Treating myelomeningocele and spina bifida

Spina bifida is a bit of a catch-all term that encompasses an array of disorders of embryonic spinal development. In its most severe form, the entire neuro-axis may be poorly formed and completely lacking any of its coverings (e.g., dura, bone, muscle, subcutaneous tissue, and skin). Unfortunately, this form is incompatible with life. Clinicians need to become familiar with how to manage severe cases, and how to recognize more subtle ones.

In a less severe form of spina bifida, myelomeningocele occurs where the most distal portions of the spine and the spinal cord have not fully formed, and the baby is born with the distal end of the spinal canal open and often leaking spinal fluid.

With the advent of prenatal vitamins (specifically folate) and prenatal testing, myelomeningoceles are less common than they were decades ago. However, this condition is still something that most pediatricians and primary care practitioners will encounter.

Myelomeningoceles are seen at higher rates in northern latitudes and in families with histories of previous births with the disorder. They are often picked up relatively early during pregnancy with modern ultrasound.

Below the level of the lesion in the spinal cord, there is no neurological function. Thus, the larger the deformity and the higher it extends up the back, the greater the neurological deficits.

Myelomeningoceles must be repaired surgically to cover the exposed spinal cord. This is usually performed within 36 hours of birth, or prenatally in rare cases. This does not restore neurological function but prevents the progressive loss of function, meningitis, and a high likelihood of death (after delivery).

The least severe forms of spina bifida involve the isolated, incomplete formation of the spinous process or lamina of the vertebrae in a small section of the spine (usually lumbar). This is known as spina bifida occulta and occurs in 5–10% of the population. Thankfully, spina bifida occulta is not associated with any neurological signs or symptoms.

There is a whole spectrum of other disorders ranging from spina bifida occulta to myelomeningocele.

The care of a child or adult with a history of myelomeningocele is complicated and is most efficiently provided through multidisciplinary spina bifida clinics. Here, multiple specialists and therapists can provide thorough evaluation and care for the affected child.

At the same time, primary care physicians will routinely see these patients and should be aware of six commonly associated conditions:

1. Tethered spinal cord
2. Ventriculoperitoneal shunt failure
3. Chiari malformation
4. Progressive scoliosis
5. Seizures
6. Other disorders (e.g., pulmonary, cardiac, renal, and gastrointestinal disorders)

Tethered spinal cord

Although the myelomeningocele defect is closed surgically at or before birth, it can remain problematic throughout the years. Problems generally arise during growth spurts due to the spinal cord sticking down to the surrounding tissues at the level of the repair scar. This phenomenon is known as tethering of the spinal cord.

A tethered spinal cord is stuck to the surrounding dura. As a result, the spinal cord stretches when the patient bends and grows. Tethering can lead to progressive neurological deficits centered around the lower extremities. Increasing low-back pain and worsening bladder function can also be components of tethering.

Look for signs and symptoms of a tethered spinal cord

When seeing a patient with a history of myelomeningocele, ask about increasing back pain and progressive loss of lower extremity function. You can assume that a patient who goes from ambulatory with braces to needing a wheelchair has a tethered spinal cord until proven otherwise. The progressive loss of function was once thought to be the normal progression of the disorder as a patient reached adulthood. Now, it is thought to be secondary to symptomatic spinal cord tethering during adolescent growth spurts.

Examine and record strength in the upper and lower extremities and compare with previous visits. If there is a decrease in strength or sensation, strongly suspect spinal cord tethering.

Also, look for progressive foot deformities such as clubfoot, pes cavus, or pes valgus. These (and increased trophic changes in the lower extremity skin) can be signs of a tethered cord.

In reality, all myelomeningocele spinal cords are tethered—but not all become symptomatic. As a result, even though imaging will show spinal cord tethering, it does not mean that something needs to be done about it. In myelomeningocele, definitive action is taken with tethering only if the tethering becomes symptomatic. This is different from the approach taken with other cases of spinal cord tethering.

If you are concerned that a patient with myelomeningocele is exhibiting signs and symptoms of symptomatic tethering, consult neurosurgery. The cord can be surgically untethered and progressive loss of neurological function can be halted.

Monitor urological function

Remember that patients with a history of myelomeningocele will have baseline neurological and urological deficits (such as a neurogenic bladder). Repeated straight catheterization is the rule. However, the patient’s urological function may deteriorate with spinal cord tethering. Patients will also be subject to frequent urinary tract infections. Patients with myelomeningocele should be followed by specialized urologists and may need diversion procedures.

Refer to physical and occupational therapists

Make sure that patients with myelomeningocele routinely see physical and occupational therapists. Patients with myelomeningocele often use adaptive equipment, particularly leg braces, wheelchairs, electronic assist systems, and more, and they frequently require adjustments and upgrades of adaptive equipment.

Ventriculoperitoneal shunt failure

Most patients with myelomeningocele will have a ventriculoperitoneal shunt in place for hydrocephalus.

So, you’ll need to get to know the shunt and its history. Often, shunt failure is less dramatic than in other hydrocephalus patients and may manifest as diminished school performance, diminished overall function, worsening upper or lower extremity function, sensory complaints, changes in bladder function, or pain complaints.

Chiari malformation

Patients with myelomeningocele all have Chiari malformations at the craniovertebral junction. A Chiari malformation is a malformation of the posterior fossa and its contents. The posterior fossa in these patients is too small for its contents which results in kinking of the medulla, cerebellar tissue projecting through the foramen magnum, and compression of the brainstem and spinal cord.

In infants, brainstem compression can cause severe brainstem and cranial nerve dysfunction; respiratory stridor, aspiration, and apneic spells may result. In these cases, the Chiari malformation may be surgically decompressed with craniectomy, but the prognosis can be very guarded. Some of these babies have a disordered internal structure of their brainstem and fail to improve with surgery. These babies may die from complications of severe brainstem dysfunction.

Watch for signs of a syrinx in older children and adults with myelomeningocele

In older children and adults, Chiari malformations are often asymptomatic. However, they can cause cavitation of the spinal cord (known as a syrinx) which leads to significant spinal cord dysfunction.

When evaluating for symptomatic Chiari malformation and a syrinx, look for signs of spinal cord and brainstem dysfunctions. Spinal cord findings would be predominantly upper motor neuron in nature (e.g., myelopathy), although there can be lower motor neuron findings in the upper extremities.

Ask about (and evaluate for) progressive upper extremity dysfunction, loss of coordination, progressive loss of lower extremity function, and gait deterioration. As well, ask about swallowing difficulties, changes in voice strength, and aspiration (indicative of lower cranial nerve dysfunctions).

Also, obtain magnetic resonance imaging (MRI) of the cervical and thoracic spinal cord if a syrinx is suspected. The syrinx may extend well into the thoracic spine.

Progressive scoliosis

Progressive scoliosis is not uncommon in patients with myelomeningocele. This and other orthopedic considerations such as contractures and hip dislocations make it invaluable to have the patient evaluated periodically by an orthopedist or a scoliosis specialist.

Seizures

Many patients with myelomeningocele (both children and adults) have seizures or other neurological disorders. Routine follow-ups with a neurologist are recommended.

Other disorders

Patients with myelomeningocele may also have associated pulmonary, cardiac, renal, and gastrointestinal disorders. Follow their general medical conditions as well as their neurological conditions.

Other forms of symptomatic spina bifida are often less dramatic than myelomeningocele—but can be disabling. These disorders generally carry a risk of spinal cord tethering, which may result in progressive neurological dysfunction over time, particularly during growth spurts. The patients may start with no neurological signs or symptoms but will begin to experience the symptoms over time. Alternatively, the signs and symptoms may be quite subtle at first.

Evaluate your patient for a possible tethered spinal cord

Patients experiencing cord tethering may present with several symptoms:

• Progressive back pain
• Urinary dysfunction
• Numbness and / or weakness in the legs
• Progressive scoliosis
• Progressive foot deformities
• Trophic skin changes in the legs
• Gait difficulty
• Muscle atrophy
• Shortening of the limbs (predominantly the legs)

Urinary dysfunction is often an early sign of tethering. Consider including formal urology consult with urometric bladder function testing.

Also, include a thorough physical and neurological exam. Don’t forget to examine the patient’s back; patients with spina bifida and spinal cord tethering often have telltale signs in the skin of their lower back.

For example, most patients with symptomatic spina bifida will have three cutaneous clues of spinal cord tethering:

1. A lipoma under the lumbar skin (suggestive of lipomyelomeningocele)
2. A cutaneous hemangioma or hairy patch in the lumbar midline skin
3. A dermal sinus tract in the low midline skin of the lumbosacral region

Recognizing a lipomyelomeningocele under the lumbar skin

Look for a nontender lump of fatty tissue under the lumbar skin. This suggests a lipomyelomeningocele which is a subcutaneous fatty mass that extends down through a defect in the lamina and dura, and into the end of the spinal cord. This unequivocally tethers the spinal cord and needs to be addressed surgically—even in a young baby.

If you observe a lipomyelomeningocele, order an MRI of the lumbar spine and consult a neurosurgeon.

Recognizing a cutaneous hemangioma in the lumbar midline skin

A cutaneous hemangioma or discoloration in the lumbar midline skin with or without a patch of hair may signal spina bifida and spinal cord tethering. This finding, particularly when associated with signs of a tethered spinal cord, should precipitate MRI or ultrasound of the lumbar spine in an infant.

Recognizing a dermal sinus tract in the low midline skin of the lumbosacral region

Also, look for a 1–2 mm dimple or sinus in the low midline skin of the lumbosacral region. There may be an associated discoloration or hair growth. Do not probe the spot since this may represent a dermal sinus tract that stretches all the way into the spinal cord. They are in direct communication with the nervous system and can result in a nervous system infection.

If you suspect a dermal sinus tract, retract at the edges of the tract. If it has no definable bottom or end, order an MRI (or ultrasound in a newborn). If the tract proves to extend to the spinal cord, it needs to be resected by a neurosurgeon.

How to treat tethering of the spinal cord

Any patient with suspected tethering of the spinal cord should undergo an MRI of the lumbar spine. Children discovered to have a tethered spinal cord should be referred to neurosurgery for an untethering procedure (whether they are symptomatic or not). The idea is to remove the tethering before spinal cord damage occurs since the spinal cord is poor at recovering lost function. On the other hand, asymptomatic adults may only require careful monitoring.

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