Central Spinal Canal Research Articles

Stenosis of lumbar intervertebral foramen: anatomic study on predisposing factors.

In Study 1 the authors measured the vertical and sagittal dimensions of the intervertebral foramen in dried lumbar vertebrae. In Study 2 the dimensions of the intervertebral foramen were measured in fresh cadaveric spines in which the soft tissues forming the foraminal walls were preserved. To investigate whether disc narrowing, or other factors related to the morphometry of lumbar vertebrae, may predispose to foraminal stenosis. Predisposing factors to foraminal stenosis have been little investigated. Previous studies suggested that narrowing of the disc space might cause a reduction in the foraminal dimensions; however, it is not clear whether such a reduction is to such an extent as to compress the nerve root within the foramen. In Study 1 the vertical and sagittal dimensions of 160 intervertebral foramens were measured on dried white spines. Measurements were performed in the presence of a normal height of the disc space, obtained using a silicone rubber disc, and repeated in the same specimen after disc removal. Foraminal dimensions were then related to the sagittal diameter of the spinal canal and the pedicle length. In Study 2, the authors evaluated the dimensions of 50 intervertebral foramens of fresh cadaveric spines, in which the soft tissues forming the foraminal walls and the nerve root were preserved. In specimens showing normal or slightly decreased disc height, the foraminal dimensions were measured before and after disc excision. In Study 1 the reduction in the foraminal height after disc removal was, on average, 6.5 mm (P < 0.0001). In both Studies 1 and 2 the sagittal dimensions of the foramen were not significantly reduced after disc removal. No significant difference was found in Study 1 in the sagittal dimensions of the foramen between specimens showing normal or degenerated facet joints. In Study 2 a compression of the nerve root within the foramen was found in one specimen, showing a concomitant central stenosis at multiple levels. A significant correlation was found between the sagittal diameters of the foramen and the sagittal diameter of the spinal canal and the pedicle length. Narrowing of the disc space significantly reduces the vertical diameter of the foramen but has no significant effects on its sagittal dimensions. In contrast, the sagittal dimensions of the foramen are strictly related to the sagittal diameter of the spinal canal and the pedicle length. These results suggest that in patients with developmental or combined stenosis of the central spinal canal, a concomitant foraminal stenosis is likely to be present, or at least should be suspected.

Spinal Primary Neoplasia/Metastasis

AbstractThis unit presents a basic protocol for conventional and fast spin echo imaging of spine for visualization of the spinal compartment to assess the extent and degree of spinal cord or cauda equina compression frequently associated with primary and metastatic neoplasia. An alternate protocol is presented for the cases e.g., neurofibromatosis with multiple bilateral neoplasms extending through the neural foramina, where a coronal acquisition may be helpful to analyze the perispinal tissues for tumor extension either inward to, or outward from, the central spinal canal.

Spinal Canal Stenosis

AbstractThis unit presents a basic protocol for fast spin echo sequences for imaging to diagnose stenosis of the spinal canal. Spinal stenosis is defined generally as a narrowing of one or more of the following: the central canal, foramina, and lateral recesses of the lumbar spine. Specifically, this stenosis can be classified into three types as defined by location: (a) stenosis of the central spinal canal, (b) stenosis of the intervertebral spinal neural foramen or foramina, and (c) stenosis of the lateral recess(es) of the central spinal canal.

Upright, Weight-Bearing, Dynamic-Kinetic MRI of the Spine: pMRI/kMRI

Purpose: To review the general clinical utility of the first dedicated magnetic resonance imaging (MRI) unit enabling upright, weight-bearing positional evaluation of the spinal column (pMRI) during various dynamic-kinetic maneuvers (kMRI) in patients with degenerative conditions of the spine. Materials & methods: This study consisted of a prospective non-statistical analysis of cervical or lumbar imaging examinations. All studies were performed on a recently introduced whole body MRI system (Stand-Up MRI, Fonar Corp, Melville, NY). The system operates at 0.6T using an electromagnet with a horizontal field, transverse to the longitudinal axis of the patient's body. Depending upon spinal level, all examinations were acquired with either a cervical or lumbar solenoidal radiofrequency receiver coil. This unit was configured with a top-front open design, incorporating a patient-scanning table with tilt, translation and elevation functions. The unique motorized patient handling system developed for the scanner allowed for vertical (upright, weight bearing) and horizontal (recumbent) positioning of all patients. The top-open construction also allowed dynamic-kinetic flexion and extension maneuvers of the spine. Patterns of bony and soft tissue change occurring among recumbent (rMRI) and upright neutral positions (pMRI), and dynamic-kinetic acquisitions (kMRI) were sought. Results: Depending on the specific underlying pathologic degenerative condition, significant alterations observed on pMRI and kMRI that were either more or less pronounced than on rMRI included: fluctuating anterior and posterior disc herniations, hypermobile spinal instability, central spinal canal and spinal neural foramen stenosis and general sagittal spinal contour changes. No patient suffered from feelings of claustrophobia that resulted in termination of the examination. Conclusion: To conclude, the potential relative beneficial aspects of upright, weight-bearing (pMRI), dynamic-kinetic (kMRI) spinal imaging on this system over that of recumbent MRI (rMRI) include: the revelation of occult disease dependent on true axial loading, the unmasking of kinetic-dependent disease, and the ability to scan the patient in the position of clinically relevant signs and symptoms. This imaging unit also demonstrated low claustrophobic potential and yielded relatively high-resolution images with little motion/chemical shift artifact.

CT and MRI characteristics of ossification of the ligamenta flava in the thoracic spine

The purpose of this study was to compare MRI findings with CT findings of mass-forming calcification/ossification of the thoracic ligamenta flava (OTLF). Twenty-one Chinese patients presented with clinical evidence of chronic and progressive thoracic spinal cord compression which included: difficulty in walking; weakness; and/or numbness of the extremities, back pain, and lower extremity paresthesias. Axial and sagittal T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) were performed through the thoracic spine on a 1.0-T Impact unit (Siemens, Erlangen, Germany). Axial CT was obtained with 5-mm contiguous sections through the thoracic region. Decompressive surgery with resection of the OTLF were carried out in all patients. Low signal intensity of the mass-forming OTLF was demonstrated at a single level (n=1) or at multiple levels (n=20) on both T1WI and T2WI. The distribution of OTLF was bilateral at all levels identified in 6 cases, unilateral at all levels in 5 patients, and both unilateral and bilateral at different levels in 10 cases. Ossification of the thoracic ligamenta flava involved the upper thoracic spine (T1-4) in 3 cases, midthoracic spine (T5-8) in 3 cases, lower thoracic spine (T9-12) in 10 cases, and more than one thoracic spinal subregion in 5 cases. Computed tomography confirmed the MR findings regarding the location and distribution of OTLF in all cases, as well as the associated evidence of central spinal canal stenosis. In addition, 5 patients revealed associated ossification of the posterior longitudinal ligament. All patients demonstrated gradual, but incomplete, clinical improvement of the radiculomyelopathy following decompressive surgery. Ossification of the posterior longitudinal ligament resulting in thoracic central spinal canal stenosis and clinical radiculomyelopathy is not uncommon in the Asian people. Ossification of the thoracic ligamenta flava can be accurately evaluated equally well by CT and MR with regard to level(s) and side(s) of involvement, as well as to the relative degree of central spinal canal stenosis and the associated compression of the thoracic spinal cord.

Spinal epidural abscess: correlation between MRI findings and outcome.

Our purpose was to determine if specific MRI findings in spinal epidural abscess (SEA), at the time of diagnosis, are associated with the clinical outcome. The clinical records and MRI studies of 18 patients with SEA were reviewed and follow-up was obtained from the outpatient medical record, telephone interview, or both. The association between findings on contrast-enhanced MRI and clinical outcome (weakness, neck or back pain, and incomplete functional recovery) was evaluated. With univariate analysis, narrowing of 50% or more of the central spinal canal (P = 0.03), peripheral contrast-enhancement (P = 0.05), and abnormal spinal cord signal intensity (P = 0.05) were associated with weakness at follow-up. Persistent neck or back pain was associated with spinal canal narrowing (P = 0.02), peripheral contrast-enhancement (P = 0.02), and an abscess longer than 3 cm (P = 0.04) on MRI. Incomplete clinical recovery was associated with both abscess length (P = 0.01) and the severity of canal narrowing (P = 0.01). Abscess length, enhancement pattern, and severity of canal narrowing can be incorporated in a grading system that can be used to predict outcome.

MR EVALUATION OF STENOSIS INVOLVING THE NEURAL FORAMINA, LATERAL RECESSES, AND CENTRAL CANAL OF THE LUMBOSACRAL SPINE

MR imaging depicts the levels, sides, and severity of physical stenoses of the central spinal canal, the lateral recesses, and the neural foramina--diagnostic information crucial for the symptomatic patient under consideration for surgical correction. In the future, it is probable that MR imaging, using standard static techniques, flow-sensitive studies, and noncontrast, intravenous gadolinium-enhanced or intrathecal gadolinium-enhanced acquisitions, will probably replace all other imaging modalities in the primary evaluation of the various subtypes of spinal stenoses.

Lumbar Spinal Stenosis: A Literature Review

This paper describes the etiology and clinical manifestations of lumbar spinal stenosis (LSS); discusses diagnosis, prognosis, and intervention; and addresses outcome studies and their implications in managing patients with lumbar spinal stenosis. LSS is a condition involving narrowing of the central spinal canal, lateral recesses, or intervertebral foramina; it is the most commonly diagnosed degenerative process associated with aging. Neurogenic intermittent claudication is a common clinical manifestation of LSS that must be differentiated from vascular claudication of the lower extremities. Although surgery is commonly performed in treating LSS, some evidence exists to support the use of a conservative approach such as orthopaedic manual physical therapy. However, controlled clinical trials with large sample sizes are lacking to offer strong support for either conservative or surgical measures. This paper provides a rationale for a manual physical therapy and exercise approach in treating LSS. Future studies need to include comparative research involving different conservative approaches, and indications for surgical versus nonsurgical management of LSS need to be more clearly defined and studied through randomized, controlled clinical trials.

MR IMAGING OF THE SPINE IN SPORTS INJURIES

MR imaging has afforded an ability to better visualize and characterize a whole host of spine abnormalities encountered in the athletic population. It remains the mainstay in the noninvasive diagnosis of most soft-tissue abnormalities occurring within and about the spine. Its role in the evaluation of central spinal stenosis, the central spinal canal, and the spinal cord is unsurpassed by other noninvasive imaging modalities. In the setting of underlying fractures, it is complementary to CT, particularly with respect to evaluating concomitant soft-tissue and ligamentous abnormalities. With its ability to image edema and reactive marrow changes, it is useful in the evaluation of osseous stress changes that may occur in the athletic population.

Observer variation in plain radiography of the lumbosacral spine.

In this study, interobserver and intraobserver variations in the interpretation of plain radiographs of the lumbosacral spine were evaluated. Three radiologists independently interpreted the radiographs from 200 consecutive outpatients, aged 13-93 years, mostly referred from general practitioners. Interobserver agreement was best for vertebral fractures, osteopenia, spondylolisthesis at L5-S1, lumbosacral junctional vertebra, reduced disc height at L4-S1 and osteophytes at L2-S1 (kappa 0.61-0.95), and poorest for spina bifida of S1, degenerative spondylolisthesis and facet joint arthrosis at T12-L4, sacroiliac joint arthrosis, narrow central spinal canal, film quality, and for decisions concerning evaluation of facet joints and spinal canal (kappa < 0.34). For several diagnoses, the number of abnormal findings differed significantly between observers (p < 0.05, McNemar's test), indicating different diagnostic thresholds. Intraobserver agreement in 36 reevaluated patients was fair to excellent for almost all variables (kappa > 0.46). Although some diagnoses related to low back pain were quite consistently evaluated, the substantial disagreement on many findings should alert clinicians and radiologists against overestimating the validity and usefulness of the examinations. To improve diagnostic consistency, it is important to reduce variation caused by different thresholds for abnormality.

Non-Discal Lumbar Radiculopathy: Combined Diagnostic Approach by CT and MR

The goal of this paper was to evaluate the different causes of non-discal radiculopathies and to determine the different sensitivity and specificity of CT and MR. We reviewed 450 patients with non-discal radiculopathy; CT was performed in all patients while MR was done only in 95 cases. MR was obtained only in case of polyradiculopathy, or if there was a discrepancy between clinical evaluation and CT findings or when sphincteral symptoms were present. The most frequent cause of non-discal radiculopathy was degenerative disk disease associated with facet joint abnormality and secondary central and lateral spinal canal stenosis. Other causes were neoplastic lesions, traumas, malformations, inflammatory processes and vascular abnormality. CT was more sensitive and specific in degenerative disc disease while MR was better at evaluating other pathology. CT still represents a satisfactory technique in evaluating patients with non-discal radiculopathy; MR must be also performed in case of discrepancy between clinical evaluation and CT findings. Directly MR examination should be reserved for patients presenting sphincteral symptoms.

Overexpression of nestin and vimentin in the ependyma of spinal cords from hydrocephalic infants

The ependyma of the spinal central canal in cases of hydrocephalus shows abnormalities which vary with the aetiology of ventricular dilatation. To determine whether these ependymal changes are developmental or reactive in nature, immunohistochemical findings were compared between nine normal controls and 12 cases of hydrocephalus (three each of congenital aqueductal stenosis. Dandy-Walker malformation, Chiari type II malformation, and post-haemorrhagic hydrocephalus) using antisera to nestin, vimentin and glial fibrillary acidic protein. The main pathological findings were disruption of ependymal layer, apparent pseudostratification of ependyma, expansion, cleft or syrinx formation in relation to the central canal, and ependymal rosette formation. In normal developing fetal spinal cord, nestin and vimentin were expressed mainly in pseudostratified ependymal cells and radial fibres in the median septum. In cases with congenital hydrocephalus (congenital aqueductal stenosis. Dandy-Walker malformation, and Chiari type II malformation), nestin was overexpressed in immature ependymal cells, and strong vimentin immunoreactivity was detected in the long tract of radial fibres in the median septum. Nestin and vimentin were also expressed in small cells and their fibres which covered areas denuded of ependymal cells in cases of Chiari type II malformation and post-haemorrhagic hydrocephalus. Two conclusions are suggested by this report. First, the ependyma of the spinal central canal in congenital hydrocephalus shows a delay in maturation of radial glial cells into mature astrocytes and ependymal cells. Second, areas of ependymal denudation may be repaired by the immature glial cells derived from subependymal cells.

Experimental hydrocephalus and hydromyelia: A new insight in mechanism of their development

One group of cats had an acrylic screw implanted into the adqueduct of Sylvius, while the other group of animals received a solution of kaolin into the cisterna magna. Three weeks later the dye phenolsulphonphthalein was instilled into the lateral ventricle to ascertain communication between CSF compartments, and thereafter the brain was perfused with formalin. As shown by planimetry of brain ventricles both groups of experimental animals developed hydrocephalus, i.e., coronal surface of brain ventricles was about 10 times larger in kaolin and about 3 times in aqueductal screw experiments than in the controls, respectively. In aqueductal screw experiments communication of CSF between lateral ventricle and subarachnoid spaces was not blocked but only restricted, i.e., an aqueductal stenosis was produced. In kaolin experiments communication of CSF between lateral ventricles and spinal subarachnoid space was blocked by thick meningeal adhesions in the upper cervical region, while the central spinal canal was dilated (hydromyelia) with enhanced CSF communication between it and the lumbar subarachnoid space. We assume that during systolic expansion of brain the CSF is displaced from the cranial cavity toward the spinal subarachnoid space which accommodates an additional volume of CSF primarily due to compliance of the spinal dural sac, while during diastole CSF recoils in the opposite direction. Thus, in case of aqueductal stenosis the undisplaced volume of CSF from the ventricles can be accommodated due to diminution of cerebral blood volume and brain parenchyma so that hydrocephalus develops over time. Since the cervical subarachnoid space is blocked in kaolin experiments the systolic brain expansion forces CSF from basal cisterns via the fourth ventricle into the aqueduct and central canal with consequent development of hydrocephalus and hydromyelia.

MANAGEMENT OF LUMBAR SPINAL STENOSIS

The term stenosis means a narrowing of the calibre of an orifice or a tube. It causes a decreased flow of fluids or gasses within the tube or compression of its solid contents (Verbiest 1976). In the case of the spinal canal, the term indicates a pathological condition causing compression of the contents of the canal, particularly the neural structures. If compression does not occur, the canal should be described as narrow but not stenotic. I have defined lumbar spinal stenosis as a “narrowing of the osteoligamentous vertebral canal and/or the intervertebral foramina causing compression of the thecal sac and/or the caudal nerve roots; at a single vertebral level, narrowing may affect the whole canal or part of it” (Postacchini 1983). This definition distinguishes between disc herniation and stenosis. A disc prolapse does cause stenosis, in the strictest sense, but the two conditions are so different in their pathogenesis and anatomical and clinical characteristics that they cannot be considered as a single pathological entity. The lumbar spinal canal consists of a central part, two lateral parts and a posterior part corresponding to the interlaminar angle. The central portion is the so-called central spinal canal, and each lateral part constitutes the nerve-root or radicular canal. The central spinal canal is rounded and occupied by the thecal sac. Stenosis of this portion is sometimes called central spinal stenosis to distinguish it from lateral spinal stenosis (nerve-root canal stenosis). This terminology implies that in central spinal stenosis the nerve-root canals may not be stenotic, but this is not the case. Stenosis of the central portion is almost always associated with stenosis of the lateral corners of the spinal canal. The term ‘spinal canal stenosis’ is therefore preferable to central spinal stenosis. The nerve-root canal is the semitubular structure through which the nerve root runs from the thecal sac to the intervertebral foramen. The proximal part of the canal, also called the subarticular or intervertebral portion, is limited anteriorly by the intervertebral disc and posterolaterally by the superior articular process and the facet joint. The distal part of the canal corresponds to the lateral recess, i.e., the lateral corner of the vertebral foramen at the level of the pedicle. Pathological narrowing of the nerve-root canal not associated with stenosis of the central spinal canal is called isolated nerve-root (or radicular) canal stenosis. The entrance and exit of the intervertebral foramen lie at the medial and lateral borders of the pedicle. Some authors (Wiltse 1984; Burton 1987) include the intervertebral foramen in the nerve-root canal, of which it is then the most distal portion. In my opinion there are valid anatomical reasons for distinguishing between the two and identifying stenosis of the intervertebral foramen as a separate condition.

Imaging Evaluation of Patents with Spinal Deformity

CT myelography and MRI provide the best means of preoperatively assessing patients with spinal deformities. Owing to its noninvasive nature and its superior soft-tissue contrast, MRI represents the single best modality in the evaluation of a patient with any deformity. MRI allows complete preoperative surgical planning and obviates the need for any additional studies. Screening of the entire cord in a patient with a deformity is best accomplished with sagittal and coronal (as needed) T1W images. These images allow assessment of the cord for compression, tethering, syrinx, enlargement, and Arnold-Chiari malformation. Evaluation of cord compression at the apex of a curve is the single most important consideration other than the diagnosis of intrinsic cord abnormality. Subsequent sagittal or axial T2W images may be helpful if specific abnormalities are noted on T1W screening images. Coronal images are particularly helpful in patients with prominent curves or in those with vertebral anomalies. Additionally, coronal images may be useful in assessing patients with suspected diastemato- myelia. Advances in hardware and software design have resulted in marked improvements in the ability to satisfactorily image all aspects of patients with spinal deformities. New phased array coils allow rapid imaging of larger por-tions of the spine. For instance, a complete MRI of the spine can be performed in a child in the same length of time that would have been necessary for a single lumbar examination when MRI was in it’s infancy. The use of fast spinecho imaging also permits more rapid acquisition times. CT myelography remains useful for those patients who cannot undergo MRI or for those with specific abnormalities such as multilevel central spinal stenosis when dynamic information obtained during the myelogram might be helpful. CT myelography represents the only means of assessing the central spinal canal of patients with metallic instrumentation in place. With the exception of these limited applications, MRI has replaced CT myelography as the imaging study of choice in the evaluation and examination of patients with spinal deformities.

MYELOGRAPHY IN THE DOG: REVIEW OF PATIENTS WITH CONTRAST MEDIUM IN THE CENTRAL CANAL

Contrast medium opacification of the spinal central canal after cisterna magna or lumbar puncture caudal to the 5th lumbar vertebra was an unusual observation during myelography. Incidental central canal opacification was more likely to occur in normal dogs or dogs with spinal cord pathology during lumbar puncture cranial to the 5th lumbar vertebra. Preferential contrast medium migration into the central canal, particularly if injected rapidly, may lead to deterioration in neurologic status. Placement of the spinal needle in the central canal during cisterna magna myelography was necessary to document the presence of hydromyelia. Case histories illustrating the above conditions were given and their significance discussed.

Enhanced resolution of histochemical distribution of glucose-6-phosphate dehydrogenase activity in rat neural tissue by use of a semipermeable membrane.

We examined the histochemical distribution of glucose-6-phosphate dehydrogenase (G6PD) activity in neural tissue using different diffusion barriers. Although polyvinyl alcohol and agar overlays permitted regional localization of G6PD, a semipermeable membrane revealed cellular differences in G6PD activity within populations of neurons. Distribution of G6PD activity in selected regions of the nervous system was examined using the membrane technique. White matter usually exhibited strong G6PD activity. The neuronal somata of the dorsal root ganglia (L4-L6) and anterior horns of the spinal lumbar enlargement demonstrated a variation in activity which was independent of somal size. Satellite cells showed intense activity when the membrane technique was used. Hippocampal pyramidal and granular cells of the dentate gyrus exhibited moderate, uniform G6PD activity, but only weak activity was seen in hippocampal and dentate molecular layers. High levels of activity were observed in the vascular endothelial cells of the brain, spinal cord, and choroid plexus, and in the ependymal cells of the spinal central canal and ventricles of the brain. The superior vestibular nucleus appeared to have little G6PD activity in either the neuron cell bodies or the surrounding parenchyma. The use of a semipermeable membrane for localization of G6PD activity in neural tissues permits enhanced resolution of neuron elements and may provide a more accurate assessment of G6PD activity in histological preparations.

Radiographic Anatomy of the Distal Dural Sac

A radio-anatomical study was performed of the distal dural sac (DS) in 121 patients subjected to myelography. In 83.4% the termination of the DS was located from the upper half of the S1-segment to the lower half of the S2-segment. In the remaining patients the dural terminations were more distally located. The average location of the DS-termination was higher than that found in a previous anatomic study. The inference is that in patients with low-back pain and sciatica, the DS tends to terminate at a higher spinal level than in a non-selected anatomic material. The caudal reduction in sagittal diameter of the DS was less than that of the frontal diameter of the sac. The linear diminution in cross-sectional area of the DS from the level of L3 towards the lumbo-sacral junction was not correlated with the degree of caudal extension of the DS into the sacrum. Thus the length of the DS and its transverse diameters are independent of each other. These results supported the view that the location of the termination of the DS (and hence that of the spinal cord) is not related to stenosis of the central spinal canal.

Preservation of the ependyma of the mouse spinal cord by various vascular perfusion procedures

Seventy-two mice were used to find out which of 13 vascular perfusion procedures gave best structural preservation of the spinal cord ependyma and central canal lumen. Best results were obtained by 3% glutaraldehyde in Tyrodes solution with 50% of normal NaCl amount, 0.06 M sucrose and 2% dextran T-40 (556 mOsmol, pH 7.2, 0–4°C). This was perfused by a peristaltic pump at 40 ml/min for 10 min through a cannula inserted in the ascending aorta. No advantage was seen by heparin pretreatment or adding a prefixation rinse. With good tissue preservation the central canal was found to be round to oval in cross-sectional profile and almost free of intraluminal material.

Immunohistochemistry of synaptic input and functional characterizations of neurons near the spinal central canal

Neurons surrounding the central canal in sacral spinal segments were functionally characterized on the basis of somatic and/or visceral afferent input, the intracellularly marked with horseradish peroxidase (HRP). Tissue sections containing portions of HRP-stained neurons were subsequently immunohistochemically examined for the presence of contacts made by axonal enlargements containing vasoactive intestinal polypeptide (VIP), substance P (SP), somatostatin (SS), Leu-enkephalin (ENK), or serotonin (5-HT). ENK- and 5-HT-containing enlargements were found to contact all neurons examined. SP and SS terminals contacted fewer neurons, and were not associated with specific functional classes. On the other hand, VIP-containing fibers contacted only those neurons receiving visceral afferent input, thus supporting the contention that VIP is contained in a population of visceral afferent fibers projecting to the gray matter surrounding the central canal at sacral levels.