{ "topic": "Myelomeningocele", "slug": "myelomeningocele", "category_id": 15132, "summary": "The most severe form of spina bifida \u2014 an open neural tube defect exposing spinal cord and nerves \u2014 its Chiari II-driven hydrocephalus, level-dependent neurologic deficits, and lifelong multidisciplinary care needs.", "written_by": "claude-sonnet", "references": [ { "title": "Kliegman R. Nelson Textbook of Pediatrics 2-Volume Set 22ed 2024", "author": null, "pages": [ 3599, 3600 ] }, { "title": "Zitelli and Davis' Atlas of Pediatric Physical Diagnosis: Expert Consult - Online", "author": null, "pages": [ 893 ] }, { "title": "Textbook of Neonatal Resuscitation (8th ed)", "author": null, "pages": [ 260 ] }, { "title": "MedStudy Pediatrics Core 11th Edition 2024-2025", "author": null, "pages": [ 437 ] }, { "title": "Gomella's Neonatology: Management, Procedures, On-Call Problems, Diseases, and Drugs, Eighth Edition", "author": "Tricia Lacy Gomella, Fabien G. Eyal and Fayez Bany-Mohammed", "pages": [ 1043 ] }, { "title": "Diagnostic Imaging: Pediatrics", "author": "A. Carlson Merrow Jr. MD", "pages": [ 1130, 1134 ] }, { "title": "Cover", "author": "Vitalsource Download", "pages": [ 8394 ] }, { "title": "Pediatric Decision-Making Strategies", "author": "Pomeranz, Albert J.", "pages": [ 122 ] } ], "short": [ { "title": "In short", "content": "- Myelomeningocele (spina bifida cystica) results from defective closure of the caudal neural tube in the third gestational week; when only the posterior vertebral elements fail to close it's a meningocele, but when neural and vertebral elements are both involved it's a myelomeningocele \u2014 most commonly in the lumbar spine.\n- Etiology is incompletely understood but polygenic/multifactorial, with folate deficiency and toxins implicated; recurrence risk is 3-4% after one affected child, rising to 10% after two affected children.\n- On exam, the defect is a saclike cystic structure covered by thin, partially epithelialized tissue, or an exposed flat neural placode with no overlying tissue; a membrane, if present, can rupture and leak CSF.\n- Neurologic level determines deficits: a low sacral lesion may cause only bowel/bladder incontinence and perineal numbness with no motor deficit; a high lumbar lesion adds flaccid lower-extremity paralysis, absent deep tendon reflexes, no response to touch/pain below the level, and in-utero positional deformities (clubfoot, hip subluxation); lesions above midlumbar tend to produce lower motor neuron signs from disruption of the conus medullaris and cord above it; upper thoracic/cervical lesions cause minimal neurologic deficit.\n- Bladder involvement varies: some children have constant urinary dribbling with a relaxed anal sphincter, while others have a high-pressure bladder with sphincter dyssynergy \u2014 both patterns require careful, ongoing urologic follow-up.\n- Nearly all myelomeningoceles cause Chiari II (Arnold-Chiari) malformation \u2014 downward displacement of the brainstem and cerebellar tonsils \u2014 obstructing CSF flow and causing hydrocephalus in about 80-85% of cases, most needing a ventriculoperitoneal shunt.\n- Associated CNS anomalies include cortical dysplasia, polymicrogyria, callosal abnormalities, and cerebellar abnormalities; long-term complications include tethered cord (usually from surgical scar tissue) and hydromyelia (CSF buildup in the central spinal canal from worsening hydrocephalus).\n- Cognitive development is affected by the Chiari II malformation itself and can be further impaired by hydrocephalus complications and shunt infections, especially in infancy; latex hypersensitivity affects about a third of patients.\n- Postoperative neurologic status is typically stable in the majority (about 73%) of patients; neurological deterioration suggests a complication \u2014 most often tethering by scar tissue (a clinical diagnosis of exclusion, with retethering symptoms in about a third of patients), but syringohydromyelia or cervical myelopathy from Chiari II should also be considered and imaged for.\n- Traditional treatment is postnatal neurosurgical closure plus lifelong multidisciplinary care (neurosurgery, urology, orthopedics, genetics, physiotherapy, primary care); the 2011 MOMS trial showed prenatal (in-utero) surgery reduces the need for a CSF shunt and improves motor outcomes at 30 months, but carries maternal and fetal risks, and a 2014 Cochrane review found evidence insufficient to broadly recommend it, though some US centers continue offering fetal surgery." } ], "long": [ { "title": "Definition", "content": "Myelodysplasias are congenital deformities resulting from defective closure of the caudal portion of the neural tube during embryonic development. When the failure of closure involves only the posterior vertebral elements, it is termed a meningocele; when it involves both neural and vertebral elements, it is a myelomeningocele (a form of spina bifida cystica). It most commonly affects the lumbar spine." }, { "title": "Epidemiology", "content": "The etiology of myelomeningocele remains incompletely understood, but as with all neural tube closure defects, a genetic predisposition exists, with both epidemiologic and familial aggregation studies indicating polygenic risk factors. The risk of recurrence after one affected child is 3-4%, rising to 10% after two prior affected children." }, { "title": "Etiology", "content": "Myelomeningocele results from failure of neural tube closure during the third gestational week, likely from a multifactorial combination of folate deficiency, environmental toxins, and genetic susceptibility." }, { "title": "Pathophysiology", "content": "Loss of neurologic function from abnormal spinal cord and nerve root development has serious downstream consequences for the developing musculoskeletal system. Myelomeningocele almost universally causes Chiari II (Arnold-Chiari) malformation \u2014 downward displacement of the brainstem and cerebellar tonsils into the spinal canal \u2014 which obstructs normal CSF flow and results in hydrocephalus in about 80-85% of cases. Other associated CNS anomalies include cortical dysplasias, polymicrogyria, callosal abnormalities, and cerebellar abnormalities. Long-term complications include tethered cord, usually from scar tissue at the surgical repair site, and hydromyelia (CSF buildup in the spinal cord's central canal) related to worsening hydrocephalus." }, { "title": "Clinical features", "content": "The defect is generally readily apparent as a saclike cystic structure covered by a thin, partially epithelialized layer of tissue, or as an exposed flat neural placode without overlying tissue; a membrane, when present, may rupture and leak CSF. Examination typically shows flaccid paralysis of the lower extremities, absent deep tendon reflexes, and lack of response to touch and pain below the lesion level, along with a high incidence of lower-extremity deformities (clubfeet, ankle/knee contractures, hip subluxation) from abnormal movement in utero. Neurologic deficit correlates with lesion level: a low sacral lesion may cause bowel and bladder incontinence and perineal numbness without motor dysfunction, while a high lumbar lesion adds lower-extremity flaccid paralysis, absent reflexes, and postural deformities; lesions above the midlumbar region tend to produce lower motor neuron signs from disruption of the conus medullaris and higher cord structures, while upper thoracic or cervical lesions cause minimal neurologic manifestation. Bladder function also varies: some children have constant urinary dribbling with a relaxed anal sphincter, while others have a high-pressure bladder with sphincter dyssynergy. Cognitive development is affected by the Chiari II malformation itself, and can be further impaired by hydrocephalus complications and shunt infections, particularly during infancy." }, { "title": "Diagnostics", "content": "Diagnosis is generally apparent on physical examination of the visible spinal defect at birth. Given the near-universal association with Chiari II malformation and hydrocephalus, cranial imaging is essential to assess for ventricular enlargement and the need for CSF diversion." }, { "title": "Treatment", "content": "Traditional management is postnatal neurosurgical closure of the defect to allow healing and prevent infection, combined with lifelong multidisciplinary team care \u2014 neonatologist, neurosurgeon, geneticist and genetic counselor, urologist, orthopedic surgeon, social worker, physiotherapist, and primary care physician (often the coordinating advocate). Most affected children require a ventriculoperitoneal shunt to prevent or control hydrocephalus, and careful, ongoing urologic follow-up is essential given the near-universal lack of normal bladder innervation and control. The Management of Myelomeningocele Study (MOMS), published in 2011, found that prenatal (in-utero) surgical repair reduced the need for a CSF shunt and improved motor outcomes at 30 months, but was associated with maternal and fetal risks; a 2014 Cochrane review judged the evidence insufficient to broadly recommend in-utero repair, though several US centers continue to offer fetal surgery." }, { "title": "Complications", "content": "Latex hypersensitivity is common, affecting about a third of patients, presumably from repeated latex exposure during multiple surgeries and catheterizations. Postoperative motor deficit remains stable in the majority of patients (about 73%); neurologic deterioration suggests a complication, most commonly tethering by scar tissue at the repair site (a clinical diagnosis of exclusion, with symptoms of retethering occurring in about a third of patients over time), though imaging should also evaluate for syringohydromyelia (causing dissociated sensory loss) or cervical myelopathy from Chiari II (causing upper-extremity spasticity and weakness)." } ], "clinical": [ { "title": "Newborn assessment", "content": "At birth, examine the visible spinal defect to characterize it as covered by thin epithelialized tissue or an exposed neural placode, and watch for CSF leakage if a membrane is present, which raises infection risk and urgency for surgical closure. Perform a careful neurologic exam to localize the lesion level: assess lower-extremity tone and reflexes (flaccid paralysis and absent deep tendon reflexes below the lesion), response to touch and pain, and look for associated deformities (clubfoot, hip subluxation) that reflect abnormal in-utero movement. Assess bladder and bowel function specifically \u2014 constant dribbling with a relaxed sphincter versus a high-pressure bladder with dyssynergy \u2014 since both patterns require urologic involvement from the outset. Obtain cranial imaging given the near-universal association with Chiari II malformation and the 80-85% likelihood of hydrocephalus requiring shunt placement." }, { "title": "Coordinating ongoing multidisciplinary care", "content": "Establish a multidisciplinary team early \u2014 neurosurgery, urology, orthopedics, genetics, physiotherapy, and a coordinating primary care physician \u2014 since myelomeningocele affects nearly every organ system and requires lifelong management rather than a single intervention. Monitor for shunt complications and infections, particularly in infancy, given their impact on cognitive development. Track motor status over time: most children remain stable postoperatively, so new neurologic deterioration should prompt evaluation for tethered cord (the most common cause, a diagnosis of exclusion), syringohydromyelia, or cervical myelopathy from Chiari II, rather than being dismissed as expected progression. Take latex precautions throughout care given the roughly one-third prevalence of latex hypersensitivity. When counseling a family considering prenatal surgery, present the MOMS trial findings accurately: prenatal repair can reduce shunt need and improve 30-month motor outcomes but carries real maternal and fetal risk, and the evidence base, per the 2014 Cochrane review, remains insufficient to make this a routine recommendation." } ] }