Pediatric spinal sonography. Part I: Anatomy and examination technique

The Dancing Cord: Inherent Spinal Cord Motion and Its Effect on Cord Dose in Spine Stereotactic Body Radiation Therapy

BACKGROUND

Spinal cord dose limits are critically important for the safe practice of spine stereotactic body radiotherapy (SBRT). However, the effect of inherent spinal cord motion on cord dose in SBRT is unknown.

OBJECTIVE

To assess the effects of cord motion on spinal cord dose in SBRT.

METHODS

Dynamic balanced fast field echo (BFFE) magnetic resonance imaging (MRI) was obtained in 21 spine metastasis patients treated with SBRT. Planning computed tomography (CT), conventional static T2-weighted MRI, BFFE MRI, and dose planning data were coregistered. Spinal cord from the dynamic BFFE images (corddyn) was compared with the T2-weighted MRI (cordstat) to analyze motion of corddyn beyond the cordstat (Dice coefficient, Jaccard index), and beyond cordstat with added planning organ at risk volume (PRV) margins. Cord dose was compared between cordstat, and corddyn (Wilcoxon signed-rank test).

RESULTS

Dice coefficient (0.70-0.95, median 0.87) and Jaccard index (0.54-0.90, median 0.77) demonstrated motion of corddyn beyond cordstat. In 62% of the patients (13/21), the dose to corddyn exceeded that of cordstat by 0.6% to 13.8% (median 4.3%). The corddyn spatially excursed outside the 1-mm PRV margin of cordstat in 9 patients (43%); among these dose to corddyn exceeded dose to cordstat >+ 1-mm PRV margin in 78% of the patients (7/9). Corddyn did not excurse outside the 1.5-mm or 2-mm PRV cord cordstat margin.

CONCLUSION

Spinal cord motion may contribute to increases in radiation dose to the cord from SBRT for spine metastasis. A PRV margin of at least 1.5 to 2 mm surrounding the cord should be strongly considered to account for inherent spinal cord motion.

Optimal Timing of Spinal Ultrasound Evaluations for Sacral Dimples in Neonates: Earlier May Not Be Better

OBJECTIVES

A spinal ultrasound (US) evaluation during the immediate postnatal period may have limited ability in evaluating filum thickness because of the spinal cord pulsation caused by a crowded subarachnoid space and the cerebrospinal fluid deficiency during this period. This study aimed to determine the optimal timing of spinal US to evaluate sacral dimples in neonates.

METHODS

This study included 585 neonates who had a clinically suspicious sacral dimple and underwent spinal US examinations between January 2015 and August 2017. Patients were classified into 1 of 2 groups based on whether measurements of all parameters were possible (group A) or not (group B). Neonatal and maternal clinical factors, including the antenatal history and US parameters, were compared between groups.

RESULTS

Group A included 443 patients, and group B included 82. Patients in group B were significantly younger (6.2 versus 31.0 days), had a younger corrective age (38.9 versus 42.5 weeks), and had a smaller body weight (3.1 versus 4.6 kg) than those in group A (all P < .005). However, no statistically significant differences were found in other patient or maternal factors (P > .05 for all). The pulsation of the conus medullaris and nerve roots of the cauda equina (14.6% versus 100%), thickening and echogenicity of the filum terminale (2.4% versus 100%), and the presence of a normal subarachnoid space (18.3% versus 100%) were significantly more difficult to detect in group B than in group A (all P < .001).

CONCLUSIONS

For an accurate evaluation, which can reduce unnecessary confusion and costs, spinal US can be delayed until neonates grow beyond 31 days, with a corrected age of older than 42.5 weeks and body weight of greater than 4.6 kg.

Ecografia computerizzata della colonna vertebrale del neonato

L'ecografia computerizzata costituisce attualemente un'utile e relativamente semplice metodica di studio del canale vertebrale e del suo contenuto, nel neonato a termine e pretermine e nel lattante normale. Viene riportata l'esperienza personale in casi normali, impiegando un apparecchio Acuson 128. Vengono discussi i vantaggi ed i limiti di tale metodica nella rappresentazione dell'anatomia del canale spinale, specie a livello lombo-sacrale, e nello screening della patologia disrafica spinale del primo anno di vita.

L'ecotomografia spinale nello studio del midollo ancorato

Scopo del presente lavoro è puntualizzare il ruolo dell'ecografia nello studio del midollo ancorato che rappresenta un'aspetto comune a molta della patologia spinale infantile e può prestarsi ad un'analisi globale dello stato dell'arte dello studio ecografico del midollo spinale, alla luce dell'esperienza acquisita negli anni e del continuo progresso tecnologico.

Dopo qualche cenno storico e alcune puntualizzazioni di carattere tecnico e di anatomia ecografica e stabilita la principale indicazione all'ecografia spinale nel neonato-lattante consistente nella ricerca delle spine bifide occulte, sospettate nel caso di masse posteriori ricoperte dalla cute o di fossette/seni dorsali, spesso associate a midollo ancorato, abbiamo illustrato i segni generici ecografici di midollo ancorato ed i differenti rilievi e potenzialità della metodica nel bilancio delle varie masse caudali responsabili dell'ancoraggio del midollo. L'eco non presenta alcun interesse nello studio diagnostico dei disrafismi spinali aperti mentre potrebbe rivelarsi utile nella ricerca postoperatoria di un eventuale riancoraggio midollare, valutato in base all'assenza della fisiologica pulsatilità del midollo. A tal proposito abbiamo recentemente effettuato una comparazione tra presenza o meno di motilità spinale valutata ecograficamente e presenza di segni clinici in pazienti precedentemente operati per disrafismo spinale.

In conclusione, lo studio ecografico del midollo spinale del neonato-lattante, pur presentando grossi limiti, trova giustificazione nella innocuità, nella facilità d'uso e nella possibilità di ottenere immagini in tempo reale. La presenza o il solo sospetto clinico di patologia disrafica impongono comunque sempre il completamento del bilancio diagnostico mediante RM/TC.

Development and Validation of a Method to Measure Lumbosacral Motion Using Ultrasound Imaging

The study aim was to validate an ultrasound imaging technique to measure sagittal plane lumbosacral motion. Direct and indirect measures of lumbosacral angle change were developed and validated. Lumbosacral angle was estimated by the angle between lines through two landmarks on the sacrum and lowest lumbar vertebrae. Distance measure was made between the sacrum and lumbar vertebrae, and angle was estimated after distance was calibrated to angle. This method was tested in an in vitro spine and an in vivo porcine spine and validated to video and fluoroscopy measures, respectively. R(2), regression coefficients and mean absolute differences between ultrasound measures and validation measures were, respectively: 0.77, 0.982, 0.67° (in vitro, angle); 0.97, 0.992, 0.82° (in vitro, distance); 0.94, 0.995, 2.1° (in vivo, angle); and 0.95, 0.997, 1.7° (in vivo, distance). Lumbosacral motion can be accurately measured with ultrasound. This provides a basis to develop measurements for use in humans.

Surgical management of intradural spinal cord tumors in children and young adults: A single-center experience with 50 patients

BACKGROUND

Intradural spinal cord tumors (IDSCTs) in children and young adults are rare diseases. This present study is aimed to demonstrate our experience with a large series of children and young adults with IDSCT.

METHODS

A total of 50 patients aged <20 years with IDSCT treated in our department between 1990 and 2010 were included in the study. Clinical, histological, and radiological findings, treatment strategies, and clinical outcome were retrospectively assessed. Depending on the relation to the spinal cord, IDSCT were dichotomized into intramedullary SCT (IMSCT) and extramedullary SCT (EMSCT). The functional outcome was evaluated with the Frankel score assessing the longest available follow-up period.

RESULTS

Mean age was 10.3 years (range 6 months-19 years). IDSCT surgery was performed in 44 patients (88%). A common first symptom in patients with EMSCT was neck and back pain (41%), whereas monoparesis of arms (43%) were often seen in patients with IMSCT. The main duration of the symptoms was longer in patients with IMSCT. The postoperative functional outcome was generally comparable to the preoperative functional condition, while better for EMSCT (P < 0.01). The functional outcome at last follow-up correlated significantly with the preoperative Frankel score (P < 0.002).

CONCLUSION

Due to the mostly mild impact of the surgery on the functional outcome, the surgical treatment of IDSCT in children and young patients can be uniquely advocated.

Sonographic findings in a neonate with Cobb syndrome

Cobb syndrome (cutaneomeningospinal angiomatosis) is a rare phacomatosis characterized by vascular abnormality of the spinal cord associated with a vascular naevus at the same metamere. We report the case of a newborn with Cobb syndrome, diagnosed by sonography of the spine and later confirmed by MRI. In neonates and young infants with dermatomal cutaneous vascular abnormalities, sonography of the spine should be used as the first imaging modality.

Ultrasonography reveals a high prevalence of lower spinal dysraphism in children with urogenital anomalies

BACKGROUND

Lower spinal dysraphism is frequently reported in anorectal anomaly combined with urogenital anomalies. The prevalence of the spinal dysraphism has not been comprehensively studied in children with simple urogenital anomalies. We evaluated the prevalence of the spinal dysraphism using ultrasound data of the lumbosacral area in children with urogenital anomalies.

METHODS

Lumbosacral ultrasound images of 259 children who underwent urological surgery with simple urogenital anomalies were reviewed by an ultrasound-specialized radiologist. The primary outcome measures were the conus medullaris (CM) level and the thickness of the filum terminale. The spinal ultrasonographic findings that were assessed in children showed abnormal spinal findings compared with the other children having normal findings. Two years later, the follow-up telephone interviews were made with the parents of the children with abnormal findings.

RESULTS

Eighteen children were differentiated as the abnormal finding group. They were suspected of spinal cord tethering. The level of CM was lower, and the filum terminale was thicker compared to the normal group [L2(lower (L)) vs. L1(L), 2.2 mm vs. 0.8 mm]. Of eighteen children, four were confirmed as tethered spinal cord with lipoma on magnetic resonance imaging by the time of surgery, and two were strongly suspected of occult spinal dysraphism (OSD) based on ultrasound findings and follow-up interviews.

CONCLUSIONS

The prevalence of OSD in children under 24 months of age with simple urogenital anomaly was higher than what was reported for the general population. Ultrasound examination of spinal structures before caudal block in children with urogenital anomaly should be considered.

Imaging of congenital anomalies and variations of the caudal spine and back in neonates and small infants

Spinal dysraphisms are categorized in open dysraphisms with prominent abnormal nervous tissue above the skinlevel and closed dysraphisms with a skin covered malformation. Especially the occult dysraphisms are marked by suspect skin masses and other dermal anomalies. The purpose of this review is to demonstrate the indications and spectrum of spinal sonography in neonates and infants. In comparison typical dysraphisms are demonstrated in sonography and MR Imaging. We demonstrate the value of ultrasound in comparison to MRI and describe a usefull handling of the methods in neonates and infants. The differentiation between the potentially dangerous dimples associated with dermal sinus, which can lead to meningitis and the harmless coccygeal dimple in the cranial gluteal cleft is presented. An inconspicious examination does not need a further imaging, but suspicious results of sonography need an MR imaging dependent of clinical conditions. Neurologically conspicious infants need MR imaging completed by sonography. Great advantages of sonography are the real time examination and the potential to show oscillations of the conus, filum and cauda equina in M-mode-imaging.

Ultrasound measurement of lumbosacral spine in children

The aim of this study was to establish normal ultrasound measurements of lumbosacral spine in children as a screening assessment of tethered cord or postoperative retethering of cord. Sonography of lumbosacral spine was performed in 108 neurologically normal children (mean age = 2.1 years) using 5- to 12-MHz linear transducer. M-mode was applied at the posterior and anterior subarachnoid spaces just below the conus medullaris and at the L(5)/S(1) dural sac to document cerebrospinal fluid pulsation of the cauda equina. The oscillation rate and amplitude were measured. Sixteen children with spinal cord anomalies (6 with low tethered cord and 10 postoperative cases of low tethered cord) were also examined. The mean posterior/anterior subarachnoid spaces of normal children were 2.6 mm/1.8 mm at the terminal dural sac. The mean oscillation amplitude and rate of the cauda equina were 0.52 mm and 121/min at the L(5)/S(1) dural sac. The oscillation amplitude at this level demonstrated a statistically significant difference between normal and abnormal groups. In conclusion, we recommend taking the fifth percentile of the normal oscillation amplitude at the L(5)/S(1) dural sac as a reference. Any oscillation amplitude of less than 0.3 mm in a symptomatic patient should alert the clinician to possible cord abnormality, cord tethering, or retethering in postoperative cases.

Potential of three-dimensional ultrasound in neonatal and paediatric neurosonography

The aim of this study was to describe the potential of three-dimensional ultrasound (3D US) in paediatric and neonatal neurosonography. The potential applications are illustrated based on our experience in 150 patients using three different 3D US techniques at two different sites. Various disease entities throughout the paediatric age have been evaluated. The potential of 3D US, including 3D US of the cerebral vessels based on colour Doppler data, is discussed based on comparison with conventional 2D US or other imaging (as available), and with regard to the literature. In our experience, 3D US is feasible in neonatal and paediatric neurosonography. It reduces imaging time, improves demonstration of complex anatomy and vasculature, and allows for evaluation of anatomy/pathology in any plane. The 3D US furthermore improves volume assessment (e.g. in hydrocephalus), and comparison with CT, MRI and during follow-up, with a potentially improved standardisation and documentation. The 3D US additionally offers an ideal modality for training and education, as the brain and the neonatal spine can be virtually rescanned at the workstation. Yet, limitations such as areas inaccessible to 2D US, limited resolution and motion artefacts have to be acknowledged. Three-dimensional US has the potential to become a valuable additional imaging tool in paediatric neurosonography.

Evaluation of spinal ultrasound in spinal dysraphism

AIMS

The aims of this study were to evaluate the role of spinal ultrasound in detecting occult spinal dysraphism (OSD) in neonates and infants, and to determine the degree of agreement between ultrasound and magnetic resonance imaging (MRI) findings.

MATERIALS AND METHODS

Eighty-five consecutive infants had spinal ultrasound over 31 months. Of these, 15 patients (age 1 day-7 months, mean 40 days; nine male) had follow-up MRI. Ultrasound and MRI findings were correlated retrospectively.

RESULTS

Six out of 15 (40%) ultrasound examinations showed full agreement with MRI, seven of 15 (47%) had partial agreement, and two of 15 (13%) had no agreement. In the present series ultrasound failed to visualize: four of four dorsal dermal sinuses, three of four fatty filum terminales, one of one terminal lipoma, two of four partial sacral agenesis, three of four hydromyelia and one of 10 low-lying cords.

CONCLUSION

Agreement between ultrasound and MRI was good, particularly for the detection of low-lying cord (90%). Therefore we recommend ultrasound as a first-line screening test for OSD. If ultrasound is abnormal, equivocal or technically limited, MRI is advised for full assessment.

Occult spinal dysraphism in the infant

The progressive neurologic dysfunction caused by occult spinal dysraphism can be prevented with early clinical recognition, radiographic diagnosis, and neurosurgical treatment. However, detection of occult spinal dysraphism in the infant is difficult because neurologic symptoms often are not apparent until the child becomes ambulatory. Occult spinal dysraphism, however, can be suspected in the asymptomatic neonate when cutaneous stigmata, such as hemangiomas, hairy patches, deep and/or eccentric dimples, or subcutaneous masses are seen over the lumbosacral spine. Because of the serious, often irreversible, sequelae of a delayed diagnosis, spinal sonography of high-risk infants with midline, lumbosacral, cutaneous stigmata should be considered as an effective, noninvasive screening method.

Intraspinal extension of paraspinal masses in infants: detection by sonography

Spinal sonography has been helpful in the study of congenital anomalies involving the spine in fetuses and infants. We have found this technique also to be useful in the detection of intraspinal extension of paraspinal masses.

Pediatric spinal sonography. Part II: Malformations and mass lesions

The most important spinal disorders in childhood are malformations and mass lesions. The sonographic appearance of the various kinds of dysraphism and their differentiation, of malformations at the cranio-cervical junction, and of mass lesions is demonstrated and illustrated. Based on our preliminary experience, spinal sonography appears to be useful as the first imaging device for the differentiation of complex malformations and as a screening method for occult dysraphism. In mass lesions spinal sonography is useful to diagnose and follow-up disease, with additional imaging procedures currently needed for confirmation of diagnosis.