Spinal Ultrasound: A Safe and Valuable, but Underutilized Imaging Modality to Evaluate Epidural Hematomas in Infants

KEY POINTS

• Spinal ultrasound is increasingly recognized for its utility as a valuable and safe diagnostic tool for spinal epidural hematomas in neonates and young infants.

• The accessibility, cost-effectiveness, and accuracy of spinal ultrasound make it an appealing alternative to magnetic resonance imaging (MRI).

• Despite all its potential benefits, spinal ultrasound remains underutilized in clinical practice. In this paper, we present a case series where spinal ultrasound was successfully used to diagnose spinal epidural hematomas in young infants.

• In this article, we present a summary of the currently available literature, which shows an emerging consensus on the advantages of spinal ultrasound for assessing spinal lesions in these patients.

INTRODUCTION

Spinal epidural hematoma (SEH) is a serious condition characterized by the accumulation of blood in the epidural space surrounding the spinal cord. Although the incidence of this condition is low, symptomatic SEH is considered a surgical emergency due to the risk of minor or major permanent neurological deficits secondary to mass effect on the adjacent neural structures. Some asymptomatic cases of SEH can be managed conservatively, but these infants also need careful monitoring and follow-up.¹ Spinal epidural hematoma can also occur as a complication of spinal surgery or procedures, such as lumbar puncture and epidural anesthesia. Other risk factors include trauma, anticoagulation, neoplasms, coagulopathies, and vascular malformations. Magnetic resonance imaging is currently considered the first-line imaging modality for diagnosing SEH, but it is expensive and can be time-consuming, particularly in infants because of the need for sedation^2,3 Spinal ultrasound, on the contrary, can be performed quickly at the bedside, is more cost-effective, and has been shown to accurately diagnose acute spinal pathologies in neonates and young infants.^4,5

In this paper, we present a case series of neonatal spinal epidural hematomas diagnosed by spinal ultrasound. Additionally, we have reviewed the existing literature on the utility of spinal ultrasound for the diagnosis of SEH in neonates and young infants with additional examples. The primary objective of this paper is to raise awareness among neonatologists, pediatricians, and radiologists regarding the advantages of spinal ultrasound as a safe and readily available imaging modality in this specific patient population. By highlighting its potential benefits and summarizing the relevant research, this paper aims to promote the appropriate use of spinal ultrasound for the timely and accurate diagnosis of this rare pathology.

CASE SERIES

Fig. 1: A 2-week-old female was imaged after lumbar puncture to rule out meningitis. Panels A and B show sagittal, and panel C shows axial imaging of the lumbosacral spine. A mildly hyperechogenic, mildly lobulated epidural hematoma was seen dorsal to the dural sac, which appeared compressed by the hematoma (outlined in panel B). The hypoechogenic distal tip of the conus medullaris as well as the mildly hyperechogenic cauda equina nerve roots were separated from the epidural hematoma by a small sliver of hypoechogenic cerebrospinal fluid. Sagittal color-coded Doppler sonography (C) confirmed that the epidural hematoma was not perfused. Axial ultrasound (D) confirmed the epidural location of the hematoma (large arrows), dorsal to the displaced and mildly compressed dural sac (arrowheads). Sagittal ultrasound (E) of a normal distal spinal canal showed that the hypoechogenic conus medullaris and the mildly hyperechogenic cauda equine nerve roots were surrounded by a wide layer of hypoechogenic cerebrospinal fluid. The epidural space was overall narrow and was filled with a small amount of hyperechogenic epidural fat

Fig. 2: A 6-week-old boy was imaged after lumbar puncture. Sagittal ultrasound (A) of the distal lumbo-sacral spinal cord revealed a homogeneous hyperechogenic tubular epidural hematoma (arrows) displacing the dural sac anteriorly. The tip of the conus medullaris was intact (small arrow). Two axial ultrasound images (B and C) show the dura separating the epidural hematoma from the dural sac (arrows). The spinal cord/conus medullaris (*) and cauda equina nerve roots (+) were seen in the center of the anteriorly displaced dural sac

Fig. 3: Sonographic imaging of a 4-week-old boy after lumbar puncture. Sagittal ultrasound of the distal lumbo-sacral spinal cord revealed an ovoid heterogeneous hyperechogenic low sacral epidural hematoma (arrow). There was no appreciable mass effect on the distal dural sac

Fig. 4: A 4-day-old girl was imaged after lumbar puncture. Sagittal ultrasound and sagittal color-coded Doppler ultrasound images of the distal lumbo-sacral spinal cord revealed (A) a mixed hyper- and hypoechogenic ovoid epidural hematoma (arrows), which resulted in mild anterior displacement of the dural sac. The heterogeneity was most likely secondary to blood sedimentation, leveling within the epidural hematoma. The axial color-coded Doppler ultrasound image (B) did not show any perfused vessels within the hematoma

Fig. 5: Ultrasound imaging of a 6-day-old boy imaged after lumbar puncture. Sagittal and axial anatomical (A), and matching color-coded Doppler ultrasound images (B) of the lumbo-sacral spinal cord revealed a tubular hyperechogenic epidural hematoma (arrows) extending along the distal lumbar spinal cord, conus medullaris and cauda equina. Follow-up matching images (C and D) 3 days later showed progressive demarcation of the hematoma with increased depiction of the hypoechogenic dura (arrowheads). A hypoechogenic filar cyst (*) was noted incidentally in its typical location

Fig. 6: A 4-week-old boy was imaged after lumbar puncture. Sagittal (A) and axial (B) ultrasound images of the distal lumbo-sacral spinal cord revealed a predominantly hypoechogenic ovoid epidural hematoma (arrows) slightly off-midline, along the right hemi-circumference of the dural sac. The hypoechogenicity indicated the chronic nature of the hematoma with progressing liquefaction and resorption

Fig. 7: A 3-week-old girl after lumbar puncture. Sagittal ultrasound (B) of the distal lumbo-sacral spinal cord revealed a homogeneous hypoechogenic tubular epidural fluid collection (arrows) causing mild anterior displacement of the dural sac. The hypoechogenic fluid collection represented cerebrospinal fluid leakage along the dural puncture site from the dural sac into the epidural space. The axial ultrasound image (B) confirmed the epidural CSF collection (arrows)

DISCUSSION

Spinal epidural hematoma is a known complication of invasive spinal procedures such as lumbar puncture. Most of these cases are asymptomatic and resolve spontaneously. The risk of spinal hemorrhage after invasive procedures increases with anatomical factors, such as vertebral abnormalities, multiple attempts at needle placement, and the use of anticoagulation or antiplatelet therapy. Other risk factors include trauma, pregnancy, coagulopathies, blood dyscrasias, and thrombocytopenia. The source of bleeding in SEH remains a topic of debate. Most authors endorse that the bleeding likely originated from the epidural venous plexus, a low-pressure network of large, thin-walled veins located in the epidural space that may be easily ruptured. Others suggest that the free arteries running near the venous plexus may be responsible for the bleeding.^1,6

Most cases of SEH resolve spontaneously without causing significant symptoms, as was the case with our patients. Symptomatic SEH is infrequent and accounts for <1% of space-occupying spinal lesions.⁷ Asymptomatic SEH can typically be managed conservatively with close monitoring involving serial neurological exams and imaging to monitor for changes in size. Symptomatic SEH, on the contrary, can cause life-threatening spinal cord compression and requires urgent surgical decompression. Common symptoms of symptomatic SEH include back pain, paresthesias, paresis, and urinary incontinence.^1,8,9 However, infants are more likely to present with less specific clinical features. Neurological deficits can be more difficult to recognize in these patients, potentially leading to delays in diagnosis.⁸ Thus, prompt and accurate imaging is crucial for early diagnosis and appropriate management.

Spinal ultrasound can efficiently and accurately diagnose spinal hematomas. Our case series shows that ultrasound can be a useful initial diagnostic modality, which may also be used for monitoring during follow-up. Compared with magnetic resonance imaging, the current first-line modality, spinal ultrasound offers more widespread accessibility, portability, and the ability to be performed quickly at the bedside.^4,10 Additionally, there have been remarkable advancements in ultrasonography in recent years due to the introduction of new-generation high-frequency ultrasound scanners. This new technology has significantly enhanced the image quality of ultrasound, effectively placing its diagnostic value at par with that of MRI in certain situations.^11–13 Furthermore, another important advantage of ultrasound over MRI, especially in young infants, is that ultrasound examinations can be performed without the need for sedation. Unlike MRI, which often requires children to remain still for an extended period inside a confined space, ultrasound is a noninvasive and generally well-tolerated procedure that can be conducted while the child is awake. This eliminates the need for sedation or anesthesia, reducing potential risks and complications. This not only improves patient comfort but also provides a safer and more convenient option.

Despite its advantages, there has been a scarcity of literature detailing the use of ultrasound for the diagnosis of SEH. Leadman et al.¹⁴ described a successful case of SEH diagnosed using ultrasound in 1988. Since then, a few other cases have been reported.⁵ Nevertheless, the existing literature suggests that spinal ultrasound may be an optimal initial diagnostic modality for the assessment of SEH in infant-aged patients. In the first 6 months of life, the human spine is primarily cartilaginous, creating an acoustic window that is ideal for transmitting ultrasound waves. The quality of ultrasound images decreases after this time-period as the progressive ossification of the spine obscures the acoustic window. Therefore, neonates and young infants are an ideal patient demographic for the use of ultrasound for the assessment of spinal lesions; it can be very useful for the evaluation of spinal lesions, such as spinal dysraphisms, tumors, trauma, and vascular malformations.

Spinal ultrasound findings in neonates and young infants show a strong correlation with MRI. Rohrschneider et al. compared spinal ultrasound and MRI findings in 24 pediatric patients (mean age 5.5 months); ultrasound correctly diagnosed spinal abnormalities in all patients.¹⁵ Similar findings were reported in smaller studies.^16,17 However, it is important to know the limitations of spinal ultrasound compared with MRI. MRI offers highly detailed anatomical images with excellent soft tissue contrast, making it particularly valuable for assessing complex spinal pathologies and providing a more comprehensive visualization of the anatomy. In addition, ultrasound is more operator-dependent and may have limitations in visualizing deep-seated structures or differentiating certain soft tissue structures.¹⁵ In more complex cases or situations where adequate visualization cannot be obtained using ultrasound, MRI may be more appropriate.

CONCLUSION

Spinal ultrasound is a painless, highly feasible, accessible, accurate, cost-effective, time-efficient, and risk-free modality for the diagnosis of spinal epidural hematomas and other lesions. It offers several advantages over MRI in the diagnosis of neonates and young infants and allows for prompt and convenient diagnosis. Neonatologists, pediatricians, and radiologists should be familiar with this easily-available imaging tool to evaluate the spine and spinal cord.

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