A 1-day-old girl is seen for routine care in the newborn nursery. The patient was born at 40 weeks and 1 day of gestation to a 21-year-old gravida 2 now para 2 mother by vaginal delivery. Pregnancy was complicated by maternal obesity, mild intermittent asthma, hyperthyroidism, allergic rhinitis, anemia, and sickle cell trait. The patient’s mother had adequate prenatal care and a normal prenatal anatomic ultrasonographic image. The mother’s medications during pregnancy included prenatal vitamins, ferrous sulfate, fluticasone nasal spray, and albuterol inhaler as needed. The patient’s newborn course has been uneventful. She has been breastfeeding without difficulty and is voiding and stooling normally. There are no parental concerns.On examination the infant is well appearing and shows no dysmorphic facial features. Her temperature is 98.1°F (36.7°C), heart rate is 128 beats/min, and respiratory rate is 48 breaths/min. Her head is normocephalic, with a flat, open, and soft anterior fontanelle. Neurologic examination reveals normal Moro, grasp, and suck reflexes and normal tone with no focal deficits. External genitalia appear normal, and a patent anus is visualized. Upper and lower extremities are without deformity. The spine examination reveals a straight spine with no sacral dimples or hair tufts. Skin examination is significant for sacral dermal melanosis and an erythematous macular patch over the lumbosacral region. The upper aspect of the gluteal cleft is characterized by a mildly asymmetrical Y-shaped crease (Fig 1). The remainder of her newborn examination findings are within normal limits. Ultrasonography and magnetic resonance imaging (MRI) reveal the diagnosis.The differential diagnosis of the patient’s lumbosacral birthmark includes a nevus simplex, hemangioma, port-wine stain, or arteriovenous malformation. The location, size, and appearance are most consistent with a nevus simplex. The midline lumbosacral location of the nevus simplex in conjunction with an asymmetrical Y-shaped upper gluteal cleft raise suspicion for closed spinal dysraphism (CSD). Spinal ultrasonography reveals a large cyst at the lower aspect of the spinal cord with extension into the upper sacrum. A well-defined conus terminating in the expected location is not identified (Fig 2). MRI at 2 weeks of age shows a sacral nerve root cyst and thickened filum terminale. These imaging studies support a diagnosis of tethered spinal cord with a terminal spinal cord cyst and fatty filum terminale in association with cutaneous findings of a lumbosacral nevus simplex and an asymmetrical Y-shaped upper gluteal cleft.CSD, also known as occult spinal dysraphism or spina bifida occulta, encompasses a variety of clinical findings secondary to embryological disorders of neurulation. It results from a failure of the 2 halves of the neural arches to fuse at the midline, and the skin overlying the defect is typically intact. (1) The incidence of both closed and open spinal dysraphism is estimated to be between 0.5 and 8 cases per 1,000 live births. (2) Defects seen in CSD include split spinal cord malformations, sacral meningeal cysts, spinal lipomas, caudal regression, sacral agenesis, cutaneous abnormalities, and tethered spinal cords.Patients with CSD can range from being asymptomatic to having severe neurologic, musculoskeletal, and genitourinary abnormalities. Cutaneous markers may be the only sign of an underlying spinal cord anomaly and are stratified into low-, intermediate-, and high-risk categories. Hypertrichosis, hemangiomas, caudal appendages, and atretic meningoceles that overlay the midline spinal region are considered high risk and require further evaluation. Children with a high anorectal malformation or cloacal malformation are also considered to be at high risk for having CSD. Intermediate-risk lesions include midline lumbosacral port-wine stains, lumbosacral nevus simplexes, lipomas, and low or intermediate anorectal malformations. The evaluation of these isolated lesions is controversial, but the incidence of underlying spinal abnormality is increased if seen in combination with other cutaneous findings, such as a deviated or asymmetrical gluteal cleft. Children with isolated dimples are in the low-risk group. (3)In patients with cutaneous findings concerning for CSD, imaging should be obtained to evaluate for spinal cord abnormalities. Ultrasonography of the spine is useful in screening neonates and young infants due to the low cost, lack of radiation, and ability to image through the unossified sacrum. However, less experienced sonographers may miss subtle findings, and equivocal findings on screening ultrasonography in low-risk patients are common and can lead to further unnecessary testing. The modality of choice for evaluating CSD is MRI of the entire spine because there are frequently multiple abnormalities present in a single patient. (4)Spinal cord abnormalities may lead to fixation of the caudal end of the spinal cord to inelastic structures, causing what is known as a tethered cord. CSD malformations associated with tethered cord syndrome include dermal sinuses, lipomyelomeningoceles, spinal lipomas, split cord malformations, and thickened filum terminale. (5) Tethered cord is best evaluated by MRI, and the finding of a conus located below the level of L2 is considered abnormal and consistent with a tethered cord. (4) The patient’s age and expected conus termination must be taken into account because the level of the conus rises as the child grows. There are reports of tethered cord syndrome in children with a conus above the level of L2. (6) Other MRI findings suggestive of tethered cord include a thickened or fatty filum terminale or conus displacement in the dorsal direction. (5)The functional sequelae of a tethered cord are known as tethered cord syndrome. The pathophysiology of tethered cord syndrome likely results from impairment of oxidative metabolism and electrical activity in a cord that is chronically stretched during growth due to tethering at the caudal end. (7) This causes dysfunction of the spinal cord and subsequent neurologic, urologic, gastrointestinal, and musculoskeletal complications. Symptoms of tethered cord syndrome can be present at birth or can manifest as the child grows and can present even in adolescence or adulthood.Infants can be completely asymptomatic or can have lower-extremity weakness, appreciable on examination or by observing for asymmetrical limb movement and positioning. As infants continue to develop, they can show motor delays, such as difficulty with crawling or walking. Older children can show slow loss of previously gained gross motor milestones and frequently present with ankle dorsiflexion weakness, leading to problems such as footdrop or the inability to heel walk. Signs of lower motor neuron dysfunction, including decreased tone, diminished reflexes, and muscle atrophy, can be seen. Children infrequently present with pain complaints, although older children and adolescents may complain of back pain and avoid twisting and flexion of the spine. (5)Urologic changes are difficult to assess in infants and children who are not toilet trained, although urodynamic studies can reveal detrusor overactivity in children with tethered spinal cord syndrome. However, this finding is also seen in healthy children with immature bladders and must be correlated with other clinical findings. (4) Older children can experience urinary and fecal incontinence, constipation, urinary urgency, and recurrent urinary tract infections. (5)Underlying spinal cord malformations (due to spinal dysraphism) and neuromuscular imbalance in the lower extremities can lead to multiple musculoskeletal deformities. These deformities are numerous and include scoliosis, kyphosis, and clubfoot deformity, as well as other limb and foot deformities. (5) These musculoskeletal sequelae tend to become more severe in children with tethered cord syndrome who are left undiagnosed and untreated. (4)Patients with CSD should be referred to a neurosurgeon for further management. Operative technique varies depending on the underlying lesion, but the goal of the surgery is to untether the spinal cord. The decision to operate on asymptomatic children with CSD is complex and is based on weighing the risks of operation versus the risks of deterioration with watchful waiting. Patients with symptoms that can be attributed to a tethered cord are typically considered for surgery. Surgical outcomes are greatly dependent on age at time of surgery and baseline dysfunction before surgery, with better neurologic, urologic, and musculoskeletal outcomes seen in younger children with less severe dysfunction. (4)Since discharge from the newborn nursery, the patient has met all the developmental milestones and has no signs of bowel or bladder dysfunction, lower-extremity weakness, or orthopedic deformities. Evaluation by urology with urodynamic testing showed normal bladder capacity and compliance. Kidney and bladder ultrasonography revealed the incidental finding of a urachal cyst and was otherwise normal.Repeated MRI of the spine obtained at 4 months of age for surgical planning revealed the conus medullaris terminated at approximately L3 and a cystic dilatation that extends to S1 and measures 3.1 × 0.6 cm. Cord parenchyma appeared to be stretched about the periphery of the cyst. A thickened and lipomatous filum terminale extends around the ventral aspect of the cystic dilatation to terminate in the lower sacrum in fatty tissue measuring 1.5 × 0.8 cm. The lower portion of the sacrum and the coccyx was slightly malformed and deviated to the left with no posterior spinal dysraphism identified (Fig 3).At 6 months of age, she underwent lumbar laminoplasty with microdissection for release of the tethered spinal cord by sectioning of fatty filum terminale and fenestration of the terminal spinal cyst. Her postoperative course and recovery were uneventful. The patient was walking at her 9-month health supervision visit.