Introduction

Low back pain is one of the most common musculoskeletal complaints encountered in clinical practice. It is the leading cause of disability in the developed world and accounts for billions of dollars in healthcare costs annually. Although epidemiological studies vary, the incidence of low back pain is estimated to be anywhere between 5% to more than 30% with a lifetime prevalence of 60% to 90%. Most occurrences of low back pain are self-limited and resolve without intervention. Approximately 50% of cases will resolve within one to two weeks. 90% of cases will resolve in six to 12 weeks. The differential for low back pain is broad, and amongst other diagnoses, should include lumbosacral radiculopathy. Lumbosacral radiculopathy is a term used to describe a pain syndrome caused by compression or irritation of nerve roots in the lower back. It can be caused by lumbar disc herniation, degeneration of the spinal vertebra, and narrowing of the foramen from which the nerves exit the spinal canal. Symptoms include low back pain that radiates into the lower extremities in a dermatomal pattern. Other accompanying symptoms can include numbness, weakness, and loss of reflexes, although the absence of these symptoms does not exclude a diagnosis of lumbosacral radiculopathy. 

Etiology

The noxious stimulus of a spinal nerve creates ectopic nerve signals that are perceived as pain, numbness, and tingling along the nerve distribution. Lesions of the intervertebral discs and degenerative disease of the spine are the most common causes of lumbosacral radiculopathy. However, any process that causes irritation of the spinal nerves can cause radicular symptoms. The differential diagnosis for lumbosacral radiculopathy should include (but is not limited to) the following:

  • Degenerative conditions of the spine (most common causes)

    • Spondylolisthesis: in the degenerative setting, this occurs as a result of a pathologic cascade including intervertebral disc degeneration, ensuing intersegmental instability, and facet joint arthropathy
    • Spinal stenosis

    • Adult isthmic spondylolisthesis is typically caused by an acquired defect in the par interarticularis

      • Pars defects (i.e. spondylolisis) in adults are most often secondary to repetitive microtrauma

  • Trauma (e.g. burst fractures with bony fragment retropulsion)

    • Clinicians should recognize spinal fractures can occur in younger, healthy patient populations secondary to high-energy injuries (e.g. MVA, fall from height) or secondary low energy injuries and spontaneous fractures in the elderly populations, including any patient with osteoporosis
    • Associated hemorrhage from the injury can result in a deteriorating clinical and neurologic exam

  • Benign or malignant tumors

    • Metastatic tumors (most common)
    • Primary tumors
    • Ependymoma
    • Schwannoma
    • Neurofibroma
    • Lymphoma
    • Lipomas
    • Paraganglioma
    • Ganglioneuroma
    • Osteoblastoma

  • Infection

    • Osteodiscitis
    • Osteomyelitis
    • Epidural abscess
    • Fungal infections (e.g. Tuberculosis)
    • Other infections: lyme disease, HIV/AIDS-defining ilnesses, Herpes zoster (HZ)

  • Vascular conditions

    • Hemangioblastoma, aterior-venous malformations (AVM)

Epidemiology

While the literature lacks concise epidemiologic data, most reports estimate about a 3% to 5% prevalence rate of lumbosacral radiculopathy in patient populations.  Moreover, the condition constitutes a significant reason for patient referral to either neurologists, neurosurgeons, or orthopedic spine surgeons.  

While the incidence of low back pain is estimated to be between 13% and 31%, the incidence of radicular symptoms in patients presenting with low back pain ranges from 12% to 40%. In the workforce, low back pain is the second greatest cause of absenteeism behind upper respiratory tract infections. About 25 million people miss one or more days of work due to low back pain, and more than five million are disabled from it. Patients with chronic back pain account for 80% to 90% of all health care expenditures. [3]

Pathophysiology

Lumbosacral radiculopathy is the clinical term used to describe a predictable constellation of symptoms occurring secondary to mechanical and/or inflammatory cycles compromising at least one of the lumbosacral nerve roots.  Patients can present with radiating pain, numbness/tingling, weakness, and gait abnormalities across a spectrum of severity.  Depending on the nerve root(s) affected, patients can present with these symptoms in predictable patterns affecting the corresponding dermatome or myotome. 

Pearls and Other Issues

Overall, lumbosacral radiculopathy is an extraordinarily common complaint seen in clinical practice and comprises a large proportion of annual doctor visits. The vast majority of cases are benign and will resolve spontaneously, and thus, conservative management is the most appropriate first step in the absence of clinical red flag symptoms. In cases where symptoms fail to resolve, imaging studies, electromyography, and nerve conduction studies can assist in making a diagnosis. 

NATIONAL LIBRARY OF MEDICINE