A significant number of children with a tethered spinal cord have a cutaneous manifestation overlying the lower spine, yet the ability to diagnose it often depends on the knowledge and familiarity of this condition by the primary care provider. Since early identification and treatment may prevent further neurologic deterioration and improve outcome if neuro-urologic injury has already occurred, it is imperative to expedite the timing of diagnosis.
The aims of this study were two-fold: (1) to determine the frequency and (2) to increase awareness of spinal cord abnormalities in a cohort of patients with a variety of subtle cutaneous lower spinal lesions.
The severity and reversibility of these metabolic disturbances correlates with timing of both diagnosis and treatment of the tethered cord. The normal spinal cord termination should be at approximately the level of the L1-L2 vertebrae, although there is a range that spans from T12-L3. Suspicion for spinal cord tethering is raised when the spinal cord terminates below the L3 vertebrae.
Most dysraphic states (neural tube defects) have a common persistent anatomic connection between the neuroectoderm and cutaneous ectoderm that prevents the conus from “ascending” up the canal with longitudinal growth of the child. These have been labeled tethered cord syndromes.
Initially, there is no significant “stretching” of the cord. But with time and somatic growth, the increased tension on the spinal cord impairs blood flow, oxidative metabolism and glucose utilization and leads to metabolic failure of intracellular mitochondria. The severity and reversibility of these metabolic disturbances involving the spinal cord correlates with timing of both diagnosis and treatment of the tethered cord.
Our group has reported that progressive neural injury occurs following delayed diagnosis. It is uncommon to find a newborn with a tethered cord having urinary incontinence and/or lower extremity abnormality on neurologic assessment. However, with continued growth, these infants either:
- fail to toilet train
- develop urinary incontinence after training
- have disturbances of micturition that lead to urinary infection
- experience fecal incontinence and/or exhibit lower extremity dysfunction with gait changes
During the past 18 months, from June 2014 to December 2015, 26 children were evaluated at Boston Children’s Hospital with subtle signs of a possible tethered spinal cord. Age at diagnosis ranged from 1 day to 12.7 years of life (median = 0.625 years). An equal number of males and females made up this cohort.
All children had a cutaneous abnormality that ranged from:
- minimal gluteal cleft asymmetry
- small midline skin dimple
- faint dermal vascular malformation
- small ‘Y’ shaped upper aspect of gluteal cleft
- subtle subcutaneous mass, low cleft formation or minor hair patch (three each), with some children having greater than one finding, that led to an investigation
Click to view slideshow: signs of tethered spinal cord
Persistent maternal inquiry led to an investigation in eight cases, or 31 percent. All children either had a spinal ultrasound, if a lesion was suspected before 3 months of age, and/or a spinal MRI to confirm the presence or absence of a tethered cord, or intraspinal defect, when investigated later. Children with an obvious skin lesion – lipoma, sinus tract or dense hair patch – were excluded.
Fourteen of 26 (54 percent) had an abnormality of their spinal cord; the remainder had no cord defect. An occult spinal dysraphism was seen on x-ray imaging in 91 percent of patients with cleft asymmetry while no one with a hair patch or a ‘Y” cleft appearance had such a defect.
In children with a small subcutaneous mass, a dermal vascular malformation or a dimple, the incidence of a tethered cord varied between 55 percent to 72 percent. Six of these 14 had no urologic or orthopedic symptoms, five (82.5 percent) of whom were less than 1 month of age when diagnosed. Seven of the remaining eight symptomatic children ranged in age from 1 to 7.7 years (median 2.3 years).
Of the 14 children with a spinal cord anomaly, 11 (79 percent) underwent urodynamic studies, while three had none. Six of the 11 (55 percent) exhibited abnormal lower urinary tract function on UDS, three of whom were less than age 1. Thus, three of 14 (21 percent), all less than age 1, already had evidence of lower urinary tract dysfunction without clinical symptoms when first diagnosed at this young age.
Early detection is dependent on the knowledge that tethered cord syndrome exists. Not every child with a cutaneous lesion has a tethered cord but every child warrants at least a spinal ultrasound within the first three months of life. After age 3 months, ultrasound is not able to penetrate the ossified vertebrae and a spinal MRI should be obtained.
Given the importance of early diagnosis and potential management, we believe that the findings of this study will increase awareness, improve diagnostic acumen and lead to prompt referral and comprehensive treatment.
About the authors:
Stuart B. Bauer, MD, is a senior associate at Boston Children’s Department of Urology and professor of surgery (urology) at Harvard Medical School.
Scellig S. D. Stone, MD, PhD, FRCSC, is the director of Movement Disorders and Deep Brain Stimulation Program, associate in neurosurgery at Boston Children’s Hospital and assistant professor at Harvard Medical School.