Spina bifida: causes, symptoms, and clinical management

Kyle Thornton

Spina Bifida

Statistics of Disease

Etiology of Spina Bifida

Pathology and Physiology of Spina Bifida

Signs and Symptoms

Diagnostic Tests

Medical Treatments

Physical Therapy of Spina Bifida

SPINA BIFIDA

Neural tube defects are the second most common congenital defects in the United States. This occurs due to a defect during early fetal development. These defects are classically of two types, open and closed. Spinal NTDs (spina bifida), anencephaly, and encephalocele are examples of open defects. Common examples of closed NTDs are lipomyelomeningocele, lipomeningocele, and tethered cord. Occasionally more than one type of NTDs can occur simultaneously.

STATISTICS OF SPNIA BIFIDA

Statistics from March, 2011, estimates that averages of 1500 babies with spina bifida are born each year. The incidence is higher for Hispanic women, almost doubling that of non-Hispanics. The bright side of the situation is that the occurrence for spina bifida, in the United States, has been decreasing. (Parker) An analysis through time reveals an incidence of 2 per 1000 during the period, 1890-1920. Between 1920 and 1949, there was a succession of high rates, tripling that of the previous years. (MacMahon & Yen, 31-33) Recent figures from 2004-2006 reveal an incidence of 1 per 2858. This decline can be attributed to prenatal diagnostic techniques as well as the judicious use of folic acid amongst women in their reproductive years. (Parker)

ETIOLOGY

Even though the exact cause of spina bifida is unknown, several risk factors have been associated with this condition. The most popular of these is the association made between NTDs and folic acid deficiency. Daily consumption of 400 µg of folic acid before conception and during early pregnancy has been recommended to reduce this risk. Researchers have found that 50-70% of NTDs can be prevented with this dose of folic acid. However, only a total of 29% of U.S. reproductive women were taking regular folic acid pills. Starting from the year 2008 in the United States and 2009 in Australia, folic acid fortification was deemed mandatory. Ever since, there has been a 19% decline in the incidence of NTDs. (Honein et al., 2981-2986)

The exact mechanism by which folic acid prevents NTDs is still unclear. However, the most recent theory states that folic acid deficiency leads to depletion in the methyl pool, leaving critical genes un-methylated, and in turn improper expression, leading to various forms of NTDs, including spina bifida. (Kumar, Abbas & Fausto, 724-725)

To check whether consanguinity was a risk factor, researches from Saudi Arabia compared new cases of spina bifida to a control sample of 72 cases. Consanguinity was found to exist amongst 89% of spina bifida parents which was much greater than the 67% of controls. (Murshid, 10-12)

Other important risk factors are decreased maternal age, previous history of miscarriages, first born infants and mothers belonging to lower socio-economic statuses. An old multicenter case referent study, from 1998, identified newer possible paternal occupational etiologies, such as low exposure to welding fumes, UV radiation, and moderate to high exposure to cleaning agents, pesticides and stainless steel dust. (Blatter et al., 283-291)

PATHOLOGY AND PHYSIOLOGY OF SPINA BIFIDA

Since malformations of the CNS account for 1/3rd of all major congenital defects, it is important to understand the pathophysiology involved with it. The development of the CNS is a complex process, and as already mentioned several etiological agents may be involved that disrupt it.

Closure of the neural tube begins by the 22nd day of gestation and is completed between the 26th and 28th day. Disorders related to abnormal closure are the most common CNS malformations. Encephaloceles and cranial meningoceles are examples of less severe cranial NTDs. More severe forms, such as anencephaly, do not survive beyond the first few days of postnatal life, and so the major concern of medical treatment is towards the NTDs. Spinal NTDs are commonly known as spina bifida. This condition is characterized by a protrusion of a variable amount of spinal parenchyma through a defect in the spine, most commonly in the lumbosacral region. In all cases, there is absence or hypoplasia of one or more vertebral arches, with variable abnormalities in the underlying meninges or spinal cord. (Kumar et al., 724-725)

Spina bifida expresses itself in several forms. On one spectrum of the disease is spina bifida occulta, which is the most benign form. This form was described by James and Lassman in 1972. In this type, the malformation becomes spontaneously arrested and does not develop through the rest of the fetal life. Proliferation of fibrocollagenous tissue and blood vessels, and hypoplasia of arachnoid nest cells eventually ensues. This results in a non-symptom-causing bony change in one or more vertebral arches, without the involvement of nerves within the spinal column. The meninges and spinal cord is intact and the defect may be marked by a small skin dimple of a tuft of hair. Spina bifida occulta occurs in 20% of the general population. (Kumar et al., 724-725)

Myelocele occurs on the other spectrum and is the most severe form. It is characterized by an exposed plaque of flattened neuroectodermal tissue. 2 other patterns of the disease exists: spinal meningoceles and meningomyeloceles. Spinal meningoceles are cystic masses filled with CSF. The wall of the cyst is covered with meninges and it does not contain spinal cord elements. Meningomyeloceles, on the other hand, are herniations of the spinal cord and meninges through a posterior vertebral defect. The meninges maybe exposed to the external environment or covered with skin. Frequently, this defect is associated with hydrocephalus and Arnold-Chiari malformation. . (Kumar et al., 724-725)

SIGNS AND SYMPTOMS

The diagnosis of spina bifida is clinical and investigations may be needed only to classify its type. A difficulty in diagnosis may present if the cystic lesions have been filled with overgrowing mesenchymal and neurological tissue, and further diagnostic techniques can aid in diagnosis. Diagnosis of the condition warrants a proper history and thorough examination. A family history of prior neural tube defects and lack of folic acid supplementation can raise clinical suspicion. Subsequently, examination of the spine typically begins with inspection. In some case a prominent cystic bulge is visible, whereas in spina bifida occulta, this bulge maybe covered with a tuft of hair or a skin dimple. It is important to inspect the spine and check the presence of herniation of the spinal cord and meninges in cases where the swelling is less prominent. The level at which this occurs should be noted in all cases. This provides physicians important clues to the neurological deficit that might co-exist. As a rule, the higher the defect, the more widespread will be the clinical manifestation. The shape of spine may also be abnormal. (Browse, 1-123)

The most common site of spinal herniation is at the lumbosacral vertebras. A lesion at this point on the spinal vertebra can cause loss of sensation and paralysis of lower limbs, bladder and bowel dysfunction. Since, myelomeningocele is associated with hydrocephalus, it is important to check for signs related to it, such as an enlarged head circumference, sunset sign, papilledema, prominent scalp veins and symptoms of vomiting and anorexia. If hydrocephalus is not treated appropriately, children may develop mental retardation. Other associated anomalies, such as Arnold Chiari malformation should also be sought out for. A defect higher up in the spine causes additional symptoms of upper limb weakness, hoarseness, dysphagia, breathing difficulties, learning disabilities, seizure disorders and eye problems. (Browse, 1-123)

DIAGNOSIS

The diagnosis of spina bifida is mostly prenatal. Mild diseases may pass unnoticed post-natal life. Very mild forms of spina bifida occulta that produce no symptoms may never be detected at all. Most commonly, the first ultrasound performed between the 16th and 18th week screens all fetuses. Fetuses with a nuchal thickness of greater than 3 mm are at high risk of having CNS defects. In such cases, a blood sample is obtained to measure the level of alpha-fetoprotein. If this is abnormally elevated, it indicates an open tube defect. However, serum AFP levels are not specific to NTDs and so further investigations are required for its confirmation. Amniocentesis and chorionic villus sampling provide definitive prenatal diagnosis and are indicated if prior tests are suspicious. Post-natally a CT scan or MRI of the spine is required to document the defect and identify the type of spina bifida. (Oats & Abraham, 37-53)

MEDICAL TREATMENT

From articles addressing the etiology of spina bifida, as well as specific medical issues, brain-behavior relationships, healthcare delivery, contextual influences of family, school, society and healthcare, the undercurrent theme is that the treatment of spina bifida requires a multidisciplinary approach, comprising of physical therapists, spinal surgeons and physicians, along with psychosocial and educational interventions. (Fletcher & Brie, 1-5)

The general trend towards the medical management of this disease is only to prevent complications. Antibiotics can be given to prevent recurrent urinary tract infections, and likewise for the spinal meninges. Surgical treatment is the main stay for closing the bony defect and covering the exposed nerves and spinal tissue. Neither medical, nor surgical treatment can cure the motor and sensory deficit associated with this disease. (Nicholas, Nicki, Brian & John, 1145-1257)

PHYSICAL THERAPY OF SPINA BIFIDA

Individuals affected by spina bifida get around in different ways. This ranges from walking without any aids or assistance to using wheelchairs. Physical therapy has been recommended to improve the outlook of those patients who have some form of disability from this condition.

Physical therapy for spina bifida patients varies with the degree of disability and the age of the patient. In relatively benign forms of the disease, such as spina bifida occulta, there may be no sensory or motor impairment, however, an individual may develop low back ache later on in life. In more severe forms, the aim of physical therapy is to allow patients obtain maximum mobility and stability in different positions. (Campel, Lindel & Palisano, 271-292)

For an infant, Range-Of-Motion exercises are essential to maintain full joint flexibility, promote circulation and prevent contractures. Mothers are taught to move an infant's leg up and out, inwards and outwards, bending the hips, knees and ankles and then straightening them out again. They are told to encourage their young infants to lift their head up from prone position and extend their arms while grabbing for toys. Counseling regarding the possibility of sensory deficit is particularly important. As the child grows older and learns to roll over, injuries due to fall become more common. Injuries can also occur with young toddlers at home. It is important to advice the mother to watch out for bruises, temperature of the water during bathing and other potential hazards. (Campel, Lindel & Palisano, 271-292)

Continuing with ROM exercises and sensory precautions, higher levels of developmental skills need to be promoted, such as, sitting balance and posture. Toddlers with total motor impairment need to be encouraged to use their upper body to crawl (commando crawling), since normal reciprocal crawling may not be possible. Physical therapy for a preschooler is aimed at optimizing experience by creating a level of independence in activities of daily life and learning, as well as improving posture for sitting and standing. Stretching and strengthening exercises are recommended both for toddlers and preschoolers. These exercises strengthen muscles of the spine by working them against resistance. It also provides stability and prevents back ache later on in life. (Campel, Lindel & Palisano, 271-292)

Orthotic devices are frequently prescribed to older children to allow maintenance of normal joint positions. Orthotic devices are external supports (braces), usually made of plastic. A standing program is important to prevent hip and leg contractures and fractures. Also, it improves social functioning and reduces the feeling of being 'different'. Assistive devices include braces, walkers, standers and parapodiums. (Campel, Lindel & Palisano, 271-292)

Physical therapy is also aimed at preventing secondary impairments and to treat them if present. To understand this more deeply, it is important to understand the secondary impairments that may be involved with each level spinal cord involvement. (Campel, Lindel & Palisano, 271-292)