27/07/2023
Just published 🔥
Systematic review and meta-analysis of predictive factors for spontaneous regression in lumbar disc herniation 💡
👉Relatively little evidence exists on predictive factors for the spontaneous regression of lumbar disc herniation (LDH), although it is a well-documented phenomenon. Without specific intervention, two-thirds of patients can expect disc regression, with 85% attaining symptom resolution within 1 year. https://brjp.org.br/article/doi/10.5935/2595-0118.20210067, https://pubmed.ncbi.nlm.nih.gov/28072796/
❓ But which patients can expect such a regression?
📊In a brand-new systematic review Rashed and colleagues included 16 studies describing 360 cases of lumbar disc herniation regression. The majority tended to be younger and male and presented with radiculopathy and L4–5 or L5–S1 disc herniation. The mean time to follow-up imaging was 11.5 months, and MRI was used as the imaging modality for all. https://thejns.org/spine/view/journals/j-neurosurg-spine/aop/article-10.3171-2023.6.SPINE23367/article-10.3171-2023.6.SPINE23367.xml
📊The probabilities of spontaneous regression with bulging, protruded, extruded, and sequestered discs (definition and figure, s. below) were:
👉 Bulging: 13.3%
👉 Protruded: 52.5%,
👉Extruded: 70.4%, and
👉 Sequestered: 93.0%, respectively.
📌 Extruded and sequestered discs were also significantly more likely to completely regress than smaller morphologies.
Other predictors of regression were:
👉 Larger baseline herniation volume (1260.16 vs 1006.71 mm3, p < 0.002),
👉 transligamentous herniation (herniations that had perforated through the posterior longitudinal ligament, PLL, p < 0.001), and
👉 higher Komori types (stronger migrating of disc herniation, p < 0.001).
❓ What are the proposed mechanisms?
💡 A number of mechanisms for spontaneous regression have been proposed, but the most supported theory is that of on autoimmune response to herniated disc fragments in the epidural space promoting neovascularization, macrophage infiltration, and ultimately phagocytosis of disc material. https://pubmed.ncbi.nlm.nih.gov/36722839/, https://pubmed.ncbi.nlm.nih.gov/35999644/
💡 It is thought that this response is exaggerated in the presence of a sequestered fragment, which is why PLL rupture is associated with regression. https://pubmed.ncbi.nlm.nih.gov/36722839/
❓ What about the relationship to symptoms?
👉 The association between symptoms and LDH regression is less well defined in the literature but is generally assumed to be positive. This was demonstrated in all qualitative studies in this review as well as in the majority of those in the previous review. https://pubmed.ncbi.nlm.nih.gov/25009200/
More interestingly, the authors describe 2 papers that show significantly increased disc regression on MRI if symptoms have been present for a shorter duration (< 1 year vs > 1 year). https://pubmed.ncbi.nlm.nih.gov/29945407/, https://pubmed.ncbi.nlm.nih.gov/34323452/
📌 This finding correlates with the improved outcomes seen with shorter symptom duration (< 12 months) in both surgical and non-surgical cohorts in the largest trials to date. https://pubmed.ncbi.nlm.nih.gov/22012528/
Classification of disc herniation: https://pubmed.ncbi.nlm.nih.gov/24768732/
A BULGING DISK refers to the generalized or focal extension of disc tissue, usually < 3 mm from the vertebral body apophysis, and is considered a normal variant.
A PROTRUDED DISK extends > 3 mm beyond the apophysis, but importantly, its herniated dimen-sions do not exceed those of the remaining disc within the disc space.
This is unlike EXTRUDED DISKS, in which at least one plane of herniated disc tissue exceeds disc space dimensions and usually extends through the posterior longitudinal ligament (PLL).
A SEQUESTRED DISK is a variant of extruded discs whereby a portion of the disc fragment is displaced beyond the outer annulus and maintains no connection with the origin disc tissues.
MIGRATED DISKS are those with extruded segments displaced away from the outer annulus and can be extruded or sequestered in morphology.
Illustration: https://www.nejm.org/doi/pdf/10.1056/nejmcp1512658
