Spina Bifida Clinical Presentation

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 symptoms of lethargy, poor feeding, irritability, stridor, ocular motor incoordination, and development delay. Older children may present with cognitive or behavioral changes, decreased strength, increased spasticity, changes in bowel or bladder function, lower cranial nerve dysfunction, back pain, and worsening spinal or lower extremity orthopedic deformities. Some patients 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.

The Chiari type II malformation may cause acute or subacute signs and symptoms of lower brainstem and/or upper cervical spinal cord compression, including laryngeal and pharyngeal paralysis, apnea, swallowing difficulty, respiratory stridor, nystagmus, and 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.

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.

The tethered 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 suggest that the spine is tethered and low-lying in the lumbar canal, with the potential for progressive, irreversible neurologic damage that requires surgical release.

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 be 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.

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

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.

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 are noted.

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.

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

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.

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 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.^[21] 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.

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.

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

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

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, which 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 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.

Ocular muscle palsies, swallowing and eating problems, and abnormal phonation are signs of cranial nerve dysfunction. These symptoms may be related to the Chiari II malformation, hydrocephalus, and/or brainstem dysplasia.

Neurologic complications in patients with myelomeningocele are related to a variety of CNS and spinal cord pathologies. Approximately 25-35% or more of children with myelomeningocele are born with hydrocephalus, and an additional 60-70% of patients with myelomeningocele develop hydrocephalus after closure of the myelomeningocele lesion. Hydrocephalus can cause expansion of the ventricles and loss of cerebral cortex and is associated with an increased risk of cognitive impairment.

Seizures occur in 10-30% of affected children and adolescents. These seizures can be related to brain malformation, or they may be a sign of shunt malfunction or infection.

The Chiari type II malformation is present anatomically in almost all patients with myelomeningocele and can result in hindbrain and/or upper cervical spinal cord dysfunction. Clinical manifestations of the Chiari II malformation are more common during infancy and, overall, are seen in 20-30% of affected children. However, symptoms can develop at any age and can manifest acutely or chronically.

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 abnormal cry, swallowing or feeding difficulties, and frequent vomiting or gastroesophageal reflux. Older children and adults may present with weakness or spasticity of the upper extremities, headache or neck pain, cerebellar dysfunction, oculomotor changes, and scoliosis.

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. However, 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. In addition, uncontrolled hydrocephalus and Chiari II malformation must be excluded as causes.

Symptoms similar to those of tethered cord syndrome can be caused by other intraspinal pathologies (eg, mass lesions of the cord, diastematomyelia, cord cavitation and narrowing, adhesions, dural bands).

Syringomyelia is caused by uncontrolled hydrocephalus that results in entry of 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%. Symptoms described include progressive scoliosis, spasticity, and increasing weakness of the extremities.

Myelomeningocele is the most common cause of neurogenic bladder dysfunction in children. The nature of the urinary tract dysfunction in myelomeningocele depends on the level and extent of the spinal cord lesion.

Disruption of the neural axis between the pons and the sacral spinal cord by the myelomeningocele may cause uninhibited detrusor contractions or dyssynergia, a lack of coordination of the external bladder sphincter that causes involuntary sphincter activity during detrusor contraction. Myelomeningocele in the sacral area can produce a lower motor neuron lesion, resulting in detrusor areflexia.

These abnormalities may occur singly or in combination and typically result in incontinence and impaired bladder emptying that can lead to vesicoureteral reflux and high voiding pressures.^[22] If untreated, this condition can lead to potentially more serious complications, including frequent infections, upper urinary tract deterioration, and, ultimately, renal failure.

The main determinant of upper urinary tract deterioration is the intravesical pressure in storage and voiding situations. A high incidence of vesicoureteral reflux and ureteral dilation is found in patients with myelomeningocele whose leak-point pressures were greater than 40 cm water.

High pressures may result from increased outlet resistance or decreased bladder wall compliance. Increased outlet resistance may be caused by sphincter dyssynergia or fibrosis of a denervated sphincter. Decreased bladder wall compliance is associated with areflexia of the detrusor. Any of these urologic dysfunctions can occur in myelomeningocele, but manifestations may vary over time because of the changing neurologic status in some of these patients.

Skin breakdown occurs in 85-95% of children with myelomeningocele before young adulthood. Recurrent decubitus ulcers can lead to prolonged morbidity and functional disability. Healing can occur if the precipitating mechanical factors are eliminated. Plastic surgical correction may be necessary in severe cases and may involve orthopedic correction of underlying postural abnormalities.

The sites and causes of skin breakdown vary by age and lesion level. Skin breakdown on the lower limb occurs in 30-50% of cases in all lesion-level groups.

The most common areas of breakdown in the thoracic-level group are the perineum and above the apex of the kyphotic curve. Overall, tissue ischemia from pressure necrosis is the most common etiology.

Older children may have higher risk of skin breakdown because of increased pressure of a larger body habitus, asymmetric weight-bearing from acquired musculoskeletal deformities, and lower limb vascular insufficiency or venous stasis.

Other frequent causes more prevalent in the younger child include casts or orthotic devices, skin maceration from urine and stool soiling, friction, shear, and burns.

Ulcers from bracing are prominent in the lower extremities, in the pelvis, and, particularly, over the bony prominences as a result of sitting. Carefully inspecting the skin on a routine basis is important because the area may be subjected to pressure for a couple of hours. The skin subsequently may be reddened, and although the patient may have no pain, the skin can develop significant full-thickness problems after only a brief period of neglect.