Spinal Dysraphism

Respiratory syncytial virus is the most common cause of hospitalization in U.S. infants, accounting for 58,000–80,000 hospitalizations and 200–300 deaths in children under 5 each year. Two prevention strategies — the long-acting monoclonal antibody nirsevimab (Beyfortus) for infants, and the maternal RSVpreF vaccine (Abrysvo) given in pregnancy — now offer Louisiana pediatricians and obstetric clinicians powerful tools to prevent severe lower respiratory tract disease. This clinical reference, originally prepared by Joseph A. Bocchini, Jr., MD, FAAP (Tulane University Department of Pediatrics / Willis-Knighton Health System) for the LA AAP, summarizes ACIP and AAP recommendations on who should receive nirsevimab, when, and how it pairs with maternal vaccination.

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Spinal Dysraphism in Children: Types, Presentation, and Management

Clinical reference for pediatricians · Louisiana Chapter, American Academy of Pediatrics

Spinal dysraphism describes a spectrum of congenital malformations of the spine and spinal cord, ranging from open neural tube defects such as myelomeningocele to subtle closed lesions that may present only with a cutaneous marker. Early recognition allows timely neurosurgical evaluation and helps preserve neurologic, urologic, and orthopaedic function.

Embryologic Origins

Spinal dysraphic states arise from errors during the formation of the embryonic nervous system. Open defects generally reflect a disturbance of primary neurulation (failure of the neural tube to close), while many closed lesions stem from abnormalities of secondary neurulation or premature disjunction of cutaneous and neural ectoderm. The flowchart below traces normal germ-layer development alongside the malformations that result when each step is disrupted.

Two-part embryology flowchart. The top panel maps normal development from zygote and blastocyst through gastrulation into ectoderm, mesoderm, and endoderm derivatives across weeks 0 to term. The bottom panel shows the corresponding malformations that arise when each developmental step is disrupted, including open and closed neural tube defects, dermoid and lipoma from the dermatome, and encephalocele.
Normal germ-layer differentiation (top) and the congenital malformations that result from disruption at each stage (bottom).

Open Neural Tube Defects: Myelomeningocele

Myelomeningocele is the prototypical open neural tube defect and a defect of primary neurulation. It can be detected prenatally through an elevated maternal serum alpha-fetoprotein and acetylcholinesterase, and on prenatal ultrasound through two characteristic cranial findings.

Prenatal ultrasound signs

  • Lemon sign — scalloping of the frontal bones giving the fetal skull a lemon-like contour.
  • Banana sign — abnormal anterior curvature of the cerebellum around the brainstem from hindbrain herniation.
Axial prenatal ultrasound of a fetal head showing the lemon sign. White arrows mark inward scalloping of the frontal bones, giving the skull a pointed, lemon-shaped contour associated with open neural tube defect. Axial prenatal ultrasound of a fetal head showing the banana sign. Red arrows mark the frontal scalloping and yellow arrows mark the cerebellum curved anteriorly around the brainstem, indicating hindbrain herniation in an open neural tube defect.
Lemon sign (left) and banana sign (right) on prenatal ultrasound.

Epidemiology and outcomes

0.7–0.8per 1,000 live births
70–75%normal IQ
~60%require a VP shunt
24–60%lifetime mortality

Lifetime mortality is most often driven by the Chiari II malformation and by unrecognized shunt malfunction. The proportion of patients ultimately requiring a ventriculoperitoneal shunt (~60%) is notably lower than older reports approaching 80%.

Initial management of the newborn

  • Surgical closure of the defect within 48–72 hours.
  • Prophylactic antibiotic coverage (ampicillin and gentamicin).
  • Head ultrasound, renal ultrasound, and spine radiograph (babygram).
  • Keep the defect covered with a moist, non-adhesive dressing.
  • Dedicated muscle-group testing to determine the affected neurologic level.

Three overarching phases guide care: initial stabilization and closure; assessment and treatment of hydrocephalus; and long-term management of shunt malfunction, Chiari II malformation, tethered cord, and syringomyelia.

Chiari II malformation

Under the unified theory, Chiari II results from underdevelopment of the posterior fossa bone with crowding by the structures of the rhombencephalon. Herniation of the brainstem, cerebellar vermis, and fourth ventricle through the foramen magnum can produce lower cranial neuropathies, swallowing dysfunction, and disordered breathing.

Sagittal MRI of the brain and cervical spine in Chiari II malformation. The images show a small posterior fossa with downward herniation of the cerebellar vermis, brainstem, and fourth ventricle through the foramen magnum into the upper cervical canal.
Sagittal MRI demonstrating hindbrain herniation through the foramen magnum in Chiari II malformation.

Prenatal versus postnatal closure

A landmark randomized trial compared prenatal closure (before 26 weeks gestation, with delivery at 37 weeks) to standard postnatal repair. Prenatal surgery was associated with a decreased shunt rate and improved functional outcome, but with an increase in preterm labor. During counseling, caution is warranted when the ventricles measure 15 mm or larger, since prenatal surgery does not appear to improve outcome in that group.

Closed Neural Tube Defects

Closed (skin-covered) dysraphic lesions are easily missed in the newborn nursery because the spinal cord is not exposed. They are, however, frequently announced by cutaneous markers over the lower back.

Cutaneous markers

Cutaneous markers appear in roughly 3% of the general population, but in about 80% of patients with spinal dysraphism; two or more often coexist. They characteristically occur in the midline of the back, above the level of the coccyx, and commonly overlie the underlying spinal lesion. Examples include hairy patches (faun’s tail), dermal sinus openings, subcutaneous lipomas, skin tags or tails, capillary malformations, and atypical dimples.

When to suspect a closed defect

  • Neurologic: lower-extremity weakness, muscle atrophy, radicular pain, abnormal gait.
  • Orthopaedic: leg-length discrepancy, foot deformities.
  • Urologic: recurring urinary tract infection, change or regression in continence.

Imaging

  • MRI is the study of choice.
  • Ultrasound can localize the conus in infants younger than 6 months, before posterior elements ossify.
  • CT is a useful adjunct in lesions with bony abnormalities.

Meningocele

A meningocele is a congenital herniation of dura and arachnoid through a bony defect in the spine. Nerve roots may be involved, but the spinal cord typically is not. Incidence is approximately 0.3–0.4 per 1,000 births. Posterior meningoceles relate to secondary neurulation, whereas anterior meningoceles arise from mesenchymal abnormalities.

Sagittal MRI of the lumbosacral spine showing a meningocele. A rounded, fluid-filled sac herniates posteriorly through a bony defect in the lower spine, without spinal cord tissue extending into the sac.
Sagittal MRI of a meningocele — a cerebrospinal-fluid-filled sac herniating through a posterior bony defect.

Spinal lipoma

Spinal lipomas form when cutaneous ectoderm separates prematurely from neural ectoderm (premature disjunction), allowing mesenchyme to enter the still-open neural groove and differentiate into fat that becomes incorporated into the cord.

Four-panel illustration of spinal lipoma formation. Panels a and b show premature disjunction of cutaneous ectoderm from neural ectoderm with mesenchyme invading the open neural groove. Panels c and d show the resulting fibrofatty stalk and lipoma fused to a distorted spinal cord along a fusion line of fat, cord, and pia-arachnoid.
Premature disjunction and formation of the fibrofatty “fusion line” that characterizes spinal lipomas.

Lipomas are classified by their relationship to the conus and cord:

  • Dorsal: the lipoma–cord interface lies entirely on the dorsal surface of the lumbar cord, always sparing the distal conus.
  • Terminal: the lipoma inserts into the caudal extremity of the conus without blending with the cord or its root entry zones.
  • Transitional: the interface is undulating and tilted, sometimes rotating the placode toward a parasagittal orientation, but neural tissue remains ventral to the interface.
  • Chaotic: the caudal portion lies ventral to the placode and engulfs neural tissue and nerve roots.
Sagittal MRI of the spine showing a spinal lipoma. A region of fatty signal is associated with the lower spinal cord, with an on-screen measurement of approximately 13.6 millimeters.
Sagittal MRI demonstrating a spinal lipoma associated with the lower cord.

Two approaches to treatment exist: prophylactic surgery to prevent symptoms (commonly around 3 months of age, the more common approach in the United States), versus operating only once the patient becomes symptomatic (more common in Europe).

Dermal sinus tract

A dermal sinus tract occurs in approximately 1 in 2,500 births. Affected children are usually neurologically normal at birth, but the risk of neurologic deficit and infection rises with age if the tract is left untreated. Although there is no consensus on timing in uncomplicated, asymptomatic cases, surgery is reasonable once the infant is physiologically ready for the procedure.

Split cord malformation

Split cord malformations (historically termed diastematomyelia) divide the spinal cord into two hemicords and often present with an overlying faun’s tail. They are separated into two types:

  • Type I: two hemicords separated by an osteocartilaginous median septum, each within its own dural sheath.
  • Type II: two hemicords within a single dural envelope, separated by a fibrous septum.
Axial MRI of the spine in a split cord malformation. The spinal cord is divided into two separate hemicords within the spinal canal at this level.
Axial MRI showing two hemicords in a split cord malformation.

Key Takeaways for the Pediatrician

  • Open neural tube defects require closure within 48–72 hours and coordinated neurosurgical care.
  • Midline lumbosacral cutaneous markers warrant a low threshold for spinal imaging, since most children with dysraphism display them.
  • MRI is the imaging study of choice; ultrasound is useful before 6 months of age.
  • New or progressive neurologic, orthopaedic, or urologic findings may signal a tethered cord and should prompt re-evaluation.

This page is an educational reference for clinicians and is not a substitute for individualized medical judgment or formal neurosurgical consultation. Adapted from a presentation by Jerome M. Volk III, M.D., LSUHSC New Orleans Department of Neurosurgery and Children’s Hospital of New Orleans.

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