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

Risk of occult spinal dysraphism based on lumbosacral cutaneous manifestations

Objectives:

Occult spinal dysraphism is a congenital failure of fusion of the posterior vertebral arches with intact skin overlying the defect. Lumbosacral cutaneous manifestations are associated with a variable risk of occult spinal dysraphism. Tethered cord syndrome is a type of occult spinal dysraphism that puts abnormal traction on the spinal cord. This study analyzed neonates and infants who were referred to our pediatric urology practice and had evidence of lumbosacral cutaneous manifestation on physical examination.

Methods:

We reviewed the presence of lumbosacral cutaneous manifestations in neonates and infants evaluated in our pediatric urology clinic at our Institution over a 6-year period (1 March, 2015–28 February, 2021) with no prior diagnosis of lumbosacral cutaneous manifestation. All patients underwent a spinal ultrasound.

Results:

The most common lumbosacral cutaneous manifestations were bifurcated/duplicated gluteal folds (33%), gluteal asymmetry (19%), and sacral dimples (14%). A total of 34 (24%) patients had an abnormal spinal ultrasound; 15 (44%) of these infants underwent a lumbar magnetic resonance imaging. A coccygeal pit was statistically marginally higher in abnormal versus normal spinal ultrasound (p = 0.07). Patients with only one lumbosacral cutaneous manifestation (N = 121) were significantly more likely to have a normal spinal ultrasound compared to those with two or more lumbosacral cutaneous manifestation (N = 17) (79% vs 53%, p = 0.03).

Conclusion:

Due to the varying risk of certain lumbosacral cutaneous manifestations with occult spinal dysraphism, all patients with a lumbosacral cutaneous manifestation should undergo spinal ultrasound. This study also highlights the importance of urodynamic studies when there are abnormal cutaneous findings. Routine physical examinations of the lumbar region for cutaneous manifestations of occult spinal dysraphism are vital to ensure prompt management of tethered cord syndrome and avoid potentially devastating consequences.

The Term Newborn: Postnatal Screening and Testing

Prenatal genetic screening, including evaluation for inherited genetic disorders, aneuploidy risk assessment, and sonographic assessment, combined with a thorough newborn examination and standard newborn screening, including blood, hearing, and congenital heart disease screening, can reveal conditions requiring further evaluation after delivery. Abnormal prenatal or newborn screening results should prompt additional diagnostic testing guided by maternal fetal medicine, perinatal genetics, or pediatric specialists.

Filum terminale lipoma revealed by screening spinal ultrasonography in infants with simple sacral dimple

PURPOSE

Spine ultrasound (US) examinations are widely performed in neonates and infants with sacral dimple to exclude associated congenital malformations. Increased utilization of, and improvements in, sonographic technology has resulted in the frequent identification of echogenic filum terminale (FT) containing fat below the conus medullaris, termed FT lipoma or fatty FT. We examined the value of screening US, especially for diagnosis of FT lipoma, in infants with "simple sacral dimple."

METHODS

This study was a retrospective review of spinal US and magnetic resonance imaging (MRI) findings performed in our hospital on full-term and preterm infants with simple sacral dimple. We reviewed the clinical records and spinal sonographic scans of 337 patients, and the MRI scans of 40 patients with simple sacral dimple. We evaluated the thickness and echogenicity of FT on US, and the presence of fat in the FT was determined by MRI.

RESULTS

In total, 50 of the 337 patients showed strong echogenic FT on US. Correlation with MRI data was possible in 40 of the 50 patients with strong echogenic FT. MRI scans of all 40 of these patients revealed the presence of fat in the FT. The maximum thickness in the strong echogenic area of the FT lipomas of these 40 patients was 1.7 ± 0.4 mm (range 1.2-2.5 mm), and the minimum thickness was 1.1 ± 0.2 mm (range 0.8-1.4 mm). Among the 40 infants, 13 (32%) had maximum FT thickness > 2 mm (mean thickness 2.2 ± 0.2 mm; range 2-2.5 mm) and 27 (68%) had echogenic FT < 2 mm thick (mean thickness 1.5 ± 0.2 mm; range 1-1.9 mm). The length of the echogenic segment on US was about 1.9-5.1 cm (mean length 3.4 ± 1.1 cm). All 40 patients showed FT lipoma without any associated abnormalities, such as cord tethering or low-lying conus. Among the total population of 337 patients, 30 (8.9%) showed borderline low-lying conus medullaris located at the L2-3 disc space or midpoint of the L3 vertebra. All 30 of these patients had borderline low-lying conus without other associated abnormalities. Filar cyst was noted in 36 of 337 patients (10.6%), without other associated abnormalities. No patient underwent surgery associated with a risk of neurological problems within a follow-up period of 10-37 months.

CONCLUSIONS

Although screening US in infants with simple sacral dimple yielded benign imaging findings, the presence of FT lipoma was common in these infants. Therefore, it is necessary to carefully observe changes in echogenicity during measurement of FT thickness on US. All FT lipomas were low risk and had no associated abnormalities, such as cord tethering or low-lying conus.