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Natural history of extruded lumbar intervertebral disc herniation
Tatsuhiko Henmi1, Koichi Sairyo, Shunji Nakano
1Department of Orthopedic Surgery, Health Insurance Naruto Hospital, Muya-cho, Naruto, Tokushima 772-8503, Japan.
Abstract:
We studied the natural history of extruded lumbar intervertebral discs using MRI. Forty-nine patients with lumbar disc herniation were included in this study. Ages ranged from 19 to 57. On the T2-weighted sagittal MR image, the signal intensity in the herniated mass was measured and the ratio to that in the original nucleus (i.e., nucleus pulposus from which they extruded) was calculated (signal intensity ratio; SIR). The relationship with SIR and duration of illness was evaluated. In ten patients who were re-examined by MRI after conservative treatment, the size of the herniation measured by T1-weighted axial MR image was compared before and after treatment. The signal intensity of HNP became higher than that of the original nucleus immediately following herniation and thereafter decreased with time, suggesting that initial hydration of the HNP occurred shortly after herniation followed by dehydration of the HNP. The size of the HNP with a SIR value of 1.2 and higher on T2-weighted MR images decrease with time, however, the HNP with a SIR below 1.2 did not show any size reduction. The SIR of 1.2 and higher is a good indicator predicting spontaneous reduction of the HNP. Dehydration in the HNP may play an important role in the reduction of the lumbar disc herniation.
Insights
Magnetic resonance imaging (MRI) reveals that lumbar disc herniation (HNP) size reduces over time, particularly when the signal intensity ratio (SIR) is 1.2 or higher. Dehydration appears crucial for spontaneous HNP reduction.
Area of Science:
- Radiology
- Orthopedics
- Neurosurgery
Background:
- Lumbar disc herniation (HNP) is a common condition affecting the spine.
- Understanding the natural history of HNP is crucial for effective treatment strategies.
- Magnetic resonance imaging (MRI) is a key diagnostic tool for evaluating HNP.
Purpose of the Study:
- To investigate the natural history of extruded lumbar intervertebral discs using MRI.
- To correlate MRI signal intensity ratio (SIR) with HNP changes over time.
- To identify predictors of spontaneous HNP reduction.
Main Methods:
- MRI analysis of 49 patients with lumbar disc herniation (ages 19-57).
- Calculation of signal intensity ratio (SIR) from T2-weighted sagittal MR images.
- Comparison of HNP size before and after conservative treatment in 10 patients using T1-weighted axial MR images.
Main Results:
- HNP signal intensity initially increased then decreased over time, suggesting hydration followed by dehydration.
- HNPs with a SIR of 1.2 or higher showed size reduction over time.
- HNPs with a SIR below 1.2 did not exhibit significant size reduction.
Conclusions:
- A SIR of 1.2 or higher on T2-weighted MRI predicts spontaneous reduction of lumbar disc herniation.
- Dehydration of the herniated disc material plays a significant role in HNP size reduction.
- MRI-based SIR is a valuable indicator for predicting HNP natural history.