How to diagnose and treat lumbar stenosis

The human spine goes through a relentless process of degeneration from 16 years old and onward. Discs desiccate, bulge, and fissure; ligaments and facets hypertrophy; osteophytes form and expand. The net effect is a gradual encroachment on the spinal canal and its contents—a process known as spinal stenosis.

The lumbar spine sees the most degenerative changes due to the significant weight and activity that it must bear. Over time, degrees of stenosis will progress and gradually squeeze the nerve roots of the cauda equina. The process of progressive spinal stenosis is slow and generally goes unnoticed.

Low back pain is not uncommon with age. However, it is more related to arthritic changes in the joints, microinstability, and resultant muscular compensation than the process of stenosis itself. Stenosis can become quite severe without any associated symptomatology.

However, the nerve roots of the cauda equina can become irritated, inflamed, and begin to cause a specific syndrome called neurogenic claudication. At times, neurogenic claudication can present with generalized low back pain and radiculopathy.

The diagnosis of symptomatic lumbar stenosis or neurogenic claudication is often made by history alone. Ask about the distribution of the pain, aggravating and relieving factors, progression over time, and associated symptoms. Be sure to always ask about red flags or indications that the patient may have a more serious or urgent condition.

Symptoms

In neurogenic claudication, the patient will feel increasing numbness, paresthesia, achiness, deep pain, heaviness, and loss of control in the legs. These symptoms typically occur after walking a short distance or just from standing erect for a certain period of time.

Classically, the patient’s symptoms will go away after sitting for 15–30 minutes. They often will not go away if the patient remains standing. As a result, you will often see these patients assume a stooped or flexed posture for symptomatic relief. The patient may report that they tolerate walking better if they do so while bent over something such as a shopping cart.

Over time, the symptoms tend to worsen. For example, the patient may report that they used to get symptoms after walking for half an hour in the supermarket, but now they can only go down one aisle before becoming symptomatic.

Symptoms can vary in intensity where the patient experiences flare-ups and improvements. Some of the severity is dependent on their activity levels (or lack thereof).

Differential diagnoses

Vascular claudication

Keep vascular claudication in mind for patients presenting with leg pain. Vascular claudication is caused by insufficient perfusion of the leg muscles due to arterial narrowing.

Vascular claudication is exercise-related (but not dependent on position) and tends to present with leg cramps rather than deep aching or paresthesia. It will usually improve rapidly with the cessation of exercise—even without sitting or bending. There are often other associated signs of vascular insufficiency in the legs in these patients.

Cauda equina syndrome

Stenosis, no matter how severe, seldom presents with acute generalized lower extremity weakness, bowel dysfunctions, or bladder dysfunctions. If a patient with stenosis presents with these symptoms, consider an acute central disc herniation causing symptomatic cauda equina compression, known as cauda equina syndrome.

Cauda equina syndrome involves bilateral pain, numbness, weakness in the lower extremities, saddle numbness, and bowel and bladder retention or incontinence. This syndrome can be a surgical emergency.

With cauda equina syndrome, magnetic resonance imaging (MRI) should disclose the offending agent. However, true cauda equina syndrome in patients with lumbar stenosis is relatively unusual. It is much more common in younger people where the intervertebral discs are plump, high in water content, and can extrude in one large piece. Nonetheless, make sure you ask about bladder and bowel function and check for neurological deficits in your patients with stenosis.

Perform four standard assessments of a patient with suspected lumbar stenosis:

1. Perform a neurological exam and screen for myelopathy
2. Perform a motor exam and check reflexes
3. Perform a sensory exam
4. Assess gain, balance, and pedal pulses

Perform a neurological exam and screen for myelopathy

Perform a standard neurological exam and include a screen for myelopathy. However, the neurological exam is often completely normal and the straight leg raise exam is usually negative.

Perform a motor exam and check reflexes

The motor exam should also be normal for patients with suspected neurogenic claudication. Deep tendon reflexes are usually normal or diminished. If the patient has hyperreflexia, consider pathologies that affect the upper motor neurons of the spinal cord or brain.

Perform a sensory exam

Often, the sensory exam is also normal with neurogenic claudication. If you do find deficits in pinprick and light touch sensation, they should be patchy, scattered, and bilateral.

Assess gait, balance, and pedal pulses

Gait and balance should be well maintained with neurogenic claudication. Remember, loss of balance may be an indicator of myelopathy. Check the patient’s pulse at the ankles and the dorsalis pedis. If you can find no pulse, the syndrome may be vascular in nature.

If a patient presents with neurogenic claudication, try a course of nonsteroidal anti-inflammatories along with physical therapy. This is a chronic ailment, so keep away from narcotics.

Discuss a trial of epidural steroid injections with the patient. While epidural injections might get the patient over a bad flare-up, they are not beneficial long-term. Remember that MRI of the lumbar spine will need to be obtained before the referral.

Exacerbations of neurogenic claudication can often be ameliorated with these relatively conservative measures. Generally, the condition will worsen over time with the patient experiencing an increasing frequency of exacerbations and greater resultant disability.

With persistent or worsening of symptoms, obtain a non-contrast MRI. Neurogenic claudication from lumbar stenosis is a clinical diagnosis, so MRI can be used to confirm the presence of stenosis. But, MRI should not be used to determine the severity. The severity of symptoms is poorly correlated with the degree of stenosis. Some patients can have mild stenosis but severe symptoms, while others can have severe stenosis on imaging but no symptoms.

Look for canal narrowing at one or multiple spinal levels. Remember, there is a good chance that there will be some profound stenosis, particularly in anyone over 60 years old. If there is no stenosis, then consider other pathologies (e.g., vascular).

If an MRI cannot be obtained, obtain a computed tomography (CT) myelogram. Myelograms are relatively reliable for spinal stenosis.

Electromyogram (EMG) and nerve conduction velocity (NCV) evaluations rarely help, and are often confusing. Do not order these tests unless you suspect other pathologies such as peripheral neuropathy.

How to treat neurogenic claudication from lumbar stenosis with surgery

With persistent or progressive neurogenic claudication, and evidence of stenosis on MRI, consult a spinal surgeon as the patient will likely benefit from surgery. Once a patient reaches this point, it is unlikely that any conservative measures will help improve their condition. Over time, their syndrome will likely get worse. The patient’s nerve roots have reached the point where they will not tolerate any further crowding. The patient will become more and more inactive, which is bad for their overall health. Under these circumstances, surgery is reasonable, relatively safe, and effective.

Spinal stenosis surgery involves the removal of parts of the lamina, overgrown facet joints, thickened ligaments, and bone spurs, which can be done through open or minimally invasive methods. This type of surgery is called spinal decompression.

Surgery usually results in significant improvement in symptoms—but it is not a cure-all. Usually, the patient will experience far less lower extremity symptoms and will demonstrate much better exercise tolerance. But, they will likely still have a degree of baseline lower back pain (typically from generalized arthritis).

Often, spinal decompression surgery does not require instrumentation and fusion unless the patient has significant malalignment of their vertebral bodies, abnormal movement between the vertebral bodies, or significant spinal deformity. If the spine surgeon recommends instrumentation and fusion in a patient without these features, recommend a second opinion to the patient.

After surgery, encourage the patient to work with a physical therapist. Patients are often profoundly deconditioned from years of decreased activity levels.

Physical therapies that involve strength and conditioning exercises which aim to return the patient to activities of daily living are strongly recommended. Furthermore, core strengthening may help with residual muscular back pain.

Sometimes a patient with baseline stenosis and neurogenic claudication will develop a severe exacerbation of pain that is radicular in nature. This may be secondary to a disc herniation occurring on top of the background stenosis.

If the pain takes on a radiculopathy quality, you’ll need to manage the patient for lumbar radiculopathy. If surgery is considered, more extensive decompression (than generally used in simple radiculopathy surgery) may be necessary.

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