Sections

Spina Bifida

Presentation

History

Myelomeningocele is diagnosed at birth or in utero. At birth, a midline defect in the posterior elements of the vertebrae is noted with protrusion of the meninges and neural elements through an external dural sac.

Although spina bifida occulta is common and almost always without consequence, some developmental abnormalities may occur—such as a spinal cord lipoma or a fibrous cord—that can cause subtle or rare neurologic signs.

A fibrous cord may extend from an interdural component of one of these developmental abnormalities to the skin, producing a dimple, an area of pigmentation, or a hairy patch at the base of the spine; such symptoms can be noted on physical examination.

Patients with a fibrous cord may have problems with micturition, or they may have subtle neurologic signs, such as a foot deformity (most commonly, a cavus foot). A prompt and thorough investigation is mandatory for any progressive neurologic signs. When a lipoma is present, there may be a lipomeningocele, a lipomyelomeningocele, or a lipomyelocele. These may be associated with areas of fluid in the cord, which may be a syringomyelia.

In general, infants with spina bifida cystica present with the following:

Lethargy
Poor feeding
Irritability
Stridor
Ocular motor incoordination
Development delay

Older children may present with the following:

Cognitive or behavioral changes
Decreased strength
Increased spasticity
Changes in bowel or bladder function
Lower cranial nerve dysfunction
Back pain
Worsening spinal or lower extremity orthopedic deformities

Some patients, however, may present with only papilledema. In any patient with myelomeningocele who presents with deterioration in neurologic, orthopedic, or urologic function, uncontrolled hydrocephalus should be excluded as a cause before any other treatment is pursued.

Chiari type II malformation

The Chiari type II malformation may cause acute or subacute signs and symptoms of lower brainstem and/or upper cervical spinal cord compression, including the following:

Laryngeal and pharyngeal paralysis
Apnea
Swallowing difficulty
Respiratory stridor
Nystagmus
Upper extremity weakness

These problems rarely are severe. A varying degree of interference with cerebellar function seems to occur, particularly with balance and coordination, which has a significant influence on ambulation, the results of physical therapy, and overall orthopedic care.

Coordination and cognitive function

Failure to control a seizure disorder, recurrence of hydrocephalus, or even low pressure hydrocephalus can cause subtle coordination defects and interruption of some cognitive functions.

Tethered spinal cord

The tethered spinal cord may be signaled by foot deformities that previously braced easily, new onset of hip dislocation, or worsening of a spinal deformity, particularly scoliosis. Progressive neurologic defects in growing children may suggest a lack of extensibility of the spine or indicate that the spine is tethered and low-lying in the lumbar canal, with the potential for progressive, irreversible neurologic damage that requires surgical release.

Physical Examination

The most obvious finding on physical examination is some degree of motor and sensory loss.^[1]Neurologic impairment is classified by traditional neurosegmental levels based on the clinically determined strength of specific muscle groups. The functional motor level does not always correspond to the anatomic level of the lesion.

In addition, it is important to realize that the motor paresis may be asymmetrical, that it may not correspond to the sensory level, and that it may result from a combination of upper and lower motor neuron lesions. Serial measurements and accurate documentation of the functional level of the lesion allow for early detection of progressive neurologic deterioration related to a variety of associated CNS problems.

In addition to determining the functional neurosegmental level, it is important to distinguish the type of paralysis, either spastic or flaccid. Most patients with myelomeningocele have a flaccid paraparesis below the spinal cord lesion.

An estimated 10-25% of patients have been reported to have a spastic paraparesis. This presentation is presumably related to an intact, but isolated, segment of cord distal to the lesion. Spastic paraparesis has been associated with a poorer prognosis for walking and higher rates of orthopedic procedures.

Neurosegmental levels and musculoskeletal complications

For the sake of general functional prognosis and anticipation of specific musculoskeletal complications, myelomeningocele patients frequently are classified as belonging to one of the following groups, based on the neurosegmental level of the lesion:

Thoracic
High lumbar
Low lumbar
Sacral

Thoracic

In the thoracic group, innervation of the upper limb and neck musculature and variable function of trunk musculature are present, with no volitional lower limb movements. Patients with thoracic malformations tend to have more involvement of the CNS and associated cognitive deficits.

High lumbar

In the high-lumbar group, variable hip flexor and hip adductor strength is characteristic. Absence of hip extension, hip abduction, and all knee and ankle movements is noted.

Low lumbar

In the low-lumbar group, hip flexor, adductor, medial hamstring, and quadriceps strength is present. The strength of the lateral hamstrings, hip abductors, and ankle dorsiflexors is variable; the strength of the ankle plantar flexors is absent.

Sacral

In the sacral-level group, strength of all hip and knee groups is present. Ankle plantar flexor strength is variable.

Complications of hydrocephalus

Involvement of the upper extremities is also common. Spasticity in the upper extremities occurs in approximately 20% of patients with myelomeningocele. It has been related to the number of shunts required to control hydrocephalus and has been shown to adversely affect independence in activities of daily living (ADL).

In patients with hydrocephalus, lack of upper extremity coordination is also seen. This lack of coordination also may be related to Chiari II malformation, motor-learning deficits, and/or delayed development of hand dominance. Affected children have problems with fine motor tasks, particularly when timed. New-onset weakness or spasticity in the upper extremities may be a hallmark of progressive neurologic dysfunction.

Spinal and lower extremity deformities

Spinal and lower extremity deformities and joint contractures are prevalent in children with myelomeningocele. Multiple factors may be involved, including intrauterine positioning, other congenital malformations, muscle imbalances, progressive neurologic dysfunction, poor postural habits, and reduced or absent joint motion.

Spinal deformities may be congenital or acquired. Vertebrae and rib anomalies are associated with congenital or early development of severe kyphotic and scoliotic deformities. Acquired scoliosis is neuromuscular in origin and is related to muscle imbalances.^[48]Increased lumbar lordosis and kyphosis of the entire spine or localized to the lumbar region are also observed. All of the spinal deformities occur more frequently in groups with higher spinal lesions.

Thoracic and high-lumbar lesions

The lower extremity deformities that occur are related to the functional level of the lesion. Thoracic and high-lumbar groups tend to have increased prevalences of the following:

Lumbar lordosis
Hip abduction and external rotation contractures
Knee flexion
Equinus contractures of the ankles

Unopposed hip flexion and adduction contractures in the high-lumbar group frequently result in dislocated hips.

Mid- and low-lumbar lesions

The mid- and low-lumbar groups often have the following deformities:

Hip and knee flexion contractures
Increased lumbar lordosis
Genu valgus and calcaneal valgus malalignment
Overpronated feet

Sacral lesions

Patients in the sacral group often exhibit mild hip and knee flexion contractures and increased lumbar lordosis with various ankle and foot positions.

Stature

Children with myelomeningocele are often short in stature. This has been related to multiple factors, including the following:

Structural issues (eg, abnormalities of the spinal column and lower limb contractures)
Functional spinal level: This influences the amount of neurotrophic input from the lower extremities on appendicular skeletal growth
Alteration in the hypothalamic-pituitary axis, with associated growth hormone deficiency

Weight

Weight should be assessed in patients with spina bifida. Because of their decreased linear limb growth and spine growth, patients should be monitored for weight using arm-span measurements, as opposed to ratios of height versus weight. During growth spurts, patients require close monitoring for the development of any deformities, from scoliosis to deformities of the lower extremities.

Cranial nerve dysfunction

Symptoms of cranial nerve dysfunction include the following:

Ocular muscle palsies
Swallowing and eating problems
Abnormal phonation

These symptoms may be related to the Chiari II malformation, hydrocephalus, and/or brainstem dysplasia.

Lower brainstem dysfunction

While symptoms are often mild, lower brainstem dysfunction is the leading cause of death in infants with myelomeningocele because of associated stridor, apnea, and aspiration pneumonitis. Common symptoms of lower brainstem dysfunction in infants include the following:

Abnormal cry
Swallowing or feeding difficulties
Frequent vomiting or gastroesophageal reflux

Older children and adults may present with the following:

Weakness or spasticity of the upper extremities
Headache or neck pain
Cerebellar dysfunction
Oculomotor changes
Scoliosis

Tethered spinal cord

A tethered spinal cord is caused by the tendency for the spinal cord to adhere to the meningocele repair and can prevent the normal cephalad migration of the cord during growth. A tethered cord is present anatomically in most children with myelomeningocele; the diagnosis of tethered cord syndrome is confirmed on the basis of clinical signs and symptoms, which can include pain, sensory changes, spasticity, and progressive scoliosis.

However, uncontrolled hydrocephalus and Chiari II malformation must be excluded as causes of these symptoms. Moreover, symptoms similar to those of tethered cord syndrome can also be caused by other intraspinal pathologies (eg, mass lesions of the cord, diastematomyelia, cord cavitation and narrowing, adhesions, dural bands).

Syringomyelia

Syringomyelia is caused by uncontrolled hydrocephalus that results in entry of cerebrospinal fluid (CSF) into the central canal of the spinal cord, causing dilatation and pressure. While this is a common MRI finding in patients with myelomeningocele, this condition is symptomatic in only 2-5% of cases. Symptoms described include the following:

Progressive scoliosis
Spasticity
Increasing weakness of the extremities

Differential Diagnoses

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Media Gallery

The lumbar region of a newborn baby with myelomeningocele. The skin is intact, and the placode-containing remnants of nervous tissue can be observed in the center of the lesion, which is filled with cerebrospinal fluid.
Myelomeningocele in a newborn.
Coronal, T1-weighted magnetic resonance imaging (MRI) scans of the brain show a Chiari II malformation. Note the stretching of the brainstem, aqueduct, and fourth ventricle.
Neonate with a lumbar myelomeningocele with an L5 neurologic level. Note the diaphanous sac filled with cerebrospinal fluid and containing fragile vessels in its membrane. Also, note the neural placode plastered to the dorsal surface of the sac. This patient underwent closure of his back and an untethering of his neural placode. The neural placode was circumnavigated and placed in the neural canal. A dural sleeve was fashioned in a way that reconstructed neural tube geometry.
Sagittal, T1-weighted magnetic resonance imaging (MRI) scan of a child after closure of his myelomeningocele. Child is aged 7 years. Note the spinal cord ends in the sacral region far below the normal level of T12-L1. It is tethered at the point at which the neural placode was attached to the skin defect during gestation. The MRI scan showed dorsal tethering, and the child complained of back pain and had a new foot deformity on examination. By definition, all children with a myelomeningocele have a tethered cord on MRI, but only about 20% of children require an operation to untether the spinal cord during their first decade of life, during their rapid growth spurts. Thus, the MRI scan must be placed in context of a history and examination consistent with mechanical tethering and a resultant neurologic deterioration.
Axial, T1-weighted MRI scan of a 15-year-old girl who was born with thoracic myelomeningocele, hydrocephalus, and Arnold-Chiari II syndrome. She was treated with a ventriculoperitoneal shunt. The ventricular system has a characteristic shape, with small frontal and large occipital horns, which are typical in patients with spina bifida. The shunt tube is shown in the right parietal region.