Unveiling the tale of the tail: an illustration of spinal dysraphisms

Intraoperative Neurophysiological Monitoring in Tethered Cord Syndrome Surgery: Predictive Values and Clinical Outcome

INTRODUCTION

"Tethered cord syndrome" (TCS) refers to a congenital abnormality associated with neurological signs and symptoms. The aim of surgery is to prevent or arrest their progression. This study reports a retrospective case series of tethered cord syndrome surgeries, supported by intraoperative neurophysiological monitoring.

METHODS

The case series comprises 50 surgeries for tethered cord syndrome in which multimodal intraoperative neurophysiological monitoring was performed using motor evoked potentials (transcranial motor evoked potentials [TcMEPs]), tibial nerve somatosensory evoked potentials (TNSEPs), and pudendal-anal reflex (PAR). The intraoperative neurophysiological monitoring results are reported and correlated with clinical outcomes.

RESULTS

Sensitivity, specificity, and negative predictive value were high for TcMEPs and TNSEPs, while PAR exhibited low sensitivity and positive predictive value but high specificity and negative predictive value. Fisher's exact test revealed a significant correlation between changes in TcMEPs, TNSEPs, and clinical outcome ( P < 0.000 and P = 0.049 respectively), but no correlation was detected between PAR and urinary/anal function ( P = 0.497).

CONCLUSIONS

While TcMEPs and TNSEPs were found to be reliable intraoperative neurophysiological monitoring parameters during tethered cord syndrome surgery, PAR had low sensitivity and positive predictive value probably because the reflex is not directly related to bladder function and because its multisynaptic pathway may be sensitive to anesthetics. New onset muscle weakness and sensory deficits were related to postoperative changes in TcMEPs and TNSEPs, whereas changes in PAR did not predict bladder/urinary impairment. Urinary deficits may be predicted and prevented with other neurophysiological techniques, such as the bladder-anal reflex.

“Spinal Dysraphism Spectrum: A Novel Protocol-based Approach for Accurate Diagnosis on Imaging”

The spectrum of spinal dysraphism includes various congenital anomalies of the spinal column and spinal cord. Clinical manifestations are varied and range from paraparesis, gastrointestinal, genitourinary, and musculoskeletal anomalies to asymptomatic cases depending on the level and extent of spinal involvement. Magnetic resonance imaging is the gold standard for assessing these complex spinal anomalies. Even for the experienced radiologist, diagnosis can be challenging in complex cases. It is essential to be aware of the normal embryological developmental stages of the spine for an adequate understanding of the complex anatomy, pathogenesis, and cliniconeuroradiological classification of spinal dysraphism, which is necessary for accurately diagnosing each case as a particular pathological entity. In this pictorial essay, we have depicted the stages and process of spinal embryogenesis, cliniconeuroradiological classification, and the imaging spectrum of spinal dysraphism. As the confusing terminologies and the numerous variants can potentially lead to misdiagnosis, we have proposed a step-wise protocol-based imaging approach to analyze each case and arrive at the correct diagnosis systematically. This would be particularly helpful in confusing and difficult cases, as accurate and early diagnosis is crucial for appropriate patient management.

Fetal MRI prior to intrauterine surgery of open neural tube defects: What does the radiologist need to know

The management of myelomeningocele study trial showed significant prognostic improvement in fetal repair before 26 weeks of gestation. Hence, surgery in utero represents the best treatment option for open-neural tube defects (NTDs). Fetal surgery of open-NTDs has specific inclusion and exclusion criteria, which can be adequately studied with fetal MRI. The main concern: the spine (spinal defects other than Myelomeningocele and Myeloschisis, the level of the lesion higher than T1 or lower than S1 and the degree of kyphosis ≥ 30°), the skull/brain (no cerebellum herniation and Chiari II malformation and the presence of any intracranial abnormality unrelated to open NTDs), the uterus (cervix length less than 2 cm, multiple gestations and placental and uterine abnormalities) and any other fetal abnormality not attributed to spinal defect. In this review, we describe the fundamental role of fetal MRI in supporting therapeutic decisions in pre-surgery intrauterine planning through the accurate and comprehensive description of findings, providing a proposal of a structured report. In addition, we describe how post-surgical MRI is important in investigating the effectiveness of surgery and detecting repairing complications.

Updates on Intraoperative Neurophysiology During Surgery for Spinal Dysraphism

Spinal dysraphism is a group of disorders resulting from an embryologic failure of spinal cord development which can lead to a radicular-medullary mechanical stretch that generates vascular compromise and hypoxic-ischemic damage to the nervous structures of the conus-cauda region.Thus, the clinical relevance of the different types of spinal dysraphism is related to the possible neurologic deficits resulting from spinal cord tethering. The clinical presentation is heterogenous: from asymptomatic to very compromised patients. The indications and the time of a detethering surgery are still subject of debate, although there is an agreement on the high standards of treatment that have to be offered by the surgery. Intraoperative neurophysiology (ION) contributes to the safety of tethered cord surgery in reducing the risks of iatrogenic neurological damages.

Role of ultrasonography in screening of spinal dysraphism in infants at risk

Background

Spinal dysraphism (SD) encompasses congenital spinal defects that result from inappropriate fusion of the different midline osseous, mesenchymal, and neural elements. The primary tools for diagnosis of SD are both spinal ultrasonography (USG) and magnetic resonance imaging (MRI). Spinal USG is growingly being used as an initial screening modality with sensitivities and accuracies equivalent to those of MRI. Anorectal malformations (ARM) have ultimate association with many other congenital abnormalities, of which spinal dysraphism is one of the most common. The main aim of study was to assess the diagnostic accuracy of spinal USG as a screening modality in comparison with MRI in infants with closed spinal dysraphism. We also endeavored to highlight the associated spinal dysraphism radiological findings in patients with either ARM or back cutaneous stigmata.

Results

Our prospective diagnostic comparative study included 33 patients, all of whom underwent both MRI and USG. Both MRI and USG showed appreciable agreement in the assessment of spinal dysraphism. In comparison with the gold standard MRI, spinal USG revealed comparable diagnostic metrics: specificity (98.6–100%), sensitivity (66.6–91.6%), PPV (90–100%) and NPV (94.1–98.7%) in diagnosis of different types of spinal dysraphism. The main clinical presentation of nineteen patients was anorectal malformation (ARM), 11 of whom (57.9%) had evidence of associated spinal dysraphism. The most common types of ARM were cloacal malformation, recto-urethral fistula, and rectal atresia with no fistula. On the other hand, sixteen patients were mainly presented with back cutaneous stigmata, 11 of whom (68.8%) had associated spinal dysraphism. The most common presenting cutaneous stigmata were low back swelling and atypical dimples.

Conclusion

The front-line screening modality for infants with closed SD should be spinal USG, however, its main limitation is the restrained time window in the first 6 months of life. Infants with ARM should be screened for spinal anomalies, especially those with high and complex types. Infants with high-risk back cutaneous stigmata should be similarly screened, as well.

Imaging of Congenital Spine Malformations

Congenital malformations of the spine and spinal cord are a large and diverse group of diagnoses, which are often broadly referred to as spinal dysraphisms (SDs). Derived from the Greek words dys (bad) and raphe (suture), the term dysraphism describes missteps in the process of forming a midline seam during the zipper-like fusion of the neural folds in primary neurulation. As such, the term "spinal dysraphism" is a designation that should technically be reserved for malformations resulting from aberrations in primary neurulation. In medical practice, however, it is a catch-all designation regularly used to describe any of the numerous abnormalities demonstrating incomplete midline closure of mesenchymal, osseous, and nervous tissue, occurring at any point during embryologic development. For the sake of clarity and completeness, this article will also include that breadth in the discussion of congenital abnormalities of the spine.

Dural splitting reconstruction in retethering after lipomeningocele repair: Technical note

Background:

Tethered spinal cord syndrome (TCS) can occur after the surgical repair of lipomeningoceles (LMCs). In these cases, the tethering results from postoperative adhesions between the spinal cord and the overlying repaired dura. A watertight dural closure using the residual dura and/or the surrounding tissues does not always provide enough space for the spinal cord and risks retethering. Here, we report a 16-year-old patient with secondary TCS following lipomeningocele repair who successfully underwent release of the tethered filum terminale utilizing a novel dural splitting reconstructive technique to attain a water-tight closure without the need for a duroplasty.

Methods:

A 16-year-old patient had a LMC repaired at birth. She now presented with progressive low back pain, and gait disturbances. The MRI documented secondary spinal cord tethering at the prior spinal dysraphism repair site.

Results:

A secondary release of the filum terminale utilizing a novel dural splitting technique to avoid the need for a duroplasty was performed.

Conclusion:

Here, in a 16-year-old patient with a recurrent tethered cord syndrome following repair of a LMC at birth, we utilized a novel dural splitting reconstruction technique and averted the need for a duroplasty.

A Practical Approach to Diagnosis of Spinal Dysraphism

Spinal dysraphisms (SDs) are congenital malformations of the spinal cord, determined by derangement in the complex cascade of embryologic events involved in spinal development. They represent a heterogeneous group ranging from mild clinical manifestations-going unnoticed or being discovered at clinical examination-to a causal factor of life quality impairment, especially when associated with musculoskeletal, gastrointestinal, genitourinary, or respiratory system malformations. Knowledge of the normal embryologic development of the spinal cord-which encompasses three main steps (gastrulation, primary neurulation, and secondary neurulation)-is crucial for understanding the pathogenesis, neuroradiologic scenarios, and clinical-radiologic classification of congenital malformations of the spinal cord. SDs can be divided with clinical examination or neuroradiologic study into two major groups: open SDs and closed SDs. Congenital malformations of the spinal cord include a wide range of abnormalities that vary considerably in imaging and clinical characteristics and complexity and therefore may represent a diagnostic challenge, even for the experienced radiologist. Online supplemental material is available for this article. ^©RSNA, 2021.