What is lumbar spinal stenosis?
Lumbar spinal stenosis is a broad term referring to the symptoms which may result from the narrowing of the spinal canal in the lower back. This may be due to age, injury, or degeneration.
Lumbar spinal stenosis occurs when the bony tunnels in the spine that transmit the spinal cord and nerve roots become narrowed. The spinal nerves (or nerve roots) typically become compressed, leading to pain in the lower back and legs.
Lumbar spinal stenosis may affect one or more anatomical compartments, including the spinal canal (lumbar canal stenosis) and intervertebral foramen (lumbar foraminal stenosis).
The spinal canal is a long tunnel running down the centre of the spine. This canal sits directly behind the bony blocks, or veterbrae (‘vertebral bodies’) which form the spine (vertebrae) and contains the spinal cord (which usually ends in the upper lumbar spine) and nerve roots. When the spinal canal is narrowed, the spinal cord and nerve roots may be compressed- this is known as lumbar canal stenosis. The lumbar spinal canal may be subdivided into other compartments, notably the lateral recess and subarticular compartments. Narrowing of the calibre of these specific compartments may give rise to ‘lateral recess stenosis’ or ‘subarticular stenosis’.
The spinal nerves (‘nerve roots’) leave the lumbar spinal canal by passing through the intervertebral foraminae. The nerves then travel to the legs, bladder and bowels where they control sensation and movement. When the intervertebral foraminae are narrowed, the nerve roots may be compressed- this is known as lumbar foraminal stenosis.
In summary, lumbar canal and foraminal stenosis are both caused by the same underlying processes, and can present in a similar fashion. The two conditions commonly co-exist and can be broadly referred to as lumbar spinal stenosis.
What causes lumbar spinal stenosis?
Lumbar spinal stenosis is common and is usually caused by osteoarthritis and disc degeneration. Typically, a combination of disc degeneration and bulging, joint and ligament thickening (‘hypertrophy’), and sometimes a slight ‘slip’ (or ‘spondylolisthesis’), causes compression of the nerve roots. Risk factors for spinal osteoarthritis and intervertebral disc degeneration include smoking, poor posture, obesity, repetitive heavy lifting, and ongoing exposure of the lower back to significant jolting or vibration (for example, racing car drivers).
Trauma can also cause spinal stenosis. This includes the kind of injury caused by picking up heavy objects improperly. The vertebrae (spinal bones) or intervertebral discs (shock absorbers between the bones) may be injured, resulting in pressure on the spinal cord and/or nerves. Spinal fractures may result in fragments of bone which intrude into the spinal canal.
Lumbar spinal stenosis may also be caused by the spread of cancer to the vertebral column, or by infection (discitis, osteomyelitis, epidural abscess).
What are the symptoms of lumbar spinal stenosis?
The symptoms of lumbar spinal stenosis can vary, and in some patients there may be no symptoms at all. The degree of compression changes with posture and activity, accounting for variations in the pattern of pain.
Symptomatic patients with lumbar stenosis typically experience pain on standing or walking, and may have trouble walking for any length of time or for long distances. They need to sit down or lean forward (such as when pushing a shopping trolley) to relieve the pain. The pain typically returns when standing upright. This pattern of pain is known as ‘neurogenic claudication’.
In severe cases of spinal stenosis, nerves to the bladder or bowel may be compressed, which can lead to incontinence (loss of control) of urine and/or faeces. Anyone who experiences problems controlling their bladder or bowels should seek urgent medical attention.
How is the diagnosis of lumbar canal stenosis made?
Making a diagnosis of lumbar stenosis can sometimes be difficult because the symptoms may mimic other conditions. For example, the leg pain of neurogenic claudication can be confused with that of vascular claudication, or poor blood supply to the legs. Vascular claudication becomes worse when you walk uphill and improves when you stand still, whilst neurogenic claudication is usually worse walking downhill and improves when you leaning forward or sitting down.
To determine the cause of you symptoms, your neurosurgeon may require several investigations. These may include computed tomography (CT), and magnetic resonance imaging (MRI). In some situations, such as when you are unable to have an MRI, you may also undergo a CT myelogram, in which CT imaging is performed while a contrast dye is injected into the spinal column. Ultrasound scans of the blood vessels in the legs are often carried out to exclude vascular insufficiency as a cause of the symptoms.
What are the treatment options for lumbar canal stenosis?
Lumbar spinal stenosis is almost always treated conservatively in the first instance. Medications to relieve pain and reduce inflammation are utillised. Analgesics include pain relievers such as paracetamol and codeine. Non-steroidal anti-inflammatory drugs (NSAIDS) include aspirin, ibuprofin and naproxen, and these relieve pain as well as reducing inflammation and swelling. Other pharmacological agents include a short course of corticosteroids (prednisolone, cortisone), as well as agents specific for nerve pain (such as pregabalin).
Other nonsurgical treatments for lumbar stenosis include physiotherapy, hydrotherapy, pilates, chiropractic, acupuncture and osteopathy. A physiotherapist can teach you exercises to help you build up and maintain strength, endurance, and flexibility for spinal stability. Some of these exercises will help strengthen your back and abdominal muscles (core muscle groups), since they help support the back. Physical therapy can also include the use of heat or ice packs, ultrasound, electrical stimulation, and massage. These treatments can relax tight muscles and ease pain or discomfort. A back brace or corset can also help support your back and may be especially helpful for people who have degeneration in more than one area of the spine.
In more severe cases, you may be prescribed a corticosteroid injection into the spinal canal. This may comprise an epidural injection. Local anesthetic may also be injected around the compressed nerve (transforaminal nerve sheath injection) and can have both diagnostic and therapeutic value.
Your neurosurgeon may also suggest that you rest your back by restricting your activities. Rest followed by a gradual return to exercise can help the back heal in some cases. Prolonged strict bed rest, however, is generally not recommended.
Severe cases of spinal stenosis may require surgery. There are several types of surgery done to relieve pressure on the spinal cord and nerves and to help strengthen the spine. The most common surgical procedures are decompressive lumbar laminectomy, laminotomy, and spinal fusion.
