Background
Spina bifida is a relatively common congenital malformation, with an incidence of 0.26 to 2.9 cases per 1 000 births, and has a broad spectrum of anatomic variations, with or without neurologic dysfunctions [
1]. Some patients are latent and classified as spina bifida occulta, without subcutaneous stigmata. Severe spinal anomalies, including spina bifida, can lead to tethered cord syndrome, in which the spinal cone is pulled caudally by lipomas, abnormal soft tissues within the sacrum, or thick filum terminale, which may develop lower extremity muscle weakness, sensory abnormalities, and bladder-rectal disturbances [
1]. Some patients involve moderate to severe neurologic symptoms and can require repeated surgery after birth [
1,
2]. Spinal abnormalities can make neuraxial anesthesia procedures difficult and result in increased neurologic complications. This syndrome also complicates the management of pregnancy and delivery and increases the need for multidisciplinary team care. Anesthesiologists are also increasingly encountering pregnant women with spina bifida, owing to continuing improvements in functional prognoses [
1,
2]. Neuraxial anesthesia for labor analgesia or cesarean section (CS) requires detailed visual information on anatomic structures that might affect the procedure.
Preprocedural imaging of the lumbar spine by computed tomography (CT) or magnetic resonance imaging (MRI) can be crucial for determining the feasibility of neuraxial anesthesia, but there are risks [
3,
4], and these modalities can be expensive. Lumbar ultrasonography (US) can be used easily, safely, and consistently to facilitate neuraxial procedures for pregnant women [
3,
4]. We present four cases of pregnant women with spina bifida who underwent lumbar US before obstetric analgesia or anesthesia.
Discussion and conclusions
Performing neuraxial anesthesia in obstetric patients with spina bifida can be challenging because of increased technical difficulty and the risk of neurologic complications. Recent systematic reviews have indicated that the lumbar US can provide anatomic information indicating the depth of the epidural space, the identity of a given intervertebral level, the location of the midline, and interspinous or interlaminar spaces [
3,
4]. In addition, lumbar US can help to improve clinical outcomes of neuraxial anesthesia [
5‐
7]. Preprocedural US might also be helpful to identify parturients compromised by spinal surgeries or diseases [
8], especially those with spina bifida before undergoing neuraxial techniques to obtain detailed images of anatomic structures or to reveal spina bifida occulta [
9]. In the present study, we performed US for four parturients before anesthetic procedures and obtained distinct images. We obtained real-time images of spinal bone abnormalities, such as insufficient fusion and dysplastic vertebral arch or body, as well as soft-tissue lesions including lipoma. These findings might help in decision-making on the anesthetic methods and in the practice of neuraxial procedures.
Successful epidural anesthesia or analgesia consists of catheter placement without complications and local spread of anesthetic to achieve adequate anesthesia or analgesia. A review of 84 obstetric patients with spina bifida who underwent neuraxial anesthesia, including 41 cases of severe spina bifida, indicated a 20% incidence of inadequate analgesia such as suboptimal or excessive block height, asymmetric block, and rapid block regression and indicated accidental dural puncture, intrathecal catheter migration, increased number of attempts, and post-procedural neurological deficit [
10]. We found a case report of a parturient with spina bifida who developed leg weakness after receiving epidural anesthesia during delivery [
11]. It is also reported that a parturient with undiagnosed spina bifida who underwent an emergent CS under spinal anesthesia developed foot drop immediately after surgery and MRI imaging revealed a low-lying cord with a fatty filum terminale and intramedullary, suggestive of needle damage [
12]. Considering these previous reports [
13,
14], general anesthesia might be preferable to neuraxial anesthesia.
In the four cases presented here, we performed lumbar US to explore the anatomical structures of the puncture sites because they had been previously diagnosed with spina bifida. In cases, 1 through 3, we chose general anesthesia rather than neuraxial anesthesia because it was difficult to predict the risk of serious complications related to neuraxial anesthesia based on merely the findings of the US and other imaging.
In case 4, we recognized the history of successful epidural labor and the detailed anatomic structures by the US and lumbar radiographic image. We diagnosed her not with spina bifida but with only incomplete fusion of the 5th vertebra alone. Consequently, we decided to place an epidural catheter at the higher level of L3/4 to avoid the anatomically abnormal regions. As the utility of performing US before neuraxial anesthesia becomes more widespread, the possibility of detecting spinal bony abnormalities, including spina bifida, may increase. During identifying the vertebral level of the puncture from the sacrum, we may notice bone defects in the middle of the sacrum or vertebral bone abnormalities, as presented in our images. We suggest that the US examination might facilitate neuraxial procedures, however, it might not always guarantee successful procedures without complications.
The use of CT and MRI are essential for the diagnosis of spina bifida. However, CT could be potentially harmful to the fetus because of radiational exposure and MRI can be expensive. We recommend the use of CT and or MRI whenever they are beneficial over risks and costs. US does not provide as detailed imaging as CT or MRI, but we showed that the US can be an alternative modality that is easy to use safely and provides consistent results. Although we presented only four cases diagnosed before anesthesia, lumbar US could provide crucial information on anatomic structures to determine anesthetic methods and safer procedures.
In conclusion, preprocedural US can be beneficial for obstetric anesthesia to explore the anatomic structures of the lumbar spine in cases of spina bifida. Preprocedural US for parturients with diagnosed or undiagnosed spina bifida can help with decision-making on anesthetic methods and improve safety related to anesthetic procedures.
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