Spina bifida: epidemiology, etiology, 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)

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)

For lesions at the level of T. 12 or above, apart from reduced motor and sensory functions in the legs, there may also be trunk involvement. Secondary impairments include: development of contractures, club feet, kyphoscoliosis of the spine and the formation of pressure sores. Treatment includes constant re-positioning and adequate wound management of pressure wounds, increasing function, such as rolling, sitting, commando crawling, and mobility by encouraging the use of wheelchairs to carry a normal life style.

Secondary impairments for upper lumbar lesions include, hip flexion contractures that may result in dislocated hips or windswept hips, absent hip extension and hyperextended trunk posture. A number of exercises exist to reduce hip contractures and its associated complications, these include: Thomas test position, cross body stretching, pelvic tilt and leg grab. Increasing mobility with reciprocating gait orthosis or Hip-Knee-Ankle-Foot orthosis and walking aids are also important. (Campel, Lindel & Palisano, 271-292)

Lower lumbar and sacral lesion impairments include foot contractures and pressure wounds on feet. Motor impairments involve the hip extensors and plantarflexors. Ambulation by the 12th month and independent ambulation by the 5th year can prevent this. Supramalleolar orthosis can also be helpful. (Campel, Lindel & Palisano, 271-292)

Another major goal for physical therapist includes assessing adequate bowel and bladder care. Since most patients with spina bifida lack intact nerve routes important for bowel and bladder continence, recurrent infections and constant dribbling can cause serious medical and social consequences. Clean intermittent catheterization has been generally agreed by urologists to provide the best technique to achieve independency and prevent complications for patients with neurogenic bladder. Surgical treatment includes creating a urinary diversion through an ileal conduit, vesicostomy or a continent stoma. (Mann, Russell, Bailey, Love & Williams, 1093-1201)

Dietary modifications, habit training and digital stimulation can greatly control bowel incontinence. Stool softeners and bulk formers increase the consistency of stools, thereby reducing stool dribbling. Laxatives can be used if the stools are too hard. In extreme cases of incontinence, a colostomy bag may be the only solution. (Mann et al., 1093-1201)

CONCLUSION:

Spina bifida is a heterogenous disorder. The most commonly associated etiology is a lack of adequate folic acid in the diet. However, consanguinity, decreased maternal age, poor socio-economic conditions, and recurrent miscarriages may also be responsible. The trend of the disease has been to the downside in many countries that supply folic acid fortified foods. This disease can be diagnosed prenatally through ultrasounds, serum AFP levels, amniocentesis or chorionic villus sampling. Fetuses that pass unrecognized by these diagnostic techniques may have the relatively benign form, spina bifida occulta, which may never come into clinical attention. Post natally, an MRI can diagnose the level of the lesion. As a rule, higher the lesion worse is clinical presentation, ranging from lower limb weakness to major neurological deficit and paraplegia. No specific surgical or medical treatments are available to correct the motor and sensory deficit but a multidisciplinary approach is used to modify the outlook of such patients.