Magnetic resonance imaging in the prone position and the diagnosis of tethered spinal cord

Procedural sedation and analgesia in pediatric diagnostic and interventional radiology: An expert DELPHI consensus document developed by the ITALIAN scientific society of anesthesia, analgesia, resuscitation and intensive care (SIAARTI)

BACKGROUND

Children undergoing diagnostic and interventional radiology procedures often require sedation to achieve immobility and analgesia if the procedure is painful. In the past decades, leading scientific organizations have developed evidence-based guidelines for procedural sedation and analgesia in children outside of the operating room. Their recommendations are being applied to procedural sedation in radiology. However, some questions remain open regarding specific aspects contextualized to the radiology setting, such as elective prone sedation, the urgency of the procedure, when venous access or airway protection is required, and others.

AIMS

To address the unresolved issues of procedural sedation and analgesia in pediatric diagnostic and interventional radiology.

METHODS

An expert panel of pediatricians, pediatric anesthesiologists, intensivists, and neuroradiologists selected topics representative of current controversies and formulated research questions. Statements were developed by reviewing the literature for new evidence, comparing expertise and experience, and expressing opinions. Panelists' agreement with the statements was collected anonymously using the DELPHI method.

RESULTS

Twelve evidence-based or expert opinion incorporate are presented, considering risks, benefits, and applicability.

CONCLUSIONS

This consensus document, developed by a multidisciplinary panel of experts involved in the field, provides statements to improve the quality of decision-making practice in procedural sedation and analgesia in pediatric radiology.

Total spine MRI for the preoperative evaluation of adolescent idiopathic scoliosis: part 1

Adolescent idiopathic scoliosis is a commonly encountered condition often diagnosed on screening examination. Underlying, asymptomatic neural axis abnormalities may be present at the time of diagnosis. At certain institutions, total spine MRI is obtained preoperatively to identify these abnormalities. We provide a framework for the radiologist to follow while interpreting these studies. In part 1, we discuss Arnold Chiari malformations, syringomyelia, and the tethered cord. In part 2, we focus on spinal cord tumors, dysraphisms, to include diastematomyelia, and vertebral anomalies.

Tethered spinal cord tension assessed via ultrasound elastography in computational and intraoperative human studies

BACKGROUND

Tension in the spinal cord is a trademark of tethered cord syndrome. Unfortunately, existing tests cannot quantify tension across the bulk of the cord, making the diagnostic evaluation of stretch ambiguous. A potential non-destructive metric for spinal cord tension is ultrasound-derived shear wave velocity (SWV). The velocity is sensitive to tissue elasticity and boundary conditions including strain. We use the term Ultrasound Tensography to describe the acoustic evaluation of tension with SWV.

METHODS

Our solution Tethered cord Assessment with Ultrasound Tensography (TAUT) was utilized in three sub-studies: finite element simulations, a cadaveric benchtop validation, and a neurosurgical case series. The simulation computed SWV for given tensile forces. The cadaveric model with induced tension validated the SWV-tension relationship. Lastly, SWV was measured intraoperatively in patients diagnosed with tethered cords who underwent treatment (spinal column shortening). The surgery alleviates tension by decreasing the vertebral column length.

RESULTS

Here we observe a strong linear relationship between tension and squared SWV across the preclinical sub-studies. Higher tension induces faster shear waves in the simulation (R2 = 0.984) and cadaveric (R2 = 0.951) models. The SWV decreases in all neurosurgical procedures (p < 0.001). Moreover, TAUT has a c-statistic of 0.962 (0.92-1.00), detecting all tethered cords.

CONCLUSIONS

This study presents a physical, clinical metric of spinal cord tension. Strong agreement among computational, cadaveric, and clinical studies demonstrates the utility of ultrasound-induced SWV for quantitative intraoperative feedback. This technology is positioned to enhance tethered cord diagnosis, treatment, and postoperative monitoring as it differentiates stretched from healthy cords.

Diagnosis and Management of Tethered Cord Syndrome

Tethered cord syndrome is a condition in which the spinal cord is tethered by pathological structures such as a tight filum terminale, intradural lipomas with or without a connecting extradural component, intradural fibrous adhesions, diastematomyelia, and neural placode adhesions following closure of a myelomeningocele.It usually occurs in childhood and adolescence as the spine grows in length, but it can also develop in adulthood. Symptoms of tethered cord syndrome are slowly progressive and varied. Incorrect diagnosis and inappropriate treatment may be provided if the physician lacks knowledge and understanding of this disease.This chapter aims to describe the pathophysiology, syndromes, diagnostic imaging, surgical treatment, and prognosis of tethered cord syndrome to enhance the understanding of this condition.

Lumbar dorsal root ganglion displacement between supine and prone positions evaluated with 3D MRI

OBJECTIVE

Pre-operative lumbar spine MRI is usually acquired with the patient supine, whereas lumbar spine surgery is most commonly performed prone. For MRI to be used reliably and safely for intra-operative navigation for foraminal and extraforaminal decompression, the magnitude of dorsal root ganglion (DRG) displacement between supine and prone positions needs to be understood.

METHODS

A prospective study of a degenerative lumbar spine cohort of 18 subjects indicated for lumbar spine surgery. Three-dimensional T2-weighted fast spin echo and T1-weighted spoiled gradient echo sequences were acquired at 3 T. Displacement and cross-sectional area (CSA) of the bilateral DRGs at 5 motion levels (L1-2 to L5-S1) were determined via 3D segmentation by 2 independent evaluators. Wilcoxon rank-sum tests without correction for multiple comparison were performed against hypothesized 1-mm absolute displacement and corresponding 24% CSA change.

RESULTS

DRG mean absolute displacement was <1 mm (p > 0.99, mean = 0.707 mm, 95% confidence interval (CI) = 0.659 to 0.755 mm), with the largest directional displacement in the dorsal-to-ventral direction from supine to prone (mean = 0.141 mm, 95% CI = 0.082 to 0.200 mm). Directional displacements caudal-to-cephalad were 0.087 mm (95% CI = 0.022 to 0.151 mm), and left-right were -0.030 mm (95%CI = -0.059 to -0.001 mm). Mean CSA change was within 24% (p > 0.99, mean = -8.30%, 95% CI = -10.5 to -6.09%). Mean absolute displacement was largest for the L1 (mean = 0.811 mm) and L2 (mean = 0.829 mm) DRGs.

CONCLUSIONS

Minimal, non-statistically significant soft tissue displacement and morphological area differences were demonstrated between supine and prone positions during 3D lumbar spine MRI.

Surgery for spina bifida occulta: spinal lipoma and tethered spinal cord

The technical evolution of the surgery for spina bifida occulta (SBO) over the course of a half-century was reviewed with special foci placed on the spinal lipoma and tethered spinal cord. Looking back through history, SBO had been included in spina bifida (SB). Since the first surgery for spinal lipoma in the mid-nineteenth century, SBO has come to be recognized as an independent pathology in the early twentieth century. A half-century ago, the only option available for SB diagnosis was the plain X-ray, and pioneers of the time persevered in the field of surgery. The classification of spinal lipoma was first described in the early 1970s, and the concept of tethered spinal cord (TSC) was proposed in 1976. Surgical management of spinal lipoma with partial resection was the most widely practiced approach and was indicated only for symptomatic patients. After understanding TSC and tethered cord syndrome (TCS), more aggressive approaches became preferred. A PubMed search suggested that there was a dramatic increase of publications on the topic beginning around 1980. There have been immense academic achievements and technical evolutions since then. From the authors' viewpoint, landmark achievements in this field are listed as follows: (1) establishment of the concept of TSC and the understanding of TCS; (2) unraveling the process of secondary and junctional neurulation; (3) introduction of modern intraoperative neurophysiological mapping and monitoring (IONM) for surgery of spinal lipomas, especially the introduction of bulbocavernosus reflex (BCR) monitoring; (4) introduction of radical resection as a surgical technique; and (5) proposal of a new classification system of spinal lipomas based on embryonic stage. Understanding the embryonic background seems critical because different embryonic stages bring different clinical features and of course different spinal lipomas. Surgical indications and selection of surgical technique should be judged based on the background embryonic stage of the spinal lipoma. As time flows forward, technology continues to advance. Further accumulation of clinical experience and research will open the new horizon in the management of spinal lipomas and other SBO in the next half-century.

Comparison of Ultrasonographic Findings between Patients with Tethered Cord Syndrome and Healthy Children

Background

Tethered cord syndrome (TCS) is a type of occult spinal dysraphism, which necessitates early detection as an essential component of patient management in reducing complications. This study aimed to compare the findings of spinal cord ultrasonography between TCS patients and healthy individuals.

Methods

The current study is a case-control study of patients who were admitted to the Akbar and Ghaem Hospitals (Mashhad, Iran) in 2019. The study population comprised 30 children with TCS aged under two years old, and the control group included 34 healthy peers of the same age. The maximum distance of the spinal cord from the posterior canal wall was measured in millimeters using ultrasonography. Demographic and sonographic findings of each participant were recorded in checklists, which were then entered into SPSS software. P values less than 0.05 were considered statistically significant.

Results

The study included 30 children with TCS and 34 healthy individuals with a mean age of 7.67±6.39 months. TCS patients had a significantly shorter maximum distance of the spinal cord from the posterior wall of the spinal canal than the control group (1.75±0.62 mm vs. 2.79±0.76, P<0.001). After performing corrective surgery, the TCS patients indicated significant improvement in this interval (1.57±0.54 mm to 2.95±0.49 mm, respectively, P=0.001).

Conclusion

In comparison to children without TCS, the spinal cord was substantially closer to the posterior canal wall in TCS patients. However, these outcomes were improved significantly in patients after surgery.

Utilizing pre- and postoperative radiological parameters to predict surgical outcomes following untethering for tethered cord syndrome in a pediatric population

OBJECTIVE

Tethered cord syndrome (TCS) can lead to significant downstream neurological deficits including gait deterioration, incontinence, and often unexplained chronic low-back pain. Surgical intervention may relieve symptoms, but there are no defined radiological parameters associated with surgical outcomes and functional status. The authors aimed to define pre- and postoperative radiological parameters for assessing surgical outcomes in TCS.

METHODS

The authors performed a single-center retrospective review of all pediatric patients treated for TCS between 2016 and 2021. Patient baseline characteristics and operative metrics included age, sex, level of conus, level of procedure, tethering pathology, symptoms at presentation, complications, improvement of symptoms, and reoperation rate. MRI measurements included pre- and postoperative anterior canal distance (ACD) and bending angle (BA).

RESULTS

Thirty-three pediatric patients were identified who underwent untethering of the spinal cord and had pre- and postoperative MRI between 2016 and 2021. The mean patient age was 5.64 ± 5.33 years. Twenty patients (60.60%) were female. Regarding the site of untethering, 31 procedures (93.93%) were performed at the lumbosacral region and 2 (6.06%) were performed at the thoracolumbar region. The conus medullaris was found above L3 in 21.21% of patients. Postoperatively, 18.18% of patients experienced complications, 48.48% showed improvement in their symptoms, and 48.48% were equivocal or had persistent symptoms. The mean preoperative ACD0 (measured from the posterior vertebral body margin [middle] to the anterior margin of the conus medullaris) was 6.15 ± 3.18 mm, the postoperative ACD0 was 2.25 ± 2.72 mm, and the average change in ACD0 was -0.90 ± 1.31 mm. The mean preoperative BA was 26.00° ± 11.56°, the mean postoperative BA was 15.92° ± 9.81°, and the average change in BA was -10.08° ± 8.80°. An optimal cutoff value for preoperative BA to predict reoperation in pediatric patients with complex TCS undergoing surgery was ≥ 31.70° (area under the curve = 0.83).

CONCLUSIONS

In surgically treated patients with TCS, certain preoperative radiological parameters may be important in predicting postoperative surgical outcomes; these parameters can be evaluated and reported to indicate patients at high risk for complications. Further prospective multicenter research is warranted to offer robust evidence of association of patient outcomes with preoperative radiological parameters in TCS.

Anorectal malformation, urethral duplication, occult spinal dysraphism (ARM-UD-OSD): a challenging uncommon association

PURPOSE

Urethral duplication (UD) is a rare malformation, which can be associated with other anomalies, like anorectal malformations (ARM). ARM has been described with occult spinal dysraphism (OSD). No ARM-UD-OSD combination has been reported.

AIM

To share our experience and to discuss the management of ARM-UD-OSD association.

METHODS

We retrospectively reviewed records of five boys with UD. Four of these had ARM-UD-OSD association. ARM was the first diagnosis in all; OSD and UD was detected during screening for associated malformation.

RESULTS

All patients underwent ARM correction, 3 after colostomy. All reached fecal continence, 3 are performing bowel management. Three patients underwent UD surgical correction. Because of symptoms' worsening, 2 children had detethering surgery. At a mean follow-up of 9.5 years, all patients have normal renal function, 3 are on clean intermittent catheterization (CIC) for neurogenic bladder (1 has a cystostomy, another one an appendicostomy).

CONCLUSIONS

UD and OSD should be considered in patients with ARM. Children with these conditions associated must be centralized in a third-level Center and management carefully planned; in particular, urethral reconstruction should be weighed, considering CIC could be required. Suspicion of neurogenic bladder must be present in OSD patient.

Novel use of nonpenetrating titanium clips for pediatric primary spinal dural closure: A technical note

BACKGROUND

Dural closure is an important part of any pediatric spinal procedure with intradural pathology to prevent post-operative cerebrospinal fluid (CSF) egress and associated complications. Utilization of nonpenetrating titanium clips is one closure option that may have technical advantages such as ease of use and amenability to a narrow surgical corridor. No data exist on the efficacy of these clips for pediatric spinal dural closure.

METHODS

A single surgeon case series of 152 pediatric patients underwent procedures involving lumbar durotomy with subsequent dural closure using the AnastoClip® nonpenetrating titanium clip closure system. Rates of infection and cerebrospinal fluid leak were measured during the follow-up period.

RESULTS

A total of 152 pediatric patients (mean age: 6.25 ± 5.85 years, 50.7 % female) underwent intradural surgery with clip closure. The mean follow-up time was 57.0 ± 28.5 months. All patients were initially indicated for procedures involving spinal durotomy, with a majority being isolated tethered cord release (84.2 %). Others required tethered cord release and excision of a lipomyelomeningocele, spinal meningioma or arachnoid cyst (15.8 %). Post operative CSF leak occurred in two (1.32 %) patients at 11 and 18 days. Only one (0.66 %) patient was diagnosed with an infection, which was in a separate patient from those that had CSF leaks.

CONCLUSION

The remarkably low incidence of post-operative CSF leak and infection with nonpenetrating titanium clips suggests a strong safety and efficacy profile for this form of dural closure in a pediatric cohort. Further research evaluating this technique is required to fully demonstrate its acceptability as a cost-effective alternative to traditional suture-based closure.

A New Framework for Investigating the Biological Basis of Degenerative Cervical Myelopathy [AO Spine RECODE-DCM Research Priority Number 5]: Mechanical Stress, Vulnerability and Time

STUDY DESIGN

Literature Review (Narrative).

OBJECTIVE

To propose a new framework, to support the investigation and understanding of the pathobiology of DCM, AO Spine RECODE-DCM research priority number 5.

METHODS

Degenerative cervical myelopathy is a common and disabling spinal cord disorder. In this perspective, we review key knowledge gaps between the clinical phenotype and our biological models. We then propose a reappraisal of the key driving forces behind DCM and an individual's susceptibility, including the proposal of a new framework.

RESULTS

Present pathobiological and mechanistic knowledge does not adequately explain the disease phenotype; why only a subset of patients with visualized cord compression show clinical myelopathy, and the amount of cord compression only weakly correlates with disability. We propose that DCM is better represented as a function of several interacting mechanical forces, such as shear, tension and compression, alongside an individual's vulnerability to spinal cord injury, influenced by factors such as age, genetics, their cardiovascular, gastrointestinal and nervous system status, and time.

CONCLUSION

Understanding the disease pathobiology is a fundamental research priority. We believe a framework of mechanical stress, vulnerability, and time may better represent the disease as a whole. Whilst this remains theoretical, we hope that at the very least it will inspire new avenues of research that better encapsulate the full spectrum of disease.

Perspectives on urological care in spina bifida patients

Spina bifida (SB) is a neurogenetic disorder with a complex etiology that involves genetic and environmental factors. SB can occur in two major forms of open SB or SB aperta and closed SB or SB occulta. Myelomeningocele (MMC), the most common neural tube defects (NTDs), occurs in approximately 1 in 1,000 births. Considering non-genetic factors, diminished folate status is the best-known factor influencing NTD risk. The methylenetetrahydrofolate reductase (MTHFR) gene has been implicated as a risk factor for NTDs. The primary disorder in the pathogenesis of MMC is failed neural tube closure in the embryonic spinal region. The clinical manifestation of SB depends on clinical type and severity. SB can be detected in the second trimester using ultrasound which will reveal specific cranial signs. The management of MMC traditionally involves surgery within 48 h of birth. Prenatal repair of MMC is recommended for fetuses who meet maternal and fetal Management of Myelomeningocele Study (MOMS) specified criteria. Urological manifestations of SB include urinary incontinence, urolithiasis, sexual dysfunction, renal dysfunction, and urinary tract infection. Renal failure is among the most severe complications of SB. The most important role of the urologist is the management of neurogenic bladder. Medical management with clean intermittent catheterization and anticholinergic treatment is generally considered the gold standard of therapy. However, when this therapy fails surgical reconstruction become the only remaining option. This review will summarize the pathogenesis, risk factors, genetic contribution, diagnostic test, and management of SB. Lastly, the urologic outcomes and therapies are reviewed.

MRI characteristics of the fetal tethered spinal cord: a comparative study

Purpose: To compare fetuses and children with confirmed tethered cord syndrome to age-matched controls to provide a reference for prenatally identifying tethered spinal cord and to identify salient points on MRI for diagnosis.Materials and Methods: This retrospective study enrolled 13 fetuses and 20 children with tethered cord syndrome, and age-matched counterparts were included as controls. The MRI features including concomitant malformations, position of the conus medullaris, and thickened filum terminale of the two patient groups were evaluated and compared. Levels of the conus medullaris were discriminated between patients and an equivalent number of controls.Results: Various concomitant malformations manifested on the MRI of all patients, and there were differences between the two patient groups. Significant differences of the level of the conus medullaris were found between the fetal and child patients (U, 26.50; Z, -3.87; p < 0.001) and between the normal fetus and child controls (U, 23.50; Z, -4.13; p < 0.001). The position of the conus medullaris was visibly lower in the patient groups than in the control groups. No significant difference in the diameters of the filum terminale was found between the fetal and child patients (p = 0.67).Conclusions: The current study's results indicate that tethered spinal cord syndrome can be diagnosed in utero with MRI combined with several characteristics, particularly the position of the conus medullaris. Special attention should be paid to the gestational age of the fetus because normal changes in spinal cord position occur with gestational development.

Retethering : A Neurosurgical Viewpoint

During the follow-up period after surgery for spinal dysraphism, a certain portion of patients show neurological deterioration and its secondary phenomena, such as motor, sensory or sphincter changes, foot and spinal deformities, pain, and spasticity. These clinical manifestations are caused by tethering effects on the neural structures at the site of previous operation. The widespread recognition of retethering drew the attention of medical professionals of various specialties because of its incidence, which is not low when surveillance is adequate, and its progressive nature. This article reviews the literature on the incidence and timing of deterioration, predisposing factors for retethering, clinical manifestations, diagnosis, surgical treatment and its complications, clinical outcomes, prognostic factors after retethering surgery and preventive measures of retethering. Current practice and opinions of Seoul National University Children’s Hospital team were added in some parts. The literature shows a wide range of data regarding the incidence, rate and degree of surgical complications and long-term outcomes. The method of prevention is still one of the main topics of this entity. Although alternatives such as spinal column shortening were introduced, re-untethering by conventional surgical methods remains the current main management tool. Re-untethering surgery is a much more difficult task than primary untethering surgery. Updated publications include strong skepticism on re-untethering surgery in a certain group of patients, though it is from a minority of research groups. For all of the abovementioned reasons, new information and ideas on the early diagnosis, treatment and prevention of retethering are critically necessary in this era.

Surgical volume of simple tethered spinal cord releases: review of a large pediatric neurosurgical service experience

OBJECTIVE

The aim of this study was to retrospectively review, from a single busy pediatric neurosurgical service, a consecutive series of patients who had undergone surgery for a simple tethered spinal cord, which was defined by a thickened or fatty filum terminale with a normal conus. The hope was to contribute to benchmark data regarding the expected frequency of surgery for this condition.

METHODS

The authors reviewed the electronic medical records of every patient with diagnosed simple tethered spinal cord, defined on spinal MRI as a thickened (> 2 mm in diameter) or fatty filum terminale, and who had undergone primary filum section at Boston Children's Hospital between 2005 and 2011.

RESULTS

A total of 208 patients met the study inclusion criteria. At the time of surgery, patients ranged in age from 0.4 to 19.8 years. One hundred forty-four (69%) patients were symptomatic with one or more of the following: bowel/bladder dysfunction, 94 (45%); neurological dysfunction, 49 (24%); scoliosis, 44 (21%); or back pain, 44 (21%). Sixty-four (31%) patients were asymptomatic and were operated on prophylactically when filum pathology was discovered during the course of a workup for clinical syndromes such as anorectal anomalies and/or suspicious cutaneous lesions. No patients in this series were operated on if they had normal MRI studies, defined as a conus tip no lower than L3 and no distal tethering lesion visualized. Over the study period, approximately 1000 major surgical cases were performed in the department every year, only 30 of which were simple detethering procedures, representing well under 5% of the service's operative volume and approximately 5 cases per surgeon per year. Clinical follow-up, available at a postoperative interval of 6.6 ± 3.8 years, demonstrated that approximately 80% of patients symptomatic with bowel or bladder involvement or neurological dysfunction had improvement or relief of their symptoms and that none of the patients treated prophylactically experienced new-onset symptoms that could be related to spinal tethering.

CONCLUSIONS

Simple detethering procedures were relatively uncommon in an active, well-established pediatric neurosurgical service and represented less than 5% of the service's total case volume per year with an average of 5 cases per surgeon per year. No patients with normal MRI studies were operated on during the study period.

Prevalence of Abnormal Urodynamic Study Results in Patients with Congenital and Idiopathic Scoliosis and Its Predictive Value for the Diagnosis of Tethered Cord Syndrome: A Single Institution Clinical Study

Study Design

A total of 110 patients with scoliosis were enrolled in this analytical cross-sectional study.

Purpose

We aimed to compare the urodynamic study (UDS) results of patients with idiopathic scoliosis (ISC) and congenital scoliosis (CSC) and to evaluate the clinical significance of abnormal UDS findings in predicting underlying tethered cord syndrome (TCS).

Overview of Literature

An abnormal UDS finding is commonly found in patients with CSC. However, there is no consensus regarding its prevalence in patients with ISC.

Methods

Using the STROBE checklist for cross-sectional studies, 110 patients with scoliosis were selected based on our inclusion and exclusion criteria. Among the patients, 76 presented with ISC and 34 with CSC. Demographic data and other details, such as the results of spine radiography, UDS, and magnetic resonance imaging of the spine in both supine and prone positions, were recorded and analyzed.

Results

Approximately 50% of patients with CSC had normal UDS findings; 8.8%, mild impairment; and 41.2%, significant abnormalities. Moreover, 67.1% of patients with ISC had normal UDS findings; 9.2%, mild impairment; and 23.7%, significant abnormalities (p =0.166). TCS was identified in 38.2% and 26.3% of patients with CSC and ISC, respectively (p =0.571). In patients with ISC, a significantly abnormal UDS finding indicated that the risk of TCS increased from 26.3% to 50% (odds ratio [OR], 4.2; p =0.009). Meanwhile, in patients with CSC, the risk was almost similar (OR, 0.8; p =0.8).

Conclusions

Even with the absence of subjective urinary symptoms, subclinical urologic impairments can be observed in a significant number of patients with ISC. An abnormal UDS finding can be a sign of underlying spinal cord tethering in a patient with ISC who is a candidate for corrective spine surgery even though it is an independent variant and is not exclusive to candidates for surgery. This finding has high clinical utility for neuro- and ortho-spine surgeons who aim to correct scoliosis (OR, 4.2; p =0.009).

The Use of Prone Magnetic Resonance Imaging to Rule Out Tethered Cord in Patients With Structural Spine Anomalies: A Diagnostic Technical Note for Surgical Decision-making

Tethered cord syndrome (TCS) is a clinical diagnosis that can be difficult to establish, as symptoms do not always match classic radiological findings, such as a low-lying conus. Surgery for spinal detethering is not without risk and does not always result in clinical improvement. Prone magnetic resonance imaging (MRI) has been described as a tool to assess the mobility of the spine. This is a technical imaging report where prone imaging was a factor that influenced the decision to defer surgery in favor of conservative management. T1 and T2 sagittal and T1 axial MRI imaging were obtained with the patient supine, and then repeated in the prone position. An anteroposterior conus movement of >10% of the canal width was considered normal. There was significant anterior movement of the conus when switching to the prone position. Surgery was deferred, and the patient improved after a regimen of intensive physical therapy. Prone MRI can be a useful tool to have in our neurosurgical armamentarium when assessing spinal cord tethering. Surgery is not recommended when normal anteroposterior movement of the conus is present.

Dynamic magnetic resonance imaging parameters for objective assessment of the magnitude of tethered cord syndrome in patients with spinal dysraphism

BACKGROUND

Dynamic magnetic resonance imaging (MRI)-based criteria for diagnosing magnitude of tethered cord syndrome (TCS) in occult spinal dysraphism are proposed.

METHODS

In this prospective, case-control design study, MRI lumbosacral spine was performed in 51 subjects [pilot group (n = 10) without TCS (for defining radiological parameters), control group (n = 10) without TCS (for baseline assessment), and study group (n = 31) with spinal dysraphism (thick filum terminale [n = 12], lumbar/lumbosacral meningomyelocoele [n = 6], and lipomyelomeningocoele [n = 13])]. The parameters compared in control and study groups included oscillatory frequency (OF), difference in ratio, in supine/prone position, of distance between posterior margin of vertebral body and anterior margin of spinal cord (oscillatory distance [OD]), with canal diameter, at the level of conus as well as superior border of contiguous two vertebrae above that level; delta bending angle (ΔBA), difference, in supine/prone position, of angle between longitudinal axis of conus and that of lower spinal cord; and sagittal and axial root angles, subtended between exiting ventral nerve roots and longitudinal axis of cord. An outcome assessment at follow-up was also done.

RESULTS

In the study group (cord tethered), significantly less movement at the level of conus (OF0, p = 0.013) and one level above (OF1, p = 0.03) and significant difference in ΔBA (p = 0.0) were observed in supine and prone positions, compared to controls. Ventral nerve root stretching resulted in sagittal/axial root angle changes. Median OF (0.04) in the lipomyelomeningocoele group was significantly less than that in control group (0.23). Median OF was also lesser in patients with thick filum terminale or meningomyelocele. Difference in median sagittal and axial root angles among the study and control groups was statistically significant (p = 0.00).

CONCLUSION

New dynamic MRI-based parameters to establish the presence and magnitude of TCS have been defined. OF measured the extent of loss of translational cord displacement in supine and prone positions; ΔBA defined the relative angulation of conus with lower spinal cord, and sagittal and axial root angles represented ventral nerve root stretching. The difference in OF or ΔBA was minimum in the group with thick filum terminale and progressively increased in the groups with lipomyelomeningocele and meningomyelocele.