Nonidiopathic Scoliosis – Types and Causes

Idiopathic structural scoliosis is the most common type of scoliosis. Rest of the scoliosis types are grouped under the term nonidiopathic scoliosis.

Nonstructural scoliosis has the lateral curvature but there is no structural abnormality in the spine. The curvature is in response to habit or a disease process like inflammation.

Postural scoliosis is a type of structural scoliosis.

Structural scoliosis, on the other hand, has the deformity due to structural changes in the spine that involves lateral curvature and rotation of the spine.

Nonidiopathic structural scoliosis is mainly of following types

Congenital Scoliosis

Congenital deformities due to failure of formation or differentiation of the vertebrae.

Neuromuscular

Leads to muscular imbalance and thus  abnormal development of the bones of the spine

Main causes are

• Cerebral palsy
• Spinocerebellar degeneration
• Friedreich’s ataxia

• • Hereditary Motor and Sensory Neuropathies
  • Syringomyelia
  • Poliomyelitis
  • Spinal muscular atrophy I-IV
  • Muscular dystrophies
    • Duchenne and Becker’s
    • Limb-girdle
    • Facio-scapulo-humeral
  • Myotonia dystrophica

• Mesenchymal disorders
  • Marfan’s syndrome
  • Ehlers-Danlos syndrome
• Spina bifida
• Neurofibromatosis

Degenerative

Degenerative scoliosis occurs in older adults. It occurs because degenerative changes lead to the weakening of the normal ligaments and other soft tissues of the spine.

In addition, arthritic changes may cause an abnormal curvature

• Causes
  • Spondylolisthesis
  • Rheumatoid disease

Miscellaneous Lesions

Tumors can cause changes in curvature due to differential growth and compensatory changes in the spine.

• Spine pathology like spine tumors
  • Osteoid osteoma
  • Osteoblastoma
  • Eosinophilic granuloma
  • Intraspinal tumors like ependymoma, astrocytoma, epidermoid cyst

Some  of the important scoliosis are discussed below

Congenital Scoliosis

[Detailed article on Congenital Scoliosis]

Congenital scoliosis is the curvature due to the imbalance of growth of the spine caused by the presence of vertebral defects. Most of these defects develop during the first 6 weeks of embryological life.

It can occur either due to failure of formation [wedge vertebra, hemivertebra] or failure of segmentation [unilateral unsegmented bar, block vertebra]

The major problems in congenital scoliosis are trunk deformation, trunk decompensation, altered neurology.

Congenital scoliosis may be associated with other congenital abnormalities like VATER, Diastematomyelia, Tethered cord, and Arnold Chiari malformation.

The patient presents with deformity of the back. Subtle deformities may not be seen unless the patient is evaluated for some other reason.

In addition to the routine spinal evaluation, some specific physical findings should be sought in patients with congenital scoliosis.

• Hair patches, lipomata, dimples, and scars may indicate an underlying vertebral defect
• A complete neurological evaluation should be done.
• Clubfoot, calf atrophy, absent reflexes, and limb atrophy could be signs of neurological involvement or associated anomalies

Anteroposterior and lateral radiographs are the basic imaging studies required for this. The serial radiographic investigation would tell about the progression of the curve.

The growth potential of the curves should be estimated to better determine the possibility of curve progression.

Myelography or MRI should be considered if diastematomyelia or a neurological abnormality is suspected.

The nonoperative treatment has a limited role in congenital scoliosis. It can be tried in curves less than 40 degrees and flexibility of 50%.

It mainly consists of bracing. The brace may also be given in the initial period to evaluate the progression of the curve.

75% of congenital curves are progressive and only 5% to 10% can be treated with bracing.

Surgery remains the main treatment in congenital scoliosis.

Progressive increase in deformity, trunk decompensation, and neural deficit are main indications of the surgery.

Depending on the causation the various procedures used are anterior/posterior fusion with or without instrumentation, hemivertebra excision, and vertebrectomy.

Scoliosis with Spondylolisthesis

Scoliosis in spondylolisthesis can be caused by muscle spasm where it is called sciatic scoliosis. It is a type of non-structural scoliosis.

Idiopathic scoliosis and spondylolisthesis may occur together.

Olisthetic scoliosis is a torsional lumbar curve in association with spondylolisthesis and results from asymmetrical slipping of the vertebra. These resolve after treatment of the spondylolisthesis.

However, in severe cases, the curves may become structural.

Neuromuscular Scoliosis

[Detailed article on Neuromuscular Scoliosis]

Neuromuscular scoliosis develops at a younger age than idiopathic curves and a larger percentage of neuromuscular curves are progressive. Usually, neuromuscular curves are long, C-shaped curves and associated pelvic obliquity.

The basic treatment methods are similar – observation, orthotic treatment, and surgery.

The goal of treatment is to maintain a spine balanced in the coronal and sagittal planes over a level pelvis.

These patients generally are less compliant with orthotic management and surgery is associated with complications like increased bleeding, less satisfactory bone stock, longer fusions, and the necessity for fusion to the pelvis.

Neuromuscular scoliosis is divided into neuropathic and myopathic causes by the  Scoliosis Research Society. Neuropathic is further divided into upper motor and lower motor neuron lesions.

Degenerative Scoliosis

[Detailed article on Degenerative Scoliosis]

Degenerative scoliosis is also called adult onset scoliosis and refers to the scoliotic curve that results because of degeneration.

Persons with degenerative scoliosis may experience no symptoms or have mild discomfort mostly.

Some patients, however, may have back pain that is worsened with standing and is relieved on lying down. The pain is worst in the morning usually and gets better with the day’s activity before worsening again over the course of the day.

Compression of roots may lead to pain in the limb or numbness.

It must be noted that the scoliotic curve is not the cause of the pain. Both, the curves and the pain, are due to degenerative changes.

The curves progress very slowly and need not always be corrected.

The treatment of degenerative scoliosis mainly focuses on the degeneration and not a correction of the curve.

Physical therapy, exercises, or pain management are the main treatment options.

Surgical treatment may be considered in selected cases which would depend on many factors like the presence of stenosis, no of vertebrae involved etc. Decompression and/or fusion are the major surgical procedures considered in degenerative scoliosis.