Lumbar radiculopathy is caused by direct injury to the nerve roots in the lumbar spine, most often when these nerves exit the neural foramina. Estimated lifetime prevalence is approximately 3% to 5% of adults, with equal amounts among men and women. The most common sources of this injury are due to disc herniation and arthritic overgrowth of the spine. It is rare that radiculopathy is caused by infection, inflammation, neoplasm, or vascular disease. Each nerve root will provide a predominant area of sensation in the leg. This is called a dermatome . Each nerve root will also provide predominant innervation to muscles in the leg; this motor assignment is called a myotome . The L5 nerve root is the most common nerve affected in lumbar radiculopathies. An L5 radiculopathy will present as pain along a dermatomal distribution, along the lateral leg to the top of the foot. Strength is diminished with foot dorsiflexion, toe extension, and both foot inversion and eversion. When nerve damage progresses, there is hip abduction weakness. The second most common nerve affected is the S1 nerve root. Examination suggesting S1 involvement will include sensory changes along the posterior leg and bottom of foot, with weakness on plantar flexion and possibly hip extension and knee flexion. Ankle reflexes may be absent. Lumbosacral myotomal and dermatomal distributions are noted in Chart 1. Radiculopathy is diagnosed clinically, although it may be recommended to perform imaging such as an MRI or CT scan to confirm this diagnosis. A noncontrast MRI or CT myelogram provides good visualization of the nerve roots. It is strongly recommended imaging be performed if there is suspicion of neoplasm, neurologic deficits, urinary changes, saddle anesthesia, severe lower extremity weakness, or abscess/inection. An electromyography (EMG) can be performed if there is any question regarding the specific nerve root involvement. With EMG testing, typically the nerve conduction testing is normal with abnormal insertional activity in muscles predominantly innervated by a specific nerve root. For severe S1 radiculopathies, the H reflex will be absent.
Most cases of lumbar radiculopathy are self-limiting. Nonetheless radiculopathy can be extremely painful. NSAIDs and activity modification are typically recommended. If severe pain continues despite NSAIDs use, short-term (3 days to 2 weeks) opioid medication can be considered. Systemic glucocorticoids can be considered. Although activity modification is recommended during acute presentation, physical therapy can be considered if pain persists over 3 weeks. Epidural steroid injections provide modest temporary benefits, lasting approximately 3 months. Surgery may be an option if disabling pain persists for 6 weeks or there is profound weakness. Presentation of cauda equina syndrome is an emergent indication for surgery.