Apparent diffusion coefficient maps in the assessment of surgical patients with lumbar spine degeneration

<div><p>Purpose</p><p>To assess the utility of apparent diffusion coefficient (ADC) maps for the assessment of patients with advanced degenerative lumbar spine disease and describe characteristic features of ADC maps in various degenerative lumbar spinal conditions.</p><p>Methods</p><p>T1-weighted, T2-weighted and diffusion weighted (DWI) MR images of 100 consecutive patients admitted to the spinal surgery service were assessed. ADC maps were generated from DWI images using Osyrix software. The ADC values and characteristic ADC maps were assessed in the regions of interest over the different pathological entities of the lumbar spine.</p><p>Results</p><p>The study included 452 lumbar vertebral segments available for analysis of ADCs. Characteristic ADC map features were identified for protrusion, extrusion and sequester types of lumbar disk herniations, spondylolisthesis, reactive Modic endplate changes, Pfirrmann grades of IVD degeneration, and compromised spinal nerves. Compromised nerve roots had significantly higher mean ADC values than adjacent (p < 0.001), contralateral (p < 0.001) or adjacent contralateral (p < 0.001) nerve roots. Compared to the normal bone marrow, Modic I changes showed higher ADC values (p = 0.01) and Modic 2 changes showed lower ADC values (p = 0.02) respectively. ADC values correlated with the Pfirrmann grading, however differed from herniated and non-herniated disks of the matched Pfirrmann 3 and 4 grades.</p><p>Conclusion</p><p>Quantitative and qualitative evaluation of ADC mapping may provide additional useful information regarding the fluid dynamics of the degenerated spine and may complement standard MRI imaging protocol for the comprehensive assessment of surgical patients with lumbar spine pathology. ADC maps were advantageous in differentiating reactive bone marrow changes, and more precise assessment of the disk degeneration state. ADC mapping of compressed nerve roots showed promise but requires further investigation on a larger cohort of patients.</p></div

Assessment of nerve root ADC.

<p>(A) ADC maps, T2-WI and merged images of left (ipsilateral) and right (contralateral) parasaggital lumbar scans of 38 y.o. male patient with right sided L5-S1 disk herniation. Regions of interest (15 mm²) were selected over the ipsilateral (arrows) contralateral (arrowheads) S1 nerve roots. (B) Axial T2-WI showing disk herniation. (C) Comparison of ADC values from the affected, contralateral, adjacent ipsilateral (S1 or L5), and adjacent contralateral nerve roots. Data calculated from 19 patients with symptomatic disk herniations. *—p < .01. ADC, apparent diffusion coefficient; T2-WI, T2-weighted image.</p

Comparison of ADC heterogeneity in various Pfirrmann degeneration grades of all intervertebral disks.

<p>Diagram showing ADC heterogeneity in intervertebral disks of Pfirrmann grades 2 through 5. 452 disks included in analysis. Significant differences were observed among all grades. ADC, apparent diffusion coefficient.</p

Assessment of ADC values from herniated and non-herniated disks in various Pfirrmann degeneration grades.

<p>Diagram of mean ADC values in herniated and non-herniated intervertebral disks stratified y the Pfirrmann grades. Significant differences were observed in the Pfirrmann grades 3 and 4. Totally 114/452 (25%) disks were included in the analysis as herniated (grade 3, n = 42; grade 4, n = 57 and grade 5, n = 15), 316/452 (70%) as non-herniated (grade 2, n = 114; grade 3, n = 150; grade 4, n = 48; grade 5, n = 4), and 22/452(5%) disks were excluded from the analysis due to spondylolisthesis or lumbar stenosis without herniation. ADC, apparent diffusion coefficient, LDH, lumbar disk herniation.</p

Sequester type of disk herniation.

<p>(A) Parasagittal ADC map, (B) sagittal T2-WI, (C) overlay and (D) axial T2-WI showing caudally migrated T2 hyperintence disk fragment occupying paraforaminal zone ADC, apparent diffusion coefficient; T2-WI, T2-weighted image.</p

Modic changes, associated ADC values and Pfirrmann grades.

<p>Modic changes, associated ADC values and Pfirrmann grades.</p

Pfirrmann disk degeneration grades and ADC maps.

<p>Appearance of various grades of disk degeneration on the ADC maps is shown on the left panel. Diagram on the right shows comparison of mean ADC values in different Pfirrmann grades (all disks included in analysis, n = 452). ADC, apparent diffusion coefficient; T2-WI, T2 weighted image.</p

Patients characteristics.

<p>Patients characteristics.</p

Protrusion type of disk herniation.

<p>(A) Sagittal ADC map and (B), corresponding T2-WI and (C) colored overlay bulging annulus fibrosus and contained nucleus pulposus of L5-S1 disk. (D)–axial T2-weighted image showing location of the disc herniation.</p

Intraoperative pictures of spinal nerve roots with various degree of inflammation.

<p>(A) 28 y.o. male with right sided L4-5 disk herniation. Representative intraoperative image after removal of the herniation shows red inflamed L5 nerve root (arrow). Right L5 nerve root ADC value is 1199 ± 113 x10^-6 mm²/s; (B) 52 y.o. male M. with left sided herniated disk at L5-S1 level. Intraoperative picture after removal of the herniation shows slightly edematous S1 nerve root (arrow). Left S1 nerve root ADC value is 1030 ± 192 x1^-6 mm²/s. ADC, apparent diffusion coefficient; LDH, lumbar disk herniation.</p