Department of Anaesthesia, Royal Free Hospital, London, UK
It is radicular pain and/or radiculopathy because of narrowing of the spinal canal and compression of the nerve roots. It may be congenital (achondroplasia, spondylolisthesis, mucopolysaccharidosis) or acquired (degeneration, Paget’s disease, acromegaly). The most common reason is degeneration of the elements of the vertebral column. It is further classified into central canal stenosis (area <1.5 cm2), lateral stenosis (nerve root canal) and stenosis of the intervertebral foramen.
The primary pathology is disc degeneration with loss of disc height, bulging of disc and hypertrophy of facet joints. The ligamentum flavum may be thickened (normal thickness is 2–4 mm) which covers the posterolateral aspect of the spinal canal, causing central spinal stenosis. The formation of osteophytes leads to the compression of nerve roots causing the symptoms. Superior articular facet hypertrophy leads to narrowing of lateral recess (normal anteroposterior diameter is >4 mm) which along with the decrease of disc height leads to lateral stenosis. Foraminal stenosis is the result of isthmic spondylolisthesis.
45.2 Clinical Features
It is a chronic condition. Symptoms of neurogenic claudication are seen with pain radiating to the lower extremity. Pain gets worse with walking and spinal extension and gets better with sitting. Numbness and weakness of the lower extremity may be seen (30 % of cases). Stenosis of lateral recess occlusion usually presents with unilateral pain localised to nerve root dermatome. Patient bends forward while walking and lumbar extension is limited. There may be decreased or absent ankle reflex (50–60 %).