What is foraminal stenosis in the cervical spine?

Foraminal Stenosis in the Cervical Spine

Foraminal stenosis in the cervical spine is a narrowing of the neural foramina (openings) through which spinal nerve roots exit, commonly causing compression of nerve roots and resulting in upper extremity radicular pain and neurological symptoms.

Definition and Anatomy

Foraminal stenosis refers specifically to the narrowing of the neural foramina in the cervical spine. These foramina are paired openings formed between adjacent vertebrae that allow passage of spinal nerve roots as they exit the spinal canal. The narrowing can occur due to several factors:

• Degenerative changes in the uncovertebral joints (joints of Luschka)
• Facet joint hypertrophy
• Disc bulging or herniation
• Osteophyte formation
• Decreased disc height

Causes and Risk Factors

The most common causes of cervical foraminal stenosis include:

• Age-related degenerative changes (most common)
• Trauma
• Congenital narrowing
• Systemic diseases such as:
  • Endocrinopathies (Cushing disease, acromegaly)
  • Calcium metabolism disorders (hypoparathyroidism, Paget disease)
  • Inflammatory diseases (rheumatoid arthritis)
  • Infectious diseases 1

Clinical Presentation

Patients with cervical foraminal stenosis typically present with:

• Neck pain
• Radicular pain (radiating down the arm in the affected nerve root distribution)
• Sensory disturbances (numbness, tingling)
• Motor weakness in the affected myotome
• Diminished reflexes

Diagnostic Imaging

According to the ACR Appropriateness Criteria, imaging options for cervical foraminal stenosis include 2:

1. MRI Cervical Spine:

   • Preferred method for evaluating suspected nerve root impingement
   • Superior soft-tissue contrast and spatial resolution
   • Correctly predicts 88% of lesions compared to 81% for CT myelography
   • Limitations: high rate of both false-positive and false-negative findings

2. CT Cervical Spine:

   • Provides excellent definition of bony elements
   • Helpful in assessing neuroforaminal stenosis secondary to uncovertebral or facet hypertrophy
   • Less sensitive than MRI for evaluation of nerve root compression

3. CT Myelography:

   • May prove useful in diagnosing foraminal stenosis when MRI is contraindicated
   • Can be considered in patients with clinically apparent radiculopathy and contraindication to MRI

4. Specialized MRI Techniques:

   • Susceptibility-weighted MRI (SW-MRI) has shown superior sensitivity (96.6%) compared to conventional T1-weighted (43.1%) and T2-weighted (65.5%) sequences for detecting osseous foraminal stenosis 3

Grading Systems

Several grading systems exist for cervical foraminal stenosis, with the most established being:

• Park system
• Kim system
• Modified Kim system

These systems classify the degree of stenosis based on MRI findings, though their clinical application may be limited by reliance on non-standard imaging and limited validation against clinical symptoms and surgical outcomes 4, 5.

Clinical Implications and Treatment Considerations

The severity of foraminal stenosis and the level of herniation can significantly impact treatment outcomes:

• Higher cervical levels of disc herniation and severe foraminal stenosis are associated with poorer outcomes from interventional treatments like interlaminar epidural steroid injections 6
• Treatment success is negatively correlated with:
  • Higher foraminal stenosis grade (odds ratio -0.425)
  • Higher spinal herniation level (odds ratio -0.925)

Common Pitfalls in Diagnosis

1. Asymptomatic Findings: Degenerative findings on MRI are commonly observed in asymptomatic patients, especially those over 30 years of age 2

2. Poor Correlation with Physical Examination: Limited evidence exists for correlation between physical examination findings and MRI evidence of cervical nerve root compression 2

3. Imaging Modality Selection: CT is less sensitive than MRI for nerve root compression but better for bony detail; choose the appropriate modality based on clinical suspicion 2

4. Overreliance on Imaging: Remember that approximately 65% of asymptomatic patients 50-59 years of age will have radiographic evidence of significant cervical spine degeneration 2

In summary, cervical foraminal stenosis is a common cause of neck pain and radiculopathy, requiring appropriate imaging for diagnosis. MRI remains the gold standard for evaluation, though CT may provide complementary information about bony structures. The clinical significance of imaging findings must always be correlated with the patient's symptoms, as incidental findings are common in asymptomatic individuals.