Magnetic resonance imaging findings in patients with low backache

Introduction: Low backache is commonly experienced by adults at some time during their lives. Though it is caused by degenerative changes, spinal stenosis, neoplasm, infection and trauma, lumbar disc degeneration is the most commonly diagnosed abnormalities associated. As Magnetic Resonance Imaging (MRI) is non invasive imaging technique with excellent spatial and contrast resolution, it has become the investigation of choice in evaluation of patients with low back pain. This study was designed to determine the patterns of degenerative disc disease on MRI in patients with low backache. Methods: A retrospective hospital based study was done by reviewing MRI report of 202 patients who underwent MRI of lumbar spine for complaint of chronic low back pain, radicular pain, neurogenic claudication or various other symptoms and signs suggestive of lumbar degenerative disc disease from January 2014 till June 2014. The patients having MRI findings of acute spinal infection, recent trauma, tumors, spinal dysraphism and metabolic conditions were excluded from the study. Results: Out of the 202 patients included in the study, 116 patients (57.4%) were male and 86 patients (42.6%) were female. The mean age of the study population was 44.26 ±15.61 (13-83) years. Multiple contiguous level disc disease was the most common type of involvement which was noted in 109 (54%) patients. Grade 4 lumbar disc degeneration (graded as per classification given by Pfirrmann et al) was noted in 65.3% (132) cases followed by Grade 2 in 25.2%(51) cases and Grade 1in 5.5% (11) cases. The most common involvement was observed at L4-L5 level (76.7%) and L5-S1 levels (55.9%) followed by L3-L4 (30.6%) in decreasing order of frequency. The most common category was disc bulge note in 46.5% (94) of cases. Nerve root compression was observed in 56% (114) of the total cases. Nerve root compromise was also noted most frequently compressing L5 nerve (28.23% of cases). Annular tear was observed in 14.4% (29) of cases and among them 20% (6) of cases had torn at two intervertebral discs. It is most frequently noted involving L4-L5 intervertebral disc (72.5% of cases), followed by L5-S1 (24.2% of cases). Conclusion: Disc generation is most common at L4-L5 level with multiple contiguous involvement of grade 4. Annular tear though not common can occur and is also common at L4-L5 level.


Introduction
Low back ache is one of the common indications for MRI in our clinical practice.It is estimated that 70-80% of adults experience low backache at some time during their lives. 1The causes of low back pain include degenerative changes, spinal stenosis, neoplasm, infection, trauma, and inflammatory or arthritic processes.Among these, lumbar disc degeneration is the most commonly diagnosed abnormalities associated with low back pain. 2 There are varieties of factors that contribute to this condition.Aging, axial loading of disc, vascular in growth, and abnormalities in collagen and proteoglycan all contribute to disc degeneration.Disc herniation with radiculopathy and chronic discogenic low back pain are the result of this degenerative process. 3I is non invasive imaging technique with excellent spatial and contrast resolution.Hence, it has become the investigation of choice in evaluation of patients with low back pain or radicular pain.It has also emerged as an investigation of choice over the other investigations for a herniated disc and become a gold standard to diagnose herniated disc. 4MRI is also useful in planning surgical management of patients with sciatica attributable to lumbar disc herniation. 5Hence, MRI is the emerging radiological diagnostic tool in the management of low back pain.However, MRI facility is not available in all the part of the country and even in the places where this investigation is available, being one of the expensive investigations, it might be beyond affordability for most of the Nepalese population.Till date, not many studies have been done in our geographical region to identify spectrum of lumbar disc pathology prevalent in this part of the world.Hence, this study was designed to determine retrospectively the patterns degenerative disc disease on MRI in patients with low back pain.The result of the study might have clinical relevance about what is to be expected in the patient with low back ache due to degenerative changes.

Material
This is hospital based retrospective study of 202 MRI reports of lumbar spine, done at Capital Hospital, Kathmandu, Nepal.Patients who underwent MRI lumbar spine for complaints of chronic low back pain, radicular pain, neurogenic claudication or various other symptoms and signs suggestive of lumbar degenerative disc disease from January 2014 till June 2014 were included in the study.Those patients having MRI findings of acute spinal infection, recent trauma, tumors, spinal dysraphism and metabolic conditions were excluded from the study.
The MRI examination was done on 0.3T Hitachi, Airis-Ventos with acquisition of the T1W, T2W, STIR images in sagittal, axial and coronal planes.The following criteria were evaluated on MRI: lumbar disk degeneration (graded as per classification given by Pfirrmann et al), disc herniation (graded as normal, bulge, protrusion, extrusion and sequestration), presence of annular tear, nerve root compromise (graded as per Pfirrmann et al classification), degenerative vertebral endplates changes (graded as per Modic classification). 6,7,8 Al the MRI reporting was done by the principal investigator.Permission for the retrospective review was taken from the hospital management.
Multiple contiguous level disc disease was noted in 109 (54%) patients, multiple level disc disease with skipped segments was noted in 19(9.4%)patients, while 74 (36.6%) patients in the study group had single level disc involvement.Grade 4 lumbar disc degeneration (graded as per classification given by Pfirrmann et al)was noted in 65.3% (132) cases followed by Grade 2 in 25.2%(51) cases and Grade 1in 5.5% (11) cases.
The incidence of various categories of disc herniation at different levels was calculated and presented in the figure 1.The most common involvement was observed at L4-L5 level (76.7%) and L5-S1levels (55.9%) followed by L3-L4 (30.6%) in decreasing order of frequency.The most common category was disc bulge note in 46.5% (94) of cases involving L4-L5 disc.Nerve root compression was observed in 55.9% (113) of the total cases.Multiple nerve compression was observed in 7.07% (8) cases.Among them, central canal stenosis was observed in 70% (79), neural foraminal narrowing in 35.4% (40).Nerve root compromise was also noted most frequently at L4-L5 level (28.23% of cases),followed by L5-S1 (25.25%) and L3-L4 (8.4%) levels in decreasing order of frequency as presented in the table 1 which shows various grades of nerve root compromise at respective disc levels.Grade 3 nerve root compression was the most common and was observed in 76% (86) of cases with nerve root compression.Figure 2, 3, 4 demonstrates common MRI findings observed in this study.
Vertebral end plate changes were seen only in 7.4% of cases (15) and most commonly at L5-S1 and L4-L5 vertebral levels with Modic Type II changes (80% of cases) being most common followed by Type I changes (46.6%).Type III changes were not identified in any of the patients in the study group.

Figure 1 .
Figure 1.Various categories of disc herniation at different levels

Figure 3 :Figure 4 :
Figure 3: T2W Sagital image shows disc desiccation at L4-L5 level with posterior-central protrusion causing narrowing of the central spinal canal Figure 4: T2W axial image shows left paracentral protrusion causing narrowing of the central spinal canal and left lateral recess.The disc is impinging left traversing nerve root.DiscussionThis retrospective study demonstrated the spectrum of MRI findings in patients with low back pain in our setting.The mean age for presentation with low back pain was 44.26 years.The age of patient presenting with low backache is