Diffusion-weighted imaging and diffusion tensor imaging of asymptomatic lumbar disc herniation

Area of Science:

• Radiology
• Neuroimaging
• Medical Physics

Background:

• Lumbar disc herniation can compress spinal nerve roots, potentially leading to radiculopathy.
• Diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) are advanced MRI techniques used to assess tissue microstructure.
• Previous studies linked symptomatic nerve root compression to increased apparent diffusion coefficient (ADC) and decreased fractional anisotropy (FA) values.

Observation:

• A 31-year-old male with asymptomatic lumbar disc herniation underwent DWI and DTI.
• Despite obvious entrapment of the left S1 nerve root by a herniated disc, standard DWI and DTI revealed no significant findings.
• Unusual findings included decreased ADC values and increased FA values in the compressed nerve root.

Findings:

• The observed decreased ADC and increased FA in an asymptomatic compressed nerve root contradict findings in symptomatic patients.
• This pattern suggests that nerve root compression without significant injury (e.g., edema, demyelination, axonal damage) may present differently on DWI/DTI.
• The results indicate that ADC and FA values may differentiate between nerve compression and actual nerve injury.

Implications:

• These findings suggest that DWI and DTI, specifically ADC and FA metrics, could serve as potential biomarkers for assessing nerve root status in radiculopathy.
• Understanding these unique diffusion characteristics in asymptomatic compression may refine diagnostic criteria and prognostic assessments.
• Further research is warranted to validate these findings and explore their clinical utility in managing lumbar disc herniation and radiculopathy.