Stickler syndrome

Definition

Scoliosis is a side-to-side (lateral) curvature of the spine of 10 degrees or greater.

Description

When viewed from the rear, the spine usually appears to form a straight vertical line. Scoliosis is a lateral (side-to-side) curve in the spine, usually combined with a rotation of the vertebrae. The lateral curvature of scoliosis should not be confused with the normal set of front-to-back spinal curves visible from the side. While a small degree of lateral curvature does not cause any medical problems, larger curves can cause postural imbalance and lead to muscle fatigue and pain. More severe scoliosis can interfere with breathing and lead to arthritis of the spine (spondylosis).

Four out of five cases of scoliosis are idiopathic, meaning their cause is unknown. Children with idiopathic scoliosis appear to be otherwise entirely healthy, and have not had any bone or joint disease early in life. Scoliosis is not caused by poor posture, diet, or carrying a heavy bookbag exclusively on one shoulder.

Idiopathic scoliosis is further classified according to age of onset:

• Infantile. Curvature appears before age three. This type is quite rare in the United States, but is more common in Europe.

• Juvenile. Curvature appears between ages three and 10. This type may be equivalent to the adolescent type, except for the age of onset.

• Adolescent. Curvature appears between ages of 10 and 13, near the beginning of puberty. This is the most common type of idiopathic scoliosis.

• Adult. Curvature begins after physical maturation is completed.

Causes are known for three other types of scoliosis:

• Congenital scoliosis is due to congenital birth defects in the spine, often associated with other structural defects.

• Neuromuscular scoliosis is due to loss of control of the nerves or muscles which support the spine. The most common causes of this type of scoliosis are cerebral palsy and muscular dystrophy.

• Degenerative scoliosis may be caused by degeneration of the discs which separate the vertebrae or arthritis in the joints that link them.

Genetic profile

Idiopathic scoliosis has long been observed to run in families. Twin and family studies have consistently indicated a genetic contribution to the condition. However, no consistent pattern of transmission has been observed in familial cases. As of 2001, no genes have been identified which specifically cause or predispose individuals to the idiopathic form of scoliosis.

There are several genetic syndromes which involve a predisposition to scoliosis. Several studies have investigated whether or not the genes which cause these syndromes may also be responsible for idiopathic scoliosis. Using this candidate gene approach, the genes responsible for Marfan syndrome (fibrillin), Stickler syndrome, and some forms of osteogenesis imperfecta (collagen types I and II) have been shown not to correlate with idiopathic scoliosis.

Attempts to map a gene or genes for scoliosis have not shown consistent linkages to any particular chromosome region.

Most researchers have concluded that scoliosis is a complex trait. As such, there are likely to be multiple genetic, environmental, and potentially additional factors that contribute to the etiology of the condition. Complex traits are difficult to study due to the difficulty in identifying and isolating multiple factors.

Demographics

The incidence of scoliosis in the general population is approximately 2-3%. Among adolescents, however, 10% have some degree of scoliosis, though fewer than 1% have curves that require treatment.

Scoliosis is found in both males and females, but a female's spinal curve is much more likely to progress than a male's. Females require scoliosis treatment about five times as often as males. The reason for these differences is not known with certainty but they may relate to increased levels of estrogen and other hormones in females.

Causes and symptoms

Scoliosis causes a noticeable asymmetry in the torso when viewed from the front or back. The first sign of scoliosis is often seen when a child is wearing a bathing suit or underwear. A child may appear to be standing with one shoulder higher than the other, or to have a tilt in the waistline. One shoulder blade may appear more prominent than the other due to rotation. In girls, one breast may appear higher than the other, or larger if rotation pushes that side forward.

Curve progression is greatest near the adolescent growth spurt. Scoliosis that begins early in life is more likely to progress significantly than scoliosis that begins later in puberty.

More than 30 states have screening programs in schools for adolescent scoliosis. These are usually conducted by physicians, school nurses or trained physical education teachers.

Diagnosis

Scoliosis is initially noticed during a screening program or during a routine physical examination conducted by a pediatrician or family physician. Confirmatory diagnosis of scoliosis is often conducted by an orthopedic surgeon. A complete medical history is taken, including questions about family history of scoliosis. The physical examination includes determination of pubertal development in adolescents, a neurological exam (which may reveal a neuromuscular cause), and measurements of trunk asymmetry. Examination of the trunk is done while the person is standing, bending over, and lying down, and involves both visual inspection and use of a simple mechanical device called a scoliometer.

If a curve is detected, one or more x rays will usually be taken to define more precisely the curve or curves. An x ray is used to document spinal maturity, any pelvic tilt or hip asymmetry, and the location, extent, and degree of curvature. The curve is defined in terms of where it begins and ends, in which direction it bends, and by an angular measure known as the Cobb angle. The Cobb angle is found by projecting lines parallel to the vertebrae tops at the extremes of the curve; projecting perpendiculars from these lines; and measuring their angle of intersection. To properly track the progress of scoliosis, it is important to project from the same points of the spine each time.

Occasionally, magnetic resonance imaging (MRI) is used, primarily to look more closely at the condition of the spinal cord and nerve roots extending from it if neurological problems are suspected.

Treatment

Treatment decisions for scoliosis are based on the degree of curvature, the likelihood of significant progression, and the presence of pain, if any.

Curves less than 20 degrees are not usually treated, except by regular follow-up for children who are still growing. Watchful waiting is usually all that is required in adolescents with curves of 20-25 degrees, or adults with curves up to 40 degrees or slightly more, as long as there is no pain.

For children or adolescents whose curves progress to 25 degrees, and who have a year or more of growth left, bracing may be required. Bracing cannot correct curvature, but may be effective in halting or slowing its progression. Bracing is rarely used in adults, except where pain is significant and surgery is not an option, as in some elderly patients.

There are two different categories of braces, those designed for nearly 24 hour per day use and those designed for night use. The full-time brace styles are designed to hold the spine in a vertical position, while the night use braces are designed to bend the spine in the direction opposite the curve.

The Milwaukee brace is a full-time brace which consists of metal uprights attached to pads at the hips, rib cage, and neck. Other types of full-time braces, such as the Boston brace, involve underarm rigid plastic molding to encircle the lower rib cage, abdomen, and hips. Because they can be worn out of sight beneath clothing, underarm braces are better tolerated and often lead to better compliance. The Boston brace is currently the most commonly used. Full-time braces are often prescribed to be worn for 22-23 hours per day, though some clinicians believe that recommending brace use of 16 hours leads to better compliance and results.

Night-use braces bend an individual's scoliosis into a correct angle, and are prescribed for eight hours of use during sleep. Some investigators have found that night-use braces are not as effective as the day-use types.

Bracing may be appropriate for scoliosis due to some types of neuromuscular disease, including spinal muscular atrophy, before growth is finished. Duchenne muscular dystrophy is not treated by bracing, since surgery is likely to be required, and since later surgery is complicated by loss of respiratory capacity.

Surgery for idiopathic scoliosis is usually recommended if:

• The curve has progressed despite bracing.

• The curve is greater than 40-50 degrees before growth has stopped in an adolescent.

• The curve is greater than 50 degrees and continues to increase in an adult.

• There is significant pain.

Orthopedic surgery for neuromuscular scoliosis is often done early in life. The goals of surgery are to correct the deformity as much as possible, to prevent further deformity, and to eliminate pain as much as possible. Surgery can usually correct 40-50% of the curve, and sometimes as much as 80%. Surgery cannot always completely remove pain.

The surgical procedure for scoliosis is called spinal fusion, because the goal is to straighten the spine as much as possible, and then to fuse the vertebrae together to prevent further curvature. To achieve fusion, the involved vertebra are first exposed, and then scraped to promote re-growth. Bone chips are usually used to splint together the vertebrae to increase the likelihood of fusion. To maintain the proper spinal posture before fusion occurs, metal rods are inserted alongside the spine, and are attached to the vertebrae by hooks, screws, or wires. Fusion of the spine makes it rigid and resistant to further curvature. The metal rods are no longer needed once fusion is complete, but are rarely removed unless their presence leads to complications.

Spinal fusion leaves the involved portion of the spine permanently stiff and inflexible. While this leads to some loss of normal motion, most functional activities are not strongly affected, unless the very lowest portion of the spine (the lumbar region) is fused. Normal mobility, exercise, and even contact sports are usually all possible after spinal fusion. Full recovery takes approximately six months.

Prognosis

The prognosis for a person with scoliosis depends on many factors, including the age at which scoliosis begins and the treatment received. Most cases of mild adolescent idiopathic scoliosis need no treatment, do not progress, and do not cause pain or functional limitations. Untreated severe scoliosis often leads to spondylosis, and may impair breathing.

Health care team roles

A pediatrician or family physician usually makes an initial diagnosis of scoliosis. Orthopedic surgeons may provide surgical treatment. Physical therapists may provide therapeutic exercises for a person with scoliosis.

Prevention

There is no known way to prevent any of the forms of scoliosis.

Key Terms

Cobb angle

A measure of the curvature of scoliosis, determined by measurements made on x rays.

Scoliometer

A tool for measuring trunk asymmetry; it includes a bubble level and angle measure.

Spondylosis

Arthritis of the spine.