My Baby Has a Dimple on His Lower Back

Korean J Pediatr. 2018 Jun; 61(vi): 194–199.

Event of ultrasonographic imaging in infants with sacral dimple

Jin Hyuk Choi, MD,^one Taekwan Lee, Doc,¹ Hyeok Hee Kwon,² Sun Kyoung Yous, MD, PhD, ³ and Joon Won Kang, MD, PhD ^{1, 2, iv}

Jin Hyuk Choi

¹Section of Pediatrics, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, Korea.

Taekwan Lee

^oneSection of Pediatrics, Chungnam National Academy Hospital, Chungnam National Academy School of Medicine, Daejeon, Korea.

Hyeok Hee Kwon

²Department of Medical Scientific discipline, Chungnam National Academy School of Medicine, Daejeon, Korea.

Sun Kyoung You

³Department of Radiology, Chungnam National Academy Infirmary, Daejeon, Korea.

Joon Won Kang

¹Section of Pediatrics, Chungnam National University Infirmary, Chungnam National University School of Medicine, Daejeon, Korea.

^twoSection of Medical Science, Chungnam National University School of Medicine, Daejeon, Korea.

⁴Brain Research Plant, Chungnam National Academy School of Medicine, Daejeon, Korea.

Received 2017 Sep 5; Revised 2017 Oct 25; Accepted 2017 Oct 31.

Abstruse

Purpose

Sacral dimples are a common cutaneous bibelot in infants. Spine ultrasonography (USG) is an effective and rubber screening tool for patients with a sacral dimple. The aim of this report was to decide the clinical manifestations in patients with an isolated sacral dimple and to review the management of spinal cord abnormalities identified with USG.

Methods

We reviewed clinical records and collected information on admissions for a sacral dimple from March 2014 through February 2017 that were evaluated with spine USG by a pediatric radiologist. During the same period, patients who were admitted for other complaints, but were constitute to have a sacral dimple were also included.

Results

This written report included 230 infants nether 6-months-old (130 males and 100 females; hateful age 52.eight±42.six days). 30-ane infants with a sacral dimple had an echogenic filum terminale, and 57 children had a filar cyst. Xx-vii patients had a low-lying spinal cord, and only one patient was suspected of having a tethered string. Follow-up spine USG was performed in 28 patients, which showed normalization or insignificant change.

Conclusion

In this study, all but 1 infant with a sacral dimple had benign imaging findings. USG can exist recommended in infants with a sacral dimple for its convenience and safety.

Keywords: Infant, Lumbosacral region, Peel abnormalities, Ultrasonography, Diagnostic imaging

Introduction

Cutaneous lesions of the lower back region could be associated with tethered string syndrome including hairy patches, subcutaneous lipomas, and dimples.1) A simple sacral dimple is less likely to be associated with tethered cord syndrome, but this is difficult to prove. It is not well known whether this is associated with other spinal string anomalies.

A sacral dimple was establish in 1.8%–7.2% of newborn infants;ii,3,4) it is a mutual pare lesion that tin can easily be institute in outpatient clinics or admission during neonatal periods. It has been reported that a dimple can be seen as a typical benign lesion when visible, less than 0.5 cm in size, and has one lesion located in the midline. Large, deep, and afar from the anus, hair, and of inverse color may be associated with other diseases.3,4,5) Nevertheless, further examination is necessary because the visual abnormalities cannot exist completely discriminated via visual exam.

Ultrasonography (USG) is a safe and cost-constructive screening method and is unremarkably used in infants with sacral dimples.6,7) It is a noninvasive screening method that does not chance radiations exposure in children, and does not require sedation. In add-on, spinal USG performed at a young historic period is effective because it can acquire relatively accurate imaging compared to postossification. Despite its many advantages, there is a proffer that USG is non required.8) Currently, limited research exists on the clinical significance of USG in sacral dimple in Korea. This study investigates the clinical features of the sacral dimple in patients with a sacral dimple, and evaluates the prevalence of accompanying diseases and the necessity of USG.

Materials and methods

1. Patients

A retrospective review of clinical information and imaging findings (lumbar spinal USG and spine magnetic resonance imaging [MRI]) was performed for the records of 304 children who were diagnosed with a sacral dimple from March 2014 through to February 2017 in Chungnam National Academy Infirmary. A USG was performed for all patients who visited for a sacral dimple. The USG findings of the patients who underwent the first US inside 6 months after their birth were analyzed.

Concrete examination including superlative and weight were investigated at the first visit. The birth history including gestational age, nascency weight, and delivery method were examined. The clinical features of sacral dimple were determined past examining the hair, skin colour, secretion, and altitude from the anus to the sacral dimple. Patients with grossly observed anal anomalies or masses, chromosomal anomalies, and multiple deformities were excluded. The menses diagram for enrollment was as fatigued in Fig. one. This report was performed with the approval of the Institutional Review Board of Chungnam National University Hospital (2017-01-022).

Menses diagram showing the enrollment of patients with a sacral dimple. CNS, central nervous organization.

2. Paradigm technique and assay

All spinal USG were performed by a unmarried pediatric radiologist (Sky) with five years of experience using an IU-22 Philips ultrasound organisation (Philips Healthcare, Bothell, WA, USA) with a linear-assortment probe (12-5 MHz). A kyphotic curvature was created past placing the patient on a minor pillow in a prone position and performing a midline scan over the spinous process. The Normal lumbar spine USG finding was as shown in Fig. 2A. We recorded the level of the tip of the conus medullaris (CM), the pulsation of CM or the nerve roots, the thickness and echogenicity of the filum terminale (FT), the presence of intraspinal mass, and normal variants including filar cysts and ventriculus terminalis.

Ultrasonography (USG) findings in patients. (A) Normal lumbar spine USG in a 4-mean solar day-erstwhile boy. Longitudinal USG shows normal beefcake of the spinal culvert and its contents. (B) Low-lying spinal cord in a 4-day-old girl. (B1) Longitudinal USG shows the tip of the conus medullaris terminating at L3–4 disc space. (B2) Sagittal T2-weighted magnetic resonance imaging confirms the level of the conus medullaris at the L3–4 disc space. (C) Echogenic filum terminale. (C1) Prominent filum terminale in a 6-calendar month-old boy. Longitudinal USG shows hyperechoic filum terminale with normal thickness (about 1.3 mm). (C2) Thick filum terminale in a 5-month-old male child. Longitudinal USG shows hyperechoic filum terminale with 2.two-mm thickness. (D) Filar cyst (arrow in D1 and D2) in a ane-month-former boy. Longitudinal (D1) and transverse (D2) USG shows well-defined, thin walled, fusiform cyst below the tip of the conus medullaris.

The echogenicity of FT was compared to adjacent roots of the cauda equina. FT was considered thick when information technology measured more than 2 mm on transverse and longitudinal US and was considered fibrous or lipomatous nature. Nosotros considered information technology as "prominent FT" when the thickness of the echogenic FT was less than 2 mm. If the tip of the CM was below the L2–three disc space, this was considered low-lying spinal cord. Nosotros defined the isolated depression CM as the tip of CM is seen at L2–iii disc space or the L3 vertebral body level without show of tethering.9) The findings of additional imaging including follow-upwardly United states of america or MRI were besides recorded.

iii. Statistical analysis

Statistical analysis was performed using IBM SPSS Statistics ver. twenty.0 (IBM Co., Armonk, NY, USA). Chi-foursquare tests, and t test were applied to the data to compare variables; P<0.05 was regarded statistically significant.

Results

1. Clinical characteristics

Of the 304 patients who underwent spinal USG, 230 patients (130 boys and 100 girls) who were younger than six months were included in the study (Fig. 1). The hateful age at commencement visit was 52.8±42.6 days (range, one–175 days), the mean height was 56.0±6.1 cm and the mean trunk weight was iv.9±1.7 kg. In birth history, the mean gestational age was 38.5±1.vii weeks, 29 patients were born as premature neonate. One hundred ninety patients were built-in at total term, and 1 patient was built-in at 42 weeks of gestational age. The mean nascency weight was 3.i±0.v kg, and 48% of the patients were delivered via cesarean section. Nigh 65% of the patients visited hospital inside 1 month of age (Fig. 3). Thirty-nine patients (17.0%) had hair, and ii patients (0.ix%) had discharge at the dimple region. 20 patients (8.7%) had pare discoloration and 6 had pare tag (2.6%). The distance from the anal verge to the dimple was 2.14±ane.01 cm (Table 1).

Age at first visit to the hospital.

Table 1

Patient profiles

Variable	Value
Demographic findings
Sexual activity, male:female person	130:100
Age at visit (day)	52.8±42.vi (1–175)
Height (cm)	56.0±six.ane (42.0–72.two)
Weight (kg)	4.9±1.seven (1.viii–10.0)
Delivery history
Gestational age (wk)	38.five±1.vii (30–42)
Preterm (<37)	29 (13.2)
Term (≥37, <42)	190 (86.4)
Postterm (≥42)	1 (0.4)
Birth weight (kg)	3.ane±0.5 (i.1–4.five)
Commitment method, VD:C/S	119:100 (52.0:48.0)
Findings of sacral dimple
Pilus	39 (17.0)
Belch	ii (0.9)
Discoloration	20 (8.7)
Skin tag	six (2.6)

2. Imaging findings

During the above-mentioned catamenia, 261 cases of USG were performed with 230 patients, of whom 28 patients underwent follow-up USG (59 cases) and 1 patient underwent a spine MRI. In the showtime USG, echogenic FT was found in 31 cases (13.5%). Prominent FT (thickness of less than 2 mm, echogenic) was found in 26 cases (hateful thickness, 1.four±0.2 mm; range, i.0–1.9 mm) and 5 cases had a thickness of more than than ii mm (thick FT) (2.4±0.4 mm; range, 2.0–ii.ix mm) (Fig. 2B). Filar cyst was identified in 57 cases and their size was 8.half dozen±2.8 mm (range, iii.vii–20.0 mm) (Fig. 2C).

The exact CM level could not be confirmed in 6 patients, but their CM levels were considered normal because the CM was visible at the renal hilum level (considered as L1–2 level). When comparing the instance of determining the CM level every bit the renal hilum level and the example of confirming the CM level, 4.half-dozen±one.0 months vs. 1.6±one.iii months (P<0.001) indicated that information technology was difficult to accurately define the CM level afterwards at to the lowest degree four.six months. There were 27 cases (11.7%) with low-lying spinal cord (Fig. second). There were 26 cases of isolated low CM in which the tip of CM was located in the L2–3 disc space or the middle body of the L3 medullaris. Only one instance presented with the CM below the midbody of L3 (Table 2).

Table 2

Initial lumbosacral ultrasound findings

Findings	No. (%)	Size or thickness (mm), mean±SD
Echogenic filum terminale
Prominent FT	26 (xi.three)	ane.4±0.2
Thick FT	5 (ii.2)	2.4±0.4
Depression-lying spinal cord
Between the L2–3 disc space and the mid body of L3 medullaris	26 (11.iii)	-
Beneath the mid body of L3	1 (0.4)	-
Filar cyst	57 (24.8)	eight.6±half dozen.two

Follow-upward USG was performed with 28 patients. Viii of 10 patients who were followed up after the echogenic FT were echogenic in follow-up, and two patients had normal findings. In xiii patients followed up with filar cyst, ane was non visible in follow-upwards, iii patients were in poor window, and 9 patients (3 times in two patients, xx cases in full) showed follow-up. The thickness of the echogenic FT and filar cyst did non change during the follow-upward period.

I patient who had a low lying spinal string (level L3–4) was suspected of cord tethering on USG and this patient had a small subcutaneous cystic lesion nether the coccygeal cartilage without intraspinal extension. The patient was a iv-day-quondam daughter who was delivered by vaginal delivery at a gestational age of 39 weeks 2 days and at a birth weight of 2.12 kg. She was admitted to neonatal intensive care unit for intrauterine growth retardation, and USG was performed for sacral dimple, which was plant incidentally during hospitalization. A sacral dimple was located in the midline, 3 mm from the anal verge. As described to a higher place, abnormal findings were detected on spinal USG and spine MRI was performed for farther evaluation. The patient was referred to a neurosurgeon; additional testing was recommended including contrast enhancement MRI and surgery was considered. However, the caregiver refused further evaluation and was the patient was discharged on his own accord.

Discussion

The sacral dimple is one of the near mutual skin lesions, simply it is a simple peel lesion in nigh cases and does non affect neurologic dysfunction. In our study, half of the patients showed normal USG finding without anomaly. The other patients had filar cyst (24.8 %), echogenic FT (13.5%), and low-lying spinal cord (11.vii%). Considering that filar cysts are too classified as normal findings in other literature,10) 74.8% of patients had normal USG findings among our patients. Although patients had abnormal findings for USG, physical test and observational findings were nonspecific except in 1 patient.

Ane of the major reasons for performing USG is early detection of the possibility of tethered cord syndrome. A tethered cord syndrome is acquired by a stretch-induced dysfunction of the caudal spinal cord and conus, that ofttimes associated with spinal dysraphism.11) In children, tethered cord syndrome typically nowadays with progressive motor and sensory dysfunction, which may include gait abnormalities and urologic symptoms.12) Although there are some asymptomatic patients with anatomic cord tethering, the patients with adult symptoms does non naturally improve without surgical untethering.thirteen) And early intervention later on symptom development is important for recovery of neurological functions.13,14,fifteen) Early diagnosis is also necessary for prevent neurological damage and adequate surgical correction.xvi)

In a review article, the incidence of abnormalities in spinal USG in children without dimple was 4.eight%, which was not significantly unlike from 3.eight% in children with a dimple.eight) This leads to questions about whether ultrasound should be performed in patients with uncomplicated sacral dimples.17,18,nineteen,twenty,21) Although only i patient among 230 needed a surgical procedure in our report, considering neurologic issues caused by tethered cord and importance of early diagnosis, USG is worthy for the screening of sacral dimples in infants. In ane study of comparing USG and MRI, USG is valuable diagnostic tool for congenital anomalies of the lower spine in infants.22) It is meaningful to perform an USG in Korea, because that the price of medical services is not expensive compared to the U.s.a. or Europe, and hospitals are readily accessible.23) Furthermore, Ohashi et al.24) reported a instance of mucopolysaccharidosis blazon Iv, which was diagnosed during sacral dimple evaluation at birth. Prompt evaluation could pb to the identification of other treatable diseases in patients.

Cord tethering can occur past FT lipoma, which is the most common cause of thick FT. Therefore, detection of aberrant FT thickening is of import.25) In most of the literature, a thickness of FT of more than 2 mm was considered thick FT. Shin et al.25) compared lumbosacral USG and MRI findings and suggested 1.ane mm every bit the optimal cutoff value for filar lipoma screening on USG. We observed prominent FT in cases of echogenic rather than nervus root, and thick FT in cases in which the thickness was more than than two mm. The incidence was xi.three% and 2.2%, respectively.

Irani et al.x) reported that the frequency of filar cysts was xi.viii %, and the brusk-term results were not significantly different from those of the normal controls. Although the origin and existence of filar cysts is not well studied, neonatal filar cysts plant in isolation on lumbar USG tin be considered equally normal variants. In our study, the incidence of filar cysts in patients with a sacral dimple was 24.eight%. Our findings showed higher prevalence than Irani et al.10); their report included more than 600 patients and infants older than 12 months were included. There were differences in the number and ages of patients, and no specific symptoms were observed in our patients.

Our written report only included patients less than 6 months old to ensure the accuracy of ultrasound images. However, there were patients who visited with a sacral dimple even after half-dozen months of age. Including these patients makes the mean age of the patients who visited the hospital with a sacral dimple two.7±4.6 months (range, 0–62.8 months); 89.5% of the patients visited the infirmary vi months after birth, and 75.1% of patients visited the hospital 3 months afterwards birth. Most of the patients had a sacral dimple during the physical examination for neonatal exam, national infant screening, and vaccination. In our study, 129 patients (56.1%) were normal and the other 100 patients had no neurological abnormalities associated with sonographic findings.9,10,26,27) In some cases, the patients did not revisit the clinic even though follow-upwardly tests were planned. This might exist considering the parents of the patients thought that their infant had no neurological abnormalities. No meaning changes were constitute in the 28 children who underwent a follow-up.

The limitations of this study included that it was a retrospective, unmarried-institutional study. The example could be made that the medical records were insufficient because of the recruitment of retrospective subjects. Future prospective studies should identify long-term clinical outcomes. Infants after 3 months had fewer than other age groups, because progressed ossification made ultrasound imaging hard. Overcoming regional biases requires investigating the clinical manifestations of the sacral dimple in Korea by studying more than patients in multiple institutions. In conclusion, almost of the patients in this study had a skilful clinical course; we found 1 case of abnormality that could lead to neurologic abnormalities in this study. Therefore, USG screening tests might be useful for children with sacral dimples.

Acknowledgments

This piece of work was supported past a inquiry fund from the Chungnam National Academy (2014-0656-01). This research was supported by Basic Science Enquiry Program through the National Inquiry Foundation of Korea (NRF), funded by the Ministry of Science, ICT & Future Planning (grant number: 2015R1C1A1A01052351). This work was presented at the Korean Pediatric Club Congress in 2016.

Footnotes

Conflicts of involvement: No potential disharmonize of interest relevant to this article was reported.

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6021363/

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