What are the implications of nerve root impingement on the cauda equina (lower spinal nerves)?

From the Guidelines

Impingement of roots to the cauda equina requires immediate medical attention, typically through urgent MRI assessment and possible surgical decompression, to prevent permanent neurological damage. The cauda equina is a bundle of nerve roots at the lower end of the spinal cord that can become compressed due to various etiologies, including lumbar disc herniation, neoplasm, infection/inflammation, spinal stenosis, and hemorrhage, as noted in the ACR Appropriateness Criteria® Low Back Pain: 2021 update 1. Symptoms of cauda equina syndrome (CES) include severe lower back pain, leg weakness or numbness, saddle anesthesia, and bladder or bowel dysfunction, which can be assessed through physical examination findings, such as those reported by Fairbank et al 1.

The imaging study of choice for evaluating suspected CES is MRI lumbar spine without IV contrast, due to its ability to accurately depict soft-tissue pathology, assess vertebral marrow, and assess the spinal canal patency 1. A prospective cohort study by Bell et al 1 recommends urgent MRI assessment in all patients who present with new-onset urinary symptoms in the context of LBP or sciatica. In cases where underlying malignancy, infection, or inflammation is clinically suspected, MRI lumbar spine without and with IV contrast may be helpful to delineate the etiology of CES 1.

Key points to consider in the management of cauda equina impingement include:

• Urgent MRI assessment to evaluate the extent of compression and guide surgical planning
• Possible surgical decompression, such as laminectomy, to relieve pressure on the nerve roots
• Rehabilitation, including physical therapy, to regain strength and function after surgery
• The importance of prompt treatment to prevent permanent neurological damage, as delayed treatment can result in irreversible damage to nerve root function, affecting mobility and control of essential bodily functions 1.

In emergency situations, a single 3-D heavily T2-weighted fat-saturated sequence protocol has been shown to be a rapid, highly sensitive tool for evaluating CES, which can improve efficiency and emergency department throughput 1. While CT lumbar spine without IV contrast can answer the question of whether or not cauda equina compression is present, MRI remains the preferred initial study due to its superior soft-tissue contrast and ability to characterize the etiology of CES 1.

From the Research

Impingement of Roots to Cauda Equina

The impingement of roots to the cauda equina is a serious medical condition that can result in significant morbidity if left untreated.

• The cauda equina syndrome is characterized by varying patterns of low back pain, sciatica, lower extremity sensorimotor loss, and bowel and bladder dysfunction 2.
• The pathophysiology of cauda equina syndrome remains unclear but may be related to damage to the nerve roots composing the cauda equina from direct mechanical compression and venous congestion or ischemia 2.
• Red flag symptoms, such as bladder dysfunction, saddle anaesthesia, and sciatica, should lead to high clinical suspicion of cauda equina syndrome 3.

Diagnosis and Treatment

• Early diagnosis is often challenging because the initial signs and symptoms frequently are subtle 2.
• Immediate magnetic resonance imaging, within 1 hour of presentation to the emergency department, is crucial in patients with suspected cauda equina syndrome to allow prompt diagnosis and treatment 3.
• Urgent decompressive surgery is usually recommended for the best outcomes, to reduce morbidity and complication rates 3, 4.
• The primary treatment involves decompression of the nerve roots, typically in the form of discectomy or laminectomy 4.

Complications and Outcomes

• The most common postoperative complications include visits to the emergency department, surgical site infection, urinary tract infection, and postoperative anemia 4.
• Intraoperative dural tears, valvular heart disease, and fluid and electrolyte abnormalities are significant risk factors for readmission to the hospital within 30 days following surgery for cauda equina syndrome 4.
• Delays in diagnosis can have devastating and life-changing consequences for patients and result in high-cost negligence claims 5.