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Clinical case: Radiculopathy and surgical treatment: want to learn more about it?

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Clinical case: Radiculopathy and surgical treatment

A surgical procedure is usually the last resort when it comes to resolving health issues. Usually, we try with pharmacotherapy or physical treatments, but if the disease is refractory to any non-invasive therapy, like this patient's neuroforaminal stenosis, it is time to get the surgery involved.

This article will discuss a case of a man whose disease (radiculopathy) and symptoms (radicular pain) are refractory to every attempted conservative measure and explain why the spinal salvage surgery is the only method that can help him.

You will find the presentation of his disease, its management and important anatomical and surgical considerations. 

Key Facts
Lumbar puncture A procedure of collecting the cerebrospinal fluid for further examinations. It is performed by the penetration into the spinal subarachnoid space (lumbar cistern) at the level of L3/L4 or L4/L5 with a needle.
Radicular pain A pain caused by the irritation of the sensory root of the spinal nerve, or the sensory component of the peripheral nerve. The pain distributes along the dermatomes of the specific nerve.
Claudication The pain in the lower limb. 
Vascular origin - arterial disease
Neurogenic orgin - narrowing of the spinal canal (stenosis) in the lumbar spine
Straight leg raising test A neurodynamic test for evaluation of the likelihood and location of the lumbar disk herniation.

After reviewing this case you should be able to describe the following:

  • The relationship between the numbering of the vertebra and the numbering of the spinal nerves; lumbar puncture and why it can be done with relative impunity.
  • What is meant by radicular pain? The relationship between radicular pain, dermatomes and muscle atrophy and weakness.
  • What is meant by claudication? How is it evaluated and treated?
  • What is meant by the straight leg raising test? How it is done?

This article is based on a case report published in the Journal "Case Reports in Surgery" in 2015, by Caroline C. Jadlowiec, Beata E. Lobel, Namita Akolkar, Michael D. Bourque, Thomas J. Devers, and David W. McFadden.
 

Case description

History & examination

A 72-year-old man was referred to the orthopedic clinic for significant low back and radicular pain in his right lower limb. The pain was refractory to all analgesics, including opioids, and corticosteroid nerve root infiltration was only effective for 1-2 days. When he tried to walk, he had neurological intermittent claudication starting in less than 50m. MRI indicated neuroforaminal stenosis at the L5-S1 level (Figures 1 & 2).

Figure 1. Axial and lateral views of adjacent lumbar vertebrae. The superior and inferior vertebral notches together form the intervertebral foramen (neuroforamen) in which the spinal nerves exit the vertebral (spinal) canal.

Remember how adjacent lumbar vertebrae are normally notched, because now we will see how does the neuroforaminal stenosis that is present in the patient change the picture in the patient's oblique MRI.

Figure 2. Oblique MRI images of lumbar spine in patient showing compressed L5 spinal nerve on right compared to left (blue arrows).

Neurological exam showed right L5 radiculopathy with a positive straight leg raising (SLR) test of 60° (Figure 3).

Figure 3. Illustration of Straight Leg Raising (SLR) test. The straight leg raise, also called Lasègue's sign, Lasègue test or Lazarević's sign, is a test done during the physical examination to evaluate whether a patient’s low back pain is associated with a herniated disk, often located at L5 (fifth lumbar spinal nerve). Courtesy of Wikipedia: https://en.wikipedia.org/wiki/Straight_leg_raise

Diagnosis & management of radiculopathy

The right tibialis anterior and extensor digitorum longus muscles showed weakness, and there was numbness and pain in the L5 dermatome, with a visual analog scale (VAS) pain score of 6–7 (with 10 being the worst pain imaginable).

With the diagnosis of L5-S1 lumbar foraminal stenosis, the patient underwent L5-S1 transforaminal lumbar interbody fusion (TLIF) surgery with a “cage” implant between L5 and S1, which was very successful. Postoperatively, the patient was free from the radicular leg pain and neurological issues.

Figure 4. Frontal and lateral radiographs showing supportive hardware (rods and pedicles screws) installed in original surgery to maintain the intervertebral spacing. The red dashed line indicates the intervertebral “cage.” Note, however, that the cage is not centrally placed, but is offset to the right.

Unfortunately, the patient’s relief did not last and three months postoperative, he complained of recurrent right lower limb pain with an L5 dermatomal distribution that was more robust than prior to surgery; his VAS score at this time was 8–9 with a positive SLR test of 15°.

Imaging showed right L5-S1 foraminal stenosis due to movement of the cage in combination with likely L5 vertebral body fracture (Figures 4&5).

Figure 5. A. myelogram (contrast injected into dural sac and then radiographs taken) showing spinal nerve compression indirectly from cage movement. B. CT myelogram also showing nerve compression resulting from cage movement. C&D. High resolution CT images showing likely compression of spinal nerve by the cage.

Complications & evolution

The pain was again unresponsive to any analgesic drugs, so surgery was again performed. Because the foraminal stenosis was severe, the surgeons decided to remove and replace the intervertebral support cage. Further, because of the potential of major intra- and postoperative complications associated with iatrogenic damage to the space surrounding the neuroforamen due to adhesion and scar tissue related to the first surgery, the surgeons adopted an anterior transperitoneal approach to ensure clear and sufficient exposure of the intervertebral disk space.

First, the patient was placed in the prone position to loosen the posterior rod, then he was placed in the supine position. The peritoneal cavity was opened by medial incision inferior to the umbilicus. The retroperitoneal wall was exposed at the bifurcation of the great vessels. The anterior longitudinal ligament was dissected to approach the intervertebral disk. From the anterior opening portal, the primary intervertebral cage was identified and carefully removed to avoid intraoperative neurovascular injury. Subsequently, the intervertebral space and fractured margin of the foraminal space were carefully and meticulously scraped under fluoroscopic guidance to decompress the nerve.

Next, a new titanium anterior cage was inserted into the intervertebral space and the anterior incision was closed. The patient was then again returned to the prone position for final rod fixation. The operation lasted 4.5 hours with only 10 mL of intraoperative bleeding. Postoperatively, the lower limb pain totally resolved, with a VAS score of 0–1 and slight numbness in the right leg. Postoperative radiological studies showed recovery of the lumbosacral disk space, including the L5-S1 foraminal space (Figure 6). There have been no recurrence and/or exacerbation of pain and numbness at 1.5 years after the revision surgery.

Figure 6. A & B. Frontal and lateral radiographic views showing hardware placement after revision surgery (blue arrows). C. Coronal CT showing symmetrical cage placement after revision surgery.

Anatomical and surgical considerations

Intervertebral discs are interposed between adjacent axial surfaces of vertebral bodies from the axis to the sacrum and are the primary bonds of connection between them (Figure 7).

Figure 7. Sagittal T2 MRI showing vertebral column and intervertebral disks. Note that for the upper disks there is a clear differentiation between the nucleus pulposus and the annulus fibrosis, but that this differentiation is no longer apparent in the lower lumbar disks. Note also the disk herniation at the L5/S1 level as in the patient described in this case.

The thicknesses of the discs vary in different regions of the column and in different part of the same disc. They are thicker anteriorly than posteriorly in the cervical and lumbar regions, contributing to the anterior convexities of these regions. In contrast, the discs are of nearly uniform thickness in the thoracic region and the anterior concavity of this part of the column is almost entirely due to the shape of the vertebral bodies.

Except for their peripheral parts, which receive a blood supply from adjacent vessels, the discs are avascular and supplied by diffusion through the spongy bone of the adjacent surfaces of the vertebrae. Hence, the vascular and avascular parts differ in reaction to injury. Each disc consists of an outer fibrocartilaginous ring called the annulus fibrosis and an inner core, the nucleus pulposus (Figure 7). The fibers of the annulus are oriented obliquely between the vertebrae and are arranged in concentric rings. The nucleus pulposus is considered to be composed of fibrocartilaginous material embedded in a gelatinous matrix, but from the time of its development in the fetus until late adult life it undergoes a continuous structural change. With increasing age the gelatinous tissue is gradually replaced by fibrocartilage that in the elderly blends with the annulus fibrosus in such a manner that there is no longer a sharp line of demarcation between the two parts of the disc (Figure 7).

Coincident with these changes is a progressive decrease in its water content: 88% at birth, at 70 years only about 70%. With this loss of water content the disk space between the vertebrae decreases and reduces the size of the neuroforamen, thus potentially compressing the exiting spinal nerves (as in this patient; in addition to disk height reduction other degenerative changes in the disk [e.g., development of osteophytes] contribute to the reduction in the size of the spinal neuroforamen). (It is also the reason why we are taller in the morning than when we go to bed – during sleeping water again seeps into the nucleus pulposus expanding each intervertebral disc). The nucleus pulposus may be considered as a water cushion associated with equalizing the distribution of pressure between vertebrae, and the absorption of mechanical shocks that are constantly being transmitted along the vertebral column. So again, the loss of this water cushion with increasing age acts to potentially compress the exiting spinal nerves.

Spinal fusion surgery is designed both to increase and maintain intervertebral depth while reducing movements between adjacent vertebrae. Both processes act to reduce pain. The spinal “cages” are the mechanism to maintain intervertebral depth, whereas fusion is accomplished using a bone graft (Figure 4). As the bone graft heals, it fuses the vertebra above and below. Although these procedures are often successful, these procedures undoubtedly reduce allowable movement between the fused vertebrae, placing additional stress on the surrounding vertebral joints. This can lead to subsequent degenerative changes on those joints as well. TLIF is done through a posterior approach. However, as in this case, failed spinal intervertebral fusion surgery occasionally requires salvage surgery when symptomatic. Posterior revision surgery may cause severe complications such as a dural tear, nerve injury, and symptomatic neurologic disorders, especially in those with lumbosacral lesions (Figures 8&9).

Figure 8. A. Spinal cord in situ showing spinal nerves in their dural sleeves that are at risk during spinal fusion surgery, especially revision surgery. B. Distal spinal cord showing conus medullaris, filum terminale and cauda equina after the dura was cut and splayed open.

Thus, the surgeons in this study used an anterior approach. Anterior salvage (revision) surgery may be a preferred technique because it minimizes muscle damage and neurologic risks, and it is associated with minimal blood loss. Among anterior approaches, the transperitoneal one to the lumbosacral junction provides clear and wide exposure.

Figure 9. Spinal cord with opened dural sac showing cauda equina in lumbar cistern.

However, the anterior approach also has potential complications such as retrograde ejaculation, impotence, and retroperitoneal fibrosis, rectus muscle hematomas, pancreatitis, femoral nerve palsy, and pseudomeningocele (the first two result from inadvertent damage to the superior hypogastric nerve plexus).

For the current case the surgeons found that the likely reason for the failed initial surgery was that the placement of the cage was too far to the right (Figure 4) which, based on a variety of imaging techniques, was shown, with likely vertebral fracture, to have caused recompression of the right L5 spinal nerve (Figures 4&5). Based on these imaging techniques the surgeons were able to proceed with the anterior approach with a high likelihood of a successful outcome.

Clinical case: Radiculopathy and surgical treatment: want to learn more about it?

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