Neural Tube Defects Clinical Presentation

Updated: Nov 26, 2018
  • Author: Nir Shimony, MD; Chief Editor: Amy Kao, MD  more...
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Presentation

History

NTDs are commonly discovered during prenatal screening and are often associated with poor prenatal care.

Most open NTDs are readily apparent at the time of birth; closed NTDs have a variable presentation.

The most common presentation of a closed NTD is an obvious abnormality along the spine such as a fluid-filled cystic mass, area of hypopigmentation or hyperpigmentation, cutis aplasia, congenital dermal sinus, capillary telangiectasia/hemangioma, hairy patch (hypertrichosis), skin appendages, or asymmetrical gluteal cleft. [20]

Common to all these patients is a fully epithelialized lesion and no visible neural tissue.

A closed NTD can present without a cutaneous marker.

The second most common reason for seeking medical attention is asymmetry of the legs and/or feet. One calf can be thinner, with a smaller foot on the same side, higher arch, and hammering or clawing of the toes.

Other children exhibit progressive spinal deformities such as scoliosis.

Some children present with a picture of progressive neurological deficits that may include weakness in one distal lower extremity, sensory loss in the same distribution, and bladder or bowel dysfunction.

Low back pain also can occur, sometimes without neurological deficit. Pain is more common in older children or adolescents.

Adults can present with the sudden onset of pain, motor and sensory loss, and bladder dysfunction after an acute trauma (e.g., fall, motor vehicle accident, placement in lithotomy position). The reason for such presentation may be related to tethering of the cord (the distal end of the spinal cord is fixed in position). [21]

Mechanical forces associated with motion may produce compression and/or vascular insufficiency.

A patient with a closed NTD such as a congenital dermal sinus with an intraspinal dermoid cyst or a neuro-enteric cyst can present with symptoms of spinal cord compression due to enlargement of the mass.

A patient with a dermal sinus also can present with bacterial meningitis or spinal abscess.

Neuro-enteric or dermoid cysts also can present with repeated bouts of aseptic meningitis due to leaking of the contents into the spinal subarachnoid space.

Functional complications most often occur during early years of life, but can manifest at any age. The prevalence of medical comorbidities depends on the level and severity of the lesion. However, urologic abnormalities (i.e., UTI and nephrolithiasis) are the most common issues among adults with NTDs. Scoliosis, pain, epilepsy, and pressure ulcers are also often reported in adult patients with myelomeningocele. [22]

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Physical

A complete neurological assessment of the newborn with an open NTD should be performed to document the many possible structural and neurological problems. This provides a baseline for future comparison.

Particularly important aspects of the evaluation are measurement of head circumference, assessment of general vigor (especially cry and sucking), upper extremity motor function, anal sphincter, and urinary stream, as well as thorough motor and sensory examination of the lower extremities and trunk.

Usually the level of sensory dysfunction is slightly greater than the dysfunction detected on the motor examination.

Motor examination involves observation of muscle bulk, spontaneous active movements, movements in response to stimulation, as well as assessment of muscle tone by palpation.

Further information regarding the level of neurological dysfunction can be obtained from evaluation of hip and foot deformities. If the disparity in segmental level between the 2 sides is more than 1 level, an occult neurological problem must be suspected (eg, hemimyelia).

The spine should be examined carefully, with determination of the size and site of the lesion. The shape of the defect, size of the placode, and health and laxity of the surrounding skin and soft tissue should be noted carefully. The presence of early spinal deformity (eg, kyphosis) also should be assessed.

Other common findings include oral clefts and renal, cardiovascular, and musculoskeletal malformations. 

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Causes

Multifactorial genetic and environmental factors have been implicated in the pathogenesis of neural tube defects (NTDs). [2]

The most common historical cause of NTDs globally is folate deficiency in the maternal diet. A slight female predominance, and the higher incidence in certain ethnic groups and in the offspring of consanguineous marriages, have suggested a genetic basis for NTDs. Chromosomal abnormalities (trisomy 13, 18, 21) are also associated with NTDs. Interestingly, concordance between monozygotic twins is higher than dizygotic twins. [23]

Possible environmental factors include geographic location, season of conception, socioeconomic class, maternal diabetes, maternal age, zinc and folate deficiencies, [24, 25] maternal alcohol abuse, maternal use of valproate, and intrauterine hyperthermia.

Seasonal trends in the birth incidence of NTDs have historically been reported. Anencephaly and spina bifida tend to occur more frequently in spring conceptions (anencephaly peaking in early spring and spina bifida in late spring). This is especially true in areas where the risk is high; however, most US studies failed to demonstrate such variations. [26, 27, 28]

Since encephaloceles do not exhibit geographic, gender, or ethnic variations, some have proposed that they occur after the completion of neurulation.

A cohort study by Jentink et al suggests that carbamazepine monotherapy in the first trimester produces fetal malformations specific to spina bifida; however, the risk is lower than for valproic acid. [29]

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