Scoliosis is defined as lateral abnormal curvature of the spine. Broadly speaking, there are two types of scoliosis – nonstructural and structural
In this type of scoliosis, the spine has a lateral curvature but there is no structural abnormality in the spine. The curvature is in response to habit or a disease process.
The spine is structurally normal with a lateral curvature, no spinal rotation, and no truncal asymmetry.
Types of nonstructural scoliosis:
- Postural– This curvature is due to prolonged use of a wrong posture. It resolves when the child is lies down.
- Compensatory – It is caused by leg-length discrepancy. There is no rotation of the vertebrae and it usually goes off on sitting.
- Sciatic This curve results from trying to avoid pain from an irritated sciatic nerve
- Inflammatory: Here a curvature in the spine is caused by an infective process such as an appendicitis. The body curves in response to the disease or abdominal muscle spasm.
- Hysterical – very rare and has an underlying psychological component
A structural scoliosis is the one that involves both a lateral curvature and rotation of the vertebrae. Most common type is the one where no cause could be found.
Most common type of scoliosis is idiopathic where the cause is not known. Idiopathic scoliosis is classified based on the age when scoliosis develops. For example in a person less than 3 years old, it is called infantile idiopathic scoliosis.
It is caused by an abnormal development of the bones of the spine for example hemivertebra or due to other paralytic disorders.
Degenerative scoliosis occurs in older adults. Degenerative changes may lead to weakening of the normal ligaments and other soft tissues of the spine. In presence of arthritic changes abnormal curvature may result
Any pathology in the spine like spine tumors may cause people to lean to the opposite side to reduce discomfort. Prolonged posturing may lead to scoliosis.
Most common type of scoliosis is idiopathic, a term used in medical literature when no cause is known. Non idiopathic structural scoliosis forms a small percentage of structural scoliosis.
Most common causes in this group are neuromuscular diseases such as cerebral palsy, poliomyelitis or muscular dystrophy or birth defects such as hemivertebra. Injury may be another cause. Infections or tumors also might give rise to curvature of the spine.
Here is the list of causes of non idiopathic structural scoliosis.
- Cerebral palsy
- Spinocerebellar degeneration
- Friedreich’s ataxia
- Hereditary Motor and Sensory Neuropathies
- Spinal tumor
- Spinal muscular atrophy I-IV (usually right sided curve)
- Muscular dystrophies
- Duchenne and Becker’s
- Limb girdle
- Fibre type disproportion
- Congenital hypotonia
- Myotonia dystrophica
- Achondroplasia and hypochondroplasia – mainly lordosis or thoracolumbar kyphosis.
- Mesenchymal disorders like Marfan’s syndrome or Ehler’s-Danlos syndrome
- Spina bifida especially thoracic type
- Rheumatoid disease
- Osteoid osteoma
- Eosinophilic granuloma
- Intraspinal tumours like ependymoma, astrocytoma, epidermoid cyst
Scoliosis in patients with spondylolisthesis
It is of three types
Sciatic scoliosis is caused by muscle spasm. It is mostly not structural and resolves with lying down or on relief of symptoms.
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.
Lastly idiopathic scoliosis and spondylolisthesis may occur together.
Neuromuscular Scoliosis and Its Types
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 is common.
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 complications like increased bleeding, less satisfactory bone stock, longer fusions, and the necessity for fusion to the pelvis.
A classification of neuromuscular scoliosis is given below [Scoliosis Research Society]-
Upper motor neuron
- Cerebral palsy
- Spinocerebellar degeneration
- Friedreich ataxia
- Charcot-Marie-Tooth Disease
- Roussy-Levy Syndrome
- Spinal cord tumor
- Spinal cord trauma
Lower motor neuron
- Other viral myelitides
- Spinal muscle atrophy
- Dysautonomia (Riley-Day syndrome)