biological investigations on paravertebral muscle biopsies of a patient with post-discotomy syndrome. RESULTS: The annulus fibrosus of the intervertebral disc is innervated by myelinated nerve fibres. Neuronal markers for pain-leading fibres were found to be positive in the dorsal region of the annulus, and especially in the posterior longitudinal ligament. Nerve ingrowth into the diseased intervertebral disc was found in chronic back pain. The main innervation of the intervertebral disc is formed by the sinuvertebral nerves. The sinuvertebral nerves are recurrent branches of the ventral rami that re-enter the intervertebral foramina to be distributed within the vertebral canal. They are mixed polysegmental nerves and nerve plexuses, each being formed by a somatic root from a ventral ramus and an autonomic root from a grey ramus communicans. The number of nerve bundles was reduced by resection of sympathetic trunks. The expression of neuronal markers in the sarcolemma of the paravertebral muscles is reduced after discotomy. CONCLUSIONS: The neuroanatomical basis of discogenic pain can be summarised as follows: 1. The intervertebral disc receives an extensive innervation, especially the annulus fibrosus. 2. Nerve extension was found into the nucleus pulposus of the degenerated disc. 3. The sinuvertebral nerve plexuses facilitate a polysegmental signal and pain spreading. 4. The innervation of the intervertebral disc is very high connected with the paravertebral muscles. 5. A local denervation of the paravertebral muscles was found in post-discotomy syndrome.