There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the Research
Implications of Mild Disc Desiccation, Height Loss, and Bulge at L5-S1
- Mild disc desiccation, height loss, and bulge at L5-S1 without spinal canal or neural foraminal stenosis can have various implications on the lumbar spine and overall health of an individual 1, 2.
- A study found that lumbar disc degeneration is the most common cause of low back pain, and MRI is the standard imaging modality for detecting disc pathology due to its advantage of lack of radiation, multiplanar imaging capability, excellent spinal soft-tissue contrast, and precise localization of intervertebral discs changes 1.
- Another study showed that extraforaminal compression of the L-5 nerve root at the lumbosacral junction can result from disc herniations, bony or ligamentous compression, and other factors such as disc space collapse or coronal wedging, which can contribute to narrowing of the extraforaminal space 3.
Clinical Outcomes and Radiographic Assessments
- A retrospective comparative study found that patients with mild-to-moderate L5-S1 foraminal stenosis had inferior clinical outcomes at the final follow-up in terms of back pain and ODI score compared to those without foraminal stenosis 4.
- The study also found that the presence of mild-to-moderate L5-S1 foraminal stenosis was associated with more aggravated sagittal balance in terms of smaller preoperative disc height, larger sagittal vertical axis, smaller lumbar lordosis, and larger pelvic incidence-lumbar lordosis mismatch 4.
- A kinetic magnetic resonance imaging study found that neural foramina decreased significantly in extension compared with flexion and neutral, and lumbar disc bulge migration and angular motion at each level contributed independently to the decrease in foraminal area in extension 5.
Diurnal Variation in Lumbar MRI
- A study found that diurnal variations in MRI signal intensity, disc height, and disc bulge occurred in asymptomatic healthy volunteers, with an average loss of signal intensity and disc height, and an increase in disc bulge at the L4-5 level 2.
- The study also found that loss of disc height was one factor in the reduction of body height, and these changes occurred randomly throughout 5 lumbar disc levels in each case 2.