The "Dehydrated" Lumbar Intervertebral Disk on MR, its Anatomy, Biochemistry and Biomechanics

Area of Science:

• Radiology
• Orthopedics
• Pain Management

Background:

• Lumbar spine MRI is commonly used to diagnose back and radicular pain.
• Reports often focus on disk margin changes causing nerve root compression.
• The clinical significance of the 'dark disk' in back pain is underemphasized.

Purpose of the Study:

• To review the concept of the 'dark disk' on MRI.
• To discuss its characteristics and clinical significance, particularly when not causing nerve root compression.

Main Methods:

• Review of T2-weighted MRI findings of lumbar spine disks.
• Classification of disks using the Pfirrmann or Thompson scale (Stage III corresponds to dark disks).
• Discussion of morphologic, chemical, and biomechanical properties of dark disks.

Main Results:

• A 'dark disk' on T2-weighted MRI signifies diminished signal intensity, indicating dehydration.
• This finding corresponds to Stage III in the Pfirrmann/Thompson disk degeneration scale.
• Dark disks possess distinct characteristics that warrant clinical consideration.

Conclusions:

• The 'dark disk' is a recognizable MRI finding associated with disk dehydration.
• Its clinical significance in the context of back pain, independent of nerve root compression, should be recognized.
• Further investigation into the role of dark disks in diagnosing back pain is suggested.