Diagnosing lumbar radiculopathy

Learn how to recognize the signs and symptoms of lumbar radiculopathy in your patients. Click here now!
Last update7th Jan 2021

Compression of lumbar nerve roots from disc herniation or overgrown spinal column components are common phenomena. Most often, they are relatively painless disorders.

On occasion, a compressed nerve root becomes irritated or inflamed and sets off a whole syndrome of pain and nerve dysfunctions. This disorder is known as radiculopathy.

Figure 1. Illustration and magnetic resonance imaging (MRI) of a disc herniation causing lumbar radiculopathy.

Lumbar radiculopathy most commonly affects the L4, L5, and S1 nerve roots. Most lumbar radiculopathies are self-limited; given time alone, the majority of radiculopathies will improve and spontaneously go away—even if the compression remains.

Figure 2. Lumbar nerve roots typically involved in lumbar radiculopathy include the L4, L5, and S1 nerve roots.

For example, if lumbar radiculopathy occurs due to a herniated disc and then resolves over a few weeks, the herniated disc material will still be pressing up against the nerve for many more weeks or months. The body will eventually erode the extra material, but this takes time. In essence, the nerve root remains compressed yet it spontaneously feels better.

When should you consider lumbar radiculopathy as a possible diagnosis?

When assessing a patient to rule out lumbar radiculopathy, always be alert for red flags—signs that the condition may be related to more serious or urgent pathologies. Ask the patient if they have a history of any of the following:

  • Cancer
  • Recent trauma
  • Osteoporosis
  • Infection
  • Rapidly progressive weakness
  • Bilateral weakness
  • Bowel or bladder dysfunctions

Symptoms

Always ask about bowel or bladder dysfunctions such as incontinence or retention. Acute spinal conditions (such as compressive metastatic tumors or cauda equina syndrome) often present with early bladder dysfunctions.

Keep the possibility of myelopathy or cauda equina syndrome in the back of your mind throughout your evaluation. These are serious conditions that may require urgent surgical intervention.

Figure 3. Myelopathy and cauda equina syndrome are important differential diagnoses for lumbar radiculopathy that may require urgent treatment.

When obtaining a patient history, also inquire about treatments that have already been initiated in your patient.

If you still suspect lumbar radiculopathy after a subjective interview, assess your patient for two main symptom characteristics:

  1. Type, onset, and duration of pain
  2. Associated symptoms
Figure 4. When lumbar radiculopathy is suspected, ask the patient about the type of pain, onset of pain, duration of pain, and associated symptoms that they may be experiencing.

Type, onset, and duration of pain

In lumbar radiculopathy, pain should be unilateral. Classically, it will be quite severe and more predominant in the leg than in the back. The pain tends to radiate from the back, through the buttock, and into the posterolateral aspect of the thigh and leg which can follow the dermatome of the affected nerve root (to a certain degree). Pain often radiates into the groin as well.

Figure 5. Pain associated with lumbar radiculopathy will be unilateral and tends to radiate from the back down through the buttock and into the posterolateral thigh and leg.

Patients tend to generalize pain and sensory symptoms, so be careful not to get too hung up on how closely the pain follows a dermatomal pattern. Pain does not have to follow a classical pattern. Most of the pain may be isolated to the buttock, the groin, a section of the leg, or the ankle. This makes forming a diagnosis quite challenging because many generalized low back pain syndromes and myofascial syndromes may radiate into part of the buttock and upper leg.

However, lumbar radiculopathy is often distinguishable because it will have a radiating quality all the way down the leg. Radicular pain can take on a host of characteristics such as shocking, searing, sharp, jabbing, or burning—and can be relentless.

Figure 6. Radicular pain associated with lumbar radiculopathy can be shocking, searing, sharp, jabbing, or burning.

Associated symptoms

When lumbar radiculopathy is suspected, ask the patient about paresthesia (pins and needles or tingling) and more unpleasant dysesthesia (burning, squeezing, crawling, or itching). These are commonly associated with radiculopathy pain and should follow a similar pattern down the leg.

Figure 7. Paresthesia and dysesthesia are commonly associated with lumbar radiculopathy.

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What to do if you suspect lumbar radiculopathy?

The diagnosis of lumbar radiculopathy is often made with history alone since physical exam findings can be rather unimpressive. On the other hand, positive findings help seal the diagnosis.

When performing a physical exam for lumbar radiculopathy, seven aspects should be considered:

  1. Observation
  2. Physical and neurological exams
  3. Crossed straight leg raising exam
  4. Straight leg raising exam
  5. Related motor dysfunction
  6. Patellar and Achilles reflexes
  7. Sensory exam

Observation

During your physical examination of a patient with suspected lumbar radiculopathy, simply observe the patient for some time. Patients with severe radiculopathy are very uncomfortable and will assume bizarre positions in an attempt to somehow alleviate the pressure on the affected nerve root. A typical position that the patient may find more comfortable is lying on the exam table with several cushions under the affected leg. A patient in the seated position may lean their body to one side or the other.

Figure 8. Watch for awkward body positioning in a patient with suspected lumbar radiculopathy.

Perform physical and neurological exams

Next, do a general physical exam and a focused neurological exam, being sure to include seven important assessments:

  1. Cerebral exam
  2. Upper extremity exam
  3. Coordination exam
  4. Cranial nerve exam
  5. Motor reflexes
  6. Sensory reflexes
  7. Deep tendon reflexes

There should be no upper extremity findings or myelopathic findings on the exam. There should also be no findings in the leg opposite to the painful leg.

Figure 9. Physical and neurological examinations are part of the assessment for patients with suspected lumbar radiculopathy.

Perform a crossed straight leg raising exam

With the patient lying on their back, gently extend the unaffected leg. If this causes pain in the affected leg, it is a strong sign of nerve root compression. This finding is called a positive crossed straight leg raising exam.

Figure 10. A positive crossed straight leg raise exam for lumbar radiculopathy will cause pain in the affected leg when the opposite leg is extended in the supine position.

Perform a straight leg raising exam

To perform a straight leg raising exam, gently lift the affected leg and keep it straight, preferably with the patient supine. Raising the leg 10–15° should not increase the pain. If it does, suspect other pathologic disorders (or even malingering).

If the patient's radiating pain is intensified by raising the leg 30–45°, there is a good chance that they’re suffering from radiculopathy from a compressed nerve root. This finding is called a positive straight leg raising exam.

Flexing the ankle while the leg is raised often makes the pain even worse. These maneuvers irritate an afflicted nerve root because they stretch the nerve over the compressive entity (e.g., a herniated disc).

Figure 11. A positive finding in a straight leg raise exam is if the pain intensifies when the affected leg is raised 30–45°. This suggests that the patient is suffering from radiculopathy from a compressed nerve root.

Interestingly, you do not usually see a positive straight leg raise exam in L4 radiculopathies, which tends to be more painful in response to extension of the leg at the hip. This exam is known as a reverse straight leg exam.

Look for related motor dysfunction

Next, look for evidence of related motor dysfunction. Remember, lumbar radiculopathy affects lower motor neurons. So, you should look for typical findings associated with lower motor neuron involvement:

  • Weakness
  • Decreased tone
  • Atrophy
  • Decreased reflexes

Look for weakness in specific muscle groups. This means that the entire leg should not be weak. Also, it is unusual for a muscle group to have no function. If radiculopathy has been going on long enough, you may see atrophy in the affected muscles. Depending on the severity, this may range from weeks to months.

Figure 12. Findings typical of lower motor neuron involvement in lumbar radiculopathy include weakness, decreased tone, atrophy, and decreased reflexes.

Affected patients tend to guard a lot, so muscle testing may be unreliable. This is often subconscious, and repeated encouragement usually gets them to make a full effort in each muscle group. If they are showing apparent weakness in several multiple groups, don’t give up! Push the exam until you are convinced of the findings.

Weakness, if present, should follow a pattern consistent with the nerve root being affected:

  • L4 compression results in quadriceps weakness.
  • L5 compression results in weakness in dorsiflexion of the foot and big toe.
  • S1 compression results in weakness in plantar flexion of the foot.
Figure 13. Weakness in lumbar radiculopathy should follow a pattern consistent with the affected nerve root. L4 compression results in quadriceps weakness, L5 compression results in weak foot and big toe dorsiflexion, and S1 compression results in weak foot plantar flexion.

Plantar flexion of the foot is best tested by having the patient heel raise on one leg at a time. The gastrocnemius is a strong muscle, and you may not be able to elicit weakness from a manual exam.

Bilateral weakness, or weakness that appears to involve multiple nerve roots, is not consistent with radiculopathy and suggests other disease processes or some psychosomatic element to the exam.

Assess patellar and Achilles reflexes

Reflex findings in patients with lumbar radiculopathy will be asymmetrical. A unilateral diminished reflex suggests nerve root dysfunction. To support your suspicion of lumbar radiculopathy, abnormal reflex findings should be associated with the affected nerve root:

  • L4 compression results in a diminished patellar reflex.
  • S1 compression produces a diminished Achilles reflex.
Figure 14. Reflex findings with lumbar radiculopathy will be asymmetrical (e.g., only diminished on the affected side). L4 compression results in a diminished patellar reflex, and S1 compression results in a diminished Achilles reflex.

Other reflex findings

Hyperreflexia or a positive Babinski sign points to an upper motor neuron process. If the Babinski sign is present, you should be suspicious of a problematic spinal cord or brain and not a lumbar nerve root.

Figure 15. Hyperreflexia or a positive Babinski sign do not indicate the presence of lumbar radiculopathy and point at an upper motor neuron process.

Perform a sensory exam

Do a sharp and light touch sensory exam in both legs and the trunk. Loss of sensation in an entire leg or both legs suggests other diseases or possibly a psychosomatic response.

Figure 16. Bilateral sensory loss is not a finding typically associated with lumbar radiculopathy.

With lumbar radiculopathy you should ideally find a specific dermatomal distribution of sensory loss that matches the nerve root that you suspect is compressed. However, sensory exams are notoriously inconsistent, so don’t be confused if there is a lack of perfect dermatomal distribution. Sensory loss approximating a whole dermatome or parts of one supports the diagnosis.

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Recommended reading

  • Cooper, G. 2015. Non-Operative Treatment of the Lumbar Spine. 1st edition. New York: Springer.
  • Devlin, VJ. 2012. Spine Secrets Plus. 2nd edition. Missouri: Mosby.
  • Longo, UG, Loppini, M, Denaro, L, et al. 2010. Rating scales for low back pain. Br Med Bull94: 81–144. PMID: 20064820
  • Louis, ED, Mayer, SA, and Rowland, LP. 2015. Merritt’s Neurology. 13th edition. Philadelphia: Wolters Kluwer.
  • Malanga, GA, Buttaci, CJ, and Rubbani, M. 2018. Lumbosacral radiculopathy. Medscapehttps://emedicine.medscape.com/
  • Michigan State University. 2020. Oswestry low back pain disability questionnaire. Michigan State Universityhttps://www.rehab.msu.edu
  • PainScale. 2020. Pain scale for lower back pain. https://www.painscale.com/
  • Physiopedia contributors. 2020. Quebec back pain disability scale. Physiopediahttps://www.physio-pedia.com

About the author

Gary R. Simonds, MD MHCDS FAANS
Professor at Virginia Tech School of Neuroscience / Virginia Tech Carilion School of Medicine and Program Director for the Division of Neurosurgery at Virginia Tech Carilion Clinic.
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