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Lumbar Radiculopathy
Clinical Vignette
A 53-year-old man had a history of occasional severe episodes of low back pain radiating down his buttock and posterior left thigh; it had begun with an athletic injury at age 17. Typically he experienced exacerbations, which lasted for a few days, every few years. Precipitating factors included sitting for prolonged periods and activities such as jogging or playing hockey. In general he “toughed out” these exacerbations by forcing himself out of bed in the morning despite the pain and continuing with his usual activities while being careful not to suddenly bend over. If his symptoms persisted, he found it necessary to use simple analgesics, low-dose muscle relaxants, and to “take it easy.” After a weekend of skiing, he developed severe left sciatica that worsened progressively over a 3-day period. The pain was excruciating; it kept him up at night and did not respond to the usual medications. Getting out of bed in the morning was very painful, and he had to force himself up despite the “paralyzing” pain. He noticed left foot drop with paresthesia over his great toe. Straining or coughing further exacerbated the discomfort. He went to see a neurosurgeon; on the way, routine jolting of the car significantly exacerbated the pain. Neurologic exam demonstrated a left foot drop, marked lumbosacral paravertebral muscle spasm, diminished lumbar lordosis, and an inability to tolerate straight leg raising on the left. Magnetic resonance imaging (MRI) demonstrated an extruded disc fragment at the L4–L5 interspace with compression of the left L5 root. A micro-hemi-laminectomy was performed, the disc fragment removed, and the nerve root decompressed. The sciatic pain was relieved the next morning.
Comment: This patient's course was typical for an intermittent, recurrent, subacute lumbosacral radiculopathy; his intermittent symptoms had always improved with conservative therapy. The sudden onset of an acute severe radiculopathy secondary to disc extrusion with excruciating pain and the rapid development of a foot drop over a few days led to successful surgical intervention.
Lumbosacral radiculopathy, frequently called “sciatica,” is one of the most common neurologic afflictions, typically affecting 1% of the population per year. Most individuals with sciatica experience some degree of chronic low back pain. These symptoms are a major cause of disability and are the primary cause of workers’ compensation disability in the United States.
Clinical Presentation
Sciatic pain may occur acutely or evolve more gradually; when the onset is sudden, it may be spontaneous or related to a specific incident, sometimes a seemingly trivial event, such as bending over to make a bed. The symptoms may be minor and clinically inconsequential or significant, requiring urgent evaluation and treatment ( Fig. 57.1 ). Depending on the specific nerve root involved, the pain may be classic “sciatica” with radiation down the posterior aspect of the leg into the foot, as seen with compression of the L5 or S1 roots ( Figs. 57.2 and 57.3 ). At higher levels, with L3 or L4 root compression, the pain may radiate to the anterior thigh. The clinical signs of lumbar radiculopathy are due to the specific level of involvement ( Table 57.1 ), and the most common levels of nerve root irritation are the L5 and S1 roots, followed less commonly by the L4 and L3 roots. It is very rare to have involvement of the higher roots (L1 and L2).
TABLE 57.1
Nerve Root Signs of Lumbar Radiculopathy
| Root | Motor Weakness | Sensory Loss | Muscle Stretch Reflexes |
|---|---|---|---|
| L3 | Iliopsoas/quadriceps | Anterior thigh | KJ diminished but still present |
| L4 | Quadriceps | Anterior thigh to below knee | KJ absent |
| L5 | Tibialis anterior | Dorsum and medial foot | Internal hamstring |
| S1 | Gastrocnemius | Lateral aspect of foot, sole, and heel | AJ absent |
AJ, Ankle jerk; KJ, knee jerk.
In the adult, the spinal cord ends between L1 and L2; therefore the nerve root compressed by disc herniation depends on whether the lesion is medial in the spinal canal or lateral in the neural foramen. The exiting root passes around the pedicle cephalad to the disc space. Therefore a lesion occurring at the disc space within the spinal canal compresses the passing root, the root with the next lower number. For example, a medial disc rupture in the spinal canal at L4–L5 will compress the L5 root, whereas less commonly the disc rupturing laterally in the neural foramen will compress the L4 root.
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